Medium-wave infrared ZGP crystal damage threshold and conversion efficiency dual-mode switchable testing device and method

Abstract

The invention relates to the field of laser testing, and discloses a medium-wave infrared ZGP crystal damage threshold and conversion efficiency dual-mode switchable testing device which comprises a 1.9 [mu] m laser light source output light path assembly. A 2.1 [mu] m laser output light path assembly; the light path switching assembly is used for switching the damage threshold testing light path assembly and the conversion efficiency testing light path assembly; the damage threshold testing light path assembly is provided with an energy meter and a high-speed camera and monitors light spot energy and surface topography changes in real time; the device provided by the invention has the advantages that the testing process is full-automatic, and the testing efficiency is high; the switching test of the laser damage threshold value and the conversion efficiency of the ZGP crystal can be realized by electrically controlling the switching optical path, the diameter and the energy of a light spot are measured in real time, the range application is wider, and comprehensive judgment is more accurate by adopting an online damage threshold value judgment method.

Description

Technical Field

[0001] The present invention relates to the field of laser testing, and specifically to a dual-mode switchable testing device and method for the damage threshold and conversion efficiency of a mid-wave infrared ZGP crystal. Background Technique

[0002] The core material of mid-wave infrared (3 - 5μm) laser technology, zinc germanium phosphate (ZGP) crystal, with its wide light transmission range and high nonlinear coefficient, is widely used in devices such as optical parametric oscillators. Its damage threshold and optical-optical conversion efficiency are key indicators determining the performance of laser systems. However, traditional testing techniques have significant defects: 1) Functional separation: The damage threshold and conversion efficiency need to be tested with independent optical paths. The equipment is redundant and the switching and calibration take dozens of minutes, unable to meet the mass production requirements; 2) Insufficient accuracy: The measurement of the spot radius depends on subjective judgment (error > 5%), and the influence of the spot frequency and pulse repetition frequency is ignored, resulting in systematic errors in the calculation of the energy density; 3) Unable to obtain the performance correlation between the damage threshold and conversion efficiency under the same beam quality: High conversion efficiency may exacerbate local energy concentration and reduce the damage threshold, making it difficult to comprehensively evaluate the crystal performance.

[0003] Therefore, there is a need to propose an integrated and switchable high-precision testing device to achieve rapid switching measurement of the damage threshold and conversion efficiency of mid-wave infrared ZGP crystals, so as to improve the testing efficiency and detection accuracy. Based on this, this application proposes a dual-mode switchable testing device and method for the damage threshold and conversion efficiency of mid-wave infrared ZGP crystals. Summary of the Invention

[0004] The purpose of the present invention is to provide a dual-mode switchable testing device and method for the damage threshold and conversion efficiency of a mid-wave infrared ZGP crystal, so as to solve the problems raised in the above background technique.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A dual-mode switchable testing device for the damage threshold and conversion efficiency of a mid-wave infrared ZGP crystal, including a 1.9μm laser light source output optical path component; a 2.1μm laser output optical path component; an optical path switching component for switching between the damage threshold testing optical path component and the conversion efficiency testing optical path component; a damage threshold testing optical path component configured with an energy meter and a high-speed camera to monitor the spot energy and surface morphology changes in real time; a conversion efficiency testing optical path component.

[0006] Preferably: The 1.9μm laser light source output optical path component includes a plurality of vertically arranged semiconductor lasers as pump sources, and the output wavelength of the semiconductor lasers is 793nm.

[0007] Preferably: The transverse pump source uses two 40W 793nm semiconductor lasers, which respectively pass through condenser lenses, and then enter the Tm:YLF crystal resonator through a 793nm dichroic mirror to generate 1.9μm laser. And the longitudinal pump source uses two 40W 793nm semiconductor lasers, which respectively pass through condenser lenses, and then enter the Tm:YLF crystal resonator through a 793nm dichroic mirror to generate 1.9μm laser. The transverse pump source and the longitudinal pump source respectively pass through a Fabry-Perot interferometer and an output coupler for enhanced output of 1.9μm laser.

