CN218242548U - High energy dual wavelength laser - Google Patents

Abstract

The application provides a large-energy dual-wavelength laser, include: the laser oscillation module comprises a pyramid prism, the output end of the pyramid prism is sequentially provided with a polarizer, a first laser module and a Gaussian mirror, the input end of the pyramid prism is sequentially provided with an electro-optic Q-switch, a 1/4 wave plate and a reflector, nanosecond pulse laser generated in the laser oscillation module transmits the Gaussian mirror, and the first laser module is a semiconductor rod-shaped laser crystal side pump; the laser frequency doubling polarization switching module comprises a first half-wave plate and a first polaroid, wherein the first half-wave plate is arranged on an input light path of the first polaroid, a frequency doubling crystal and a third half-wave plate are sequentially arranged on a transmission light path of the first polaroid, a second polaroid is arranged on a reflection light path of the first polaroid, and a second half-wave plate is arranged on a reflection light path of the second polaroid. The laser is more suitable for the fields of laser ranging, laser photoelectric countermeasure, atmospheric detection and the like, and has higher requirements on the laser.

Description

High energy dual wavelength laser

technical field

The present application relates to the technical field of lasers, in particular to a high-energy dual-wavelength laser.

Background technique

With the development of solid-state laser technology, high-energy solid-state lasers have been widely used in more and more fields, and then the stability, reliability and environmental applicability of lasers in the fields of laser ranging, laser photoelectric countermeasures, and atmospheric detection have been proposed. Higher requirements, that is, higher requirements are put forward for the performance improvement of lasers.

In order to meet the higher requirements for laser performance in the fields of laser ranging, laser photoelectric countermeasures, and atmospheric detection, a technical idea of increasing the output energy and polarization of dual-wavelength lasers has been proposed.

Utility model content

This application provides a high-energy dual-wavelength laser to meet the higher requirements for lasers in the fields of laser ranging, laser photoelectric countermeasures, and atmospheric detection.

A high-energy dual-wavelength laser provided by the present application includes: a laser oscillation module and a laser frequency doubling polarization switching module, the laser oscillation module and the laser frequency doubling polarization switching module are optically connected, and the laser oscillation module is used to generate A nanosecond pulsed laser with a wavelength of 1064nm, the laser frequency doubling polarization switching module is used to output a dual-wavelength polarization state switchable laser; wherein:

The laser oscillation module includes a corner cube, the output of the corner cube is sequentially provided with a polarizer, the first laser module and a Gaussian mirror, and the input of the corner cube is sequentially provided with an electro-optical Q-switching switch, a 1/4 wave sheet and reflector, the nanosecond pulse laser generated in the laser oscillation module is transmitted through the Gaussian mirror, and the first laser module is side-pumped by a semiconductor rod-shaped laser crystal;

The laser frequency doubling polarization switching module includes a first half-wave plate and a first polarizer, the first half-wave plate is arranged on the input optical path of the first polarizer, and the transmission optical path of the first polarizer is A frequency doubling crystal and a third half-wave plate are set in sequence, a second polarizer is set on the reflection optical path of the first polarizer, and a second half-wave plate is set on the reflection light path of the second polarizer.

Optionally, the above-mentioned high-energy dual-wavelength laser further includes a laser amplification module, the laser amplification module is arranged on the transmission optical path from the laser oscillation module to the laser frequency doubling polarization switching module, and is used for the laser oscillation Energy amplification of nanosecond pulsed laser output by the module;

The laser amplification module includes sequentially setting a first isolator, a first beam expander, a second laser module, a second isolator, a second beam expander, a third laser module, an optical rotator and a fourth laser module; The second laser module, the third laser module and the fourth laser module are slab side pumped.

Optionally, in the above-mentioned high-energy dual-wavelength laser, the laser oscillation module also includes

The first 45° reflector, the laser amplification module also includes a second 45° reflector, a third 45° reflector, a fourth 45° reflector and a fifth 45° reflector, the laser frequency doubling polarization switching module Including the sixth 45° reflector;

The second 45° reflector is arranged on the reflected light path of the first 45° reflector and the incident light path of the first isolator; the third 45° reflector and the fourth 45° reflector It is arranged between the second laser module and the second isolator, and the third 45° reflector is arranged on the output optical path of the second laser module, and the fourth 45° reflector is arranged on The reflected light path of the third 45° reflector and the incident light path of the second isolator; the fifth 45° reflector is arranged on the output light path of the fourth laser module, and the sixth 45° The reflector is arranged on the reflected optical path of the fifth 45° reflector, and the sixth 45° reflector is arranged on the input optical path of the first half-wave plate.

Optionally, in the above-mentioned high-energy dual-wavelength laser, the laser frequency doubling polarization switching module further includes a seventh 45° reflector and a dichroic mirror, and the seventh 45° reflector is arranged at the second half-wavelength On the output optical path of the plate, the dichroic mirror is arranged on the output optical path of the third half-wave plate and on the reflection optical path of the seventh 45° reflector.

Optionally, in the above-mentioned high-energy dual-wavelength laser, the laser frequency doubling polarization switching module further includes a focusing lens and a collimating lens, and the focusing lens is arranged between the first polarizer and the frequency doubling crystal, The collimator lens is arranged between the frequency doubling crystal and the third half-wave plate.

