CN108923241B - Passive Q-switched laser based on polarization synthesis laser gain - Google Patents
Passive Q-switched laser based on polarization synthesis laser gain Download PDFInfo
- Publication number
- CN108923241B CN108923241B CN201810830986.3A CN201810830986A CN108923241B CN 108923241 B CN108923241 B CN 108923241B CN 201810830986 A CN201810830986 A CN 201810830986A CN 108923241 B CN108923241 B CN 108923241B
- Authority
- CN
- China
- Prior art keywords
- laser
- switched
- mirror
- passive
- polarized
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- 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
- H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
-
- 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
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Optics & Photonics (AREA)
- Lasers (AREA)
Abstract
The invention discloses a passive Q-switched laser based on polarization synthesis laser gain, which comprises: the laser comprises a pumping source, a focusing coupling mirror group, a total reflection mirror, a polarized laser medium, a half-wave plate, a polaroid, a passive Q-switched crystal and an output mirror, wherein: the pump source, the focusing coupling mirror group, the total reflection mirror, the polarized laser medium, the half-wave plate, the polaroid, the passive Q-switched crystal and the output mirror are sequentially and coaxially arranged, and the total reflection mirror and the output mirror form a resonant cavity; the polarized laser medium and the half-wave plate form a polarized synthesis gain control functional module, the gain of the passive Q-switched laser is controlled by rotating the half-wave plate, and the pulse frequency of the passive Q-switched laser is effectively controlled. The scheme of the invention can realize gain control of the passive Q-switched laser under the conditions of not changing pumping power, not influencing crystal heat effect and keeping the stable state of the resonant cavity, thereby achieving the technical effect of effectively adjusting the frequency of the passive Q-switched laser.
Description
Technical Field
The invention relates to the technical field of lasers, in particular to a passive Q-switched laser based on polarization synthesis laser gain.
Background
The passive Q-switched laser has the advantages of small volume, low cost and compact structure, and has wide market application prospect in laser engraving, display, stage scenery and the like.
Passive Q-switching is often used in continuously pumped lasers to obtain high repetition rate pulsed laser output. It can be seen from the characteristics of the passive Q-switched technology that a key point for forming laser pulses is that the gain of the laser reaches the threshold of the laser, and in a continuously pumped passive Q-switched laser, the chaotic phenomenon that the time and the frequency for generating the laser pulses are different often occurs, because the threshold of the laser in each mode is different in a multimode state, and in order to obtain stable pulsed Q-switched laser output under the condition, the laser needs to keep operating in a single transverse mode.
In order to realize single-mode operation of the laser, the pumping power of the laser is required to be in a stable state, namely the focal length of a thermal lens generated by a gain medium of the laser is unchanged, and the loss of a resonant cavity of the laser is unchanged, so that the Q-switched laser can obtain fixed-frequency laser output with stable pulses. When the pump power changes, the single-mode operation condition of the laser is destroyed, and the passive Q-switching pulse and the frequency stability are destroyed.
The factors influencing the pulse frequency of the passive Q-switching mainly include the pumping power, the reflectivity of an output mirror and a resonant cavity, wherein once the parameters of the output mirror and the resonant cavity are determined, the parameters of the Q-switching laser are also determined, and the frequency can be locally adjusted only by changing the pumping power. The change of the pumping power will affect the thermal effect of the crystal, causing the change of the stable state of the resonant cavity, and the resonant cavity needs to be adjusted to obtain the Q-switched laser with stable frequency. Therefore, the output frequency of the passively Q-switched laser can not be effectively adjusted by adopting a conventional method in the operation process, so that the wide application of the passively Q-switched laser is limited.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a passive Q-switched laser based on polarization synthesis laser gain.
The invention provides a passive Q-switched laser based on polarization synthesis laser gain, which comprises: the laser comprises a pumping source 1, a focusing coupling mirror group 2, a total reflection mirror 3, a polarized laser medium 4, a half-wave plate 5, a polaroid 6, a passive Q-switched crystal 7 and an output mirror 8, wherein:
the pump source 1, the focusing coupling mirror group 2, the total reflection mirror 3, the polarized laser medium 4, the half-wave plate 5, the polaroid 6, the passive Q-switched crystal 7 and the output mirror 8 are sequentially and coaxially arranged optically;
the total reflection mirror 3 and the output mirror 8 form a resonant cavity;
the pump light generated by the pump source 1 is firstly converged by the focusing coupling mirror group 2, then passes through the total reflection mirror 3, and finally is absorbed by the polarized laser medium 4, so that the polarized laser medium particles are transited to the upper laser energy level to form particle number reversal, and the gain of the passive Q-switched laser is improved;
when the gain of the passive Q-switched laser is increased to be higher than a first preset threshold value, laser in the resonant cavity starts to oscillate, and the laser beam is finally output through the output mirror 8.