[0008] Preferably: The 2.1μm laser output optical path assembly includes a double-end pumped single crystal Ho:YAG laser with a U-shaped cavity structure, and the laser gain medium is a Ho:YAG crystal with a length of 100mm and a doping concentration of 0.3at%. The resonator is composed of a zero-degree total reflection mirror, two 45-degree cavity mirrors and an output coupler.

[0009] Preferably: Both end faces of the Ho:YAG crystal are coated with a film layer that is highly transmissive to the oscillating light of 2.1μm and the pump light of 1.9μm, and the surfaces of the two cavity mirrors are coated with a film that is highly reflective to 2.1μm at a 45° angle and highly transmissive to 1.9μm.

[0010] Preferably: The optical path switching assembly includes an electrically controlled rotating table, and the reflecting mirror is fixedly installed on the middle bracket of the electrically controlled rotating table and is controlled by an electrically controlled rotating shaft. One side of the electrically controlled rotating table is electrically connected to an electric control component, and the electric control component includes a power-on key, a power-off key, a height adjustment rotary knob, an angle adjustment rotary knob, a circuit board, a fan and connecting wires for controlling the electrically controlled rotating table and the reflecting mirror installed thereon.

[0011] Preferably: The ZGP crystal device of the damage threshold test optical path assembly is wrapped with indium platinum and placed in a water-cooled copper heat sink with the temperature controlled at 16°C. And the damage threshold test optical path assembly is equipped with an energy meter and a high-speed camera to monitor the laser output energy, the laser spot size and the crystal surface morphology.

[0012] Preferably: The conversion efficiency test optical path assembly includes a ring cavity composed of four cavity mirrors. Among them, the input mirror is highly transmissive to the 2.1μm pump light and highly reflective to the signal light; the cavity mirror is highly reflective to the signal light and highly transmissive to the idler light; the output mirror is highly transmissive to the pump light and the idler light and has a reflectivity of Rs = 50% to the signal light. The ZGP crystal is wrapped with indium platinum and placed in a water-cooled copper heat sink and installed on an adjustment bracket that can adjust the angle between the crystal and the pump light. The laser output at the output mirror includes the remaining 2.1μm pump light, signal light and idler light, and the lens is highly transmissive to the 2.1μm pump light and highly reflective to the signal light and the idler light.

[0013] According to the usage method of a mid-infrared ZGP crystal damage threshold and conversion efficiency dual-mode switchable test device described above, the working process of the damage threshold test optical path component is as follows. Along the transmission direction of the laser beam, the spot radius value of the laser at a certain position on the crystal interface is measured using the 90 / 10 knife-edge method. The test method of the 90 / 10 knife-edge method is to measure the position points X90% and X10% corresponding to the knife-edge when the transmitted power is 90% and 10% of the laser power respectively. Laser energy density: The incident power of the laser is P (W), the repetition frequency of the laser pulse is RF (kHz), and the spot area of the laser at a specific position is S (mm). Then the average laser energy density at this position is

[0014]

[0015] The peak laser energy density at this position is

[0016]

[0017] Then the peak laser energy density on the incident surface of the ZGP crystal is:

[0018]

[0019] The incident laser irradiates the ZGP crystal for 30 s. The camera monitors that no damage occurs to the crystal and the film layer, and the value of the laser damage threshold is calculated based on the laser energy density.

