CN108666854B - Picosecond laser - Google Patents
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- CN108666854B CN108666854B CN201810908080.9A CN201810908080A CN108666854B CN 108666854 B CN108666854 B CN 108666854B CN 201810908080 A CN201810908080 A CN 201810908080A CN 108666854 B CN108666854 B CN 108666854B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
- H01S3/0057—Temporal shaping, e.g. pulse compression, frequency chirping
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- 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
- H01S3/10061—Polarization control
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- 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
- H01S3/1083—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 using parametric generation
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- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- 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
- H01S3/1086—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 using scattering effects, e.g. Raman or Brillouin effect
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/30—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects
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Abstract
The invention discloses a picosecond laser, which comprises a seed laser component and a pulse width compression component, wherein the pulse width compression component compresses laser output by the seed laser component to ps-level, the picosecond laser is also provided with an energy amplification component, the energy amplification component is provided with two laser rods distributed along a light path, and laser transmitted into the energy amplification component emits light after being amplified at least twice by one of the laser rods. The picosecond laser provided by the invention is provided with a seed laser component, a pulse width compression component and an energy amplification component, wherein laser compressed by the pulse width compression component is amplified by the energy amplification component and then is output to the outside, and the laser of the energy amplification component is subjected to at least two amplification treatments of one laser rod along a light path, so that the obtained laser has larger energy so as to meet the use requirement.
Description
Technical Field
The invention relates to the technical field of optical instruments, in particular to a picosecond laser.
Background
In recent years, the continuous technical innovation of laser medical products for treating skin pigment diseases has the great breakthrough in energy and light spot morphology, and the picosecond laser with the pulse width shortened to be nearly 10 times of that of a traditional Q machine has the greatest technical progress, and the picosecond laser single pulse energy is nearly thousands times higher than that of picosecond laser in industrial processing, so that pigment diseases which cannot be treated by the traditional Q machine can be treated. Such high energy picosecond lasers have significant clinical advantages in medical cosmetology.
The prior art discloses a picosecond laser capable of realizing hundred picosecond pulse width output, nanosecond laser generated by a seed source laser firstly realizes first energy amplification through a single-path double-path laser rod which is arranged in parallel with the seed source laser rod, the amplified laser sequentially passes through a series of optical devices which are arranged along the light transmission direction, the light transmission direction and the transmission form are changed for a plurality of times, finally the laser enters an SBS medium pool to realize compression, the compressed laser again realizes second energy amplification through the single-path double-path laser rod, and finally the picosecond laser is output through an upstream light path.
The disadvantage of this structure is that: after beam expansion and energy amplification of seed light, the threshold value of stimulated Brillouin scattering is relatively high, the laser threshold value is generally above 100mJ, local vaporization points are easy to generate near the focal point, a medium around the local vaporization points can deteriorate after absorbing the energy of laser light and generate a plurality of tiny bubbles, the service life of SBS can be shortened, and the output light pulse waveform generates great pulsation, so that the output stability of the laser is seriously reduced.
Disclosure of Invention
The invention aims to ensure that the SBS medium cannot be vaporized in the working process to cause unstable output waveforms by reasonably arranging the layout of the compression stage and the amplification stage. Therefore, the picosecond laser energy and pulse width before entering the amplifying stage are strictly unchanged, the size of the output energy of the whole laser is controlled through the inter-stage delay of the amplifying system, the thermal focal length of the laser is ensured to be stable in the process of adjusting the output energy of the laser, and the divergence angle of the laser is unchanged when the energy is changed.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention discloses a picosecond laser, comprising:
the seed laser component is used for generating and outputting seed laser;
the pulse width compression assembly is used for compressing the pulse width of the seed laser, and the seed laser output by the seed laser assembly is output to the pulse width compression assembly through the focusing mirror;
the optical path between the seed laser component and the pulse width compression component is provided with a second polaroid and a third quarter wave plate, the horizontally linearly polarized laser output by the seed laser component passes through the second polaroid and becomes circularly polarized light wave after passing through the third quarter wave plate, one end of the pulse width compression component, which is far away from the second polaroid, is provided with a reflecting focusing mirror, the laser beam converged by the focusing mirror of the pulse width compression component reaches the reflecting focusing mirror and is focused in the SBS medium pool and returns along the original path, and the reverse Stokes laser generated by the pulse width compression component passes through the third quarter wave plate and becomes vertically polarized laser and is reflected and output by the second polaroid;
the picosecond laser also comprises an energy amplification component, wherein the energy amplification component receives the laser reflected by the second polaroid and amplifies and outputs the laser;
the energy amplifying assembly is provided with two laser rods distributed along the light path, and laser transmitted into the energy amplifying assembly is emitted after being amplified at least twice by one of the laser rods.