Optionally, the surface of the polarizer 6 is plated with a P-light high-transmittance film and an S-light high-reflectance film, and after the polarizer 6 is inserted into the resonant cavity, only light in the P-polarization direction is allowed to oscillate back and forth in the resonant cavity.
Optionally, the passive Q-switched crystal 7 is a crystal for Q-switched pulsed laser based on crystal saturable absorption characteristics.
Optionally, the pump source 1 is a direct output semiconductor laser, and the wavelength corresponds to the absorption peak of the polarized laser medium 4;
the focusing coupling mirror group 2 is composed of two cylindrical mirrors and a convex lens, wherein the cylindrical mirrors are orthogonally arranged, one surface of each cylindrical mirror is a plane, the other surface of each cylindrical mirror is a convex surface, and the planes of the cylindrical mirrors are opposite to the pumping source 1.
Optionally, the pump source 1 is a fiber-coupled semiconductor laser, and the wavelength corresponds to the absorption peak of the polarized laser medium 4;
the focusing coupling lens group 2 is composed of two plano-convex lenses, and the convex surfaces are opposite.
Optionally, the total reflection mirror 3 is one of a plane mirror, a concave mirror and a convex mirror, and a side facing the polarized laser medium 4 is plated with a laser high reflection film.
Optionally, when the thermal effect of the polarized laser medium 4 is smaller than a first preset threshold, the total reflection mirror 3 is a plane mirror; when the thermal effect of the polarized laser medium 4 is greater than a second preset threshold, the total reflection mirror 3 is a concave mirror or a convex mirror, and the concave surface or the convex surface of the total reflection mirror faces the polarized laser medium 4.
Optionally, the polarized laser medium 4 is a laser medium with polarization property and has a crystal optical axis.
Optionally, the half-wave plate 5 is a polarizer and made of a uniaxial crystal, the light-passing surface is parallel to the optical axis of the polarized laser medium 4, and the light-passing direction is perpendicular to the optical axis of the polarized laser medium 4.
Optionally, the output mirror 8 is a plano-concave mirror or a plano-convex mirror, a concave surface or a convex surface of which faces the polarized laser medium 4, and a side facing the polarized laser medium 4 is plated with a partially transmissive laser reflection film.
The passive Q-switched laser based on the polarization synthesis laser gain controls the gain of the passive Q-switched laser by rotating the half-wave plate, and changes the pulse frequency of the passive Q-switched laser, thereby realizing the technical effects of realizing gain control and obtaining the Q-switched laser with stable frequency under the conditions of not changing the pumping power, not influencing the heat effect of a crystal and keeping the stable state of a resonant cavity, namely the passive Q-switched laser per se. Compared with the prior art, the technical scheme of the invention can realize that the passive Q-switched laser can effectively adjust the frequency in the running process without damaging the stability of a pulse sequence, and realize the wide application of the passive Q-switched laser.
Drawings
Fig. 1 is a schematic structural diagram of a passively Q-switched laser based on polarization-combined laser gain according to an embodiment of the present invention;
FIG. 2(a) is a schematic diagram of a gain control structure of a polarization-combined laser according to an embodiment of the present invention;
FIG. 2(b) is an exploded view of the polarization of a polarized laser medium according to an embodiment of the present invention;
fig. 3 is a diagram illustrating a relationship between a pulse frequency and θ of a passively Q-switched laser based on a gain of a polarization-combined laser according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.
Fig. 1 is a schematic structural diagram of a passively Q-switched laser based on polarization-combined laser gain according to an embodiment of the present invention, as shown in fig. 1, the passively Q-switched laser includes: the laser comprises a pumping source 1, a focusing coupling mirror group 2, a total reflection mirror 3, a polarized laser medium 4, a half-wave plate 5, a polaroid 6, a passive Q-switched crystal 7 and an output mirror 8, wherein:
the pump source 1, the focusing coupling mirror group 2, the total reflection mirror 3, the polarized laser medium 4, the half-wave plate 5, the polaroid 6, the passive Q-switched crystal 7 and the output mirror 8 are sequentially and coaxially arranged optically;
the total reflection mirror 3 and the output mirror 8 form a resonant cavity.