Optionally, in the above-mentioned high-energy dual-wavelength laser, the second laser module includes 58 bars, the power of each bar is 120W, the peak power of a single module is 7000W, the pump pulse width is 270μs, and the crystal size of the bars is It is 155mm×40mm×6.5mm, the lengths of undoped parts at both ends are 10mm respectively, and the doping concentration of Nd ³⁺ in the middle part is 0.5%.

Optionally, in the above-mentioned high-energy dual-wavelength laser, the third laser module and the fourth laser module both include 83 bars, the power of each bar is 120W, and the peak power of a single module is 10000W. The width is 270μs, the size of the slab crystal is 180mm×50mm×8.5mm, the lengths of the undoped parts at both ends are 15mm respectively, and the doping concentration of Nd ³⁺ in the middle part is 0.7%.

Optionally, in the above-mentioned high-energy dual-wavelength laser, the wavelength of the electro-optic Q-switched switch is 300-1100 nm, the voltage extinction ratio is >2000:1, the 1/4 voltage is 3.3 kV, and the damage threshold is >500 MW/cm ² ; the 1/ The coating center wavelength of the 4-wave plate is 1064nm, and the damage threshold is >20J/cm ² .

Optionally, in the above-mentioned high-energy dual-wavelength laser, the first laser module includes a semiconductor pump and a laser crystal, the wavelength of the semiconductor pump is 809.6 nm, the spectral width is 1.4-2 nm, and the peak power of a single module is 5000 W. The pump pulse width is 300μs; the laser crystal is Nd:YAG cylindrical rod crystal, the doping concentration of Nd ³⁺ is 0.5%, the length is 75-85mm, the end face diameter is 5-7mm, the transmittance of the coating is >99%, and the damage Threshold >5GW/cm ² .

Optionally, in the above-mentioned high-energy dual-wavelength laser, the laser oscillation module further includes a fixing member, and the reflecting mirror and the Gaussian mirror are jointly arranged on the fixing member.

The high-energy dual-wavelength laser provided by this application realizes the dual-wavelength laser with switchable polarization state output by the laser through the combination of a laser oscillation module and a laser frequency doubling polarization switching module. In the laser oscillation module, a corner cube prism is used to fold the nanosecond pulse laser to form a U-shaped folded cavity structure, which can not only help control the size of the laser oscillation module, facilitate use, but also improve the efficiency of the laser. Moreover, the combined use of Gaussian mirrors in the laser oscillation module is beneficial to wide filling of the active medium and weak diffraction on hard-edged holes, and helps to improve the beam quality of the near-field and far-field output lasers output by the laser oscillation module. In the laser frequency doubling polarization switching module, the frequency doubling crystal uses the first half-wave plate, the second half-wave plate and the third half-wave plate to realize the frequency doubling and polarization state switching of the nanosecond pulse laser. Therefore, the high-energy dual-wavelength laser provided by this application is more suitable for the higher requirements for lasers in the fields of laser ranging, laser photoelectric countermeasures, and atmospheric detection.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments or prior art. Obviously, the accompanying drawings in the following description are only some of the present application. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

FIG. 1 is a schematic structural diagram of a high-energy dual-wavelength laser provided according to some embodiments of the present application;

FIG. 2 is a schematic structural diagram of a corner cube provided according to some embodiments of the present application;

FIG. 3 is a schematic structural diagram of another high-energy dual-wavelength laser provided according to some embodiments of the present application;

Fig. 4 is a schematic structural diagram of a second laser module provided according to some embodiments of the present application;

Fig. 5 is a maximum output energy and stability test diagram of a high-energy dual-wavelength laser provided according to some embodiments of the present application;

Figure 6(a) is a laser wavelength curve diagram 1 provided according to some embodiments of the present application;

Figure 6(b) is a laser wavelength graph 2 provided according to some embodiments of the present application;

Fig. 7 is a diagram of the output laser pulse width of a high-energy dual-wavelength laser according to some embodiments of the present application.

in:

100-laser oscillation module, 101-cube prism, 102-polarizer, 103-first laser module, 104-Gaussian mirror, 105-electro-optic Q-switch, 106-1/4 wave plate, 107-mirror, 108 -The first 45° mirror, 200-frequency doubling polarization switching module, 201-the first half-wave plate, 202-the first polarizer, 203-frequency doubling crystal, 204-the third half-wave plate, 205-the second polarization 206-second half-wave plate, 207-focusing lens, 208-collimating lens, 209-mirror, 210-dichroic mirror, 211-sixth 45°reflecting mirror, 300-laser amplification module, 301- The first isolator, 302-the first beam expander, 303-the second laser module, 3031-the first heat sink structure, 3032-single-sided semiconductor pump array, 3033-slab crystal, 3034-the second heat sink structure ; 304-the second isolator, 305-the second beam expander, 306-the third laser module, 307-optical rotator, 308-the fourth laser module, 309-the third 45° reflector, 310-the fourth 45° Reflector, 311-the second 45° reflector, 312-the fifth 45° reflector.

detailed description

In order to enable those skilled in the art to better understand the technical solutions in the present disclosure, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described The embodiments are only some of the embodiments of the present disclosure, not all of them. Based on the embodiments in the present disclosure, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present disclosure.