Further, the seed laser component consists of a first total reflecting mirror, a small aperture diaphragm, a Q switch component, a first polaroid, a first quarter wave plate, a first laser rod, a second quarter wave plate and an output mirror, and the output beam of the seed laser component is a horizontal linear polarized laser beam.
Further, a beam expanding unit is arranged between the pulse width compression assembly and the energy amplifying assembly;
the beam expanding unit comprises a beam expanding lens group which receives the vertical polarized laser reflected by the first reflecting mirror and enters the beam expanding lens group, the vertical polarized laser expanded by the beam expanding lens group is contracted by the second aperture diaphragm and then becomes horizontal oscillation laser after passing through the half wave plate, and the horizontal oscillation laser enters the energy amplifying assembly after passing through the third polarizing plate.
Further, the energy amplifying assembly comprises a second laser rod for receiving the laser output by the third polaroid, the laser amplified by the second laser rod is transmitted to the third laser rod through the second reflecting mirror and the third reflecting mirror for energy amplification, the laser output by the third laser rod is transmitted to the second total reflecting mirror through the fourth quarter wave plate, the laser transmitted to the second total reflecting mirror is reflected along an original light path, the laser is changed into vertical polarized laser after passing through the fourth quarter wave plate again, and the vertical polarized laser sequentially passes through the third laser rod and the second laser rod for energy secondary amplification and is output to the outside through the reflection of the third polaroid.
Further, an optically active crystal is arranged between the second laser rod and the third laser rod along the light path.
Further, the energy amplifying assembly comprises a second laser rod for receiving the laser output by the third polaroid, the laser amplified by the second laser rod is transmitted to the third total reflection mirror through the fifth quarter wave plate, the laser transmitted to the third total reflection mirror is reflected along an original light path and is changed into vertical polarized laser after passing through the fifth quarter wave plate again, secondary energy amplification is carried out by the second laser rod, the amplified laser is reflected to the fourth reflection mirror through the third polaroid, and the laser reflected by the fourth reflection mirror is transmitted into the third laser rod through the half wave plate and the fourth polaroid in sequence for energy amplification;
the laser amplified by the energy of the third laser rod passes through a sixth quarter wave plate, is reflected by a fourth total reflection mirror and passes through the sixth quarter wave plate again to become vertical polarized laser, and the vertical polarized laser is reflected by the fourth polaroid and output to the outside.
Further, the energy amplifying assembly comprises a second laser rod for receiving the laser output by the third polaroid, the second laser rod is used for amplifying the energy, the amplified laser is transmitted to the third total reflection mirror through the fifth quarter wave plate, the third total reflection mirror is used for reflecting the laser transmitted to the third total reflection mirror along an original light path and changing the laser into vertical polarized laser after passing through the fifth quarter wave plate again, the second laser rod is used for amplifying the energy for the second time, the amplified laser beam is reflected to the fourth reflection mirror through the third polaroid, and the laser reflected by the fourth reflection mirror is transmitted to the third laser rod through the half wave plate and the fourth polaroid in sequence for amplifying the energy and outputting the energy to the outside.