In an embodiment of the present invention, the surface of the polarizer 6 is plated with a P-light high-transmittance film and an S-light high-reflectance film, and after the polarizer 6 is inserted into the resonant cavity, only light in the P-polarization direction is allowed to oscillate back and forth in the resonant cavity.
In an embodiment of the present invention, the passive Q-switching crystal 7 is a crystal for Q-switching to obtain pulsed laser based on a crystal saturable absorption characteristic.
The pump light generated by the pump source 1 is firstly converged by the focusing coupling mirror group 2, then passes through the total reflection mirror 3, and finally is absorbed by the polarized laser medium 4, so that the polarized laser medium particles are transited to the upper laser energy level to form particle number reversal, and the gain of the passive Q-switched laser is improved;
when the gain of the passive Q-switched laser is increased to be higher than a first preset threshold, laser in the resonant cavity starts to oscillate, because the polarizing plate 6 in the resonant cavity has the function of P-polarization high-transmittance and S-polarization high-reflectance, P-polarized light can penetrate through the polarizing plate 6, laser beams oscillate back and forth in the resonant cavity, and S-polarized light is directly reflected out of the resonant cavity, horizontal P-polarized light is output after passing through the polarizing plate 6, then the horizontal P-polarized light reflected back by the output mirror 8 sequentially passes through the passive Q-switched crystal 7, the polarizing plate 6, the half-wave plate 5, the polarized laser medium 4 and the reflecting mirror 3, then is reflected back into the resonant cavity by the reflecting mirror 3, and finally is output by the output mirror 8 after sequentially passing through the polarized laser medium 4, the half-wave plate 5, the polarizing plate 6 and the passive Q-switched crystal 7.
The first preset threshold may be 2g0l＝L-lnR-2σgsn0lsWherein g is0For passively Q-switched laser small signal gain, L is the gain length of the polarized laser medium 4, L is the intrinsic loss of the passively Q-switched laser, R is the reflectivity of the output mirror 8, σgsFor the ground state absorption cross section of the passively Q-switched crystal 7, n0To be controlled by the particle density of the dynamically Q-switched crystal 7,/sThe thickness of the passive Q-switched crystal 7.
With the continuous increase of the light intensity of the laser beam in the cavity, the transmittance T of the passive Q-switched crystal 7 is a function of the light intensity I, and the specific expression is as follows: t ═ exp [ -a ]0ls/(1+I/Is)]Wherein a is0Is the small signal absorption coefficient of the passively Q-switched crystal 7, ls is the thickness of the passively Q-switched crystal 7, IsIn order to passively adjust the Q crystal 7 saturation light intensity, when the light beam intensity in the cavity reaches the passively adjust Q crystal 7 saturation light intensity, the saturable absorber transmittance in the passively adjust Q crystal 7 is improved, the resonant cavity loss is reduced, the difference value of the gain and the loss is larger, the light intensity is gradually improved in the process of reciprocating in the cavity, therefore, the laser only needs to be oscillated back and forth in the resonant cavity for limited times, most of the upper energy level particles stored in the polarized laser medium 4 are released, then the laser gain is rapidly reduced until the gain of the passively adjust Q laser is lower than the first preset threshold value, and the laser pulse is stopped. From the output of the passive Q-switched laser, the laser pulse light intensity is increased, slowed and reduced until the process of termination, and the laser only needs to oscillate back and forth for limited times in the resonant cavity, so that nanosecond-level laser pulses are formed.
The polarized laser medium 4 and the half-wave plate 5 constitute a polarized composite gain control functional module, when the gain of the passive Q-switched laser reaches a first preset threshold value, laser oscillation is formed in the resonant cavity, the oscillation laser between the polarizing plate 6 and the output mirror 8 is P polarized light, the P polarized light is projected according to the optical axis direction of the half-wave plate 5 after passing through the half-wave plate 5 for the first time, the P polarized light is decomposed into polarized light in two vertical directions, the polarized laser medium 4 has polarization characteristics, the stimulated emission cross sections in the two polarization directions are different, the small signal gain is equal to the product of the stimulated emission cross section and the doped particles in the unit volume of the polarized laser medium 4, the gains of the polarized laser medium 4 to the linearly polarized light in the two directions are different, and the proportion of the linearly polarized light in the two directions can be changed by rotating the half-wave plate 5, therefore, the effect of controlling the gain of the synthesized laser is achieved, and the larger the gain of the passive Q-switched laser is, the shorter the period of reaching the first preset threshold of the gain of the passive Q-switched laser is, that is, the larger the frequency of the passive Q-switched laser is at the moment.