Fig. 1 is a schematic structural diagram of a high-energy dual-wavelength laser provided according to some embodiments. As shown in Figure 1, the high-energy dual-wavelength laser provided by the embodiment of the present application includes a laser oscillation module 100 and a laser frequency doubling polarization switching module 200; The module 200 is used for laser frequency doubling and polarization state switching to output dual-wavelength polarization state switchable laser; the laser oscillation module 100 is optically connected to the laser frequency doubling polarization switching module 200, and the 1064nm nanosecond pulse laser generated by the laser oscillation module 100 is transmitted to Laser frequency doubling polarization switching module 200. In some embodiments, the 1064nm nanosecond pulse laser generated by the laser oscillation module 100 is energy amplified and then transmitted to the laser frequency doubling polarization switching module 200 .

As shown in Figure 1, in some embodiments, the laser oscillation module 100 includes a corner cube prism 101, the corner cube prism 101 is used to realize the cavity folding of the laser oscillation module 100, and realize the plano-concave folding cavity design of the laser oscillation module 100, a On the one hand, it can replace two or more mirrors, reduce the volume of the laser, and is more conducive to practical applications; on the other hand, based on the structural advantages of the corner cube, the beam quality and efficiency of the laser can be improved.

Fig. 2 is a schematic structural diagram of a corner cube provided according to some embodiments. As shown in Figure 2, one end of the corner cube prism 101 is provided with three mutually perpendicular reflective surfaces, and the other end is provided with an incident surface, and the laser light in the laser oscillator module 100 enters the corner cube prism 101 from the incident surface of the corner cube prism 101, and The three reflective surfaces of the corner cube prism 101 perform three total reflections, and then the outgoing light is always parallel to the incident light but opposite to the transmission direction of the incident light, and the outgoing position and incident position of the light beam on the prism are always relative to the optical axis of the prism Symmetrical, even if the incident angle of the laser is not zero, it will still be reflected by 180°, and the insensitivity to the incident angle can greatly improve the mechanical stability of the structure of the laser oscillation module 100 .

In some embodiments of the present application, the corner cube 101 includes an input end and an output end, and the input end and the output end pass through the incident surface. Due to the reversibility of the optical path, the input end of the corner cube prism 101 is not limited to be used for the direction of the corner cube prism. 101 The input light and the output end are not limited to be used to output light from the corner cube prism 101, that is, the input end of the corner cube prism 101 can both input laser light and output laser light, and the output end of the corner cube prism 101 can output laser light and can also output laser light. Enter the laser.

In some embodiments of the present application, the parameters of the corner cube prism 101 are designed according to the actual optical path requirements; for example, the ratio of the outer diameter d to the height h is about 1.3, such as the outer diameter d is 150mm, and the height h is 115mm; three mutually perpendicular The angle tolerance of the plane is <2′; the wavefront distortion is <λ/10@1064nm.

In some embodiments of the present application, a polarizer 102 , a first laser module 103 , and a Gaussian mirror 104 are sequentially arranged at the output end of the corner cube prism 101 . The first laser module 103 is used for the laser oscillation module 100 to generate the nanosecond pulse laser to provide the pump source and the gain medium; the polarizer 102 is used to adjust the polarization state of the laser in the transmission optical path to ensure the polarization of the nanosecond pulse laser output by the laser oscillation module 100 The state is linearly polarized; the Gaussian mirror 104 is used to output nanosecond pulsed laser light with a wavelength of 1064nm.

In some embodiments of the present application, the input end of the corner cube prism 101 is provided with an electro-optic Q-switching switch 105, a 1/4 wave plate 106 and a mirror 107 in sequence. The 1/4 wave plate 106 is arranged on the electro-optic Q-switching switch 105 and the mirror Between 107, the electro-optic Q-switching switch 105 and the 1/4 wave plate 106 jointly realize the pressurized laser output adjustment of the laser. The mirror 107 is used as the cavity mirror of the laser oscillation module, the central wavelength of the coating is 1064nm, and the reflectivity is >99.9%. Exemplarily, the mirror 107 is a plane mirror.

In some embodiments, the first laser module 103 is side-pumped by a semiconductor rod-shaped laser crystal, so that the first laser module 103 has a higher beam quality, and the nanosecond pulse laser generated by the laser oscillation module has a smaller The divergence angle can extend the range of laser ranging, etc., so that it is suitable for wider applications of lasers in various fields. Exemplarily, the first laser module 103 includes a semiconductor pump and a laser crystal, the wavelength of the semiconductor pump is 809.6nm, the spectral width is 1.4-2nm, the peak power of a single module is 5000W, and the pump pulse width is 300μs; the laser crystal is Nd: YAG cylindrical rod-shaped crystal, Nd ³⁺ doping concentration is 0.5%, length 75-85mm, end face diameter 5-7mm, coating transmittance>99%, damage threshold>5GW/cm ² @1064nm.

The Gaussian mirror 104 is used as the laser cavity mirror of the laser oscillation module 100. Compared with the concave mirror used in the traditional solution, the Gaussian mirror 104 has a circularly symmetric reflectivity distribution provided by a super-Gaussian function, and has the highest reflectivity value in the center , especially for unstable plano-concave laser resonators, it is very beneficial to wide filling of active medium and weak diffraction on hard-edge holes, so it is more conducive to better near-field and far-field beam quality. In some embodiments, the coating center wavelength of the Gaussian mirror 104 is 1064nm, the base material is fused silica, the diameter is >4mm, the laser damage threshold is >10J/cm ² @1064nm, the reflectivity is 65%-85%, and the radius of curvature is -800 ~-1300mm.