Further, the energy amplifying assembly comprises a second laser rod for receiving the output of the third polaroid, the laser amplified by the second laser rod sequentially passes through the fourth reflector and the fifth reflector and enters the third laser rod for energy amplification after passing through the fourth polaroid, the amplified laser is transmitted to the fourth total reflector through the fifth quarter wave plate, the laser transmitted to the fourth total reflector is reflected along an original light path by the fourth total reflector and is changed into vertically polarized laser after passing through the fifth quarter wave plate again, and the vertically polarized laser is amplified by the third laser rod and is reflected and output to the outside through the fourth polaroid.
In the technical scheme, the picosecond laser provided by the invention has the following beneficial effects:
1. the layout of the compression stage and the amplification stage is reasonably arranged, so that the SBS medium pool cannot be vaporized in the working process, and the output energy and the pulse width stability after pulse width compression (before entering the energy amplifier) are ensured;
2. the output energy is controlled by the inter-stage delay of the amplifying system, so that the pulse width is strictly unchanged in the process of adjusting the output energy of the laser, and the thermal focal length of the laser is stable.
When the light beam enters the SBS medium pool, the stimulated Brillouin scattering threshold value is reached near the focusing point, the back-transmitted Stokes light is generated, and the Stokes light compresses the laser pulse width in the transmission process.
The output energy of the seed laser is generally very small and is generally less than 10mJ, the threshold value when the seed laser directly enters the SBS medium pool to form stimulated Brillouin scattering is relatively small, the threshold value is generally less than 3mJ at the moment, the situation that the waveform of an output light beam is unstable and the pulse width change is very large due to the fact that local vaporization is not generated near a laser focus is avoided; however, after the beam expansion and the energy amplification of the seed light, the threshold value of stimulated brillouin scattering is relatively high, the threshold value is generally more than 100mJ, local vaporization points are easy to generate near the focal point, a medium around the local vaporization points can deteriorate after absorbing the energy of laser light and generate a plurality of tiny bubbles, the medium deterioration can reduce the service life of an SBS medium pool, the bubbles can influence the light transmission, and the energy is absorbed by the medium to generate great pulsation on the output light pulse energy and pulse width, so that the output stability of the laser is seriously reduced. This arrangement is the most significant point of application in distinction to other SBS based pulse width compression.
In the process of amplifying the energy of the laser, the pulse width, the divergence angle polarization state and the like of the laser are not changed, and only the energy is increased.
Finally, the structural layout of the picosecond laser (the seed laser with energy output of a few mJ enters SBS first and then enters the amplifying stage) is unprecedented in the published materials at home and abroad.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings may be obtained according to these drawings for a person having ordinary skill in the art.
FIG. 1 is a schematic diagram of the optical path of a first embodiment of a picosecond laser according to the present disclosure;
FIG. 2 is a schematic diagram of the optical path of an energy amplification assembly of a second embodiment of a picosecond laser according to the present disclosure;
FIG. 3 is a schematic diagram of the optical path of an energy amplifying assembly of a third embodiment of a picosecond laser according to the present disclosure;
fig. 4 is a schematic diagram of the optical path of an energy amplifying assembly of a fourth embodiment of a picosecond laser according to the present disclosure.
Reference numerals illustrate:
1. a seed laser assembly; 2. a pulse width compression assembly; 3. an energy amplification assembly; 4. a second polarizing plate; 5. a third quarter wave plate; 6. a first mirror; 7. a beam expander group; 8. a second aperture stop; 9. a half wave plate; 10. a third polarizing plate; 11. a fourth polarizing plate; 12. a fifth quarter wave plate; 13. a third total reflection mirror; 14. a fourth total reflection mirror; 15. a fourth mirror; 16. a fifth reflecting mirror; 17. a sixth quarter wave plate;
101. a first total reflection mirror; 102. a first aperture stop; 103. a Q-switch assembly; 104. a first polarizing plate; 105. a first quarter wave plate; 106. a first laser bar; 107. a second quarter wave plate; 108. an output mirror;
201. a focusing mirror; 202. an SBS medium pool; 203. a reflective focusing mirror;
301. a second laser bar; 302. a third laser bar; 303. a second mirror; 304. a third mirror; 305. an optically active crystal; 306. a fourth quarter wave plate; 307. a second total reflection mirror.