In an embodiment of the present invention, the pump source 1 is a directly output semiconductor laser, and the output pump light is decomposed into two directions of pump light from a beam cross section, and the wavelength corresponds to the absorption peak of the polarized laser medium 4; the focusing coupling lens group 2 consists of two cylindrical lenses and a convex lens which are orthogonally arranged, in order to reduce spherical aberration brought by the cylindrical lenses, one surface of each cylindrical lens is a plane, the other surface of each cylindrical lens is a convex surface, and the plane of each cylindrical lens is opposite to the pumping source 1; the two cylindrical mirrors in the focusing coupling mirror group 2 shape the pump light in two directions decomposed by the pump source 1 into approximately parallel light beams, and the convex lenses in the focusing coupling mirror group 2 focus the approximately parallel light beams.
In another embodiment of the present invention, the pump source 1 is a semiconductor laser coupled to output by an optical fiber, the wavelength corresponds to the absorption peak of the polarized laser medium 4, and since the optical fiber has a homogenization effect, the divergence angles in any direction on the cross section of the pump beam output by the pump source 1 are the same; the focusing coupling mirror group 2 is composed of two plano-convex lenses, the convex surfaces of the plano-convex lenses are opposite, the convex mirror close to the pumping source 1 converts the light beam output by the pumping source 1 into parallel light, and the convex mirror far away from the pumping source 1 focuses the parallel light.
In an embodiment of the present invention, the total reflection mirror 3 may be a plane mirror, a concave mirror, or a convex mirror, when the thermal effect of the polarized laser medium 4 is very small, for example, smaller than a second preset threshold, the light passing through the polarized laser medium 4 is approximately parallel light, the total reflection mirror 3 is a plane mirror, and one side facing the polarized laser medium 4 is plated with a laser high reflection film; when the thermal effect of the polarized laser medium 4 is obvious, for example, greater than a third preset threshold, in order to achieve better effect, in order to make the incident light and the reflected light of the total reflection mirror 3 coincide, the total reflection mirror 3 is a concave mirror or a convex mirror, the concave surface or the convex surface of the polarization laser medium 4 faces the polarization laser medium 4, and one side of the polarization laser medium 4 faces the polarization laser medium is plated with a laser high-reflection film, wherein the choice of the concave or convex surface of the holophote 3 is determined by the distance between the holophote 3 and the polarization gain medium 4, such as when the polarization gain medium 4 produces a positive thermal lens effect, the amplified laser light generated by the linearly polarized light passing through the polarized laser medium 4 is converged, and at this time, when the distance between the total reflection mirror 3 and the polarization gain medium 4 is smaller than the thermal focal length of the polarization laser medium 4, the total reflection mirror 3 is a convex mirror; when the distance between the total reflection mirror 3 and the polarization gain medium 4 is greater than the thermal focal length of the polarization laser medium 4, the total reflection mirror 3 is a concave mirror.
The second preset threshold and the third preset threshold may be equal or unequal, and the specific data may be determined according to the needs of the actual application, which is not specifically limited in the present invention.
In an embodiment of the present invention, the polarized laser medium 4 is a laser medium having a polarization property, such as Nd: YVO4, Nd: YAP, Nd: YLF, etc., which have crystal optical axes and the laser light passing through the polarized laser medium 4 has polarization characteristics after being pumped.
In an embodiment of the present invention, the half-wave plate 5 is a polarization device, and is generally made of a uniaxial crystal, and the light-passing surface thereof is parallel to the optical axis of the polarized laser medium 4, and the light-passing direction thereof is perpendicular to the optical axis of the polarized laser medium 4, when the polarized laser light is incident on the surface of the half-wave plate 5, the laser light in two polarization directions, which are parallel to the optical axis and perpendicular to the optical axis, can be projected, and the refractive indexes of the two light beams are different, and when the two light beams are transmitted in the light-passing direction, the two light beams generate a phase difference. When the thickness of the crystal reaches a certain thickness, the phase difference generated by the two beams of light is pi, the wave plate is a half-wave plate, at the moment, after the polarized laser is transmitted by the half-wave plate 5, the polarization state is not changed, the polarized laser is still linearly polarized light, but the polarization direction is changed, and the polarization direction after transmission and the incident polarization direction are symmetrical by an optical axis.