The electro-optic Q-switching method of the electro-optic Q-switching switch 105 is usually divided into two types: depressurization type and pressurization type. Potassium, lithium niobate) service life. The specific implementation method is: by adjusting the second time delay to control the duration of the high voltage on the electro-optic crystal, the λ/4 voltage is instantly withdrawn, the threshold in the cavity is rapidly increased, and it returns to the off state. By adjusting the duration of the λ/4 voltage , to "cut off" the laser pulse delay, and adjust the output laser pulse width. For 1/4 wave plate, coating center wavelength is 1064nm, damage threshold > 20J/cm ² ; electro-optic Q-switched switch, wavelength 300-1100nm, voltage extinction ratio > 2000:1, 1/4 voltage 3.3kV, damage threshold > 500MW/ cm ² @1064nm, 10ns.

In the embodiment of the present application, the laser oscillation module 100 is used to generate nanosecond pulse laser with a wavelength of 1064nm, and then in the process of generating nanosecond pulse laser by the laser oscillation module 100, the laser oscillates in the resonant cavity of the laser oscillation module 100, Finally, it is output by the Gaussian mirror 104, and the energy output that the laser oscillation module 100 can achieve is >120mJ@1064nm, 15.5ns.

In some embodiments of the present application, the laser oscillation module 100 also includes a fixing part, and the Gaussian mirror 104 and the reflecting mirror 107 are arranged on the fixing part together, and are used to coordinately adjust the positions of the Gaussian mirror 104 and the reflecting mirror 107, effectively reducing the external temperature, The vibration of the hygrometer disturbs the positions of the Gaussian mirror 104 and the reflective mirror 107 , so as to further improve the stability of the optical path of the laser oscillation module 100 . Exemplarily, the fixing element has a small coefficient of thermal expansion.

The laser frequency doubling polarization switching module 200 includes a first half-wave plate 201 and a first polarizer 202, the first half-wave plate 201 is arranged on the input optical path of the first polarizer 202, and the transmission optical path of the first polarizer 202 is successively multiplied frequency crystal 203 and the third half-wave plate 204, the second polarizer 205 and the second half-wave plate 206 are arranged in turn on the reflection optical path of the first polarizer 202, and the second half-wave plate 206 is arranged on the reflection of the second polarizer 205 on the light path.

The nanosecond pulse laser is transmitted to the laser frequency doubling polarization switching module 200, and then transmitted to the first polarizer 202 after being rotated by the first half-wave plate 201. The laser is divided into two beams by the first polarizer 202 according to the polarization state, and the P polarized light The S-polarized light is reflected by the first polarizer 202 and transmitted on the reflection optical path of the first polarizer 202 . The laser light on the optical path transmitted by the first polarizer 202 is transmitted to the frequency doubling crystal 203, and the frequency doubling crystal 203 generates a 532nm frequency doubling laser. The laser light on the optical path reflected by the first polarizer 202 is reflected by the second polarizer 205, and is parallel to the laser light on the optical path transmitted by the first polarizer 202, so that the output dual-wavelength laser can be transmitted in the same direction, which is convenient for use.

In the embodiment of the present application, the central wavelength of the coating of the first half-wave plate 201 is 1064nm, which is used to rotate and change the energy ratio of the laser in the two linear polarization directions of P and S, so as to achieve the final output energy at the wavelength of 1064nm and 532nm Adjustable; the central wavelength of the coating of the third half-wave plate 204 is 532nm, which is used to change the polarization state through rotation to realize the free switching of the two polarization states of S and P; the central wavelength of the coating of the second half-wave plate 206 is 1064nm. In order to change the polarization state by rotation, the free switching between S and P polarization states can be realized. For example, the first half-wave plate 201, the third half-wave plate 204, and the second half-wave plate 206 use an achromatic zero-order wave plate, which has the advantage of having a very high damage threshold and being insensitive to environmental influences in the wavelength range , to improve the engineering stability of the laser system, the material is magnesium fluoride crystal, the phase delay accuracy should be <λ/120, the wavefront distortion should be <λ/8, and the damage threshold should be >2GW/cm ² , 10J/cm ² , 20ns.

The first polarizer 202 and the second polarizer 205 cooperate to separate P-polarized light and S-polarized light in the laser. Exemplarily, the first polarizer 202 and the second polarizer 205 have a polarization extinction ratio>25dB and a damage threshold>20J/cm ² .

In some embodiments of the present application, the frequency doubling crystal 203 adopts a KTP crystal, the KTP crystal forms an angle of 45° with the optical axis that transmits the first polarizer 202, and the transmittance of the end face coating of the KTP crystal is >99.8%@532nm, so as to obtain Optimum frequency doubling efficiency and avoidance of second harmonic output fluctuations.