Detailed Description
In order to make the technical scheme of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings.
See fig. 1;
the picosecond laser of the present invention comprises:
a seed laser component 1, wherein the seed laser component 1 is used for generating and outputting seed laser;
the pulse width compression assembly 2 outputs the seed laser output by the seed laser assembly 1 to the pulse width compression assembly 2 through the focusing mirror 201, and the pulse width compression assembly 2 compresses the pulse width of the seed laser;
the optical path between the seed laser component 1 and the pulse width compression component 2 is provided with a second polaroid 4 and a third quarter wave plate 5, the horizontally linearly polarized laser output by the seed laser component 1 passes through the second polaroid 4 and becomes circularly polarized light wave after passing through the third quarter wave plate 5, one end of the pulse width compression component 2, which is far away from the second polaroid 4, is provided with a reflection focusing mirror 203, the laser beam converged by the focusing mirror 201 of the pulse width compression component 2 reaches the reflection focusing mirror 203 and is focused in the SBS medium pool 202 and returns along the original path, and the reverse Stokes laser generated by the pulse width compression component 2 passes through the third quarter wave plate 5 and is formed into vertically polarized laser and is reflected and output by the second polaroid 4;
the picosecond laser also comprises an energy amplifying component 3, wherein the energy amplifying component 3 receives the laser reflected by the second polaroid 4 and amplifies and outputs the laser;
the picosecond laser also comprises an energy amplifying component 3, wherein the energy amplifying component 3 receives the laser reflected by the second polaroid 4 and amplifies and outputs the laser;
the energy amplifying assembly 3 has two laser rods distributed along the optical path, and the laser transmitted into the energy amplifying assembly 3 is emitted after being amplified at least twice by one of the laser rods.
Specifically, the embodiment specifically discloses a novel picosecond laser which is provided with three main components of a seed laser component 1, a pulse width compression component 2 and an energy amplification component 3. The seed laser component 1 is used as a local oscillation level laser system to generate seed laser, and transmits the seed laser to a pulse width compression component 2 at the downstream of the seed laser component along an optical path, and the seed laser compresses the 2-6 ns level pulse width laser to 250-600 ps level laser through the compression of the pulse width compression component 2. Then, the output is outputted to the outside by the amplification of the energy amplification block 3. The picosecond laser disclosed by the embodiment amplifies the compressed laser in the laser rod for multiple times through the cooperation of the optical device, so that the laser with larger external output energy is realized, and the use requirement is met.
The seed laser component consists of a first total reflecting mirror 101, a small aperture diaphragm 102, a Q switch component 103, a first polaroid 104, a first quarter wave plate 105, a first laser rod 106, a second quarter wave plate 107 and an output mirror 108, and the output beam of the seed laser component is a horizontally linear polarized laser beam.
Wherein, a beam expanding unit is arranged between the pulse width compression assembly 2 and the energy amplifying assembly 3;
the beam expanding unit comprises a beam expanding lens group 7 which is used for receiving the vertically polarized laser reflected by the first reflecting mirror 6, the vertically polarized laser after being expanded by the beam expanding lens group 7 is contracted by a second small-hole diaphragm 8 and then is changed into horizontally oscillating laser after passing through a half wave plate 9, and the horizontally oscillating laser enters the energy amplifying assembly 3 after passing through a third polarizing plate 10.
The above is the process of the picosecond laser of the present invention in which the seed laser is generated by the seed laser assembly 1 and compressed to the ps-stage by the pulse width compression assembly 2.