Wherein the polarizer 6 is placed at brewster angle or 45 degrees with respect to the optical axis and can be replaced by a PBS spectroscope, a glan prism.
In an embodiment of the present invention, the output mirror 8 may be a plano-concave mirror or a plano-convex mirror, and the concave surface or the convex surface faces the polarized laser medium 4, and the side facing the polarized laser medium 4 is plated with a partially transparent laser reflection film.
Fig. 2(a) is a schematic structural diagram of gain control of polarization-combined laser according to an embodiment of the present invention, and as shown in fig. 2(a), after P-polarized light output by the polarizer 6 passes through the rotatable half-wave plate 5, the polarization direction of the light beam changes, and the included angle between the polarized light and the x-axis of the polarized laser medium 4 changes. FIG. 2(b) is an exploded view of the polarization of a polarized laser medium according to an embodiment of the present invention, and as shown in FIG. 2(b), assuming that the polarization direction of the polarized light and the x-axis of the polarized laser medium 4 form an angle θ, the light intensity I will be oscillated0Projected to the x and y directions of the polarized laser medium 4 respectively, the light intensity in the x direction is Ix＝I0sin2Light intensity in theta, y direction is Iy＝I0cos2Theta, since the polarized laser medium 4 has different gains for light in the x and y directions, the gains in the x and y directions are assumed to be G, respectivelyxAnd GyThe amplified light intensity of the laser amplifier passing through the polarized laser medium 4 for the second time is Ix＝I0Gx 2sin2θ，Iy＝I0Gy 2cos2Theta, gain of the passively Q-switched laser after the action of the half-wave plate 5 is G2＝[(Gx 2-Gy 2)sin2θ+Gy 2]Therefore, when the value of theta is changed, the gain of the polarization synthesis of the passive Q-switched laser can be controlled.
When the frequency of the passive Q-switched laser needs to be changed, the included angle theta between the polarization direction of the P polarized light and the x axis of the polarized laser medium 4 after passing through the half-wave plate 5 is changed by changing the included angle between the optical axis of the half-wave plate 5 and the P polarized light, and at the moment, the frequency of the passive Q-switched laser is also changed. Assuming that the gain of the polarized laser medium 4 in the x-axis direction is larger than that in the y-axis direction, when the half-wave plate rotates to a certain angle and the theta angle is 90 degrees, the gain of the passive Q-switched laser is G2＝Gx 2Corresponding to the maximum gain of the Q-switched laser, the larger the gain of the passive Q-switched laser means that the shorter the period of reaching the first preset threshold of the gain of the passive Q-switched laser is, that is, corresponding to the maximum frequency of the Q-switched laser, when the corresponding θ angle is 0 degree, the gain of the passive Q-switched laser is G2＝Gy 2The same applies to the minimum gain and frequency of the passively Q-switched laser.
According to the relation between the pumping power and the laser gain and the polarization synthesis gain expression, the relation between the polarization gain and the pumping power and the repetition frequency interval t can be obtained, finally, the relation between the repetition frequency interval t and theta can be obtained by utilizing the condition that the gain and the loss are equal when the Q-switched pulse is generated, and further, the Q-switched laser frequency can be controlled.
The specific calculation process is as follows:
g0l＝KPint (1)
wherein, g0For passively Q-switched laser small signal gain, t is the repetition frequency interval, PinFor the pumping power of the pump source 1, K represents a coefficient between the pumping energy of the pump source 1 and the small signal gain, and l is the gain length of the polarized laser medium 4.
The gain of a passively Q-switched laser can be expressed as:
G＝exp(g0l)＝exp(KPint) (2)
wherein, KxAnd KyIs the pump energy in the x and y directions of the polarized laser medium 4 as a function of the small signal gain.
By using the equal relation between gain and loss to obtain
[exp(2*KxPint)-exp(2*KyPint)]sin2θ+exp(2*KyPint)＝exp(L-ln R) (3)
Wherein L is the inherent loss of the passively Q-switched laser, and R is the reflectivity of the output mirror 8. By using the relationship between the period and the repetition frequency f, we can obtain:
[exp(2*KxPin/f)-exp(2*KyPin/f)]sin2θ+exp(2*KyPin/f)＝exp(L-ln R) (4)
equation (4) is a transcendental equation, where the pulse frequency f is a function of θ, when the pump power is constant.