In some embodiments of the present application, the laser frequency doubling polarization switching module 200 further includes a focusing lens 207 and a collimating lens 208; The laser focusing of the polarizer 202 is transmitted to the frequency doubling crystal 203; the collimating lens 208 is arranged between the frequency doubling crystal 203 and the third half-wave plate 204, and is used to collimate and transmit the laser beam output by the frequency doubling crystal 203 to the first half-wave plate 204 Three-half wave plate 204. The focusing lens 207 and the collimating lens 208 can effectively adjust the spot size on the transmission optical path of the frequency-doubled laser. The parameters of the focusing lens 207 and the collimating lens 208 are specifically designed according to the frequency doubling crystal and actual needs. The transmittance of the focusing lens 207 is >99.9%@1064nm, the damage threshold is >15J/cm ² , and the transmittance of the collimating lens 208 is > 99.9%@532, damage threshold >15J/cm ² .

In some embodiments of the present application, the laser frequency doubling polarization switching module 200 further includes a seventh 45° reflector 209 and a dichroic mirror 210, and the seventh 45° reflector 209 is arranged on the output optical path of the second half-wave plate 206 , the dichroic mirror 210 is arranged on the reflection optical path of the seventh 45° reflector 209 and is located on the output optical path of the third half-wave plate 204, and the dichroic mirror 210 is used for transmitting the laser light output by the third half-wave plate 204 and Reflect the laser light reflected by the seventh 45° reflector 209 . The dichroic mirror 210 is used as the final output mirror of the laser frequency doubling polarization switching module 200 to realize the output of the laser with a wavelength of 1064nm and the laser with a wavelength of 532nm in the same optical path. Exemplarily, the coating parameters of the dichroic mirror 210 are reflectance>99.5@1064nm and transmittance>99%@532nm. The reflectivity of the seventh 45° mirror 209 is >99.9%@1064nm, and the damage threshold is >20J/cm ² .

The high-energy dual-wavelength laser provided in the embodiment of the present application can realize the output of S-polarized or P-polarized laser light at a single wavelength, which helps to meet different application requirements.

In some embodiments of the present application, the 1064nm nanosecond pulse laser generated by the laser oscillation module 100 is amplified by the laser amplification module and then transmitted to the laser frequency doubling polarization switching module 200 . Fig. 3 is a schematic structural diagram of another high-energy dual-wavelength laser provided according to some embodiments. As shown in FIG. 3 , the high-energy dual-wavelength laser provided in the embodiment of the present application also includes a laser amplification module 300, and the laser amplification module 300 is arranged on the transmission optical path from the laser oscillation module 100 to the laser frequency doubling polarization switching module 200 for The energy amplification of the 1064nm nanosecond pulsed laser generated by the laser oscillation module 100 further ensures that the high-energy dual-wavelength laser can have high-energy laser output.

For example, as shown in FIG. 3 , in the laser amplification module 300 provided in some embodiments of the present application, a first isolator 301 , a first beam expander 302 , a second laser module 303 , and a second isolator are arranged in sequence. 304 , a second beam expander 305 , a third laser module 306 , an optical rotator 307 and a fourth laser module 308 . However, in the embodiment of the present application, the laser amplification module 300 is not limited to the structure shown in FIG. 3 .

In the embodiment of the present application, the 1064nm nanosecond pulse laser generated by the laser oscillation module 100 is transmitted to the laser amplification module 300, and passes through the first isolator 301, the first beam expander 302, the second laser module 303, and the second isolator in sequence. 304, the second beam expander 305, the third laser module 306, the optical rotator 307 and the fourth laser module 308, and finally realize the amplification of laser energy.

The first isolator 301 is used to prevent the return light generated by spontaneous radiation in the optical path at the rear end of the first isolator 301 from being reflected back into the optical path at the front end of the first isolator 301, causing damage to the devices in the optical path at the front end of the first isolator 301, so as to facilitate large Lifetime of Energy Dual Wavelength Lasers. For example, the center wavelength coating of the first isolator 301 is 1064nm, the aperture is 10-20mm, the damage threshold is >10J/cm ² @1064nm, the transmittance is >94%, and the peak isolation is >35dB.

The first beam expander 302 is used to expand and collimate the laser beam passing through the first isolator 301 . The laser spot expanded and collimated by the first beam expander 302 has a larger mode volume, which can match the diameter of the laser spot with the size of the second laser module 303 . As an example, the lens coating of the first beam expander 302 is 1064nm laser damage threshold>20J/cm ² , the beam expansion magnification is 1.2-1.5 times, and the spot diameter after beam expansion is 4.2-5.3mm, so that the laser beam transmitted in the laser amplification module 300 The high coupling ratio is coupled into the second laser module 303 .

The second isolator 304 is used to block the return light generated by spontaneous radiation in the optical path at the rear end of the second isolator 304 from being reflected back into the optical path at the front section, so as to prevent the returned light from damaging the devices in the optical path at the front end of the second isolator 304, In order to improve the service life of the high-energy dual-wavelength laser. For example, the center wavelength coating of the second isolator 304 is 1064nm, the aperture is 10-20mm, the damage threshold is >10J/cm ² @1064nm, the transmittance is >94%, and the peak isolation is >35dB.

The second beam expander 305 is used to expand and collimate the laser beam passing through the second isolator 304 . The laser spot expanded and collimated by the second beam expander 305 has a larger mode volume, which can match the diameter of the laser spot with the size of the third laser module 306 . For example, the lens coating of the second beam expander 305 has a damage threshold of 1064nm laser > 20J/cm ² , the beam expansion ratio is 1.5-2 times, and the spot diameter after beam expansion is 5.3-7mm, so that the laser beam transmitted in the laser amplification module 300 has a high The outcoupling of the coupling ratio enters the third laser module 306 .

The optical rotator 307 is used to rotate the polarization direction of the linearly polarized light to increase the laser amplification energy. Its central wavelength is 1064nm, the rotation angle is 90°, and the transmittance is >99.5%.

In the embodiment of the present application, the second laser module 303 , the third laser module 306 and the fourth laser module 308 are the core components to realize the amplification of the 1064nm nanosecond pulse laser generated by the laser oscillation module 100 . As an example, the second laser module 303, the third laser module 306, and the fourth laser module 308 are slab-side pumped, which can not only help to ensure the advantages of beam quality, but also have low thermal effect, high conversion efficiency, small volume, Long life and other advantages.

Fig. 4 is a schematic structural diagram of a second laser module provided according to some embodiments. As shown in FIG. 4 , the second laser module 303 includes a first heat sink structure 3031 , a single-side semiconductor pump array 3032 , a slab crystal 3033 and a second heat sink structure 3034 . The outside of the single-sided semiconductor pumping array 3032 is in close contact with the first heat sink structure 3031, and the center wavelength of the pumping light is 809.2nm, which is incident on the slab crystal 3033 from the top along the direction of the solid arrow. The slab crystal 3033 adopts a bonded crystal structure, both ends are non-doped YAG, the middle structure is doped with Nd ³⁺ , the cut angle of the end face is 45°, and the laser is zigzag inside the slab, which can effectively reduce the thermal effect. Improve energy amplification efficiency and control beam quality. The second heat sink structure 3034 is in close contact with the slab crystal 3033, and through high-efficiency water cooling and heat dissipation, the crystal is precisely temperature-controlled to prevent the quality of the beam from rapidly deteriorating due to thermal effects. The structures of the third laser module 306 and the fourth laser module 308 may refer to the structure of the second laser module 303 .

In some embodiments of the present application, the second laser module 303 includes 58 bars, the power of each bar is 120W, the peak power of a single module is 7000W, the pump pulse width is 270μs, and the crystal size of the bars is 155mm×40mm× 6.5mm, the length of the undoped part at both ends is 10mm, the doping concentration of Nd ³⁺ in the middle part is 0.5%, the energy of the front laser can be amplified to 270mJ through the second laser module 303, and the corresponding extraction efficiency is about 7.9%. The third laser module 306 and the fourth laser module 308 both include 83 bars, the power of each bar is 120W, the peak power of a single module is 10000W, the pump pulse width is 270μs, and the crystal size of the bars is 180mm×50mm× 8.5mm, the length of the undoped part at both ends is 15mm, and the doping concentration of Nd ³⁺ in the middle part is 0.7%, which can further increase the laser energy to 700mJ, and the corresponding extraction efficiency is about 10.7%.

In some embodiments of the present application, the laser amplification module 300 further includes a third 45° reflector 309 and a fourth 45° reflector 310, and the third 45° reflector 309 and the fourth 45° reflector 310 are arranged on the second laser Between the module 303 and the second isolator 304, the third 45° reflector 309 is arranged on the output light path of the second laser module 303, and the fourth 45° reflector 310 is arranged on the reflection light path of the third 45° reflector 309 , the second isolator 304 is disposed on the reflection light path of the fourth 45° mirror 310 . The third 45° reflector 309 and the fourth 45° reflector 310 cooperate to realize the laser return in the laser amplification module 300 to form a U-shaped optical path structure, reduce the size of the laser amplification module 300, and further reduce the volume of the high-energy dual-wavelength laser. Exemplarily, the coating reflectivity of the third 45° mirror 309 and the fourth 45° mirror 310 is >99.9%@1064nm, and the damage threshold is >20J/cm ² .

In some embodiments of the present application, the laser oscillation module 100 also includes a first 45° reflector 108, the laser amplification module 300 also includes a second 45° reflector 311, and the first 45° reflector 108 is arranged on the output of the Gaussian mirror 104 On the optical path, the second 45° reflector 311 is arranged on the reflection optical path of the first 45° reflector 108 and the second 45° reflector 311 is located on the input optical path of the first isolator 301, and then passes through the second 45° reflector The laser light reflected by 311 is transmitted to the first isolator 301 . The first 45° reflector 108 and the second 45° reflector 311 realize the reentry of the optical path when the laser light generated by the laser oscillation module 100 is transmitted to the laser amplifier module 300 , which helps to control the size of the high-energy dual-wavelength laser. Exemplarily, the reflectivity of the first 45° mirror 108 and the second 45° mirror 311 is >99.9%@1064nm, and the damage threshold is >20J/cm ² .

In some embodiments of the present application, the laser amplification module 300 also includes a fifth 45° reflector 312, the laser frequency doubling polarization switching module 200 also includes a sixth 45° reflector 211, and the fifth 45° reflector 312 is arranged on the fourth On the output light path of the laser module 308, the sixth 45° reflector 211 is arranged on the reflected light path of the fifth 45° reflector 312 and the sixth 45° reflector 211 is arranged on the input light path of the first half-wave plate 201, and then The laser light reflected by the sixth 45° mirror 211 is transmitted to the first half-wave plate 201 . The fifth 45° reflector 312 and the sixth 45° reflector 211 realize the reentry of the optical path when the laser beam is amplified by the laser amplification module 300 and transmitted to the laser frequency doubling polarization switching module 200, which helps to further control the size of the high-energy dual-wavelength laser size. Exemplarily, the reflectivity of the fifth 45° mirror 312 and the sixth 45° mirror 211 is >99.9%@1064nm, and the damage threshold is >20J/cm ² .

Fig. 5 is a maximum output energy diagram of a high-energy dual-wavelength laser provided according to some embodiments of the present application. As shown in Figure 5, by using the energy meter (PE25BF-C) of Ophir Company to test the laser output energy of the high-energy dual-wavelength laser of the embodiment of the present application, the laser oscillator generates laser energy of 120.7mJ, which is increased to 723.5mJ through the laser amplifier , and the energy instability within 4 hours under the maximum output energy is <1.83% rms.

Attenuate the energy by setting the laser attenuation module, and then use the YOKOGAWA (AQ6373B) spectrum analyzer to test the output laser wavelength. Fig. 6(a) is a laser wavelength graph 1 provided according to some embodiments of the present application, and Fig. 6(b) is a laser wavelength graph 2 provided according to some embodiments of the present application. As shown in Figure 6(a) and Figure 6(b), the wavelengths of the dual-wavelength lasers generated by the high-energy dual-wavelength laser are 1064.43nm and 532.11nm respectively, fully meeting the use requirements.

Fig. 7 is a graph of output laser pulse width data of a high-energy dual-wavelength laser according to some embodiments of the present application. As shown in Figure 7, using RIGOL (DS2302A) oscilloscope and Thorlabs (DET10A/M) silicon-based detector to measure the pulse width of the maximum energy output laser reaches 18.3ns. Therefore, the embodiment of the present application provides a high-energy dual-wavelength laser, which can realize linearly polarized high-energy laser output.

High-energy dual-wavelength lasers usually adopt the method of intracavity multi-media series connection, although they can achieve a single pulse energy laser output of several hundred mJ, but their repetition frequency is usually lower than 20Hz. The back-and-forth oscillation, passing through the distorted laser medium many times, the beam quality deteriorates rapidly after the laser goes back and forth many times, and the large divergence angle seriously affects the range and accuracy of laser ranging. This application will adopt the MOPA laser amplification method of Nd:YAG side-pumped oscillator and two-stage side-pumped slab amplifier, which can have the advantages of high beam quality and high energy output, and finally solve the problem of double laser amplification at the current repetition rate of 50-100Hz. The problem of further increasing the wavelength laser energy can achieve 1064nm and 532nm dual wavelengths to achieve energy output of 700mJ and above.

The high-energy dual-wavelength laser provided in this embodiment can also realize laser output with different polarization combinations at two wavelengths. The laser beam output by the laser oscillator module 100 and the laser amplifier 200 is P linearly polarized light as an example for illustration.

Fine-tune the first half-wave plate so that the laser is fully reflected by the first polarizer, then passes through the second polarizer, the second half-wave plate, and the seventh 45° full-reflection mirror, and finally output by the dichroic mirror, testing 1064nm single wavelength The maximum energy of the laser is 711.4mJ. The slight decrease in energy is mainly due to the coating loss of the optical device. The energy instability within 4 hours is <1.52% rms. By adjusting the second half-wave plate, the output of S and P linearly polarized light is realized respectively, and the output energy Almost the same; the polarization extinction ratio of >30dB and high polarization extinction ratio is used to split the two kinds of linearly polarized laser beams respectively, and the polarization extinction ratio is >22dB. It shows that this application can realize high-energy 1064nm laser output, and can freely switch the polarization state.

Fine-tune the first half-wave plate to adjust the polarization state of the laser to P-linearly polarized light, which is transmitted through the first polarizer. Since the dichroic mirror completely reflects the 1064nm laser, a single-wavelength laser of 532nm is finally realized, with a maximum energy of 391.3mJ, 4 The energy instability within hours is less than 1.79% rms, and the output of S and P linearly polarized light can be achieved by adjusting the second half-wave plate, and the polarization beamsplitter prism with >30dB high polarization extinction ratio is used to split the two kinds of linearly polarized laser light Test, polarization extinction ratio> 21dB. It shows that this application can realize high-energy 532nm laser output, and can freely switch the polarization state.

Adjust the first half-wave plate so that the energy ratio of the two polarization states is close to 1:1, that is, the energy of the transmitted light and reflected light of the laser through the first polarizer is equal, and finally realize the dual-wavelength laser of 1064nm and 532nm, through the dichroic mirror Spectroscopic test, the maximum energy of 1064nm wavelength is 350.3mJ, the maximum output energy of 532nm wavelength is 200mJ, and the energy instability within 4 hours is less than 2.3% rms. S and P linear polarization state switching can be realized by adjusting the second half-wave plate and the third half-wave plate respectively, and the tested polarization extinction ratios are all >20dB. It shows that this application can simultaneously realize high-energy 1064nm and 532nm dual-wavelength laser output, and can switch the respective polarization states.

In this way, the high-energy dual-wavelength laser provided by the embodiment of the present application can achieve a laser output with a maximum energy of 700mJ. At the same time, the energy ratio at the dual wavelengths of 1064nm and 532nm can be adjusted, and the polarization state can be switched freely, which is very conducive to improving the laser distance measurement. The practical application effect in fields such as laser distance measurement can meet the higher requirements for lasers in fields such as laser ranging.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them; although the present disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present disclosure.

Claims (10)

1. A high-energy dual-wavelength laser, characterized in that, includes: a laser oscillation module and a laser frequency doubling polarization switching module, the laser oscillation module is optically connected to the laser frequency doubling polarization switching module, and the laser oscillation module is used To generate a nanosecond pulse laser with a wavelength of 1064nm, the laser frequency doubling polarization switching module is used to output a dual-wavelength polarization state switchable laser; wherein: The laser oscillation module includes a corner cube, the output of the corner cube is sequentially provided with a polarizer, the first laser module and a Gaussian mirror, and the input of the corner cube is sequentially provided with an electro-optical Q-switching switch, a 1/4 wave sheet and reflector, the nanosecond pulse laser generated in the laser oscillation module is transmitted through the Gaussian mirror, and the first laser module is side-pumped by a semiconductor rod-shaped laser crystal; The laser frequency doubling polarization switching module includes a first half-wave plate and a first polarizer, the first half-wave plate is arranged on the input optical path of the first polarizer, and the transmission optical path of the first polarizer is A frequency doubling crystal and a third half-wave plate are set in sequence, a second polarizer is set on the reflection optical path of the first polarizer, and a second half-wave plate is set on the reflection light path of the second polarizer. 2. The high-energy dual-wavelength laser according to claim 1, further comprising a laser amplification module, the laser amplification module is arranged on the transmission optical path from the laser oscillation module to the laser frequency doubling polarization switching module , for the energy amplification of the nanosecond pulse laser output by the laser oscillation module; The laser amplification module includes a first isolator, a first beam expander, a second laser module, a second isolator, a second beam expander, a third laser module, an optical rotator and a fourth laser module; The second laser module, the third laser module and the fourth laser module are slab side pumped. 3. The high-energy dual-wavelength laser according to claim 2, wherein the laser oscillation module also includes a first 45° reflector, and the laser amplification module also includes a second 45° reflector, a third 45° °reflector, the fourth 45°reflector and the fifth 45°reflector, the laser frequency doubling polarization switching module includes the sixth 45°reflector; The second 45° reflector is arranged on the reflected light path of the first 45° reflector and the incident light path of the first isolator; the third 45° reflector and the fourth 45° reflector It is arranged between the second laser module and the second isolator, and the third 45° reflector is arranged on the output optical path of the second laser module, and the fourth 45° reflector is arranged on The reflected light path of the third 45° reflector and the incident light path of the second isolator; the fifth 45° reflector is arranged on the output light path of the fourth laser module, and the sixth 45° The reflector is arranged on the reflected optical path of the fifth 45° reflector, and the sixth 45° reflector is arranged on the input optical path of the first half-wave plate. 4. The high-energy dual-wavelength laser according to claim 1, wherein the laser frequency doubling polarization switching module also includes a seventh 45° reflector and a dichroic mirror, and the seventh 45° reflector is set On the output optical path of the second half-wave plate, the dichroic mirror is arranged on the output optical path of the third half-wave plate and on the reflection optical path of the seventh 45° reflector. 5. The high-energy dual-wavelength laser according to claim 1, wherein the laser frequency doubling polarization switching module also includes a focusing lens and a collimating lens, and the focusing lens is arranged on the first polarizer and the Between the frequency doubling crystals, the collimator lens is arranged between the frequency doubling crystals and the third half-wave plate. 6. The high-energy dual-wavelength laser according to claim 2, wherein the second laser module includes 58 bars, each bar has a power of 120W, a single module peak power of 7000W, and a pump pulse width of The slab crystal size is 155mm×40mm×6.5mm, and the lengths of the undoped parts at both ends are 10mm respectively. 7. The high-energy dual-wavelength laser according to claim 2, wherein the third laser module and the fourth laser module both include 83 bars, each bar has a power of 120W, and the peak value of a single module The power is 10000W, the pump pulse width is 270μs, the size of the slab crystal is 180mm×50mm×8.5mm, and the lengths of the undoped parts at both ends are 15mm respectively. 8. The high-energy dual-wavelength laser according to claim 1, wherein the wavelength of the electro-optic Q-switched switch is 300-1100nm, the voltage extinction ratio is >2000:1, the 1/4 voltage is 3.3kV, and the damage threshold is >500MW/ cm ² ; the coating center wavelength of the 1/4 wave plate is 1064nm, and the damage threshold is >20J/cm ² . 9. The high-energy dual-wavelength laser according to claim 1, wherein the first laser module includes a semiconductor pump and a laser crystal, the wavelength of the semiconductor pump is 809.6nm, and the spectral width is 1.4-2nm. The peak power of a single module is 5000W, and the pump pulse width is 300μs; the laser crystal is a Nd:YAG cylindrical rod crystal with a length of 75-85mm and an end diameter of 5-7mm. The transmittance of the coating is >99%, and the damage threshold is >5GW/ cm ² . 10. The high-energy dual-wavelength laser according to claim 1, wherein the laser oscillation module further comprises a fixing member, and the reflecting mirror and the Gaussian mirror are jointly arranged on the fixing member.

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