WO2011016170A1 - 波長変換レーザ及び画像表示装置 - Google Patents
波長変換レーザ及び画像表示装置 Download PDFInfo
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- WO2011016170A1 WO2011016170A1 PCT/JP2010/003852 JP2010003852W WO2011016170A1 WO 2011016170 A1 WO2011016170 A1 WO 2011016170A1 JP 2010003852 W JP2010003852 W JP 2010003852W WO 2011016170 A1 WO2011016170 A1 WO 2011016170A1
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/0602—Crystal lasers or glass lasers
- H01S3/0612—Non-homogeneous structure
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
- H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
- H01S3/109—Frequency multiplication, e.g. harmonic generation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
- H04N9/3129—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] scanning a light beam on the display screen
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- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
- H04N9/3141—Constructional details thereof
- H04N9/315—Modulator illumination systems
- H04N9/3161—Modulator illumination systems using laser light sources
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/0619—Coatings, e.g. AR, HR, passivation layer
- H01S3/0621—Coatings on the end-faces, e.g. input/output surfaces of the laser light
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/0627—Construction or shape of active medium the resonator being monolithic, e.g. microlaser
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/094076—Pulsed or modulated pumping
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/094084—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light with pump light recycling, i.e. with reinjection of the unused pump light, e.g. by reflectors or circulators
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
- H01S3/09415—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
- H01S3/16—Solid materials
- H01S3/1601—Solid materials characterised by an active (lasing) ion
- H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
- H01S3/1611—Solid materials characterised by an active (lasing) ion rare earth neodymium
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
- H01S3/16—Solid materials
- H01S3/163—Solid materials characterised by a crystal matrix
- H01S3/1671—Solid materials characterised by a crystal matrix vanadate, niobate, tantalate
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
- H01S3/16—Solid materials
- H01S3/163—Solid materials characterised by a crystal matrix
- H01S3/1671—Solid materials characterised by a crystal matrix vanadate, niobate, tantalate
- H01S3/1673—YVO4 [YVO]
Definitions
- the present invention relates to an internal resonator type wavelength conversion laser in which a wavelength conversion element is inserted in a resonator of a solid-state laser, and an image display device using the same.
- Wavelength conversion lasers that perform wavelength conversion on converted waves have been developed.
- an internal resonator type wavelength conversion laser in which a wavelength conversion element is inserted into a resonator of a solid-state laser has a feature that it can perform wavelength conversion with high efficiency because it uses a resonator structure.
- the microchip solid-state laser using a sub-mm to several-mm laser medium is expected to have various applications because of its small size and W-class output.
- the combination of the microchip solid-state laser and the internal cavity type wavelength conversion laser has been tried to be applied in a wavelength region where the semiconductor laser cannot oscillate directly, or in a region where a giant pulse or a high frequency is required.
- Patent Document 1 proposes a laser that includes a plurality of laser media having fluorescence spectrum bands at least partially overlapping each other in a resonator, increases the fluorescence spectrum width, and covers a wide wavelength range.
- Patent Document 3 proposes a resonator having two wavelengths sharing one reflecting mirror is configured using two kinds of solid-state laser media and three reflecting mirrors, and sum frequency mixing is performed by a nonlinear optical crystal. A configuration is proposed.
- the internal resonator type wavelength conversion laser has a problem that a spectral width is narrow and speckle noise called speckle noise is generated. That is, in the internal cavity type wavelength conversion laser, in order to enable highly efficient wavelength conversion, a single mode and a narrow band of a solid-state laser are required. However, in order to reduce speckle noise, it is necessary to widen the spectral width of the wavelength-converted laser light. Further, even when a temperature change or the like occurs, it is demanded that the spectrum width of the wavelength conversion laser light is stably wide.
- JP 2005-93624 A Japanese Patent Laid-Open No. 2008-4882 JP 2006-66436 A
- An object of the present invention is to provide a wavelength conversion laser that stably outputs a low-coherent wavelength conversion laser beam having a wide spectrum width even when a temperature change occurs, and an image display device using the same.
- a wavelength conversion laser device includes an excitation light source that emits excitation light, a solid-state laser having a resonator, and a wavelength conversion element disposed in the resonator, A first laser medium and a second laser medium, which are at least two types of laser media; the first laser medium oscillates a solid-state laser beam having a first oscillation wavelength; and the second laser medium has a second oscillation wavelength.
- the at least two types of laser media are excited by the pumping light emitted from a common pumping light source, and the solid laser has a portion where the pumping light is the first laser medium.
- a solid-state laser beam having an oscillation wavelength is configured to oscillate, and the wavelength conversion element in the resonator includes the solid-state laser beam having the first oscillation wavelength and the second oscillation wavelength, the first oscillation wavelength, and the first oscillation wavelength. It converts into the 2nd harmonic and sum frequency of 2 oscillation wavelengths, and the said 2nd harmonic and the said sum frequency are generated simultaneously.
- the intensity ratio of the solid-state laser light having the first oscillation wavelength and the second oscillation wavelength can be kept constant even if the wavelength of the excitation light changes. For this reason, even when a wavelength conversion element that simultaneously generates the first oscillation wavelength, the second harmonic of the second oscillation wavelength, and the sum frequency is used, there is a large bias in these three wavelengths in the spectrum distribution of the wavelength-converted light. A wide spectral width can be maintained without occurring. Therefore, a wavelength conversion laser that stably outputs a low-coherent wavelength conversion laser beam having a wide spectrum width can be realized even when the temperature of the excitation light changes due to a temperature change or the like.
- FIG. 1 is a schematic configuration diagram of a wavelength conversion laser 100 according to Embodiment 1 of the present invention.
- the wavelength conversion laser 100 includes an excitation laser diode (LD) 1 (excitation light source), a condensing optical system 2, a laser medium 3 (first laser medium), and a laser medium 4 (second Laser medium), laser medium 5 (first laser medium), and wavelength conversion element 7.
- LD excitation laser diode
- condensing optical system 2 a laser medium 3 (first laser medium), and a laser medium 4 (second Laser medium), laser medium 5 (first laser medium), and wavelength conversion element 7.
- the pumping LD 1 that is a semiconductor laser emits pumping light that excites the laser media 3, 4, and 5.
- the excitation light emitted from the excitation LD 1 is condensed by the condensing optical system 2 so as to overlap with the solid-state laser light that resonates in the laser media 3, 4, and 5.
- the excitation light is incident on the laser medium 3, the laser medium 4, and the laser medium 5 in this order, and is absorbed by each laser medium.
- the laser medium 3 and the laser medium 5 have the same Nd: YVO 4 although the Nd concentration is different, and oscillate solid laser light having the same oscillation wavelength IR1 (first oscillation wavelength).
- the laser medium 4 is made of Nd: GdVO 4 and oscillates solid-state laser light having an oscillation wavelength IR2 (second oscillation wavelength) different from IR1.
- the solid-state laser of the present embodiment has a configuration in which a portion (laser medium 4) made of the second laser medium is disposed between two portions (laser media 3 and 5) made of the first laser medium.
- the laser media 3, 4 and 5 are directly joined in this order. Further, the laser medium 5 and the wavelength conversion element 7 are directly joined.
- the resonator of the solid-state laser is composed of a surface 3 a on the excitation light incident side in the laser medium 3 and a surface 7 b on the wavelength conversion light emission side in the wavelength conversion element 7. Therefore, the wavelength conversion element 7 is arranged in the resonator of the solid-state laser.
- the surface 3a on the excitation light incident side of the resonator of the solid laser is provided with an AR coat (antireflection coating) of excitation light and an HR coat (reflection coating) of solid laser light and wavelength converted light, While transmitting excitation light, it reflects solid laser light and wavelength converted light.
- the surface 7b on the wavelength conversion light emission side of the resonator of the solid laser is provided with an HR coat of solid laser light and an AR coat of wavelength conversion light, and reflects the solid laser light while converting the wavelength. Transmit light.
- the laser medium 3 is made of Nd: YVO 4 having an Nd concentration of 1% and a thickness of 0.2 mm.
- the laser medium 4 is made of Nd: GdVO 4 having an Nd concentration of 1% and a thickness of 0.7 mm.
- the laser medium 5 is made of Nd: YVO 4 having an Nd concentration of 3% and a thickness of 0.4 mm.
- the laser media 3 and 5 oscillate solid-state laser light IR1 (oscillation wavelength IR1) having a center wavelength of 1064.1 nm.
- the laser medium 4 oscillates solid-state laser light IR2 (oscillation wavelength IR2) having a center wavelength of 1062.8 nm.
- the wavelength conversion element 7 is made of MgO: LiNbO 3 (PPLN) having a domain-inverted periodic structure and is a very thin wavelength conversion element of 0.5 mm.
- the polarization inversion period is 7 ⁇ m.
- the wavelength conversion element 7 of the present embodiment is characterized by having a very wide phase matching tolerance. Therefore, it is possible to generate the second harmonic SHG1 of the solid-state laser light IR1, the second harmonic SHG2 of the solid-state laser light IR2, and the sum frequency SFG1 of the solid-state laser lights IR1 and IR2 with one wavelength conversion element. it can.
- a single wavelength conversion element performs wavelength conversion for a plurality of wavelengths at the same time, whereby a highly efficient and small wavelength conversion laser can be obtained.
- FIG. 2A shows the spectral distribution of wavelength converted light output from the wavelength conversion laser 100.
- the wavelength converted light SHG1 is the second harmonic (center wavelength 532.1 nm) from the solid-state laser light IR1.
- the wavelength converted light SHG2 is the second harmonic (center wavelength 531.4 nm) from the solid-state laser light IR2.
- the wavelength converted light SFG1 is the sum frequency (center wavelength 531.8 nm) of the solid-state laser beams IR1 and IR2.
- FIG. 2B is a spectral distribution of the wavelength-converted light that is output when the excitation light absorption of the laser medium 4 becomes very large with respect to the excitation light absorption of the laser medium 3 and the laser medium 5 (this is shown in FIG. 2B).
- This is a comparative example of the wavelength conversion laser 100 of the present embodiment.
- the solid-state laser light IR2 oscillating in the resonator becomes very large with respect to the solid-state laser light IR1, so that the spectrum distribution of the wavelength-converted light to be output is biased.
- SHG2 is preferentially output.
- variety of wavelength conversion light becomes narrow, coherency increases, and interference noise (speckle noise) will appear.
- the present embodiment has a characteristic configuration capable of avoiding a large deviation in the spectrum distribution of wavelength-converted light and an increase in interference noise.
- the present wavelength conversion laser 100 includes a laser medium 3 having an oscillation wavelength IR1, a laser medium 5, and a laser medium 4 having an oscillation wavelength IR2. These laser media 3, 4 and 5 are excited by excitation light emitted from the same semiconductor laser.
- the excitation light condensed by the condensing optical system 2 enters the laser medium 3, then enters the laser medium 4, and then enters the laser medium 5. .
- the laser media 3 and 5 having the oscillation wavelength IR1 and the laser medium 4 having the oscillation wavelength IR2 are used. For this reason, even when the pumping light wavelength changes, the ratio of the pumping light absorption amount can be kept constant between these two types of laser media having different oscillation wavelengths.
- the intensity of the solid-state laser light having the oscillation wavelength IR1 and the intensity of the solid-state laser light of the solid-state laser light IR2 can be kept constant.
- the wavelength-converted light can be output without causing a large bias in these three wavelengths in the spectrum distribution of the wavelength-converted light.
- the excitation light incident on the resonator of the solid-state laser is dispersed and absorbed by a plurality of laser media (laser media 3 to 5). For this reason, the exothermic point by absorption of excitation light can be disperse
- FIG. 3 shows a simulation result of the absorption rate of the excitation light in each of the laser media 3 to 5 of the first embodiment.
- the excitation LD 1 emits 808 nm excitation light in an environment of 25 ° C., but the wavelength of the excitation light changes as the temperature changes.
- the horizontal axis in FIG. 3 indicates the wavelength shift amount in which the wavelength of the excitation light from the excitation LD 1 has changed from 808 nm.
- the vertical axis indicates the ratio between the absorption rate and the absorption amount of each of the laser media 3 to 5.
- Nd: YVO 4 and Nd: GdVO 4 having Nd as an active ion have an absorption peak wavelength at 808 nm, the absorption coefficient takes a peak value when the excitation light wavelength is 808 nm, and the absorption coefficient decreases as the wavelength changes from 808 nm.
- the absorptance of the laser medium 3 in FIG. 3 decreases as the wavelength changes from 808 nm, and the absorptance decreases. That is, when the wavelength changes from 808 nm, the light absorption coefficient in the laser medium 3 and the laser medium 4 decreases. For this reason, the amount of excitation light incident on the laser medium 5 increases, and the absorption rate of the excitation light in the laser medium 5 increases.
- the laser medium 4 when the wavelength of the excitation light changes from 808 nm, an increase in the amount of light passing through the laser medium 3 and a decrease in the absorption coefficient of the laser medium 4 occur simultaneously. For this reason, the laser medium 4 maintains an absorptance of around 50% even when the wavelength of the excitation light changes.
- the ratio of the absorptance of the laser medium 3 and the laser medium 5 having the oscillation wavelength IR1 to the absorptance of the laser medium 4 having the oscillation wavelength IR2 is 0.9 to The range is 1.1.
- the ratio of the amount of absorption between laser media having different oscillation wavelengths can be kept constant. For this reason, even if the wavelength of excitation light changes, a wide spectrum width can be maintained without causing a large bias in the spectrum distribution of the wavelength-converted light that is emitted.
- the ratio of the absorptance between the laser medium 3 with the oscillation wavelength IR1 and the laser medium 4 with the oscillation wavelength IR2 is Greater than 2. For this reason, a large deviation occurs in the spectrum width of the wavelength-converted light emitted as in the comparative example shown in FIG. 2B.
- laser media 3 and 5 (Nd: YVO 4 ) having an oscillation wavelength IR1 are arranged before and after a laser medium 4 (Nd: GdVO 4 ) having an oscillation wavelength IR2, and the Nd ion concentration of the laser medium 5 is This is a preferable form higher than the Nd ion concentration of the laser medium 3.
- the change in the absorptance of the laser medium is mainly caused by a decrease in the absorption coefficient due to a change in the wavelength of the excitation light. At this time, in order to maintain the total absorption rate of the laser medium, it is necessary to increase the length of the laser medium or increase the active ion concentration.
- the amount of excitation light incident on the laser medium 4 is ensured by first increasing the length of the laser medium 3 on which the excitation light is incident or increasing the active ion concentration. I can't do it.
- the active ion concentration of the laser medium 5 is set higher than that of the laser medium 3 in order to keep the total absorption rate constant. Increasing the length of the laser medium leads to an increase in cost and an increase in size. For this reason, it is preferable to increase the active ion concentration of the laser medium 5 as in the present embodiment.
- the excitation light incident on the laser medium 5 becomes the remainder absorbed by the laser medium 3 and the laser medium 4 provided on the incident side of the laser medium 5. For this reason, the power of the excitation light incident on the laser medium 5 is smaller than the power of the excitation light incident on the laser medium 3. For this reason, even if the active ion concentration of the laser medium 5 is higher than that of the laser medium 3, the temperature increase of the laser medium due to absorption of the excitation light can be suppressed to a small level.
- Nd: YVO 4 is used for the laser media 3 and 5 having the oscillation wavelength IR1
- Nd: GdVO 4 is used for the laser medium 4 having the oscillation wavelength IR2
- adjacent laser media are adjacent to each other. This is a preferred form of joining.
- a vanadate-based laser medium having Nd as an active ion has a large stimulated emission cross-sectional area, and can oscillate even when the crystal length is short.
- a plurality of laser media are used in this embodiment, since YVO 4 and GdVO 4 are the same crystal system, the refractive index and the thermal expansion coefficient are almost equal. Therefore, it can be handled as one crystal by joining these laser media.
- the bonding strength between the crystals can be obtained and processing such as cutting can be performed.
- the laser medium length is short in order to maintain the condensed state of the excitation light. Therefore, if a laser medium composed of Nd: YVO 4 and Nd: GdVO 4 is joined as in the above configuration, there is no crystal spacing and each crystal length can be shortened.
- “joining” refers to a state in which the air layer is in close contact without sandwiching the air layer.
- Nd YVO 4 having an oscillation wavelength longer than that of the laser medium 4 is used for the laser medium 3 on which the excitation light first enters.
- this embodiment is a preferred mode in which a laser medium having a longer oscillation wavelength is used on the excitation light incident side of the laser medium to be joined.
- the excitation light is first incident on a laser medium having a long oscillation wavelength, thereby raising the temperature of the laser medium having a long oscillation wavelength.
- the oscillation wavelength shifts to the longer wavelength side, so that the difference in the oscillation wavelength becomes larger as the temperature rises, and the spectrum width of the wavelength converted light to be output is further expanded.
- the peak of the absorptance of the laser medium 3 when the wavelength of the excitation light in the present embodiment changes is 45%. This is a preferable form in which the peak of the absorption rate of the excitation light of the laser medium on which the excitation light first enters is 10% or more and 75% or less.
- the peak of the absorption rate of the laser medium 3 When the peak of the absorption rate of the laser medium 3 is larger than 75%, a sufficient amount of incident excitation light to the laser medium 4 is not secured near the peak of the absorption rate, and the ratio of the absorption amount between the laser media (laser medium 4 / The laser medium 3 + 5) becomes 0.35 or less, which causes a bias in the spectral distribution.
- the peak of the absorption rate of the laser medium 3 is smaller than 10%, the absorption rate of the laser medium 4 cannot be maintained around 50% when the wavelength of the excitation light changes, and the spectral distribution is biased.
- the absorption peak of the excitation light of the laser medium on which the excitation light first enters is preferably 20% or more and 67% or less. By setting it within this range, the ratio of the amount of absorption between the laser media can be suppressed to a range of 0.5 to 2, and low-coherent light with no bias in the spectral distribution can be obtained.
- a wide stripe LD is used, but a multi-stripe type LD or an LD having a wavelength lock mechanism can also be used.
- the condensing optical system 2 a combination of a plurality of lenses may be used. Further, the pumping LD 1 and the laser medium 3 may be brought close to each other and the condensing optical system may be omitted.
- end faces of the solid-state laser resonator according to the first embodiment are configured as planes
- a concave mirror may be used as the end face of the resonator, or another optical component such as a lens may be inserted into the resonator.
- the excitation light wavelength changes due to temperature change, but the excitation light wavelength also changes due to variations among lots of excitation LDs.
- the excitation light wavelength changes due to various reasons, it is possible to stably output wavelength-converted laser light having a wide spectral width.
- Nd as the laser medium 3 and 5: GdVO 4 Nd as the laser medium 4: GdVO are 4 using, but not limited thereto. That is, the laser mediums 3 and 5 and the laser medium 4 may have different oscillation wavelengths.
- a laser medium other than Nd: GdVO 4 is used as the laser medium 3 and 5, and Nd: GdVO 4 is used as the laser medium 4.
- Other laser media may be used. Note that the two laser media have different oscillation wavelengths means that the center wavelengths at which the two laser media oscillate are different from each other.
- the difference between the oscillation wavelength IR1 and the oscillation wavelength IR2 differs depending on the laser medium to be used, it is desirable to increase the spectral width of the wavelength-converted laser light to be obtained if the difference is increased.
- the difference between the oscillation wavelength IR1 and the oscillation wavelength IR2 is 1 nm or more, it is possible to realize a good image display or illumination with less interference noise (speckle noise) for applications in the image field and the illumination field. .
- Nd as the laser medium 4: GdVO are 4 using, but not limited thereto. That is, the laser mediums 3 and 5 and the laser medium 4 may have different oscillation wavelengths.
- a laser medium other than Nd: YVO 4 is used as the laser medium 3 and 5, and Nd: GdVO 4 is used as the laser medium 4.
- Other laser media may be used. Note that the two laser media have different oscillation wavelengths means that the center wavelengths at which the two laser media oscillate are different from each other.
- the difference between the oscillation wavelength IR1 and the oscillation wavelength IR2 differs depending on the laser medium to be used, it is desirable to increase the spectral width of the wavelength-converted laser light to be obtained if the difference is increased.
- the difference between the oscillation wavelength IR1 and the oscillation wavelength IR2 is 1 nm or more, it is possible to realize a good image display or illumination with less interference noise (speckle noise) for applications in the image field and the illumination field. .
- FIG. 4 shows a schematic configuration of the wavelength conversion laser 200.
- the same reference numerals are used for the same configurations as those in the first embodiment, and the detailed description thereof is omitted.
- the wavelength conversion laser 200 has two laser media, a laser medium 32 (first laser medium) and a laser medium 42 (second laser medium).
- the laser medium 32 is made of Nd: YVO 4 with an Nd concentration of 1% and a thickness of 0.3 mm
- the laser medium 42 is made of Nd: GdVO 4 with an Nd concentration of 1% and a thickness of 0.7 mm.
- An end surface 42b of the laser medium 42 on the solid laser light emission side is provided with an AR coat of solid laser light and an HR coat of excitation light, and reflects the excitation light while transmitting the solid laser light.
- the excitation light emitted from the excitation LD 1 enters the laser medium 32 that oscillates at the oscillation wavelength IR 1, then enters the laser medium IR 2 laser medium 42, is reflected by the end face 42 b, and then enters the laser medium 32 again.
- the solid-state laser resonator of the wavelength conversion laser 200 includes an end face 32 a of the laser medium 32 and an end face 72 b of the wavelength conversion element 72.
- the end surface 32a on the excitation light incident side of the laser medium 32 is provided with an AR coat of excitation light and an HR coat of solid laser light, which transmits the excitation light while reflecting the solid laser light.
- the end face 72b on the wavelength conversion light emission side of the wavelength conversion element 72 is provided with an HR coat of solid laser light and an AR coat of wavelength conversion light, and the end face 72b reflects the solid laser light.
- the wavelength-converted light a and the wavelength-converted light b are transmitted and output.
- the wavelength conversion element 72 uses MgO: LiNbO 3 (PPLN) having a domain-inverted periodic structure, and the thickness thereof is a very thin wavelength conversion element of 0.7 mm.
- the polarization inversion period is formed at 6.8 ⁇ m, and the polarization inversion period structure is inclined 14 degrees in the example of the present embodiment with respect to the optical axis of the resonator of the solid-state laser.
- the end surface 72a on the excitation LD1 side of the wavelength conversion element 72 is provided with an AR coat of solid-state laser light and an HR coat of wavelength-converted light.
- the end face 72a transmits the solid-state laser light while wavelength-converted light is transmitted. To reflect.
- the wavelength conversion element 72 generates the second harmonic SHG1 of the solid-state laser light IR1, the second harmonic SHG2 of the solid-state laser light IR2, and the sum frequency SFG1 of the solid-state laser lights IR1 and IR2.
- wavelength converted light a is generated from the solid laser light traveling in the right direction in FIG. 4, and wavelength converted light b is generated from the solid laser light traveling in the left direction. That is, when the polarization inversion periodic structure of the wavelength conversion element 72 is inclined from the optical axis of the resonator of the solid-state laser, the wavelength converted light a and the wavelength converted light b are emitted with an inclination. In the wavelength conversion laser 200, the wavelength conversion light a and the wavelength conversion light b are emitted with an inclination of +0.5 deg and ⁇ 0.5 deg from the optical axis of the resonator of the solid-state laser, respectively.
- the wavelength-converted light b is reflected from the end face 72 a, is then emitted from the end face 72 b, and is output without entering the laser medium 32 and the laser medium 42.
- the wavelength-converted light a and the wavelength-converted light b are emitted with an inclination in opposite directions (the wavelength-converted light a is emitted with an inclination of + ⁇ with respect to the optical axis of the resonator of the solid-state laser, and the wavelength-converted light b is Therefore, the light beams are output as two beams inclined from the optical axis of the resonator of the solid-state laser.
- the wavelength conversion laser 200 is configured such that the excitation light is incident again on the laser medium 32 having the oscillation wavelength IR1 by the reflection surface 42b of the excitation light. That is, the excitation light enters the laser medium 32 having the oscillation wavelength IR1, then enters the laser medium 42 having the oscillation wavelength IR2, is then reflected by the reflecting surface 42b, and reenters the laser medium 32 having the oscillation wavelength IR1. Thereby, similarly to the effect of the first embodiment, even when the wavelength of the excitation light is changed, the ratio of the absorption amount of the laser medium 32 having the oscillation wavelength IR1 and the laser medium 42 having the oscillation wavelength IR2 is not largely biased. Wavelength converted light having a stable and wide spectral width can be output.
- the laser medium 32 and the laser medium 42 are integrated by direct bonding.
- the laser medium 42 and the wavelength conversion element 72 are held by a spacer so that the resonator of the solid-state laser does not collapse.
- the laser medium 42 and the wavelength conversion element 72 may be integrated by applying an HR coat of excitation light, an AR coat of solid-state laser light, and an HR coat of wavelength conversion light to the interface.
- the wavelength conversion laser 200 has an HR coat of excitation light on the wavelength conversion element side end face 42b of the laser medium 42 having the oscillation wavelength IR2, and the wavelength conversion element 72 is a polarization inversion period inclined with respect to the optical axis of the solid-state laser resonator.
- a preferred embodiment having a structure and having an end face 72a that reflects the wavelength-converted light generated by the wavelength conversion element 72, and the wavelength-converted light is output as two beams without entering the laser media 32 and 42. It is.
- the present wavelength conversion laser 200 has a reflection coating of excitation light on the wavelength conversion element side end face 42b of the laser medium 42 farthest from the excitation LD1, so that the excitation light required in the present invention has an oscillation wavelength IR1.
- the two laser media 32 and 42 can pass through the laser medium first, then pass through the laser medium with the oscillation wavelength IR2 and then enter the laser medium with the oscillation wavelength IR1 again.
- the wavelength conversion light b is prevented from passing through the laser medium 32 and the laser medium 42 by reflecting the wavelength conversion light b at the end face 72 a between the laser medium 42 and the wavelength conversion element 72.
- the wavelength-converted light is incident on the laser medium 32 and the laser medium 42, a part of the wavelength-converted light is absorbed, resulting in a decrease in output of the wavelength-converted light and heat generation of the laser medium.
- the wavelength converted light generated by the wavelength conversion element 72 is reflected by the end surface 72a of the wavelength conversion element 72 on the laser medium side.
- the present invention is not limited to this. It suffices if the solid-state laser resonator has an interface that reflects light so that wavelength-converted light is not incident on the laser media 32 and 42.
- the wavelength conversion light generated by the wavelength conversion element 72 may be reflected by the end face 42b of the laser medium 42 on the wavelength conversion element 72 side.
- a mirror member that reflects the wavelength-converted light generated by the wavelength conversion element 72 may be provided between the end face 42b and the end face 72a.
- One side is inclined by + ⁇ and the other side by ⁇ . In this way, the wavelength-converted light is separated and output as two beams of the wavelength-converted light a and the wavelength-converted light b, thereby avoiding interference between the two and eliminating output fluctuations.
- the reflection coating of the excitation light is formed on the wavelength conversion element side end face 42b of the laser medium 42, and the excitation light is incident on the laser medium 32 having the oscillation wavelength IR1 and then incident on the laser medium 42 having the oscillation wavelength IR2. Then, the wavelength-converted light having a broad spectrum width can be stably output by the configuration in which the wavelength-converted light is then reflected by the reflecting surface 42b and re-incident on the laser medium 32 having the oscillation wavelength IR1, so It is difficult to receive.
- the polarization inversion periodic structure of the wavelength conversion element 72 is tilted from the optical axis of the solid-state laser resonator, and the solid-state laser resonator has an interface that reflects the wavelength-converted light generated by the wavelength conversion element 72.
- the wavelength-converted light is output as two beams (wavelength-converted light a and wavelength-converted light b) without being incident on the laser media 32 and 42, the wavelength-converted light is hardly affected by interference. Absent.
- the wavelength conversion laser 200 of the present embodiment can output stable wavelength-converted light without output fluctuation due to interference.
- the number of laser media can be reduced by using the reflection coat of excitation light and wavelength converted light formed between the laser medium and the wavelength conversion element and the inclination of the above-described polarization inversion periodic structure.
- the output of the wavelength-converted light and the efficiency can be increased, and the wavelength-converted light can be output stably without fluctuation of the output.
- FIG. 5 shows a schematic configuration of the wavelength conversion laser 300.
- the same reference numerals are used for the same components as those in the above-described embodiment, and the detailed description thereof is omitted as appropriate.
- the wavelength conversion laser 300 includes four lasers: a laser medium 33 (first laser medium), a laser medium 43 (second laser medium), a laser medium 53 (first laser medium), and a laser medium 63 (second laser medium). Includes medium.
- the laser medium 33 is made of Nd: GdVO 4 crystal having an Nd concentration of 0.5% and a thickness of 0.4 mm
- the laser medium 43 is made of Nd: YVO 4 crystal having an Nd of 3% and a thickness of 0.25 mm
- the laser medium 53 is made of an Nd: GdVO 4 crystal having an Nd concentration of 3% and a thickness of 0.65 mm
- the laser medium 63 is made of an Nd: YVO 4 crystal having an Nd concentration of 3% and a thickness of 0.9 t.
- the laser medium 33 and the laser medium 53 oscillate solid-state laser light having an oscillation wavelength IR2 as the first oscillation wavelength.
- the laser medium 43 and the laser medium 63 oscillate solid-state laser light having an oscillation wavelength IR1 as the second oscillation wavelength.
- the excitation light emitted from the excitation LD 1 enters the laser medium 33 having the oscillation wavelength IR 2, then enters the laser medium 43 having the oscillation wavelength IR 1, then enters the laser medium 53 having the oscillation wavelength IR 2, and finally the oscillation wavelength IR 1. Incident on the laser medium 63.
- the laser medium 33, the laser medium 43, the laser medium 53, and the laser medium 63 are joined by direct joining.
- the wavelength conversion element 73 is made of LiTiO 3 having a polarization inversion periodic structure and has a thickness of 1 mm.
- the wavelength conversion element 73 can simultaneously generate the second harmonics SHG1 and SHG2 of the solid-state laser beams having the oscillation wavelengths IR1 and IR2 and their sum frequency SFG1.
- the laser medium 63 and the wavelength conversion element 73 are joined by direct joining.
- the end surface 33a on the excitation light incident side of the laser medium 33 is provided with an AR coat of excitation light, an HR coat of solid laser light, and an HR coat of wavelength converted light.
- the end face 73b on the wavelength conversion light emission side of the wavelength conversion element 73 is provided with an HR coat of solid laser light and an AR coat of wavelength conversion light, and the end face 73b serves as an output face of the wavelength conversion light.
- the resonator of the solid-state laser of the wavelength conversion laser 200 is composed of an end face 33 a of the laser medium 33 and an end face 73 b of the wavelength conversion element 73.
- the wavelength conversion laser 300 is a preferable mode in which the excitation light emitted from the semiconductor laser is incident on two types of laser media alternately twice or more. Even when the absorption coefficient of the laser medium changes significantly due to the change in the wavelength of the excitation light, the ratio of the absorption rates of the excitation light of the two types of laser media can be made constant. Thereby, wavelength conversion light with a wide spectrum width can be output in a very wide temperature range.
- the pumping light emitted from the semiconductor laser is alternately incident on the two types of laser media twice, but the pumping light is incident on the two types of laser media alternately three times or more. It is good.
- FIG. 6 shows a schematic configuration of the wavelength conversion laser 400.
- the same reference numerals are used for the same components as those in the above-described embodiment, and detailed description thereof is omitted as appropriate.
- the wavelength conversion laser 400 includes three laser media: a laser medium 34 (first laser medium), a laser medium 44 (second laser medium), and a laser medium 54 (first laser medium).
- the end face 54b of the laser medium 54 on the wavelength conversion element side is provided with an HR coat of excitation light and an AR coat of solid laser light, which reflects the excitation light and transmits the solid laser light.
- the laser medium 34 is made of Nd: YVO 4 with Nd 1% and a thickness of 0.2 mm
- the laser medium 44 is Nd: GdVO 4 with Nd 1% and a thickness of 0.7 mm
- the laser medium 54 is made of Nd: YVO 4 with Nd 3% and a thickness of 0.2 mm.
- the excitation LD1 side end surface 34a of the laser medium 34 is provided with an AR coat of excitation light and an HR coat of solid laser light, and transmits the excitation light while reflecting the solid laser light.
- MgO: LiNbO 3 (PPLN) whose polarization inversion periodic structure is inclined with respect to the optical axis of the solid-state laser resonator is used for the wavelength conversion element 72.
- the end face 72a of the wavelength conversion element 72 on the laser medium 54 side is provided with an HR coat of wavelength converted light and an AR coat of solid laser light, which reflects the wavelength converted light and transmits the solid laser light.
- the resonator of the solid-state laser of the wavelength conversion laser 400 is composed of an end face 34 a of the laser medium 34 and an end face 72 b of the wavelength conversion element 72.
- the excitation light emitted from the excitation LD 1 enters the laser medium 34 having the oscillation wavelength IR 1 and then enters the laser medium 44 having the oscillation wavelength IR 2. Next, the excitation light enters the laser medium 54 having the oscillation wavelength IR1, is reflected by the end face 54b, enters the laser medium 44 having the oscillation wavelength IR2, and finally enters the laser medium 34 having the oscillation wavelength IR1.
- the present wavelength conversion laser 400 is a preferable mode in which the excitation light emitted from the semiconductor laser (excitation LD1) is incident twice or more alternately on two types of laser media.
- the ratio of the absorption rates of the excitation light of the two types of laser media can be made constant. Thereby, wavelength conversion light with a wide spectrum width can be output in a very wide temperature range.
- the pumping light emitted from the semiconductor laser is alternately incident on the two types of laser media twice.
- the pumping light is incident on the two types of laser media alternately three times or more. It is good.
- the wavelength conversion laser 400 has an HR coat of excitation light on the wavelength conversion element side end face 54b of the laser medium 54 having the oscillation wavelength IR1, and the wavelength conversion element 72 has a polarization inversion period inclined with respect to the optical axis of the solid-state laser resonator.
- the structure has an end face 72a that reflects the wavelength-converted light generated by the wavelength conversion element 72, and the wavelength-converted light is output as two beams without entering the laser media 34, 44, and 54. This is a preferred form.
- the laser medium 54 farthest from the pumping LD 1 has a reflection coating for pumping light, so that the laser medium 44 and 34 are reincident on the pumping LD 1 side of the laser medium 54.
- the excitation light is alternately incident on the plurality of types of laser media 34, 44 and 54.
- the wavelength conversion light b is prevented from passing through the laser media 34, 44 and 54 by reflecting the wavelength conversion light b at the end face 72 a between the laser medium 54 and the wavelength conversion element 72. That is, when the wavelength converted light passes through the laser medium, a part of the wavelength converted light is absorbed by the laser medium. For this reason, the output of the wavelength-converted light is reduced and the laser medium generates heat. Therefore, in the present embodiment, the wavelength converted light is reflected at the end face between the laser medium 54 and the wavelength conversion element 72. Thereby, it is possible to prevent a part of the wavelength converted light from being absorbed by the laser medium, so that the conversion efficiency and output power of the wavelength converted light can be improved.
- the wavelength converted light generated by the wavelength conversion element 72 is reflected by the end surface 72a of the wavelength conversion element 72 on the laser medium side.
- the present invention is not limited to this. It suffices if the solid-state laser resonator has an interface that reflects light so that wavelength-converted light does not enter the laser media 34, 44, and 54.
- the wavelength conversion light generated by the wavelength conversion element 72 may be reflected by the end face 54 b of the laser medium 54 on the wavelength conversion element 72 side.
- a mirror member that reflects the wavelength-converted light generated by the wavelength conversion element 72 may be provided between the end face 54b and the end face 72a.
- the wavelength conversion element side end face 54b of the laser medium 54 is formed with a reflection coat of excitation light, and the excitation light emitted from the excitation LD 1 is incident on the two types of laser media alternately twice or more, thereby stabilizing
- wavelength-converted light having a wide spectral width can be generated, so that the wavelength-converted light is hardly affected by interference.
- the polarization inversion periodic structure of the wavelength conversion element 72 is tilted from the optical axis of the solid-state laser resonator, and the solid-state laser resonator has an interface that reflects the wavelength-converted light generated by the wavelength conversion element 72.
- the wavelength-converted light is output as two beams (wavelength-converted light a and wavelength-converted light b) without being incident on the laser medium 34, 44 and 54, the wavelength-converted light is not affected by interference. I hardly receive it.
- the wavelength conversion laser 400 according to the present embodiment can output stable wavelength-converted light without output fluctuation due to interference.
- the number of laser media can be reduced by using the reflection coat of excitation light and wavelength converted light formed between the laser medium and the wavelength conversion element and the inclination of the above-described polarization inversion periodic structure.
- the output of the wavelength-converted light and the efficiency can be increased, and the wavelength-converted light can be output stably without fluctuation of the output.
- FIG. 7 shows a schematic configuration of the wavelength conversion laser 500.
- the same reference numerals are used for the same components as those in the above-described embodiment, and the detailed description thereof is omitted as appropriate.
- the wavelength conversion laser 500 receives the excitation LD 1, the condensing optical system 2, laser media 35, 44 and 55 arranged in this order from the condensing optical system 2 side, and solid laser light emitted from the laser medium 55. And a concave mirror 8 disposed at a position where the solid-state laser light that has passed through the wavelength conversion element 75 is incident.
- wavelength conversion laser 500 excitation light, solid-state laser light, and wavelength conversion light oscillate with linearly polarized light in the vertical axis direction of the paper surface.
- a-cut Nd: YVO 4 and Nd: GdVO 4 are used as the laser medium, and the laser medium oscillates with polarized light in the direction perpendicular to the paper surface.
- This wavelength conversion laser 500 is different from the above-described embodiment in that laser medium materials having the same composition are arranged so that their optical axes are in different directions.
- the laser medium 35 (first laser medium) is a-cut Nd: YVO 4 with Nd 1% and thickness 0.2 mm.
- the laser medium 45 (second laser medium) is c-cut Nd: YVO 4 with Nd 3% and thickness 0.7 mm.
- the laser medium 55 (first laser medium) is a-cut Nd: YVO 4 with Nd 3% and thickness 0.4 mm, and has the same crystal axis as the laser medium 35.
- the oscillation wavelength varies depending on the optical axis direction of the crystal.
- Nd YVO 4 oscillates with a center wavelength of 1064.1 nm in the c-axis direction and oscillates with a center wavelength of 1066.5 nm in the a-axis direction.
- the laser medium 35 and the laser medium 55 that are a-axis cuts oscillation is performed with priority in the c-axis direction, and oscillation is performed at the wavelength IR1 (center wavelength 1064.1 nm) as the first oscillation wavelength.
- the laser medium 45 having the c-axis cut oscillates at the wavelength IR3 (center wavelength 1066.5 nm) in the a-axis direction as the second oscillation wavelength.
- the axes of the laser media 35, 45, and 55c that are tetragonal with respect to the optical axis of the resonator are arranged in two kinds of directions, the vertical direction and the parallel direction, to set the oscillation wavelength. It has a different structure.
- the wavelength conversion element 75 uses MgO: LiNbO 3 (PPLN) having a domain-inverted periodic structure, and its end face is polished so as to have a Brewster angle with respect to the optical axis of the solid-state laser resonator.
- the wavelength conversion element 75 is arranged so as to have a Brewster angle with respect to the optical axis of the solid-state laser resonator so that the polarization direction Dp of the solid-state laser light oscillated by the laser medium 45 having the c-axis cut is shown in FIG. It is fixed in the direction of the vertical axis of the page.
- the wavelength conversion element 75 has a very wide phase matching tolerance with a very thin thickness of 0.6 mm through which the solid laser beam passes.
- the oscillation wavelength IR1 and the oscillation wavelength IR3 are linearly polarized light in the same direction by using the Brewster angle. Therefore, the wavelength conversion element 75 can simultaneously generate the second harmonic SHG1 of the solid-state laser light IR1, the second harmonic SHG3 of the solid-state laser light IR3, and the sum frequency SFG3 of the solid-state laser lights IR1 and IR3. .
- the excitation LD 1 side end face 35 a of the laser medium 35 is provided with an AR coat of excitation light and an HR coat of solid laser light.
- the end face 35 a transmits the excitation light while reflecting the solid laser light.
- the concave mirror 8 is provided with an HR coat of solid-state laser light and an AR coat of wavelength-converted light.
- the concave mirror 8 reflects the solid-state laser light and transmits the wavelength-converted light.
- the resonator of the solid-state laser of the wavelength conversion laser 500 is composed of the concave mirror 8 and the end face 35 a of the laser medium 35.
- AR coating of excitation light and solid-state laser light is applied to each end surface between adjacent laser media of the laser media 35, 45, and 55, and the excitation light and solid-state laser light can be transmitted through the end surfaces. ing.
- the end face 55b of the laser medium 55 on the wavelength conversion element 75 side is provided with an AR coat of solid laser light and an HR coat of wavelength converted light, and the end face 55b transmits the solid laser light. Reflects wavelength converted light. Since the wavelength converted light d generated by the wavelength conversion element 75 is reflected by the end face 55b of the laser medium 55, it is output without passing through the laser media 35, 45 and 55.
- the wavelength converted light c generated from the solid state laser light passing through the wavelength conversion element 75 in the right direction and the wavelength converted light d generated from the solid state laser light passing through the left direction are output as two beams.
- the wavelength conversion laser 500 includes a laser medium having an oscillation wavelength IR1 and a laser medium having an oscillation wavelength IR3. These two types of laser media are excited by excitation light emitted from the same semiconductor laser.
- the excitation light enters the laser medium 35 having the oscillation wavelength IR1, enters the laser medium 45 having the oscillation wavelength IR3, and then enters the laser medium 55 having the oscillation wavelength IR1.
- the ratio of the absorption amount of the excitation light having the oscillation wavelength IR1 and the excitation light having the oscillation wavelength IR3 can be made to be a constant ratio even if the wavelength of the excitation light changes. As a result, the spectrum width of the output wavelength converted light can be maintained in a wide state.
- the present wavelength conversion laser 500 is a preferred form in which the same laser medium material is disposed so that the optical axes are in different directions. According to the configuration of this embodiment, since the same laser medium material can be used, it is possible to reduce the cost while enabling oscillation of a plurality of wavelengths.
- the wavelength conversion laser arranges the c-axis of a tetragonal laser medium in two directions, the vertical direction and the parallel direction, with respect to the optical axis of the resonator, thereby varying the oscillation wavelength, and Using a star angle, a solid laser beam having different oscillation wavelengths and linearly polarized light in the same direction is oscillated in the resonator, and the second harmonic and the sum frequency are simultaneously generated by the wavelength conversion element in the resonator. is there.
- the wavelength conversion of a plurality of wavelengths can be performed simultaneously and a wide range Wavelength converted light having a spectral width can be obtained.
- the wavelength-converted light having such a wide spectrum width has no interference noise and can be widely used in the fields of video and illumination.
- the wavelength conversion element 75 is disposed at the Brewster angle, the emitted wavelength conversion light is shifted from the optical axis of the solid-state laser resonator, and the wavelength conversion light is reflected between the laser medium and the wavelength conversion element.
- the wavelength-converted light d generated from the left-pointed solid-state laser light in FIG. 7 is partially absorbed and attenuated when entering the laser medium, but this configuration prevents this and reduces the output and efficiency of the wavelength-converted light. Can be increased.
- the wavelength-converted light d produces an output fluctuation when it coincides with the optical axis of the solid-state laser resonator, but the output fluctuation can be eliminated by shifting the wavelength-converted light from the optical axis of the resonator.
- the wavelength conversion element 75 is arranged to have a Brewster angle in order to lock the polarization direction.
- the configuration is not limited to the above as long as it gives a loss to one polarized light such as a polarizer.
- a laser medium other than the vanadate-based laser medium may be used as long as the laser medium is a tetragonal crystal. You can also.
- FIG. 8 shows a schematic configuration of the wavelength conversion laser 600.
- the same reference numerals are used for the same components as those in the above-described embodiment, and the detailed description thereof is omitted as appropriate.
- the wavelength conversion laser 600 is different from the configuration of the fifth embodiment in that it includes laser media 36, 46, 56, and 66 instead of the laser media 35, 45, and 55 of the fifth embodiment. .
- the wavelength conversion laser 600 oscillates excitation light, solid-state laser light, and wavelength converted light with linearly polarized light in the vertical axis direction of the paper surface of FIG.
- the wavelength conversion laser 600 includes four lasers: a laser medium 36 (first laser medium), a laser medium 46 (third laser medium), a laser medium 56 (second laser medium), and a laser medium 66 (first laser medium). It has a medium.
- the laser medium 36 is a-cut Nd: YVO 4 with Nd 1% and thickness 0.1 mm.
- the laser medium 46 is Cd-cut Nd: YVO 4 with Nd 3% and thickness 0.2 mm.
- the laser medium 56 is a-cut Nd: GdVO 4 with Nd 2% and thickness 0.2 mm.
- the laser medium 66 is a-cut Nd: YVO 4 with Nd 3% and thickness 0.2 mm.
- the laser medium 36 and the laser medium 66 oscillate at a wavelength IR1 (center wavelength 1064.1 nm) as a first oscillation wavelength.
- the laser medium 46 oscillates at a wavelength IR3 (center wavelength 1066.5 nm) as a third oscillation wavelength.
- the laser medium 56 oscillates at a wavelength IR2 (center wavelength 1062.8 nm) as the second oscillation wavelength.
- Excitation light emitted from the excitation LD 1 is incident on the laser medium 36, 46, 56, 66 in this order.
- the end face 36a of the laser medium 36 is provided with an AR coat of excitation light and an HR coat of solid laser light.
- the end face 36a transmits the excitation light while reflecting the solid laser light.
- the solid-state laser resonator of the wavelength conversion laser 600 is composed of the end surface 36 a of the laser medium 36 and the concave mirror 8.
- the wavelength conversion element 75 is disposed so as to have a Brewster angle with respect to the optical axis of the solid-state laser resonator, and locks the polarization direction of the solid-state laser light oscillated by the c-cut laser medium 46. .
- the end surface 66b on the wavelength conversion element 75 side of the laser medium 66 is provided with an AR coat of solid laser light and an HR coat of wavelength converted light, and the end face 66b transmits the solid laser light while wavelength converted light. d is reflected.
- Each end surface between the adjacent laser media of the laser media 36, 46, 56, and 66 is provided with an AR coat of excitation light and an AR coat of solid laser light. Can be transmitted.
- the wavelength conversion element 75 has a very thin thickness of 0.6 mm through which solid-state laser light passes, and has a very wide phase matching tolerance.
- the sum frequency SFG1 (sum frequency of IR1 and IR2) and SFG2 (sum frequency of IR2 and IR3) ) And SFG3 (sum frequency of IR1 and IR3) are generated simultaneously.
- the wavelength conversion laser 600 includes a laser medium 36 and a laser medium 66 having an oscillation wavelength IR1, a laser medium 56 having an oscillation wavelength IR2, and a laser medium 46 having an oscillation wavelength IR3.
- the three types of laser media are emitted from the same semiconductor laser. Excited by the excitation light, the excitation laser light enters the laser medium 36 having the oscillation wavelength IR1, and then enters the laser medium 56 having the oscillation wavelength IR2 and the laser medium 46 having the oscillation wavelength IR3, and then the laser medium having the oscillation wavelength IR1. This is a preferred form of incident on 36.
- the wavelength-converted light has a plurality of peaks, so that coherency is lowered and interference noise can be reduced.
- the absorption medium has the greatest fluctuation in the laser medium on which the excitation light first enters.
- the excitation light is incident on the laser medium having the same oscillation wavelength as the laser medium that is incident first, thereby compensating for the absorption amount of the excitation light and widening.
- the wavelength-converted light having a spectral width can be obtained stably.
- the type of laser medium in the solid-state laser is not limited to two or three. That is, the number of types of laser mediums may be two or more, for example, four or more.
- the solid-state laser has n types of lasers including first to n-th laser media that oscillate solid-state laser beams having first to n-th oscillation wavelengths (n is an integer of 2 or more) having different oscillation wavelengths.
- the n types of laser media including a medium can be configured to be excited by the excitation light emitted from the common excitation light source.
- the excitation light is incident on the portion made of the first laser medium, it is made incident on the portion made of a laser medium other than the first laser medium, and then incident on the portion made of the first laser medium, If the solid-state laser light having the first to nth oscillation wavelengths oscillates in the resonator, wavelength-converted light having a wide spectral width can be stably obtained as described above.
- FIG. 9 shows a schematic configuration of the wavelength conversion laser 700.
- the same reference numerals are used for the same components as those in the above-described embodiment, and the detailed description thereof is omitted as appropriate.
- the wavelength conversion laser 700 three laser media of a laser medium 37 (first laser medium), a laser medium 47 (second laser medium), and a laser medium 57 (first laser medium) are sandwiched between two non-laser media 9.
- the non-laser medium 9 is composed only of YVO 4 and does not oscillate.
- the solid-state laser resonator of the present wavelength conversion laser 700 is formed by the side surface 9a of the laminated structure of the laser medium and the concave mirror 8. Further, a wavelength conversion element 77 is disposed between the laminated structure and the concave mirror 8.
- the wavelength conversion laser 700 has a configuration in which the excitation light from the excitation LD 1 is incident from the side surface of the solid-state laser resonator.
- the excitation light emitted from the excitation LD 1 enters the laser medium 37, the laser medium 47, and the laser medium 57 in this order after passing through the non-laser medium 9.
- the laser medium 37 is made of Nd: YVO 4 having an Nd concentration of 2% and a thickness of 0.1 mm.
- the laser medium 47 is made of Nd: GdVO 4 having an Nd concentration of 6% and a thickness of 0.1 mm.
- the laser medium 57 is made of Nd: YVO 4 having an Nd concentration of 6% and a thickness of 0.1 mm.
- the non-laser medium 9 is made of YVO 4 having a thickness of 0.3 mm in both the upper and lower portions of FIG.
- the non-laser medium 9 is composed of the same YVO 4 as the laser medium 37 and the laser medium 57 that are bonded adjacent to each other, and is used to make the refractive index the same at the bonded interface.
- the laser medium 37 and the laser medium 57 oscillate solid-state laser light having an oscillation wavelength IR1 as a first oscillation wavelength.
- the laser medium 47 oscillates solid-state laser light having an oscillation wavelength IR2 as the second oscillation wavelength.
- the excitation light emitted from the excitation LD 1 enters the laser medium 37 having the oscillation wavelength IR 1, then enters the laser medium 47 having the oscillation wavelength IR 2, and then enters the laser medium 57 having the oscillation wavelength IR 1.
- Both side surfaces 9a and 9b of the laminated structure composed of the laser media 37, 47 and 57 and the two non-laser media 9 are mirror-polished.
- the side surface 9a of the laminated structure is subjected to HR coating of solid laser light, while the side surface 9b is subjected to AR coating of solid laser light.
- the wavelength conversion element 77 is made of MgO: LiNbO 3 (PPLN) having a polarization inversion periodic structure, and the thickness thereof is 1.5 mm. Further, the polarization inversion period of the wavelength conversion element 77 is 7 ⁇ m, but a phase step of 0.3 period is formed at a position of 0.3 mm from both ends and has a very wide phase matching tolerance.
- the wavelength conversion element 77 can simultaneously generate the second harmonic SHG1 of the solid-state laser light IR1, the second harmonic SHG2 of the solid-state laser light IR2, and the sum frequency SFG1 of the solid-state laser lights IR1 and IR2.
- the end face 77a of the wavelength conversion element 77 on the laminated structure side is provided with an HR coat of wavelength conversion light and an AR coat of solid laser light, and the end face 77a reflects the wavelength conversion light while reflecting the solid laser light. Make it transparent.
- the end face 77b of the wavelength conversion element 77 on the concave mirror 8 side is provided with wavelength converted light and an AR coat of solid laser light, and the wavelength converted light and solid laser light are transmitted through the end face 77b.
- the wavelength conversion laser 700 is a so-called side-pumped laser, and, as described above, the excitation light is incident from the side direction of the solid-state laser resonator, and the incident order of the excitation light to the laser medium is as described above.
- the same effects as the configuration of the first embodiment can be obtained, and low-coherent wavelength-converted light can be stably obtained.
- FIG. 10 shows a schematic configuration of the image display apparatus 1000.
- the same components as those in the first to seventh embodiments are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.
- the image display apparatus 1000 is a laser projector having a wavelength conversion laser 100 that emits green laser light, a red LD 1010 that emits red laser light, and a blue LD 1020 that emits blue laser light.
- the light emitted from the red LD 1010 and the blue LD 1020 is collimated by the collimator 1025 and combined with the light emitted from the wavelength conversion laser 100 by the combining prism 1030.
- the combined light is shaped into light having a rectangular and uniform intensity by the illumination optical system 1040.
- the illumination optical system 1040 includes a cross lenticular lens and a condenser lens.
- the shaped beam illuminates the spatial light modulator 1050 through the PBS 1060 which is a polarization beam splitter.
- the spatial light modulator 1050 is made of reflective LCOS (Liquid Crystal On On Silicon), and expresses gradation by rotating the polarization.
- the modulated light reflected from the spatial light modulator 1050 and passed through the PBS 1060 is enlarged and projected onto the display surface 1080 by the projection lens 1070.
- the red LD 1010 and the blue LD 1020 use multimode LDs to broaden the spectrum distribution.
- the wavelength conversion laser 100 described in detail in the first embodiment expands the spectrum distribution by simultaneously outputting the second harmonic and the sum frequency of the solid-state laser beams IR1 and IR2 having different wavelengths.
- the image display apparatus 1000 includes a low-coherent wavelength conversion laser 100 that stably outputs the second harmonic and the sum frequency from a plurality of solid-state laser beams having different wavelengths even when there is a temperature change, and the output wavelength-converted light.
- This is a preferable embodiment having an element 1050 that performs the modulation of the above.
- speckle noise which is image noise
- speckle noise can be reduced, and high-quality images can always be displayed.
- speckle noise which is image noise
- the wavelength conversion laser of the present invention is preferably used for a green laser having particularly high visibility. Since green has high visibility, speckle noise is easily recognized by viewers. By using the wavelength conversion laser of the present invention to generate green laser light, speckle noise is not recognized by the viewer.
- Spatial light modulator 1050 modulates red, green, and blue laser light in a time-sharing manner. That is, red, blue, and green laser beams are sequentially emitted from the laser light sources of the respective colors. Therefore, the green wavelength conversion laser 100 also repeats emission and stop of the wavelength conversion light.
- the image display apparatus 1000 has a laser light source that oscillates red, blue, and green wavelengths. At least a green laser light source uses a wavelength conversion laser that outputs wavelength converted light having a wide spectral width. Depending on the temperature of the wavelength-converted light output from the wavelength-converted laser, the wavelength-converted laser light is emitted from the semiconductor laser intermittently. This is a preferred form for reducing spectral changes.
- the pumping LD 1 of the wavelength conversion laser 100 repeats heat generation and cooling of the LD chip by an intermittent operation that repeatedly emits and stops the excitation light, and causes a temperature change in the LD chip within the time during the emission.
- FIG. 11A shows a state in which the spectrum width of the excitation light is broadened by changing the excitation light wavelength from CW (continuous oscillation) operation to intermittent operation.
- FIG. 11B shows how the absorption coefficient changes in the laser medium when the center wavelength of the excitation light changes.
- the absorption of the excitation light is distributed to a plurality of laser media having different oscillation wavelengths, it is preferable that the change in the absorption coefficient is small. By reducing the change in the absorption coefficient, it is possible to reduce the spectrum change due to the temperature of the wavelength converted light output from the wavelength conversion laser 100. As a result, the image display apparatus 1000 can always be free from speckle noise.
- FIG. 12 to 14 show a schematic waveform of the current injected into the excitation LD 1 in the wavelength conversion laser 100 and the wavelength distribution of the excitation light.
- the injection current to the pumping LD 1 is modulated and an intermittent operation is performed.
- the stepwise intermittent operation in FIG. 13 and the sawtooth intermittent operation in FIG. 14 are preferable modulation operations of the wavelength conversion laser 100.
- 13 and 14 is a wavelength conversion laser having a wavelength conversion element in a resonator of a solid-state laser.
- the solid-state laser includes at least a laser medium having an oscillation wavelength IR1 and a laser medium having an oscillation wavelength IR2.
- the two types of laser media are excited by the pumping light emitted from the same semiconductor laser (pumping LD1), and the solid-state laser light having the oscillation wavelength IR1 and the oscillation wavelength IR2 oscillates in the resonator of the solid-state laser.
- the conversion element 7 simultaneously generates the second harmonics SHG1 and SHG2 and the sum frequency SFG1 of the oscillation wavelength IR1 and the oscillation wavelength IR2 to operate the semiconductor laser intermittently and during operation of the semiconductor laser (excitation light emission).
- the first injection current is smaller than the second injection current.
- the initial injection current refers to the average injection current in the first half during operation of the semiconductor laser (excitation LD1)
- the late injection current refers to the average injection current in the second half during operation of the semiconductor laser.
- the initial injection current is made smaller than the late injection current by modulating the injection current value stepwise. Further, in the example of FIG. 14, after increasing to the threshold current, the injection current is modulated in a sawtooth shape so that the first injection current is smaller than the second injection current.
- the center wavelength of the excitation light emitted from the excitation LD 1 tends to monotonously increase with respect to the injection current in addition to the temperature. For this reason, making the early injection current smaller than the late injection current has the effect of lowering the temperature and the injection current value in the first half and expanding the short wavelength side component of the spectral distribution of the excitation light emitted from the excitation LD1. Further, in the case of obtaining the same total output as the rectangular operation of FIG.
- the late injection current is set higher than that of the rectangular operation of FIG. At this time, in the late injection current portion, the spectral distribution of the excitation light is extended to the longer wavelength side.
- the wavelength distribution of the excitation light is greatly expanded, and the change in the absorption coefficient with respect to the excitation light center wavelength of the laser medium becomes very gradual.
- the absorption of the excitation light is distributed to laser media having different oscillation wavelengths, but the change in the bias of the absorption amount of the laser medium is reduced by reducing the change in the absorption coefficient with respect to the change in the central wavelength of the excitation light. Can be suppressed. Thereby, low-coherent wavelength-converted output light can be stably obtained even if the temperature or the like changes.
- a spatial light modulator such as a transmissive liquid crystal or DMD can be used as the spatial light modulator for wavelength converted light of the image display device.
- the transmissive liquid crystal may have a configuration in which a liquid crystal surface is used as a display surface without using a projection lens.
- the modulation element is not limited to the spatial light modulation element, and may be configured to combine the intensity modulation of the wavelength converted light and the scanning optical system.
- a lenticular lens is used for the illumination optical system, but the present invention is not limited to this, and a rod integrator or a fly-eye lens can be used.
- the example in which the wavelength conversion laser 100 detailed in the first embodiment is applied has been described.
- the present invention is not limited to this, and the wavelength conversion laser 200 described in detail in the second to seventh embodiments. 300, 400, 500, 600 or 700 can also be applied.
- the present invention is not limited to the above-described first to eighth embodiments, and may be configured by combining the first to eighth embodiments.
- the host material of the laser medium is not limited to vanadate crystals, and garnet crystals such as YAG, polycrystals such as ceramics, and glass can be used.
- the active ion material is not limited to Nd as long as it is a material that oscillates laser, such as Yb. Moreover, it is good also as a structure which adds optical components, such as a mirror and a lens, as needed.
- LN or LT having a polarization inversion periodic structure is used for the wavelength conversion element, but other nonlinear optical crystals can also be used. Further, the domain-inverted structure may be configured to change the period by design.
- the wavelength to be output is not limited, and a configuration in which lasers of various colors such as blue, yellow, and red are output. Good.
- the wavelength conversion laser according to the present invention includes an excitation light source that emits excitation light, a solid-state laser having a resonator, and a wavelength conversion element disposed in the resonator, and the solid-state laser includes at least 2 A first laser medium and a second laser medium, each of which is a type of laser medium, wherein the first laser medium oscillates a solid state laser beam having a first oscillation wavelength, and the second laser medium is a solid state having a second oscillation wavelength.
- the laser beam oscillates the at least two types of laser mediums are excited by the pumping light emitted from a common pumping light source, and the solid-state laser is incident on a portion of the first laser medium. And then entering the part made of the second laser medium and then entering the part made of the first laser medium, thereby causing the first oscillation wavelength and the second oscillation in the resonator.
- the solid-state laser light is configured to oscillate, and the wavelength conversion element in the resonator is configured to convert the solid-state laser light having the first oscillation wavelength and the second oscillation wavelength into the first oscillation wavelength and the second oscillation wavelength. It converts into the 2nd harmonic and sum frequency of an oscillation wavelength, and the said 2nd harmonic and the said sum frequency are generated simultaneously.
- the solid-state laser includes at least two types of laser media, and the two types of laser media are excited by excitation light emitted from a common excitation light source.
- the excitation light has entered (1) the part made of the first laser medium, (2) the light entered the part made of the second laser medium, and (3) the light then made incident on the part made of the first laser medium.
- the solid-state laser light having the first oscillation wavelength and the second oscillation wavelength oscillates in a well-balanced manner in the resonator of the solid-state laser.
- the pumping light absorption amounts (pumping light absorption) of the two types of laser media are obtained by making the pumping light incident on the portion made of the first laser medium as in the above (3).
- the ratio is maintained to be constant. For example, when the wavelength of the pumping light deviates from the optimum value due to a change in ambient temperature or the like, the absorption coefficient of the pumping light in the first laser medium in (1) is lowered, and the absorption rate of the pumping light is lowered.
- the amount of excitation light incident on the second laser medium in (2) above increases, while a decrease in the absorption coefficient of the second laser medium also occurs at the same time.
- the absorptance of the second laser medium in (2) above Even if the wavelength of light changes, the absorptance is not changed and maintained. Further, as the absorption coefficient of the excitation light in the first laser medium and the second laser medium in (1) and (2) decreases, the amount of excitation light incident on the first laser medium in (3) increases. The absorption rate of the excitation light in the first laser medium in (3) increases. Therefore, the ratio of the total absorptance of the first laser medium in (1) and (3) above to the absorptance of the second laser medium in (2) is substantially independent of the amount of change in the wavelength of the excitation light. It is held constant.
- the intensity ratio of the solid state laser light of the first oscillation wavelength and the second oscillation wavelength can be kept constant. For this reason, even when a wavelength conversion element that simultaneously generates the first oscillation wavelength, the second harmonic of the second oscillation wavelength, and the sum frequency is used, there is a large bias in these three wavelengths in the spectrum distribution of the wavelength-converted light. A wide spectral width can be maintained without occurring. As described above, according to the above configuration, it is possible to realize a wavelength conversion laser that stably outputs a low-coherent wavelength conversion laser beam having a wide spectral width even when the wavelength of the excitation light changes due to a temperature change or the like. .
- the solid-state laser has a configuration in which a portion made of the second laser medium is disposed between two portions made of the first laser medium, and the excitation light source among the two portions made of the first laser medium. It is preferable that the active ion concentration at the site where the excitation light emitted from the laser beam is incident later is higher than the active ion concentration at the site where the excitation light is incident first.
- the part made of the second laser medium is arranged between the two parts made of the first laser medium. For this reason, the exothermic point by absorption of excitation light can be dispersed in a plurality of parts.
- the active light concentration of the part where the excitation light emitted from the excitation light source is incident later (the part where the excitation light power is smaller) is given first. Since the active ion concentration is higher than the active ion concentration at the site incident on the laser beam (the site where the pumping light power is higher), the temperature rise of the laser medium due to absorption of the pumping light can be suppressed to be small in total. As a result, a decrease in wavelength conversion efficiency due to heat generation of the laser medium can be efficiently prevented, so that a highly efficient and high output wavelength conversion laser can be realized.
- the first laser medium is Nd: YVO 4
- the second laser medium is Nd: GdVO 4
- the first laser medium and the second laser medium are joined.
- YVO 4 and GdVO 4 are the same crystal system, the refractive index and the thermal expansion coefficient are almost equal. Therefore, by joining the first laser medium and the second laser medium made of these crystal systems, they can be handled as one crystal. In this way, by directly bonding the crystals of the two types of laser medium, the bonding strength between the crystals can be obtained and processing such as cutting can be easily performed. In addition, since the length of the laser medium can be shortened by this joining, it is advantageous for maintaining the condensing state of the excitation light. Further, Nd: YVO 4 having an oscillation wavelength longer than that of the second laser medium is used as the first laser medium on which the excitation light first enters.
- the temperature of the laser medium having a long oscillation wavelength is further increased.
- the oscillation wavelength shifts to the longer wavelength side, so that the difference in the oscillation wavelength becomes larger as the temperature rises, and the spectrum width of the wavelength-converted light to be output can be further expanded.
- a reflection coat of the excitation light is formed on an end face on the wavelength conversion element side of a portion made of the first laser medium or the second laser medium that is disposed farthest from the excitation light source, and the solid-state laser resonator Further including an interface that reflects the wavelength-converted light generated by the wavelength conversion element without entering the laser medium, the wavelength conversion element being a polarization inversion period inclined with respect to the optical axis of the solid-state laser resonator It is preferable that the wavelength-converted light is separated and output as two beams.
- the reflection coating of the excitation light is formed on the end surface on the wavelength conversion element side of the portion made of the first laser medium or the second laser medium that is disposed farthest from the excitation light source,
- the excitation light reflected by the coat can be efficiently incident again on the laser medium disposed on the excitation light source side, and the number of stacked laser media can be reduced.
- the wavelength-converted light since it has an interface that reflects the wavelength-converted light generated by the wavelength conversion element without entering the laser medium, the wavelength-converted light is prevented from being absorbed by the laser medium, and the wavelength-converted light is output. The reduction and the heat generation of the laser medium are suppressed. Thereby, wavelength conversion light can be output with high efficiency.
- the wavelength conversion element has a polarization inversion periodic structure that is inclined with respect to the optical axis of the solid-state laser resonator, the wavelength conversion light is output in two beams (without being reflected by the interface). And a return beam reflected and output from the interface).
- the solid-state laser has a configuration in which the optical axis directions of the part made of the first laser medium and the part made of the second laser medium are arranged in different directions, and the solid-state laser having the first oscillation wavelength and the second oscillation wavelength is arranged. It is preferable that the laser light oscillates in the resonator as linearly polarized light in the same direction.
- the first laser medium and the second laser medium can be made to have different oscillation wavelengths by arranging the same laser medium material so that the optical axis directions are different from each other. Since the same laser medium material can be used for the part made of the first laser medium and the part made of the second laser medium, the cost can be reduced.
- the first laser medium and the second laser medium are tetragonal laser crystals, and the c-axis of the first laser medium and the second laser medium is perpendicular to and parallel to the optical axis of the resonator.
- the oscillation wavelengths of the first laser medium and the second laser medium are made different, and the wavelength conversion element is arranged with respect to the optical axis of the solid-state laser resonator. It is preferable that the solid laser beams having the first oscillation wavelength and the second oscillation wavelength are oscillated in the resonator as linearly polarized light in the same direction by arranging the Brewster angles.
- the first oscillation wavelength and The solid-state laser light having the second oscillation wavelength is oscillated in the resonator as linearly polarized light in the same direction.
- wavelength conversion of a plurality of wavelengths can be realized simultaneously, and wavelength converted light having a wide spectrum width can be obtained.
- the wavelength-converted light having such a wide spectrum width has no interference noise and can be used widely and suitably in the field of video and illumination.
- the solid-state laser includes at least three types of laser media further including a third laser medium that oscillates a solid-state laser beam having a third oscillation wavelength, and the at least three types of laser media are emitted from a common pumping light source. After being excited by the excitation light, the solid-state laser is incident on at least a part made of the second laser medium and a part made of the third laser medium after the excitation light is made incident on the part made of the first laser medium. Then, it is preferable to be configured so as to be incident on a portion made of the first laser medium.
- the wavelength-converted light has a plurality of peaks in a well-balanced manner, so that coherency is reduced and interference noise can be reduced.
- the amount of excitation light absorbed by different types of laser media as described above. It is necessary to keep the ratio of (or absorption rate) constant. For example, when the wavelength of pumping light changes due to environmental temperature changes, etc., and the absorption coefficient of each laser medium fluctuates, the amount of pumping light absorbed most varies because of the laser medium (the first 1 laser medium).
- the excitation light passes through a laser medium (second laser medium and third laser medium) other than the first laser medium, it is excited to a laser medium (first laser medium) having the same oscillation wavelength as that of the first incident laser medium.
- Incident light is used to compensate for fluctuations in the amount of excitation light absorbed.
- a wavelength conversion laser that stably outputs a low-coherent wavelength conversion laser beam having a wide spectrum width can be realized even when the temperature of the excitation light changes due to a temperature change or the like.
- the solid-state laser includes n types of laser media including first to n-th laser media that oscillate solid-state laser beams having first to n-th oscillation wavelengths (n is an integer of 2 or more) having different oscillation wavelengths.
- the n types of laser media are excited by the pumping light emitted from a common pumping light source, and the solid-state laser has the first laser medium after the pumping light is incident on the portion made of the first laser medium.
- the solid-state laser light having the first to nth oscillation wavelengths oscillates in the resonator by being incident on a portion made of a laser medium other than the above and then entering a portion made of the first laser medium.
- the wavelength conversion element in the resonator converts the solid-state laser light having the first to nth oscillation wavelengths into the second harmonic and the sum frequency of the first to nth oscillation wavelengths, and the second Harmonic and sum frequency It is preferable to generate the.
- the peak of the absorption rate of the excitation light of the first laser medium at a portion where the excitation light emitted from the excitation light source first enters is 10% or more and 75% or less.
- the ratio of the amount of absorption between the first laser medium and the second laser medium can be suppressed to a suitable range of 0.5 to 2, and the low coherent wavelength with no bias in the spectral distribution Converted light can be obtained.
- the solid-state laser is configured such that the excitation light is incident on the portion made of the first laser medium and the portion made of the second laser medium alternately twice or more.
- the absorption rate of the excitation light of the two types of laser media can be made constant. This makes it possible to output wavelength-converted light having a wide spectrum width in a very wide temperature range.
- An image display device includes any one of the wavelength conversion lasers described above and an element that modulates wavelength conversion light output from the wavelength conversion laser.
- low-coherent wavelength-converted light having a stable spectrum distribution can be used even when a temperature change occurs, so that speckle noise, which is image noise, is reduced, and high-quality Images can be displayed stably.
- the image display device includes a red laser light source that oscillates a red wavelength, a green laser light source that oscillates a green wavelength, and a blue laser light source that oscillates a blue wavelength, and the green laser light source is the wavelength conversion laser.
- the red laser light source, the green laser light source, and the blue laser light source sequentially emit laser light for each color, and the wavelength conversion laser repeats emission and stop of the excitation light. It is desirable to widen the spectrum width of the excitation light by operation and reduce the spectrum change due to the temperature change of the wavelength converted light.
- the wavelength conversion laser capable of generating the low-coherent wavelength conversion light having a stable spectrum distribution even when the temperature change or the like is generated is used as the green laser light source, it is easily recognized green. Speckle noise can be removed.
- the laser light sources of the respective colors emit red, blue, and green laser light sequentially in a time-division manner, the wavelength conversion laser that oscillates the green wavelength repeats emission and stop of the wavelength conversion light. . Since this wavelength conversion laser performs an intermittent operation in which the excitation light is repeatedly emitted and stopped, the excitation light source repeats heat generation and cooling, and causes a temperature change in the excitation light source within the time during which the excitation light is emitted.
- the wavelength of the excitation light emitted from the excitation light source is changed, and the spectrum width is expanded. If the spectral width of the excitation light is expanded by the intermittent operation of the excitation light source, the amount of change due to the excitation light center wavelength of the absorption coefficient of each laser medium is reduced. Since the wavelength conversion laser distributes the absorption of the excitation light to a plurality of laser media having different oscillation wavelengths, if the amount of change in the absorption coefficient of each laser medium is small, the spectrum change due to the temperature change of the output wavelength conversion light is reduced. Can be reduced. As a result, a high-quality image display device free from speckle noise can be realized.
- the wavelength conversion laser may convert a first-stage injection current that is an average injection current of the first half of an injection current injected into the excitation light source during operation of the excitation light source into an average of the second half of the injection current. It is preferable to make it smaller than the late injection current which is the injection current.
- the center wavelength of the excitation light emitted from the excitation light source tends to increase monotonously with respect to the injection current. For this reason, making the first injection current smaller than the second injection current as in the above configuration lowers the temperature and the injection current value of the first half of the injection current and shortens the spectral distribution of the excitation light emitted from the excitation light source. There is an effect of expanding the wavelength side component. Since the initial injection current is set to be small, it is possible to set the late injection current to be large, and thereby the spectral distribution of the excitation light can be extended to the long wavelength side.
- the wavelength distribution of the pumping light is greatly expanded, and the change of the absorption coefficient with respect to the pumping light center wavelength of each laser medium becomes very gradual.
- the wavelength conversion laser distributes the absorption of the excitation light to a plurality of laser media having different oscillation wavelengths, if the amount of change in the absorption coefficient of each laser medium is small, the spectrum change due to the temperature change of the output wavelength conversion light is reduced. Can be reduced. As a result, a high-quality image display device free from speckle noise can be realized.
- the wavelength conversion laser of the present invention can be used for each wavelength conversion laser that requires low coherence.
- it is suitable for low-coherent high-efficiency compact lasers in the field of video and lighting.
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Abstract
Description
以下、本発明の一実施の形態について、図面を参照しながら説明する。
次に、本発明の実施の形態2による波長変換レーザ200について、図4を参照しながら説明する。図4は、波長変換レーザ200の概略構成を示している。なお、図4において、前述の実施の形態1と同様の構成については同一の参照符号を用い、その詳細な説明を省略する。
次に、本発明の実施の形態3による波長変換レーザ300について、図5を参照しながら説明する。図5は、波長変換レーザ300の概略構成を示している。なお、図5において、前述の実施の形態と同様のものについては、同一の参照符号を用い、その詳細な説明を適宜省略する。
次に、本発明の実施の形態4による波長変換レーザ400について、図6を参照しながら説明する。図6は、波長変換レーザ400の概略構成を示している。なお、図6において、前述の実施の形態と同様のものについては、同一の参照符号を用い、その詳細な説明を適宜省略する。
次に、本発明の実施の形態5による波長変換レーザ500について、図7を参照しながら説明する。図7は、波長変換レーザ500の概略構成を示している。なお、図7において、前述の実施の形態と同様のものについては、同一の参照符号を用い、その詳細な説明を適宜省略する。
次に、本発明の実施の形態6による波長変換レーザ600について、図8を参照しながら説明する。図8は、波長変換レーザ600の概略構成を示している。なお、図8において、前述の実施の形態と同様のものについては、同一の参照符号を用い、その詳細な説明を適宜省略する。
次に、本発明の実施の形態7による波長変換レーザ700について、図9を参照しながら説明する。図9は、波長変換レーザ700の概略構成を示している。なお、図9において、前述の実施の形態と同様のものについては、同一の参照符号を用い、その詳細な説明を適宜省略する。
次に、本発明の実施の形態8における画像表示装置1000について、図10ないし図14を参照しながら説明する。図10は、画像表示装置1000の概略構成を示している。なお、図10において、前述の実施の形態1~7と同様のものについては、同一の参照符号を用い、その詳細な説明を適宜省略する。
Claims (13)
- 励起光を出射する励起光源と、
共振器を有する固体レーザと、
前記共振器内に配置される波長変換素子とを含み、
前記固体レーザは、少なくとも2種類のレーザ媒質である第1レーザ媒質と第2レーザ媒質とを含み、前記第1レーザ媒質は第1発振波長の固体レーザ光を発振すると共に、前記第2レーザ媒質は第2発振波長の固体レーザ光を発振し、
前記少なくとも2種類のレーザ媒質は、共通の前記励起光源から出射される前記励起光で励起され、
前記固体レーザは、前記励起光が前記第1レーザ媒質からなる部位に入射した後、前記第2レーザ媒質からなる部位に入射し、その後に前記第1レーザ媒質からなる部位に入射することによって、前記共振器内で前記第1発振波長及び前記第2発振波長の固体レーザ光が発振するように構成され、
前記共振器内の前記波長変換素子は、前記第1発振波長及び前記第2発振波長の固体レーザ光を、当該第1発振波長及び当該第2発振波長の第2高調波及び和周波に変換し、当該第2高調波及び当該和周波を同時に発生させることを特徴とする波長変換レーザ。 - 前記固体レーザは、前記第1レーザ媒質からなる2つの部位の間に前記第2レーザ媒質からなる部位が配置された構成であり、
前記第1レーザ媒質からなる2つの部位のうち、前記励起光源から出射された前記励起光が後に入射される部位の活性イオン濃度が、前記励起光が先に入射される部位の活性イオン濃度よりも高いことを特徴とする請求項1記載の波長変換レーザ。 - 前記第1レーザ媒質がNd:YVO4であると共に、前記第2レーザ媒質がNd:GdVO4であり、
前記第1レーザ媒質と前記第2レーザ媒質とが接合されていることを特徴とする請求項1又は2記載の波長変換レーザ。 - 前記励起光源から最も遠くに配された前記第1レーザ媒質又は前記第2レーザ媒質からなる部位の前記波長変換素子側の端面に前記励起光の反射コートが形成されており、
前記固体レーザ共振器内に、前記波長変換素子で発生した波長変換光をレーザ媒質に入射させることなく反射する界面をさらに含み、
前記波長変換素子は、前記固体レーザ共振器の光軸に対して傾斜した分極反転周期構造を有し、前記波長変換光を2つのビームとして分離出力することを特徴とする請求項1記載の波長変換レーザ。 - 前記固体レーザは、前記第1レーザ媒質からなる部位と前記第2レーザ媒質からなる部位との光学軸方向を異なる方向に配置した構成であり、
前記第1発振波長及び前記第2発振波長の固体レーザ光が同一方向の直線偏光として前記共振器内で発振することを特徴とする請求項1記載の波長変換レーザ。 - 前記第1レーザ媒質及び前記第2レーザ媒質は、正方晶のレーザ結晶であり、
前記第1レーザ媒質及び前記第2レーザ媒質のc軸を、前記共振器の光軸に対して垂直方向及び平行方向の2種類の方向に異ならせて配置することにより、当該第1レーザ媒質及び当該第2レーザ媒質の発振波長を異ならせると共に、
前記波長変換素子を前記固体レーザ共振器の光軸に対してブリュースター角となるように配置することにより、前記第1発振波長及び前記第2発振波長の固体レーザ光を同一方向の直線偏光として前記共振器内で発振させることを特徴とする請求項5記載の波長変換レーザ。 - 前記固体レーザは、第3発振波長の固体レーザ光を発振する第3レーザ媒質をさらに含む少なくとも3種類のレーザ媒質を含み、
前記少なくとも3種類のレーザ媒質は、共通の前記励起光源から出射される前記励起光で励起され、
前記固体レーザは、前記励起光が前記第1レーザ媒質からなる部位に入射した後、少なくとも前記第2レーザ媒質からなる部位及び前記第3レーザ媒質からなる部位に入射し、その後に前記第1レーザ媒質からなる部位に入射するように構成されていることを特徴とする請求項1記載の波長変換レーザ。 - 前記固体レーザは、それぞれ発振波長が異なる第1~第n発振波長(nは2以上の整数)の固体レーザ光を発振する第1~第nレーザ媒質を含むn種類のレーザ媒質を含み、
前記n種類のレーザ媒質は、共通の前記励起光源から出射される前記励起光で励起され、
前記固体レーザは、前記励起光が前記第1レーザ媒質からなる部位に入射した後、前記第1レーザ媒質以外のレーザ媒質からなる部位に入射し、その後に前記第1レーザ媒質からなる部位に入射することによって、前記共振器内で前記第1~第n発振波長の固体レーザ光が発振するように構成され、
前記共振器内の前記波長変換素子は、前記第1~第n発振波長の固体レーザ光を、当該第1~第n発振波長の第2高調波及び和周波に変換し、当該第2高調波及び当該和周波を同時に発生させることを特徴とする請求項1記載の波長変換レーザ。 - 前記励起光源から出射された前記励起光が最初に入射する部位における前記第1レーザ媒質の前記励起光の吸収率のピークは、10%以上かつ75%以下であることを特徴とする請求項1記載の波長変換レーザ。
- 前記固体レーザは、前記励起光が前記第1レーザ媒質からなる部位と前記第2レーザ媒質からなる部位とを交互に2回以上入射するように構成されていることを特徴とする請求項1記載の波長変換レーザ。
- 請求項1ないし10の何れか1項に記載の波長変換レーザと、
前記波長変換レーザから出力される波長変換光の変調を行う素子とを含むことを特徴とする画像表示装置。 - 赤色の波長を発振する赤色レーザ光源と、
緑色の波長を発振する緑色レーザ光源と、
青色の波長を発振する青色レーザ光源とを含み、
前記緑色レーザ光源は前記波長変換レーザを含み、
前記赤色レーザ光源、前記緑色レーザ光源及び前記青色レーザ光源は、色毎にレーザ光を順次出射し、
前記波長変換レーザは、前記励起光の出射と停止とを繰り返す前記励起光源の間欠動作により、前記励起光のスペクトル幅を拡げ、前記波長変換光の温度変化によるスペクトル変化を低減することを特徴とする請求項11記載の画像表示装置。 - 前記波長変換レーザは、前記励起光源の動作中に当該励起光源へ注入される注入電流の前半部の平均注入電流である前期注入電流を、当該注入電流の後半部の平均注入電流である後期注入電流よりも小さくすることを特徴とする請求項12記載の画像表示装置。
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JP2011075673A (ja) * | 2009-09-29 | 2011-04-14 | Casio Computer Co Ltd | 光源装置、投影装置及び投影方法 |
JP2013526726A (ja) * | 2010-05-18 | 2013-06-24 | コーニング インコーポレイテッド | 複波長光システム |
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JP5417268B2 (ja) * | 2010-06-28 | 2014-02-12 | 富士フイルム株式会社 | 内視鏡システム |
CN104914568A (zh) * | 2014-09-30 | 2015-09-16 | 罗小波 | 一种可机械式无级调节透光率的光介质*** |
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