Through numerical solution, a corresponding relation of the pulse frequency of the passively Q-switched laser with θ can be obtained, fig. 3 is a schematic diagram of a numerical relation of the pulse frequency of the passively Q-switched laser based on polarization-combined laser gain with an included angle θ according to an embodiment of the present invention, as shown in fig. 3, the laser frequency increases with the increase of θ, when θ is 90 degrees, the pulse frequency of the passively Q-switched laser is the largest, and when θ is 0 degrees, the pulse frequency of the passively Q-switched laser is the smallest.
In an embodiment of the present invention, the pump source 1 adopts a semiconductor laser coupled and output by an optical fiber, and the output pump light has a wavelength of 808nm and a power of 30W; the focusing coupling lens group 2 consists of two plano-convex lenses, and the convex surfaces are opposite; focal lengths of the plano-convex lenses are respectively 50mm and 100mm, and two mirror surfaces of each plano-convex lens are plated with 808nm antireflection films with transmittance of more than 99.5%; the full-reflection cavity mirror 3 is a plano-concave lens, the concave surface of the full-reflection cavity mirror faces the polarized laser medium 4, the curvature radius of the full-reflection cavity mirror 3 is 100mm, and a 1064nm high-reflection film with the reflectivity of more than 99.9% is plated on the concave mirror surface of the plano-concave lens; the polarized laser mediumMass 4 is 3X 10mm Nd: YVO4Both end faces of the crystal are plated with 1064nm antireflection films with the transmittance of more than 99.9%; the light transmission caliber of the half-wave plate 5 is 10mm, both sides of the half-wave plate are plated with anti-reflection films of 1064nm, and the transmittance is more than 99%; the passive Q-switched crystal 7 is Cr: YAG crystal, coated with 1064nm anti-reflection film on both sides, with light-transmitting aperture of 10mm and initial transmittance of 90%; the output mirror 8 is a 1064nm flat output mirror and is coated with a 1064nm laser reflection film, and the reflectivity reaches 85%.
In an embodiment of the present invention, the pump light generated by the semiconductor laser coupled and output by the optical fiber is converged by the two plano-convex lenses, passes through the total reflection mirror 3, and is finally reflected by the Nd: YVO4As absorbed, the gain of the passively Q-switched laser increases. When the gain of the passive Q-switched laser is increased to be higher than a first preset threshold, laser in the resonant cavity starts to oscillate, due to the action of the polarizing plate 6 in the resonant cavity, horizontal P-polarized light is output after passing through the polarizing plate 6, and then the horizontal P-polarized light reflected back by the output mirror 8 firstly passes through the passive Q-switched crystal 7, the polarizing plate 6, the half-wave plate 5 and the Nd: YVO4And then, the light is reflected back to the resonant cavity through the reflector 8 and then sequentially passes through Nd: YVO4The pulse Q-switched laser comprises a half-wave plate 5, a polarizing plate 6 and a passive Q-switched crystal 7, and is finally output through an output mirror 8.
When the frequency of the passive Q-switched laser needs to be changed, the included angle between the optical axis of the half-wave plate 5 and the P polarization is changed, the included angle theta between the polarization direction of linearly polarized light after passing through the half-wave plate 5 and the x axis of the linear laser medium is changed, and at the moment, the frequency of the passive Q-switched laser is changed. When the half-wave plate rotates to a certain angle and the corresponding theta angle is 0 degree, the gain of the passive Q-switched laser is G2＝Gy 2At this time, when the θ angle is 90 degrees corresponding to the lowest frequency of the passively Q-switched laser, the gain of the passively Q-switched laser is G2＝Gx 2This time corresponding to the highest frequency of the passively Q-switched laser.