[0020] The beneficial effects of the present invention compared with the prior art are as follows:

[0021] The device of the present invention has a fully automatic test process and high test efficiency; it can realize the switching test of the laser damage threshold and conversion efficiency of the ZGP crystal by electronically controlling the switching of the optical path, measure the spot diameter and energy in real time, has a wider applicable range, and uses an online damage threshold discrimination method for comprehensive discrimination, which is more accurate. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the device of the present invention;

[0023] Figure 2 It is an optical path diagram of the device of the present invention;

[0024] Figure 3 It is a three-dimensional structural diagram of the high-precision hollow rotary table and electronic control device of the present invention;

[0025] Figure 4 It is a conversion efficiency diagram of the crystal device (210312) in the embodiment of the present invention;

[0026] Figure 5 It is a conversion efficiency diagram of the crystal device (210316) in the embodiment of the present invention;

[0027] Figure 6 This is the conversion efficiency diagram of the crystal device (210313) in the embodiment of the present invention.

[0028] In the figure: 101 - semiconductor laser with an output wavelength of 793 nm; 102 - plano-convex lens with a focal length of 40 mm; 103, 105 - dichroic mirrors, coated with a 793 nm high-transmission film and a 1.9 μm high-reflection film; 104 - Tm:YLF crystal with a doping concentration of 2 at.%; 106 - YAG sheet; 107 - output coupling mirror of the Tm:YLF laser; 108, 110, 111 - total reflection mirrors; 109 - plano-convex lens with a focal length of 200 mm; 112 - 1.9 μm volume Bragg reflector; 201 - dichroic mirror, coated with a 1.9 μm high-transmission film and a 2.1 μm high-reflection film; 202 - Ho:YAG crystal with a doping concentration of 0.6 at.%; 203 - acousto-optic modulator, coated with a 2 μm antireflection film; 204 - output coupling mirror of the Ho:YAG laser, coated with a 2.1 μm partial reflection film; 205 - total reflection mirror; 206 - 2.1 μm half-wave plate; 207 - all-optical reflection mirror; 208 - 2.1 μm volume Bragg reflector; 301 - copper heat sink bracket; 302 - zinc germanium phosphide crystal; 303 - camera; 304 - cooling water; 5 - electronic control device; 6 - hollow rotary table; 401 - total reflection mirror; 402 - dichroic mirror, coated with a 2.1 μm high-transmission film and a 3 - 5 μm high-reflection film; 403 - copper heat sink bracket; 404 - zinc germanium phosphide; 405 - output mirror of the OPO, coated with a 2.1 μm high-transmission film and a 3 - 5 μm partial transmission film; 406 - cooling water. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Embodiment 1

[0031] Please refer to Figures 1 - 4 , a mid-wave infrared ZGP crystal damage threshold and conversion efficiency dual-mode switchable test device and method in the figure, including a 1.9 μm laser light source output optical path component; a 2.1 μm laser output optical path component; an optical path switching component for switching between a damage threshold test optical path component and a conversion efficiency test optical path component; a damage threshold test optical path component configured with an energy meter and a high-speed camera to monitor the spot energy and surface morphology changes in real time; a conversion efficiency test optical path component.

[0032] In this embodiment, the output optical path component of the 1.9-μm laser source includes several vertically arranged semiconductor lasers as pump sources, and the output wavelength of the semiconductor lasers is 793 nm. The transverse pump source uses two 40-W 793-nm semiconductor lasers that respectively pass through condenser lenses and then enter the Tm:YLF crystal resonator through a 793-nm dichroic mirror to generate 1.9-μm laser. The longitudinal pump source also uses two 40-W 793-nm semiconductor lasers that respectively pass through condenser lenses and then enter the Tm:YLF crystal resonator through a 793-nm dichroic mirror to generate 1.9-μm laser. The transverse pump source and the longitudinal pump source respectively pass through a Fabry-Perot interferometer and an output coupling mirror for enhanced output of the 1.9-μm laser. The output optical path component of the 2.1-μm laser includes a double-end-pumped single-crystal Ho:YAG laser with a U-shaped cavity structure, and the laser gain medium is a Ho:YAG crystal with a length of 100 mm and a doping concentration of 0.3 at%. The resonator is composed of a zero-degree total reflector, two 45-degree cavity mirrors, and an output coupling mirror. Both end faces of the Ho:YAG crystal are coated with a film layer that is highly transmissive to the oscillating light of 2.1 μm and the pump light of 1.9 μm, and the surfaces of the two cavity mirrors are coated with a film that is highly reflective to 2.1 μm at a 45° angle and highly transmissive to 1.9 μm.