Embodiment one:
referring to fig. 1, fig. 1 shows a schematic optical path diagram of a first embodiment of the picosecond laser of the invention;
as an embodiment of the first energy amplifying assembly 3 of the present invention:
the energy amplifying assembly 3 in this embodiment includes a second laser rod 301 that receives the laser light output by the third polarizer 10, the laser light amplified by the second laser rod 301 is transmitted to the third laser rod 302 through the second mirror 303 and the third mirror 304 to be energy amplified, the laser light output by the third laser rod 302 is transmitted to the second total reflection mirror 307 through the fourth quarter wave plate 306, and the laser light transmitted thereto is reflected by the second total reflection mirror 307 along the original optical path, and is changed into vertically polarized laser light after passing through the fourth quarter wave plate 306 again, and then is output to the outside through the reflection of the third polarizer 10 after energy is secondarily amplified after passing through the third laser rod 302 and the second laser rod 301 in sequence.
First, the first embodiment describes the structure and principle of the energy amplifying assembly 3 for realizing the two-way and two-way energy amplification. The structure and the optical path are as above, firstly, the laser passes through the first energy amplification of the second laser rod 301, and is continuously transmitted to the third laser rod 302 along the optical path to carry out the second energy amplification, then the laser which is subjected to the energy amplification twice is reflected back along the original optical path through the second total reflection mirror 307, and the laser passes through the third laser rod 302 and the energy amplification of the second laser rod 301 again, and finally, the laser is reflected to the outside by the third polaroid 10 to output the laser with larger energy; in the embodiment, the amplification of the laser passing through the second laser rod 301 and the third laser rod 302 twice is realized through the cooperation of the optical devices, namely the double-path and double-path energy amplification is realized, the high-energy laser is obtained, the use requirement is met, the equipment is simplified, and the use cost is reduced.
Preferably, in this embodiment, there is an optically active crystal 305 disposed along the optical path between the second laser bar 301 and the third laser bar 302. The present embodiment mounts an optically active crystal 305 in the optical path between the second laser bar 301 and the third laser bar 302 in order to reduce thermally induced depolarization effects during amplification.
Embodiment two:
referring to fig. 2, fig. 2 is a schematic diagram showing the optical path of an energy amplifying assembly 3 of a second embodiment of the picosecond laser of the present invention;
as an embodiment of the second energy amplifying assembly 3 of the present invention:
the energy amplifying assembly 3 in this embodiment includes a second laser rod 301 that receives the laser light output by the third polarizer 10, the laser light amplified by the second laser rod 301 is transmitted to the third total reflection mirror 13 through the fifth quarter wave plate 12, the beam reflected by the third total reflection mirror 13 is changed into the vertically polarized laser light after passing through the fifth quarter wave plate again, the vertically polarized laser light enters the second laser amplifying rod again to amplify the energy, the amplified laser light is reflected by the third polarizer 10 onto the fourth reflector 15, the laser light reflected by the fourth reflector 14 is changed into the horizontally oscillating laser light after passing through the half wave plate 9, and the horizontally oscillating laser light is transmitted into the third laser rod 302 through the fourth polarizer 11 to amplify the energy;
the laser light amplified by the energy of the third laser rod (302) passes through a sixth quarter wave plate (17), is reflected by a fourth total reflection mirror (14) and passes through the sixth quarter wave plate (17) again to become vertical polarized laser light, and the vertical polarized laser light is reflected and output to the outside through the fourth polaroid (11).
The second embodiment is an energy amplifying component 3 with another structure, which realizes the energy amplification of 'one-way double-way + one-way double-way'; the method comprises the following steps: the laser amplified by the second laser rod 301 is reflected back along the original optical path by the third total reflection mirror 13, and amplified again by the second laser rod 301, at this time, the energy amplification of one single-path and double-path is completed, then, the laser is amplified again by the third laser rod 302 after being transmitted by the third polarizer 10 and the fourth reflector 15, the laser output by the light emitting end of the third laser rod 302 is reflected back to the third laser rod 302 along the original optical path by the fourth total reflection mirror 14, the energy amplification of the laser is again completed, at this time, the energy amplification of one single-path and double-path is completed once by the above transmission, and finally, the laser is reflected to the outside by the fourth polarizer 11.
Embodiment III:
referring to fig. 3, fig. 3 is a schematic view showing an optical path of an energy amplifying assembly 3 of a third embodiment of the picosecond laser of the present invention;
as an embodiment of the third energy amplifying assembly 3 of the present invention:
the energy amplifying assembly 3 in this embodiment includes a second laser rod 301 that receives the laser light output by the third polarizer 10, the laser light is energy amplified by the second laser rod 301, the amplified laser light is transmitted to the third total reflection mirror 13 through the fifth quarter wave plate 12, the laser light transmitted thereto is reflected by the third total reflection mirror 13 along the original optical path and is changed into vertically polarized laser light after passing through the fifth quarter wave plate 12 again, the energy is secondarily amplified by the second laser rod 301, the amplified laser light is reflected by the third polarizer 10 to the fourth mirror 15, and the laser light reflected by the fourth mirror 15 is sequentially transmitted to the third laser rod 302 through the half wave plate 9 and the fourth polarizer 11, so as to be energy amplified and output to the outside.
The principle of the energy amplifying assembly 3 in this embodiment is basically the same as that of the second embodiment, but this embodiment further simplifies the structure of the second embodiment, and realizes the laser energy amplification of "one-way double-way+one-way single-way", the laser amplified once by the third laser rod 302 is directly output to the outside, and the laser in this embodiment is subjected to the energy amplification three times, which can also meet the use requirement, and further simplifies the structure.
Embodiment four:
as can be seen in the view of figure 4,
the energy amplifying assembly 3 includes a second laser rod 301 that receives the output of the third polarizer 10, the laser amplified by the second laser rod 301 sequentially passes through the fourth reflector 15 and the fifth reflector 16 and enters the third laser rod 302 after passing through the fourth polarizer 11 to amplify the energy, the amplified laser is transmitted to the fourth total reflection mirror 14 through the fifth quarter wave plate 12, the laser transmitted thereto is reflected by the fourth total reflection mirror 14 along the original optical path and is changed into vertically polarized laser after passing through the fifth quarter wave plate 12 again, and the vertically polarized laser is amplified by the third laser rod 302 and then is reflected and output to the outside through the fourth polarizer 11.
The fourth embodiment is another structure of the energy amplifying assembly 3, which realizes the energy amplification of "one-way single-way + one-way double-way".
In the technical scheme, the picosecond laser provided by the invention has the following beneficial effects:
1. the layout of the compression stage and the amplification stage is reasonably arranged, so that the SBS medium pool cannot be vaporized in the working process, and the output energy and the pulse width are ensured to be stable;
2. the output energy is controlled by the inter-stage delay of the amplifying system, so that the pulse width is strictly unchanged in the process of adjusting the output energy of the laser, and the thermal focal length of the laser is stable.
When the light beam enters the SBS medium pool, the stimulated Brillouin scattering threshold value is reached near the focusing point, the back-transmitted Stokes light is generated, and the Stokes light compresses the laser pulse width in the transmission process.
The output energy of the seed laser is generally very small and is generally less than 10mJ, the threshold value when the seed laser directly enters the SBS medium pool to form stimulated Brillouin scattering is relatively small, the threshold value is generally less than 3mJ at the moment, the situation that the waveform of an output light beam is unstable and the pulse width change is very large due to the fact that local vaporization is not generated near a laser focus is avoided; however, after the beam expansion and the energy amplification of the seed light, the threshold value of stimulated brillouin scattering is relatively high, the threshold value is generally more than 100mJ, local vaporization points are easy to generate near the focal point, a medium around the local vaporization points can deteriorate after absorbing the energy of laser light and generate a plurality of tiny bubbles, the medium deterioration can reduce the service life of an SBS medium pool, the bubbles can influence the light transmission, and the energy is absorbed by the medium to generate great pulsation on the output light pulse energy and pulse width, so that the output stability of the laser is seriously reduced. This arrangement is the most significant point of application in distinction to other SBS based pulse width compression.
In the process of amplifying the energy of the laser, the pulse width, the divergence angle polarization state and the like of the laser are not changed, and only the energy is increased.
In the application, the output energy and pulse width of the seed laser are invariable all the time, and the output laser energy and picosecond pulse width are stable after SBS occurs; when the output energy of the laser is regulated, the output parameters of the seed laser are kept unchanged, and the energy is regulated by controlling the injection energy of the amplifying system and the discharge delay between the amplifying stages, so that the laser pulse width of the laser output cannot be changed along with the regulation of the output energy. This control method is an important control means for ensuring that the pulse width is constant. Other lasers based on SBS perform pulse compression generally by amplifying the energy of the seed light, then performing pulse compression, and then performing energy amplification once to twice. This is most of the most inadvisable in medical lasers because in clinic the physician will use the energy density as the dose of the laser, but in practice the power density of the laser is the most direct and meaningful physical quantity when the laser interacts with the skin. When the energy is regulated, only the pulse width of the laser is unchanged, and the energy density has clinical guiding significance. For example, in order for a doctor to treat freckles with different sizes, the doctor only needs to directly change the size of a laser spot through a hand tool, and the whole machine can automatically adjust energy to ensure the constant energy density. If the pulse width of the laser is unchanged, the power density is unchanged before and after adjustment, and the action effect is the same; if the pulse width of the process is smaller, the power density is larger although the energy density is not changed before and after adjustment, and the action effect is increased. The advantage of adjusting the energy by delay is that the output energy can be controlled accurately and the divergence angle of the laser does not change when the energy or frequency is changed.
Finally, the structural layout of the picosecond laser (the seed laser with energy output of a few mJ enters SBS first and then enters the amplifying stage) is unprecedented in the published materials at home and abroad.
While certain exemplary embodiments of the present invention have been described above by way of illustration only, it will be apparent to those of ordinary skill in the art that modifications may be made to the described embodiments in various different ways without departing from the spirit and scope of the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive of the scope of the invention, which is defined by the appended claims.
Claims (8)
1. A picosecond laser, comprising:
a seed laser assembly (1), the seed laser assembly (1) being configured to generate and output a seed laser;
the pulse width compression assembly (2), the seed laser output by the seed laser assembly (1) is output to the pulse width compression assembly (2) through the focusing mirror (201), and the pulse width compression assembly (2) compresses the pulse width of the seed laser;
the optical path between the seed laser component (1) and the pulse width compression component (2) is provided with a second polaroid (4) and a third quarter wave plate (5), horizontal linearly polarized laser output by the seed laser component (1) is changed into circularly polarized laser after passing through the second polaroid (4) and passing through the third quarter wave plate (5), one end, far away from the second polaroid (4), of the pulse width compression component (2) is provided with a reflecting focusing mirror (203), laser beams converged by the focusing mirror (201) of the pulse width compression component (2) reach the reflecting focusing mirror (203) and are focused in the SBS medium pool (202) and return along the original path, and reverse Stokes laser generated by the pulse width compression component (2) is formed into vertical polarized laser after passing through the third quarter wave plate (5) and is reflected and output by the second polaroid (4);
the picosecond laser also comprises an energy amplifying component (3), wherein the energy amplifying component (3) receives the laser reflected by the second polaroid (4) and amplifies and outputs the laser;
the energy amplification assembly (3) is provided with two laser rods distributed along an optical path, and laser transmitted into the energy amplification assembly (3) is emitted after being amplified at least twice by one of the laser rods.
2. The picosecond laser according to claim 1, wherein the seed laser assembly (1) is composed of a first total reflection mirror (101), a pinhole diaphragm (102), a Q-switch assembly (103), a first polarizer (104), a first quarter wave plate (105), a first laser rod (106), a second quarter wave plate (107) and an output mirror (108), and the seed laser assembly (1) outputs a horizontally linearly polarized laser beam.
3. A picosecond laser according to claim 1, characterized in that there is a beam expansion unit between the pulse width compression assembly (2) and the energy amplification assembly (3);
the beam expanding unit comprises a beam expanding lens group (7) which receives the vertical polarized laser reflected by the first reflecting mirror (6), the vertical polarized laser after beam expansion by the beam expanding lens group (7) is contracted by a second small hole diaphragm (8) and then becomes horizontal oscillation laser after passing through a half wave plate (9), and the horizontal oscillation laser enters an energy amplifying assembly (3) after passing through a third polarizing plate (10).
4. A picosecond laser according to claim 3, wherein the energy amplifying assembly (3) comprises a second laser rod (301) for receiving the laser light output by the third polarizer (10), the laser light amplified by the second laser rod (301) is transmitted to the third laser rod (302) through a second reflecting mirror (303) and a third reflecting mirror (304) for energy amplification, the laser light output by the third laser rod (302) is transmitted to a second total reflecting mirror (307) through a fourth quarter wave plate (306), and the laser light transmitted thereto is reflected by the second total reflecting mirror (307) along an original optical path, and is changed into vertically polarized laser light after passing through the fourth quarter wave plate (306) again, and the vertically polarized laser light passes through the third laser rod (302) and the second laser rod (301) in turn for energy secondary amplification and is output to the outside through the reflection of the third polarizer (10).
5. A picosecond laser according to claim 4, characterized in that there is an optically active crystal (305) located along the optical path between the second (301) and third (302) laser bars.
6. A picosecond laser according to claim 3, wherein the energy amplifying assembly (3) comprises a second laser rod (301) for receiving the laser light output by the third polarizer (10), the laser light amplified by the second laser rod (301) is transmitted to the third total reflection mirror (13) through the fifth quarter wave plate (12), the laser light transmitted to the third total reflection mirror (13) is reflected along the original optical path and passes through the fifth quarter wave plate (12) again to become vertically polarized laser light, the second energy amplification is performed by the second laser rod (301), the amplified laser light is reflected to the fourth reflection mirror (15) through the third polarizer (10), and the laser light reflected by the fourth reflection mirror (15) is sequentially transmitted to the third laser rod (302) through the half wave plate (9) and the fourth polarizer (11) for energy amplification;
the laser light amplified by the energy of the third laser rod (302) passes through a sixth quarter wave plate (17), is reflected by a fourth total reflection mirror (14) and passes through the sixth quarter wave plate (17) again to become vertical polarized laser light, and the vertical polarized laser light is reflected and output to the outside through the fourth polaroid (11).
7. A picosecond laser according to claim 3, wherein the energy amplifying assembly (3) comprises a second laser rod (301) for receiving the laser light output by the third polarizer (10), the laser light is amplified by the second laser rod (301), the amplified laser light is transmitted to the third total reflection mirror (13) through the fifth quarter wave plate (12), the laser light transmitted to the third total reflection mirror (13) is reflected along the original optical path and passes through the fifth quarter wave plate (12) again to become vertically polarized laser light, the second laser light is amplified by the second laser rod (301), the amplified laser light is reflected to the fourth reflection mirror (15) through the third polarizer (10), and the laser light reflected by the fourth reflection mirror (15) is transmitted to the third laser rod (302) through the half wave plate (9) and the fourth polarizer (11) in turn to be amplified and output to the outside.
8. A picosecond laser according to claim 3, wherein the energy amplifying assembly (3) comprises a second laser rod (301) for receiving the output of the third polarizer (10), the laser light amplified by the second laser rod (301) sequentially passes through a fourth reflector (15) and a fifth reflector (16) and enters the third laser rod (302) to amplify the energy after passing through the fourth polarizer (11), the amplified laser light is transmitted to the fourth total reflector (14) through a fifth quarter wave plate (12), the laser light transmitted to the fourth total reflector (14) is reflected along an original optical path and becomes vertically polarized laser light after passing through the fifth quarter wave plate (12) again, and the laser light is reflected to the outside through the fourth polarizer (11) after being amplified by the third laser rod (302).
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