From the above, the passive Q-switched laser based on the gain of the polarization-combined laser provided by the invention controls the gain of the passive Q-switched laser by rotating the half-wave plate, and changes the pulse frequency of the passive Q-switched laser, so that the technical effects of realizing gain control and obtaining the Q-switched laser with stable frequency by the passive Q-switched laser under the conditions of not changing the pumping power, not influencing the thermal effect of the crystal and keeping the stable state of the resonant cavity are realized. Compared with the prior art, the technical scheme of the invention can realize that the passive Q-switched laser can effectively adjust the frequency in the running process without damaging the stability of a pulse sequence, and realize the wide application of the passive Q-switched laser.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A passively Q-switched laser based on polarization-combined laser gain, the passively Q-switched laser comprising: the laser comprises a pumping source (1), a focusing coupling mirror group (2), a total reflection mirror (3), a polarized laser medium (4), a half-wave plate (5), a polaroid (6), a passive Q-switched crystal (7) and an output mirror (8), wherein:
the pump source (1), the focusing coupling mirror group (2), the total reflection mirror (3), the polarized laser medium (4), the half-wave plate (5), the polaroid (6), the passive Q-switched crystal (7) and the output mirror (8) are sequentially and coaxially arranged;
the total reflection mirror (3) and the output mirror (8) form a resonant cavity;
the pump light generated by the pump source (1) is firstly converged by the focusing coupling mirror group (2), then passes through the total reflection mirror (3), and finally is absorbed by the polarized laser medium (4), so that the polarized laser medium particles transition to the upper laser level to form population inversion, and the gain of the passive Q-switched laser is improved;
when the gain of the passive Q-switched laser is increased to be higher than a first preset threshold value, the laser in the resonant cavity starts to oscillate, the laser beam is finally output through the output mirror (8), and the first preset threshold valueThe threshold value is 2g0l＝L-lnR-2σgsn0lsWherein g is0For the passive Q-switched laser small signal gain, L is the gain length of the polarized laser medium (4), L is the inherent loss of the passive Q-switched laser, R is the reflectivity of the output mirror (8), sigmagsIs the ground state absorption cross section of the passively Q-switched crystal (7), n0Is the particle density of the dynamically Q-switched crystal (7)/sIs the thickness of the passively Q-switched crystal (7);
the surface of the polaroid (6) is plated with a P light high-transmittance film and an S light high-reflection film, and after the polaroid (6) is inserted into the resonant cavity, only P polarized light is allowed to oscillate back and forth in the resonant cavity in the cavity;
and changing the included angle between the half-wave plate (5) and the P polarized light by rotating the half-wave plate (5), wherein the included angle between the P polarized light and the x axis of the polarized laser medium (4) is changed, so that the frequency of the passive Q-switched laser is changed.
2. The passively Q-switched laser according to claim 1, wherein the passively Q-switched crystal (7) is a crystal for Q-switched pulsed laser based on crystal saturable absorption characteristics.
3. The passively Q-switched laser according to claim 2, characterized in that the pump source (1) is a direct output semiconductor laser, the wavelength corresponding to the absorption peak of the polarized laser medium (4);
the focusing coupling mirror group (2) is composed of two cylindrical mirrors and a convex lens, wherein the cylindrical mirrors are orthogonally arranged, one side of each cylindrical mirror is a plane, the other side of each cylindrical mirror is a convex surface, and the planes of the cylindrical mirrors are opposite to the pumping source (1).
4. The passively Q-switched laser according to claim 2, wherein the pump source (1) is a fiber-coupled-out semiconductor laser with a wavelength corresponding to the absorption peak of the polarized laser medium (4);
the focusing coupling lens group (2) consists of two plano-convex lenses, and the convex surfaces of the two plano-convex lenses are opposite.
5. The passively Q-switched laser according to any one of claims 2 to 4, wherein the all-reflecting mirror (3) is one of a plane mirror, a concave mirror and a convex mirror, and a side facing the polarized laser medium (4) is coated with a laser high-reflection film.
6. The passive Q-switched laser according to claim 5, characterized in that when the thermal effect of the polarized laser medium (4) is less than a second preset threshold, the light passing through the polarized laser medium (4) is parallel light, and the total reflection mirror (3) is a plane mirror; when the heat effect of the polarized laser medium (4) is greater than a third preset threshold value, the incident light and the reflected light of the total-reflection mirror (3) are overlapped, the total-reflection mirror (3) is a concave mirror or a convex mirror, and the concave surface or the convex surface of the total-reflection mirror faces the polarized laser medium (4).
7. The passively Q-switched laser according to claim 2, wherein the polarized laser medium (4) is a laser medium with polarization properties and has a crystal optical axis.
8. The passive Q-switched laser according to claim 2, characterized in that the half-wave plate (5) is a polarizing device made of a uniaxial crystal with a light-passing surface parallel to the optical axis of the polarized laser medium (4) and a light-passing direction perpendicular to the optical axis of the polarized laser medium (4).