[0033] Further, the optical path switching component includes an electrically controlled rotating table, and the reflecting mirror is fixedly installed on the middle bracket of the electrically controlled rotating table and is controlled by an electrically controlled rotating shaft. One side of the electrically controlled rotating table is electrically connected to an electrical control component, and the electrical control component includes a power-on button, a power-off button, a height adjustment rotary knob, an angle adjustment rotary knob, a circuit board, a fan, and connecting wires for controlling the electrically controlled rotating table and the reflecting mirror installed thereon. The ZGP crystal device of the damage threshold test optical path component is wrapped with indium-platinum and placed in a water-cooled copper heat sink with the temperature controlled at 16°C. The damage threshold test optical path component is equipped with an energy meter and a high-speed camera to monitor the laser output energy, the laser spot size, and the surface morphology of the crystal. The conversion efficiency test optical path component includes a ring cavity composed of four cavity mirrors. Among them, the input mirror is highly transmissive to the 2.1-μm pump light and highly reflective to the signal light; the cavity mirror is highly reflective to the signal light and highly transmissive to the idler light; the output mirror is highly transmissive to the pump light and the idler light and has a reflectivity of Rs = 50% to the signal light. The ZGP crystal is wrapped with indium-platinum and placed in a water-cooled copper heat sink and installed on an adjustment bracket that can adjust the angle between the crystal and the pump light. The laser output at the output mirror includes the remaining 2.1-μm pump light, signal light, and idler light, and the lens is highly transmissive to the 2.1-μm pump light and highly reflective to the signal light and the idler light.

[0034] The working process of the optical path component for damage threshold testing is as follows. Along the transmission direction of the laser beam, the spot radius value of the laser at a certain position on the crystal interface is measured using the 90 / 10 knife-edge method. The test method of the 90 / 10 knife-edge method is to measure the position points X90% and X10% (unit: mm) corresponding to the knife-edge when the transmitted power is 90% and 10% of the laser power respectively. The spot radius at the laser incident surface position of the ZGP crystal actually measured is shown in Table 1.

[0035] Table 1 Data table of spot radius

[0036] Spot radius w data (mm) x - axis 0.236 y - axis 0.246

[0037] Laser energy density: If the incident power of the laser is P (W), the repetition frequency of the laser pulse is RF (kHz), and the spot area at a specific position of the laser is S (mm), then the average laser energy density at this position is

[0038]

[0039] The peak laser energy density at this position is

[0040]

[0041] Then the peak laser energy density at the incident surface of the ZGP crystal is:

[0042]

[0043] The incident laser irradiates the ZGP crystal for 30 s, and the camera monitors that no damage occurs to the crystal and the film layer. The value of the laser damage threshold is calculated based on the laser energy density.

[0044] According to Table 1, it is measured that Paverage = 18.30 mJ, that is, its laser damage threshold is 18.30 mJ / mm 2 .

[0045] In this embodiment, the optical path remains unchanged, and the ZnGeP2 crystal device to be tested is replaced. The size of the No. 210316 ZnGeP2 crystal is 15 mm × 15 mm × 6 mm. First, place the crystal device on the copper heat sink bracket 301, make it fit tightly with the bracket, and at the same time introduce cooling water to maintain 16 degrees. Adjust the all-optical mirror 207 on the hollow rotating table 6 so that the mirror forms a 45-degree angle with the pump light. After waiting for 2 min to stabilize, gradually increase the input power, keep each measurement for 30 s, and observe and record the state of the crystal light-transmitting surface through the camera 303. When the crystal surface is damaged, the input power is 18.32 mJ, and the calculated laser damage threshold is 2.010 J / cm2.

[0046]

[0047] Then, take out the ZnGeP2 crystal device numbered 210316, and place it on the copper heat sink bracket 403, making it fit tightly with the bracket. At the same time, introduce cooling water to maintain a temperature of 16°C. Adjust the total reflection mirror on the high-precision hollow rotary table so that the mirror is parallel to the incident direction of the pump light, and make the pump light enter the ring cavity through the total reflection mirror. Each measurement requires the optical path to be stable for 30 s. Record the values using a power meter respectively. When the pump power is 12.4 W, the output power is 2.1 W; when the pump power is 15.9 W, the output power is 4.6 W; when the pump power is 19.3 W, the output power is 7.4 W; when the pump power is 22.6 W, the output power is 9.6 W. The slope efficiency is obtained by fitting as 74.4%. Refer to Figure 5 。

[0048] Example 2

[0049] In this example, the optical path remains unchanged, and the ZnGeP2 crystal device to be measured is replaced. The size of the ZnGeP2 crystal numbered 210313 is 6 mm × 6 mm × 20 mm. First, place the crystal device on the copper heat sink bracket 301, making it fit tightly with the bracket. At the same time, introduce cooling water to maintain a temperature of 16°C. Adjust the total reflection mirror 207 on the hollow rotary table 6 so that the mirror forms a 45-degree angle with the pump light. After waiting for 2 min to stabilize, gradually increase the input power. Each measurement is maintained for 30 s. Observe and record the state of the light-passing surface of the crystal through the camera 303. When the surface of the crystal is damaged, the input power is 18.36 mJ, and the laser damage threshold is calculated to be 2.014 J / cm2.

[0050]

[0051] Then, take out the ZnGeP2 crystal device numbered 210316, and place it on the copper heat sink bracket 403, making it fit tightly with the bracket. At the same time, introduce cooling water to maintain a temperature of 16°C. Adjust the total reflection mirror on the high-precision hollow rotary table so that the mirror is parallel to the incident direction of the pump light, and make the pump light enter the ring cavity through the total reflection mirror. Each measurement requires the optical path to be stable for 30 s. Record the values using a power meter respectively. When the pump power is 12.4 W, the output power is 2.2 W; when the pump power is 15.9 W, the output power is 4.7 W; when the pump power is 19.3 W, the output power is 7.1 W; when the pump power is 22.6 W, the output power is 9.2 W. The slope efficiency is obtained by fitting as 68.8%. Refer to Figure 6 。

[0052] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0053] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A testing device for dual-mode switchable damage threshold and conversion efficiency of mid-wave infrared ZGP crystal, characterized in that, Comprising: 1.9μm laser light source output optical path component; 2.1μm laser output optical path component; an optical path switching component for switching between a damage threshold test optical path component and a conversion efficiency test optical path component; a damage threshold test optical path component configured with an energy meter and a high-speed camera to monitor the spot energy and surface topography changes in real time; a conversion efficiency test optical path component.

2. The dual-mode switchable test device for the damage threshold and conversion efficiency of a mid-wave infrared ZGP crystal according to claim 1, wherein: The 1.9μm laser light source output optical path component includes a plurality of vertically arranged semiconductor lasers as pump sources, and the output wavelength of the semiconductor lasers is 793nm.

3. A mid-wave infrared ZGP crystal damage threshold and conversion efficiency dual-mode switchable test device according to claim 2, characterized in that: The horizontal pump source uses two 40W 793nm semiconductor lasers respectively passing through condenser lenses, and then entering the Tm:YLF crystal resonator through a 793nm dichroic mirror to generate 1.9μm laser, and the vertical pump source uses two 40W 793nm semiconductor lasers respectively passing through condenser lenses, and then entering the Tm:YLF crystal resonator through a 793nm dichroic mirror to generate 1.9μm laser. The horizontal pump source and the vertical pump source respectively pass through a Fabry-Perot interferometer and an output coupler for enhanced output of 1.9μm laser.

4. A mid-wave infrared ZGP crystal damage threshold and conversion efficiency dual-mode switchable test device according to claim 3, characterized in that: The 2.1μm laser output optical path component includes a double-end pumped single crystal Ho:YAG laser with a U-shaped cavity structure, and the laser gain medium is a Ho:YAG crystal with a length of 100mm and a doping concentration of 0.3at%. The resonator is composed of a zero-degree total reflector, two 45-degree cavity mirrors and an output coupler.

5. A dual-mode switchable test device for the damage threshold and conversion efficiency of a mid-wave infrared ZGP crystal according to claim 4, characterized in that: Both end faces of the Ho:YAG crystal are coated with a film layer that is highly transmissive to the oscillating light of 2.1μm and the pump light of 1.9μm, and the surfaces of the two cavity mirrors are coated with a film that is highly reflective to 2.1μm at a 45° angle and highly transmissive to 1.9μm.

6. A mid-wave infrared ZGP crystal damage threshold and conversion efficiency dual-mode switchable test device according to claim 5, characterized in that: The optical path switching component includes an electrically controlled rotating table, and a reflecting mirror is fixedly installed on the middle bracket of the electrically controlled rotating table and controlled by an electrically controlled rotating shaft. One side of the electrically controlled rotating table is electrically connected with an electrical control component, and the electrical control component includes a power on key, a power off key, a height adjustment rotary knob, an angle adjustment rotary knob, a circuit board, a fan and connecting wires for controlling the electrically controlled rotating table and the reflecting mirror installed thereon.

7. A mid-wave infrared ZGP crystal damage threshold and conversion efficiency dual-mode switchable test device according to claim 6, characterized in that: The ZGP crystal device of the damage threshold test optical path component is wrapped with indium platinum and placed in a water-cooled copper heat sink with the temperature controlled at 16°C, and the damage threshold test optical path component is configured with an energy meter and a high-speed camera to monitor the laser output energy, the laser spot size and the crystal surface topography.

8. A mid-wave infrared ZGP crystal damage threshold and conversion efficiency dual-mode switchable test device according to claim 7, characterized in that: The conversion efficiency test optical path component includes an annular cavity composed of four cavity mirrors. Among them, the input mirror is highly transmissive to the 2.1μm pump light and highly reflective to the signal light; the cavity mirror is highly reflective to the signal light and highly transmissive to the idler light; the output mirror is highly transmissive to the pump light and the idler light and has a reflectivity of Rs = 50% to the signal light. The ZGP crystal is wrapped with indium platinum and placed in a water-cooled copper heat sink, and is installed on an adjustment bracket that can adjust the angle between the crystal and the pump light. The laser output at the output mirror includes the remaining 2.1μm pump light, signal light and idler light, and the lens is highly transmissive to the 2.1μm pump light and highly reflective to the signal light and idler light.

9. A method for using a testing device with dual-mode switchable damage threshold and conversion efficiency of a mid-wave infrared ZGP crystal according to any one of claims 1-8, characterized in that: The working process of the damage threshold test optical path component is as follows. Along the transmission direction of the laser beam, the spot radius value of the laser at a certain position on the crystal interface is measured by the 90 / 10 knife-edge method. The test method of the 90 / 10 knife-edge method is to measure the position points X90% and X10% corresponding to the knife-edge when the transmitted power is 90% and 10% of the laser power respectively. Laser energy density: The incident power of the laser is P (W), the repetition frequency of the laser pulse is RF (kHz), and the spot area of the laser at a specific position is S (mm). Then the average laser energy density at this position is The peak laser energy density at this position is Then the peak laser energy density on the incident surface of the ZGP crystal is: The incident laser irradiates the ZGP crystal for 30 s, and the camera monitors that no damage occurs to the crystal and the film layer. The numerical value of the laser damage threshold is calculated based on the laser energy density.

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