9. The passively Q-switched laser according to claim 2, characterized in that the output mirror (8) is a plano-concave or plano-convex mirror, the concave or convex surface of which is directed towards the polarized laser medium (4), and the side directed towards the polarized laser medium (4) is coated with a partially transmissive laser reflection film.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810830986.3A CN108923241B (en) | 2018-07-25 | 2018-07-25 | Passive Q-switched laser based on polarization synthesis laser gain |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810830986.3A CN108923241B (en) | 2018-07-25 | 2018-07-25 | Passive Q-switched laser based on polarization synthesis laser gain |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108923241A CN108923241A (en) | 2018-11-30 |
| CN108923241B true CN108923241B (en) | 2020-01-17 |
Family
ID=64416977
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810830986.3A Active CN108923241B (en) | 2018-07-25 | 2018-07-25 | Passive Q-switched laser based on polarization synthesis laser gain |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108923241B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109687273A (en) * | 2019-01-03 | 2019-04-26 | 中国科学院福建物质结构研究所 | A kind of laser |
| CN110880670A (en) * | 2019-11-29 | 2020-03-13 | 山东大学 | High-efficiency optical parametric oscillator with adjustable threshold value |
| CN112993729B (en) * | 2021-02-02 | 2022-10-28 | 长春理工大学 | Low-quantum-loss 1.6-micrometer high-peak-power pumping source of medium-wave optical parametric oscillator |
| CN113839296B (en) * | 2021-08-18 | 2024-04-05 | 大族激光科技产业集团股份有限公司 | Wavelength locking LD resonance pumping picosecond amplifier |
| CN115810974A (en) * | 2023-02-10 | 2023-03-17 | 长春理工大学 | Flat-top laser device of gradually-doped passive Q-switched crystal and output method |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100470965C (en) * | 2006-04-18 | 2009-03-18 | 北京国科世纪激光技术有限公司 | A pulse width adjustable laser |
| US20120140782A1 (en) * | 2010-12-07 | 2012-06-07 | Raytheon Company | Low timing jitter, single frequency, polarized laser |
| CN103337775B (en) * | 2013-06-09 | 2015-12-23 | 中国电子科技集团公司第十一研究所 | A kind of fiber end face pump laser |
-
2018
- 2018-07-25 CN CN201810830986.3A patent/CN108923241B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN108923241A (en) | 2018-11-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108923241B (en) | Passive Q-switched laser based on polarization synthesis laser gain | |
| WO2020207434A1 (en) | Laser and laser radar | |
| US4016504A (en) | Optical beam expander for dye laser | |
| KR101324265B1 (en) | A laser apparatus | |
| EP1500174B1 (en) | Laser cavity pumping method and laser system thereof | |
| CN108988117B (en) | Laser amplifier based on polarization synthesis laser gain | |
| US5359622A (en) | Radial polarization laser resonator | |
| CN109196737B (en) | Efficient laser system for third harmonic generation | |
| CN107046222B (en) | Inner cavity optical parametric oscillator for realizing similar dual-wavelength output | |
| US4127828A (en) | Optical beam expander for dye laser | |
| CN112260051B (en) | 1342nm infrared solid laser | |
| CN111431021A (en) | Laser with orthogonal polarization output | |
| CN110265862A (en) | A kind of laser of high light beam quality | |
| JP3410108B2 (en) | A range finding system using an eye-safe laser with a Brewster angle Q-switch in a single cavity cavity of both the pump laser and the optical parametric oscillator | |
| JP2020127000A (en) | Passive Q-switched solid-state laser with compressed pulse width | |
| CN106451058B (en) | Laser transverse mode adjustable passive Q-switched microchip laser | |
| CN210379761U (en) | Laser with high beam quality | |
| CN107069414B (en) | Small hundred picosecond laser beauty instrument | |
| CN115473116A (en) | Pulse laser space shaping device and method based on non-uniform saturable absorber | |
| CN212182756U (en) | Laser with orthogonal polarization output | |
| CN112636146B (en) | High-power mode-locked disc laser | |
| KR100514665B1 (en) | Apparatus and method for beam cleaning laser oscillator using stimulated Brillouin scattering | |
| CN112993729B (en) | Low-quantum-loss 1.6-micrometer high-peak-power pumping source of medium-wave optical parametric oscillator | |
| WO2009079730A2 (en) | Prism and compact unidirectional single-frequency planar ring cavity laser without intracavity elements | |
| CN115939919B (en) | Solid laser based on Kerr lens mode locking |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |