Composite cavity nonlinear laser frequency conversion device

Abstract

The invention discloses a composite cavity nonlinear laser frequency conversion device. The device comprises a laser gain module, a first resonant cavity, a second resonant cavity and a nonlinear crystal, the laser gain module is used for radiating the laser of the first wavelength and the laser of the second wavelength; the first resonant cavity is used for generating first oscillation laser, the wavelength of the first oscillation laser is a first wavelength, and the first oscillation laser is not output to the first resonant cavity; the second resonant cavity is used for generating second oscillation laser, the second oscillation laser is injected into the first resonant cavity, and the wavelength of the second oscillation laser is a second wavelength; and the nonlinear crystal is arranged in the first resonant cavity and is used for carrying out frequency conversion on the first oscillation laser and the second oscillation laser to generate frequency conversion laser, and the frequency conversion laser is output by the first resonant cavity. According to the invention, the characteristics of intra-cavity frequency conversion and extra-cavity frequency conversion are combined, the mode matching of the nonlinear crystal is easy to realize, the frequency conversion efficiency is effectively improved, and a new way is provided for generating high-power and high-beam-quality frequency conversion laser.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and more specifically to a composite cavity nonlinear laser frequency conversion device. Background Art

[0002] Laser sources are widely used in many fields such as science, economy and military. With the development of society, the demand for special wavelength lasers is increasing. In addition to exploring new laser working media, nonlinear optical frequency conversion of optical materials is also an effective way to enrich laser wavelengths. In a stably working nonlinear crystal, there are multiple nonlinear effects such as frequency doubling, sum frequency and difference frequency. Laser outputs of different wavelengths can be obtained by replacing different filter devices. According to the location of the nonlinear crystal in the laser resonant cavity or outside the cavity, the frequency conversion method is divided into two methods: intracavity frequency conversion and extracavity frequency conversion. Intracavity frequency conversion makes full use of the advantages of high intracavity laser power density and is easy to obtain high conversion efficiency and output power. However, since intracavity frequency doubling realizes the frequency conversion of two wavelength lasers, it is necessary to adjust the two laser beams to be collinear in the cavity to achieve phase matching of the nonlinear crystal, and the optical path debugging is more difficult; extracavity frequency conversion is easy to obtain good beam quality, simple structure and easy to achieve phase matching of nonlinear crystals, but due to the single pass of the laser through the nonlinear crystal, the frequency conversion efficiency is low. Summary of the invention

[0003] The present invention provides a composite cavity nonlinear laser frequency conversion device to solve at least one of the problems existing in the prior art.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a composite cavity nonlinear laser frequency conversion device, which comprises a laser gain module, a first resonant cavity, a second resonant cavity and a nonlinear crystal, wherein the nonlinear crystal is arranged in the first resonant cavity;

[0006] The laser gain module is used to radiate laser light of a first wavelength and laser light of a second wavelength;

[0007] The first resonant cavity is used to generate a first oscillating laser, the wavelength of the first oscillating laser is a first wavelength, and the first oscillating laser does not output the first resonant cavity;

[0008] The second resonant cavity is used to generate a second oscillating laser, the wavelength of the second oscillating laser is a second wavelength, and the second oscillating laser is injected into the first resonant cavity;

[0009] The nonlinear crystal is used to perform frequency conversion on the first oscillating laser and the second oscillating laser to generate frequency-converted laser, and the frequency-converted laser is output by the first resonant cavity.

[0010] Optionally, the first resonant cavity comprises a first reflector, a first beam splitter and a second beam splitter, the second resonant cavity comprises a first reflector and a first output mirror, the laser gain module is arranged between the first reflector and the first beam splitter, and the nonlinear crystal is arranged between the first beam splitter and the second beam splitter;

[0011] The first reflector is used to reflect the laser light of the first wavelength and the laser light of the second wavelength, the first beam splitter is used to reflect the laser light of the first wavelength to the second beam splitter and transmit it through the nonlinear crystal, the first beam splitter is also used to transmit the laser light of the second wavelength and output frequency-converted laser light; the second beam splitter is used to reflect the laser light of the first wavelength back to the first beam splitter and the first reflector, the laser light of the first wavelength oscillates in the first resonant cavity to generate a first oscillated laser light, and the second beam splitter is also used to transmit the second oscillated laser light;

[0012] The first output mirror is used to reflect the laser light of the second wavelength back to the first beam splitter to generate a second oscillating laser light, transmit the second oscillating laser light to output the second resonant cavity, and inject the second oscillating laser light into the first resonant cavity through the second beam splitter.

[0013] Optionally, the device further comprises a birefringent filter disposed between the laser gain module and the first reflector, wherein the birefringent filter is placed in a Brewster angle manner and is used to convert the laser light of the first wavelength into a laser light of the first wavelength in a horizontal polarization state, and convert the laser light of the second wavelength into a laser light of the second wavelength in a horizontal polarization state;

[0014] The birefringent filter is also used to adjust the intensities of the first oscillation laser light and the second oscillation laser light.

[0015] Optionally, the laser gain module includes a first laser gain module for outputting laser light of a first wavelength and a second laser gain module for outputting laser light of a second wavelength.

[0016] Optionally, the first resonant cavity includes a second reflector, a second beam splitter and a third beam splitter, the second resonant cavity includes a third reflector and a second output mirror, the first laser gain module is arranged between the second reflector and the third beam splitter, the nonlinear crystal is arranged between the third beam splitter and the second beam splitter, and the second laser gain module is arranged between the third reflector and the second output mirror;

[0017] The second reflector is used to reflect the laser light of the first wavelength, the third beam splitter is used to reflect the laser light of the first wavelength to the second beam splitter and transmit the laser light through the nonlinear crystal, and is also used to output frequency-converted laser light; the second beam splitter is used to reflect the laser light of the first wavelength back to the third beam splitter and the second reflector, and the laser light of the first wavelength oscillates in the first resonant cavity to generate a first oscillated laser light;

[0018] The third reflector is used to reflect the laser of the second wavelength back to the second output mirror to generate a second oscillating laser, and the second oscillating laser is output through the second output mirror. The second output mirror is also used to inject the second oscillating laser into the first resonant cavity through the second beam splitter.

[0019] Optionally, the device also includes a birefringent filter arranged between the first laser gain module and the second reflector, the birefringent filter is placed in a Brewster angle manner, and is used to convert the first wavelength laser into a first wavelength laser in a horizontally polarized state, and is also used to adjust the intensity of the first oscillating laser.

[0020] Optionally, the device further comprises a shaping lens for shaping the second oscillating laser outputted from the second resonant cavity so that the second oscillating laser achieves mode matching with the first oscillating laser.

[0021] Optionally, the device further includes a fourth reflector, and the fourth reflector is used to adjust the optical path of the second oscillator laser output by the second resonant cavity so that the second oscillator laser injected into the first resonant cavity is colinear with the first oscillator laser.

[0022] Optionally, the device further comprises a temperature regulating module for regulating the temperature of the nonlinear crystal.

[0023] Optionally, the laser gain module includes a laser gain medium and a pump source, and the device further includes a cooling module for cooling the laser gain medium.

[0024] The beneficial effects of the present invention are as follows:

[0025] The present invention forms a composite cavity by coupling a first resonant cavity and a second resonant cavity, injects a second oscillating laser output from the second resonant cavity into the first resonant cavity, realizes frequency conversion between the first oscillating laser and the second oscillating laser through a nonlinear crystal, and generates a frequency-converted laser output to the outside of the first resonant cavity; the laser optical path of the present invention is easy to adjust, and combined with the frequency conversion inside the first resonant cavity and the frequency conversion outside the second resonant cavity, it is easy to realize mode matching of the nonlinear crystal, effectively improve the frequency conversion efficiency, and obtain a high-power and high-beam quality frequency-converted laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0027] Figure 1 The composite cavity nonlinear frequency conversion laser device based on Nd:YAG in the first embodiment of the present invention is shown;

[0028] Figure 2 A composite cavity nonlinear frequency conversion laser device based on Nd:YAG and Nd:YVO4 in the second embodiment of the present invention is shown. DETAILED DESCRIPTION

[0029] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0030] The present invention provides a composite cavity nonlinear laser frequency conversion device, which combines the advantages of high frequency conversion efficiency in the cavity and easy phase matching of frequency conversion outside the cavity to obtain high-power and high-quality beam frequency conversion laser. The device includes a laser gain module, a first resonant cavity, a second resonant cavity and a nonlinear crystal. The nonlinear crystal is arranged inside the first resonant cavity.

[0031] The laser gain module is used to output a laser of a first wavelength and a laser of a second wavelength;

[0032] The laser gain module includes a laser gain medium and a pump source, wherein the laser gain medium material can be crystal or glass, and the laser gain medium can be the same medium or different media; the laser gain module can radiate laser light of a first wavelength and laser light of a second wavelength; the pump source can be pumped in a side pumping and / or end pumping mode, and can also be continuous pumping or quasi-continuous pumping.

[0033] The first resonant cavity is used to generate a first oscillating laser, which does not output the first resonant cavity, and has a wavelength of the first oscillating laser. The second resonant cavity is used to generate a second oscillating laser, and has a wavelength of the second oscillating laser. The nonlinear crystal converts the frequency of the first oscillating laser and the second oscillating laser to generate a frequency-converted laser, which is output through the first resonant cavity.

[0034] Figure 1 The present invention is a composite cavity nonlinear frequency conversion laser device based on Nd:YAG, wherein the first resonant cavity comprises a first reflector 1, a first beam splitter 4, a second beam splitter 10 and a birefringent filter 2, the second resonant cavity comprises a first reflector 1, a first output mirror 5 and a birefringent filter 2, a laser gain module 3 is arranged between the first reflector 1 and the first beam splitter 4, and a nonlinear crystal 11 is arranged between the first beam splitter 4 and the second beam splitter 10;

[0035] The first reflector 1 is used to reflect the laser light of the first wavelength and the laser light of the second wavelength back to the laser gain module, the first beam splitter 4 is used to reflect the laser light of the first wavelength to the nonlinear crystal and transmit the laser light of the second wavelength to the first output mirror 5, the first beam splitter 4 is also used to output the frequency-converted laser light, and the second beam splitter 10 is used to reflect the laser light of the first wavelength back to the nonlinear crystal to generate the first oscillating laser light 1-1;

[0036] The first output mirror 5 is used to reflect part of the laser light of the second wavelength back to the first reflector 1, and the laser light of the second wavelength oscillates in the second resonant cavity to generate the second oscillated laser light 2-1. The first output mirror 5 is also used to transmit the second oscillated laser light 2-1 out of the second resonant cavity, and the second oscillated laser light 2-1 is injected into the first resonant cavity through the second beam splitter 10;

[0037] The birefringent filter 2 is arranged between the laser gain module 3 and the first reflector 1. The birefringent filter 2 is placed in a Brewster angle manner and is used to convert the laser of the first wavelength into the laser of the first wavelength in a horizontal polarization state and convert the laser of the second wavelength into the laser of the second wavelength in a horizontal polarization state. The birefringent filter 2 is also used to adjust the intensity of the first polarized laser 1-1 and the second oscillating laser 2-1.

[0038] The device also includes a fourth reflector and a shaping lens. The fourth reflector can be a reflector group. The reflector group includes a first high-reflection mirror 6 and a second high-reflection mirror 9. The first high-reflection mirror 6 is used to reflect the second oscillation laser 2-1 output by the second resonant cavity. The shaping lens can be a shaping lens group. The shaping lens group includes a first lens 7 and a second lens 8. The first lens 7 and the second lens 8 are arranged between the first high-reflection mirror 6 and the second high-reflection mirror 9. The first lens 7 and the second lens 8 are used to shape the second oscillation laser 2-1. The second oscillation laser 2-1 reflected by the first high-reflection mirror 6 is shaped by the first lens 7 and the second lens 8. The shaped second oscillation laser 2-1 is reflected by the second high-reflection mirror 9 and injected into the first resonant cavity. The positions and angles of the first high-reflection mirror 6 and the second high-reflection mirror 9 are adjusted to make the first oscillation laser 1-1 and the shaped second oscillation laser 2-1 collinear to achieve phase matching.

[0039] A temperature regulating module for regulating the temperature of the nonlinear crystal 11 is provided inside the nonlinear crystal 11 to avoid a decrease in the laser output power and the laser beam quality caused by an uneven temperature field inside the nonlinear crystal 11; the laser gain module 3 includes a laser gain medium and a pump source, and also includes a cooling module for cooling the laser gain medium to avoid a decrease in the laser output power and the laser beam quality caused by an excessively high temperature inside the laser gain module.

[0040] The first reflecting mirror 1 is coated with a high reflection film for the first oscillating laser 1-1 and the second oscillating laser 2-1; the first beam splitter 4 is coated with a high reflection film for the first oscillating laser 1-1, and a high transmittance film for the second oscillating laser 2-1 and the frequency conversion laser 3-1; the second beam splitter 10 is coated with a high reflection film for the first oscillating laser 1-1 and the frequency conversion laser 3-1, and is also coated with a high transmittance film for the second oscillating laser 2-1; the first output mirror 5 is coated with a high transmittance film for the second oscillating laser 2-1; the first high reflection mirror 6 is coated with a high reflection film for the second oscillating laser 2-1; the second high reflection mirror 9 is coated with a high reflection film for the second oscillating laser 2-1.

[0041] Figure 2 A composite cavity nonlinear frequency conversion laser device based on Nd:YAG and Nd:YVO4, the device comprises a first resonant cavity, a second resonant cavity, a laser gain module, a birefringent filter 2 and a nonlinear crystal 11, the laser gain module comprises a first laser gain module 18 for outputting a laser of a first wavelength and a second laser gain module 14 for outputting a laser of a second wavelength, the second laser gain module 14 generates a laser of a second wavelength in a horizontal polarization state;

[0042] The first resonant cavity includes a second reflector 15, a third beam splitter 17, a second beam splitter 10 and a birefringent filter 2, the second resonant cavity includes a third reflector 16 and a second output mirror 13, a first laser gain module 18 is arranged between the second reflector 15 and the third beam splitter 17, a nonlinear crystal 11 is arranged between the third beam splitter 17 and the second beam splitter 10, and a second laser gain module 14 is arranged between the third reflector 16 and the second output mirror 13;

[0043] The second reflector 15 is used to reflect the laser light of the first wavelength to the third beam splitter 17, and the third beam splitter 17 is used to reflect the laser light of the first wavelength to the second beam splitter 10, and is also used to output the frequency-converted laser light; the second beam splitter 10 is used to reflect the laser light of the first wavelength to the third beam splitter 17, and the laser light of the first wavelength oscillates in the first resonant cavity to generate the first oscillated laser light 1-1, and the first oscillated laser light 1-1 does not output the first resonant cavity;

[0044] The third reflector 16 is used to reflect the laser light of the second wavelength, and the second output mirror 13 is used to reflect the laser light of the second wavelength back to the third reflector 16. The laser light of the second wavelength oscillates in the second resonant cavity to generate the second oscillated laser light 2-1. The second output mirror 13 is also used to transmit the second oscillated laser light 2-1 out of the second resonant cavity and inject it into the first resonant cavity through the second beam splitter 10.

[0045] The birefringent filter 2 is placed between the first laser gain module 18 and the second reflector 15. The birefringent filter 2 is placed in a Brewster angle manner to convert the laser of the first wavelength into the laser of the first wavelength in a horizontally polarized state. The intensity of the first oscillating laser is adjusted by adjusting the angle of the birefringent filter 2.

[0046] The device also includes a fourth reflector and a shaping lens, Figure 2 The fourth reflector is a reflector group, including a first high reflector 6, a second high reflector 9 and a third high reflector 12. The shaping lens can be a shaping lens group, which includes a first lens 7 and a second lens 8. The first lens 7 and the second lens 8 are arranged between the first high reflector 6 and the second output mirror 13. The first lens 7 and the second lens 8 are used to shape the second oscillation laser 2-1. The first high reflector 6, the second high reflector 9 and the third high reflector 12 are used to reflect the shaped second oscillation laser 2-1; the shaped second oscillation laser 2-1 is reflected by the second beam splitter 10 and injected into the first resonant cavity; the positions and angles of the first high reflector 6, the second high reflector 9 and the third high reflector 12 are adjusted so that the first oscillation laser 1-1 is collinear with the shaped second oscillation laser 2-1 to achieve phase matching, thereby achieving the highest frequency conversion efficiency and high frequency conversion laser output efficiency.

[0047] A temperature regulating module for regulating the temperature of the nonlinear crystal 11 is arranged inside the nonlinear crystal 11 to avoid the decrease of laser output power and laser beam quality caused by the uneven temperature field inside the nonlinear crystal 11; the first laser gain module 18 includes a first laser gain medium and a first pump source, and also includes a first cooling module for cooling the first laser gain medium, wherein the material of the first laser gain medium can be crystal or glass, and the pumping mode of the first pump source can be side pumping and / or end pumping, and can also be continuous pumping or quasi-continuous pumping; the second laser gain module 14 includes a second laser gain medium and a second pump source, and also includes a second cooling module for cooling the second laser gain medium.

[0048] The third beam splitter 17 is coated with a high reflection film of the first oscillator laser 1-1, and is also coated with a high transmittance film of the second oscillator laser 2-1 and the frequency conversion laser 3-1. The second reflector 15 is coated with a high reflection film of the first oscillator laser 1-1. The third reflector 16 is coated with a high reflection film of the second oscillator laser 2-1. The second output mirror 13 is coated with a partial anti-reflection film of the second oscillator laser 2-1. The first high reflection mirror 6, the second high reflection mirror 9 and the third high reflection mirror 12 are all coated with a high reflection film of the second oscillator laser 2-1.

[0049] The composite cavity nonlinear laser frequency conversion device provided by the present invention couples a first resonant cavity and a second resonant cavity to form a composite resonant cavity, and realizes the frequency conversion of the laser beam by combining the nonlinear crystal with the intra-cavity frequency conversion and the extra-cavity frequency conversion, so it is easy to realize the mode matching of the nonlinear crystal and effectively improve the frequency conversion efficiency; and the laser optical path of the present invention is easy to adjust, the structure is compact, the design is flexible, and the matching of the laser phase inside and outside the cavity is easy to realize.

[0050] In the first specific embodiment of the present invention, Figure 1 The invention is a composite cavity nonlinear frequency conversion laser device based on Nd:YAG, which includes a first resonant cavity, a second resonant cavity, a laser gain module 3, a nonlinear crystal 11, a birefringent filter 2, a first high-reflection mirror 6, a first lens 7, a second lens 8, and a second high-reflection mirror 9. The first resonant cavity includes a first reflector 1, a first beam splitter 4, a second beam splitter 10, and a birefringent filter 2; the second resonant cavity includes a first reflector 1, a first output mirror 5, and a birefringent filter 2. The laser gain module 3 includes a laser gain medium and a pump source (the laser gain medium and the pump source are not in the Figure 1 The material of the laser gain medium may be crystal or glass, the pumping mode of the pump source may be side pumping and / or end pumping, or may be continuous pumping or quasi-continuous pumping, and the laser gain medium may also include a cooling device (the cooling device is not shown in FIG. Figure 1 As shown in the figure, this embodiment uses cooling water for water cooling to avoid excessively high internal temperature of the laser gain medium, which may cause a decrease in laser output power and laser beam quality. In this embodiment, the material of the laser gain medium is Nd:YAG crystal, the doping concentration is 1%, and the size is D3 mm×80 mm, where D3mm means that the outer diameter of the crystal rod is 3 mm, and the surface of the Nd:YAG crystal rod is coated with a high-transmittance film for 808nm, 1064nm and 1319nm lasers, and the transmittance of the high-transmittance film is greater than 99%; the pump source is a quasi-continuously operated semiconductor 808nm laser, and a side pumping method is used to output quasi-continuous 1064nm laser and 1319nm laser, the first wavelength laser is a 1319nm laser, and the second wavelength laser is a 1064nm laser.

[0051] The first resonant cavity includes a first reflector 1, a first beam splitter 4, a second beam splitter 10 and a birefringent filter 2, the second resonant cavity includes a first reflector 1, a first output mirror 5 and a birefringent filter 2, the first resonant cavity and the second resonant cavity are coupled to form a composite cavity, the laser gain module 3 is placed between the birefringent filter 2 and the first beam splitter 4, and outputs 1064nm laser and 1319nm laser; the birefringent filter 2 is a quartz crystal, which is placed at the Brewster angle, and the 1319nm laser is operated as a 1319nm laser in a horizontal polarization state, and the 1064nm laser is operated as a 1064nm laser in a horizontal polarization state, and the angle of the birefringent filter 2 is rotated to adjust the intensities of the 1064nm oscillating laser and the 1319nm oscillating laser. After adjustment, the intensities of the 1064nm oscillating laser and the 1319nm oscillating laser can be the same or different. In this embodiment, the intensities of the 1064nm oscillating laser and the 1319nm oscillating laser are adjusted to be equal.

[0052] The first oscillator laser 1-1 generated by the first resonant cavity is a 1319nm oscillator laser, which does not output the resonant cavity. The second oscillator laser 2-1 generated by the second resonant cavity is a 1064nm oscillator laser, which is output from the second resonant cavity through the first output mirror 5; the second oscillator laser 2-1 is reflected by the first high-reflection mirror 6, shaped by the first lens 7 and the second lens 8, and then reflected by the second beam splitter 10 and injected into the first resonant cavity. The first oscillator laser 1-1 and the shaped second oscillator laser 2-1 are frequency-converted by the nonlinear crystal 11 to generate a frequency-converted laser 3-1, which is output by the first beam splitter 4. The frequency-converted laser 3-1 is a 589nm frequency-converted laser.

[0053] The surface of the first reflecting mirror 1 close to the birefringent filter 2 is coated with a high reflection film of 1064nm oscillating laser and 1319nm oscillating laser, and the reflectivity is greater than 99%; the surface of the first beam splitter 4 close to the birefringent filter 2 is coated with a high reflection film of 1319nm oscillating laser, and the reflectivity is greater than 99%, and a high transmittance film of 1064nm oscillating laser and 589nm frequency conversion laser, and the transmittance is greater than 99%; the surface of the second lens 10 close to the first beam splitter 4 is coated with a high reflection film of 1319nm oscillating laser and 589nm frequency conversion laser, and the reflectivity is greater than 99%, and the surface of the side away from the first beam splitter 4 is coated with a high transmittance film of 1064nm oscillating laser, and the transmittance is greater than 99%; the surface of the first output mirror 5 close to the birefringent filter 2 is coated with a partial anti-reflection film of 1064nm oscillating laser, and the transmittance of the partial anti-reflection film is 20%.

[0054] Figure 1The first high-reflection mirror 6 and the second high-reflection mirror 9 are used to adjust the optical path of part of the second oscillation laser output from the second resonant cavity, so that the second oscillation laser 2-1 injected into the first resonant cavity is collinear with the first oscillation laser 1-1; the shaping lens is a shaping lens group, including a first lens 7 and a second lens 8, the first lens 7 and the second lens 8 are arranged between the first high-reflection mirror 6 and the second high-reflection mirror 9, and are used to shape the 1064nm oscillation laser output from the second resonant cavity to achieve mode matching with the 1319nm oscillation laser in the first resonant cavity. The first high-reflection mirror 6 and the second high-reflection mirror 9 are both coated with a high-reflection film for the 1064nm oscillation laser, and the reflectivity is greater than 99%. The second high-reflection mirror 9 is used to reflect the shaped 1064nm oscillation laser from the outside of the second resonant cavity into the first resonant cavity to achieve intra-cavity and extra-cavity combination; the angle between the first high-reflection mirror 6 and the second high-reflection mirror 9 is adjusted to achieve the collinearity of the shaped 1064nm oscillation laser and the 1319nm oscillation laser, and meet the phase matching condition of the nonlinear crystal 11.

[0055] The nonlinear crystal 11 is an LBO crystal, the cutting angle of the nonlinear crystal 11 is θ=90°, φ=0°, and the temperature is controlled at 40°C to meet the optimal phase matching required for the sum frequency conversion of the 1064nm oscillating laser and the 1319nm oscillating laser to 589nm; the surface of the nonlinear crystal 11 is coated with a high-transmittance film of the 1064nm oscillating laser, the 1319nm oscillating laser and the 589nm frequency conversion laser, and the transmittance is greater than 99%, and the generated frequency conversion laser is output by the first beam splitter 4; the nonlinear crystal 11 includes a temperature adjustment module, and the temperature adjustment module in this embodiment is a temperature controller (the temperature controller is Figure 1 (not shown), the nonlinear crystal 11 detects the temperature through a temperature controller and controls the temperature in real time; the temperature controller includes a crystal furnace and a temperature sensor, the crystal furnace is made of copper, and the temperature sensor is a platinum resistor. The current output is controlled by a PID algorithm, that is, the crystal furnace is heated. The temperature control accuracy is ±0.05, which avoids the influence of the difference in sum frequency effect caused by the uneven temperature field of the nonlinear crystal 11. The nonlinear crystal 11 is set in the first resonant cavity, combining the intra-cavity frequency conversion and the extra-cavity frequency conversion, realizing the high efficiency of the intra-cavity frequency conversion and the easy mode matching of the nonlinear crystal by the extra-cavity frequency conversion.

[0056] Specifically, the laser gain module 3 radiates 1064nm laser and 1319nm laser by side pumping, and the first and second oscillating lasers are generated in the first resonant cavity and the second resonant cavity respectively. The first oscillating laser is a 1319nm oscillating laser, which is not output from the first resonant cavity; the second oscillating laser is a 1064nm oscillating laser, which is output from the second resonant cavity by the first output mirror 5; by adjusting the angle of the birefringent filter 2, the intensity of the 1064nm oscillating laser and the 1319nm oscillating laser is equal, ensuring that a high-power and high-quality laser beam is generated during frequency summing; the 1064nm oscillating laser is reflected by the first high-reflection mirror 6 and then passes through the first The lens 7 and the second lens 8 are shaped to achieve mode matching of the 1064nm oscillating laser and the 1319nm oscillating laser; the angle between the first high-reflection mirror 6 and the second high-reflection mirror 9 is adjusted so that the 1064nm oscillating laser after beam shrinkage shaping is reflected into the first resonant cavity through the second high-reflection mirror 9, so that the 1319nm oscillating laser and the 1064nm oscillating laser are colinear and meet the LBO crystal phase matching; the LBO crystal is placed in the first resonant cavity to achieve efficient frequency conversion of the 1064nm and 1319nm oscillating lasers, and generate a 589nm frequency conversion laser with high power and high beam quality, and the frequency conversion laser is output by the first beam splitter 4 to the outside of the first resonant cavity.

[0057] In this embodiment, the 1064nm oscillating laser is reflected by the first high-reflection mirror 6, and the 1064nm oscillating laser is shaped by the first lens 7 and the second lens 8. By adjusting the angle between the first high-reflection mirror 6 and the second high-reflection mirror 9, the shaped 1064nm oscillating laser is injected into the first resonant cavity through the reflection of the second high-reflection mirror 9, so as to realize that the 1064nm oscillating laser and the 1319nm oscillating laser are in the same line, and the phase matching condition of the nonlinear crystal is met; the 1319nm oscillating laser and the 1064nm oscillating laser are frequency-converted by the nonlinear crystal 11 to generate a 589nm frequency-converted laser. The composite cavity nonlinear laser frequency conversion device of this embodiment has a compact structure, combines the advantages of intra-cavity sum frequency and extra-cavity sum frequency, has the advantages of high sum frequency efficiency, easy adjustment of laser co-linearity and good laser mode matching, and can generate a frequency-converted laser with high conversion efficiency, high power and high beam quality.

[0058] In a second specific embodiment of the present invention, Figure 2 The invention is a composite cavity nonlinear frequency conversion laser device based on Nd:YAG and Nd:YVO4, which comprises a first laser gain module 18, a second laser gain module 14, a first resonant cavity, a second resonant cavity, a birefringent filter 2 and a nonlinear crystal 11.

[0059] The first laser gain module 18 is placed in the first resonant cavity to generate a laser with a wavelength of 1319nm. The 1319nm laser oscillates in the first resonant cavity to generate a first oscillation laser 1-1. The first oscillation laser 1-1 is a 1319nm oscillation laser, which does not output the first resonant cavity. The first laser gain module 18 includes a first laser gain medium and a first pump source (the first laser gain medium and the first pump source are in Figure 2 The first laser gain module 18 further includes a first cooling module for cooling the first laser gain medium (the first cooling module is Figure 2 The second laser gain module 14 is arranged in the second resonant cavity, generating a laser with a wavelength of 1064 nm. The second resonant cavity generates and outputs a second oscillating laser 2-1. The second oscillating laser 2-1 is a 1064 nm oscillating laser. The second laser gain module 14 includes a second laser gain medium and a second pump source (the second laser gain medium and the second pump source are connected in Figure 2 The second laser gain medium material may be crystal or glass. The pumping mode of the second pump source may be side pumping and / or end pumping, or continuous pumping or quasi-continuous pumping. The second laser gain medium 14 further includes a second cooling module for cooling the second laser gain medium (the second cooling module is in Figure 2 ). In this embodiment, the first cooling module and the second cooling module are both cooled by cooling water to avoid excessive internal temperature of the second laser gain medium causing a decrease in laser output power and laser beam quality. In this embodiment, the material of the first laser gain medium is Nd:YAG crystal, and the material of the second laser gain medium is Nd:YVO4 crystal; the first pump source and the second pump source are both quasi-continuously operated semiconductor 808nm lasers, the first pump source and the second pump source are both side pumped, the first laser gain module generates 1319nm laser, and the second laser gain module generates 1064nm laser in the horizontal polarization direction.

[0060] The first laser gain medium is a Nd:YAG crystal rod with a doping concentration of 1% and a size of D3 mm×80 mm. The surface of the Nd:YAG crystal rod is coated with a high-transmittance film for 808nm and 1319nm lasers, and the transmittance is greater than 99%; the second laser gain medium is a Nd:YVO4 crystal rod with a doping concentration of 1%, and the size of the crystal rod is 20mm×3mm×3mm. The surface of the Nd:YVO4 crystal rod is coated with a high-transmittance film for 808nm and 1064nm lasers, and the transmittance is greater than 99%.

[0061] The first resonant cavity includes a second reflector 15, a third beam splitter 17, a second beam splitter 10 and a birefringent filter 2, the second resonant cavity includes a third reflector 16 and a second output mirror 13, the first resonant cavity and the second resonant cavity are coupled to form a composite resonant cavity, the first laser gain module 18 is placed in the first resonant cavity, and outputs a laser with a wavelength of 1319nm; the birefringent filter 2 is a quartz crystal, which is placed at the Brewster angle, and the 1319nm oscillating laser in the first resonant cavity is operated as a laser of the first wavelength in a horizontally polarized state, the angle of the birefringent filter 2 is rotated, and the intensity of the 1319nm oscillating laser is adjusted. After adjustment, the intensity of the 1319nm oscillating laser can be the same as or different from the intensity of the 1064nm oscillating laser generated by the second resonant cavity.

[0062] The first oscillator laser 1-1 generated by the first resonant cavity is a 1319nm oscillator laser, which does not output the resonant cavity; the second laser gain module 14 outputs a laser of a second wavelength in a horizontally polarized state, and the second oscillator laser 2-1 generated by the second resonant cavity is a 1064nm oscillator laser, which is output from the second resonant cavity through the second output mirror 13; the second oscillator laser 2-1 is injected into the first resonant cavity through the second beam splitter 10, and the first oscillator laser 1-1 and the second oscillator laser 2-1 are frequency-converted by the nonlinear crystal 11 to generate a frequency-converted laser 3-1, and the frequency-converted laser 3-1 is output from the first resonant cavity by the third beam splitter 17, and the frequency-converted laser 3-1 is a 589nm frequency-converted laser.

[0063] The surface of the second reflector 15 close to the birefringent filter 2 is coated with a high-reflection film of 1319nm oscillating laser, and the reflectivity is greater than 99%; the surface of the third beam splitter 17 close to the birefringent filter 2 is coated with a high-reflection film of 1319nm oscillating laser, and the reflectivity is greater than 99%, and is also coated with a high-transmittance film of 589nm frequency conversion laser, and the transmittance is greater than 99%; the surface of the second beam splitter 10 close to the third beam splitter 17 is coated with high-reflection films of 1319nm oscillating laser and 589nm frequency conversion laser, and the reflectivity is greater than 99%, and the surface of the side away from the third beam splitter 17 is coated with a high-transmittance film of 1064nm oscillating laser, and the transmittance is greater than 99%; the surface of the third reflector 16 close to the second laser gain module 14 is coated with a high-reflection film of 1064nm oscillating laser, and the reflectivity is greater than 99%, and the second output mirror 13 is coated with a partial anti-reflection film of 1064nm oscillating laser, and the transmittance of the partial anti-reflection film is 40%.

[0064] The shaping lens of this embodiment is a shaping lens group, including a first lens 7 and a second lens 8, which are arranged between the second output mirror 13 and the first high-reflection mirror 6, and are used to shape part of the 1064nm oscillating laser output by the second resonant cavity, so that the shaped 1064nm oscillating laser and the 1319nm oscillating laser in the first resonant cavity can achieve mode matching; the fourth reflector is a reflector group, including a first high-reflection mirror 6, a second high-reflection mirror 9 and a third high-reflection mirror 12, the first high-reflection mirror 6, the third high-reflection mirror 12 The first high-reflection mirror 6 and the second high-reflection mirror 9 are both coated with a high-reflection film for 1064nm oscillating laser, with a reflectivity greater than 99%; the reflector group is used to reflect the shaped 1064nm oscillating laser, and reflect the shaped 1064nm oscillating laser from outside the second resonant cavity into the first resonant cavity to achieve intra-cavity and extra-cavity combination; the positions and angles of the first high-reflection mirror 6, the second high-reflection mirror 9 and the third high-reflection mirror 12 are adjusted to achieve the colinearity of the shaped 1064nm oscillating laser and the 1319nm oscillating laser, and meet the phase matching conditions of the nonlinear crystal 11.

[0065] The birefringent filter 2 is a quartz crystal. The birefringent filter 2 is arranged between the first laser gain module 18 and the second reflector 15. The Brewster angle is set to operate the 1319nm laser inside the first resonant cavity into a 1319nm laser in a horizontally polarized state. The intensity of the 1319nm oscillating laser is adjusted by adjusting the angle of the birefringent filter 2.

[0066] The nonlinear crystal 11 is an LBO crystal, the cutting angle of the nonlinear crystal is θ=90°, φ=0°, and the temperature is controlled at 40°C, which satisfies the optimal phase matching required for the sum frequency conversion of the 1064nm oscillating laser and the 1319nm oscillating laser to 589nm; the surface of the nonlinear crystal is coated with a high-transmittance film of the 1064nm oscillating laser, the 1319nm oscillating laser and the 589nm frequency conversion laser, and the transmittance is greater than 99%, and the frequency conversion laser is output by the third beam splitter 17; the nonlinear crystal 11 includes a temperature adjustment module, and the temperature adjustment module in this embodiment is a temperature controller (the temperature controller is Figure 2 (not shown), the nonlinear crystal 11 detects the temperature through a temperature controller and controls the temperature in real time; the temperature controller includes a crystal furnace and a temperature sensor, the crystal furnace is made of copper, and the temperature sensor is a platinum resistor. The current output is controlled by a PID algorithm, that is, the crystal furnace is heated. The temperature control accuracy is ±0.05, which avoids the influence of the difference in sum frequency effect caused by the uneven temperature field of the nonlinear crystal 11. The nonlinear crystal 11 is set in the first resonant cavity, combining the intra-cavity frequency conversion and the extra-cavity frequency conversion, realizing the high efficiency of the intra-cavity frequency conversion and the easy mode matching of the nonlinear crystal by the extra-cavity frequency conversion.

[0067] Specifically, the first laser gain module 18 radiates 1319nm laser light by side pumping, oscillates in the first resonant cavity to form 1319nm oscillating laser light, and the laser light does not output the first resonant cavity; the second laser gain module 14 radiates 1064nm laser light by side pumping, oscillates in the second resonant cavity to form 1064nm oscillating laser light, and outputs the second resonant cavity; the 1064nm oscillating laser light is shaped by the first lens 7 and the second lens 8, and the 1064nm oscillating laser light and the 1319nm oscillating laser light are ...oscillating in the first resonant cavity. Mode matching of 19nm oscillating laser; the shaped 1064nm oscillating laser is injected into the first resonant cavity through reflection by the first high-reflection mirror 6, the third high-reflection mirror 12 and the second high-reflection mirror 9, so that the 1319nm oscillating laser and the 1064nm oscillating laser are colinear, satisfying the phase matching of the LBO crystal; the 1319nm oscillating laser and the shaped 1064nm oscillating laser are frequency-converted through the nonlinear crystal 11 to generate a 589nm frequency-converted laser with high power and high beam quality, and the frequency-converted laser is output by the third beam splitter 17 to the outside of the first resonant cavity.

[0068] In this embodiment, the 1064nm oscillating laser generated by the second resonant cavity is shaped by the first lens 7 and the second lens 8, and the shaped 1064nm laser is injected into the first resonant cavity by adjusting the angles between the first high-reflection mirror 6, the third high-reflection mirror 12 and the second high-reflection mirror 9, so that the 1064nm oscillating laser and the 1319nm oscillating laser are collinear, meeting the phase matching condition of the nonlinear crystal; the 1319nm oscillating laser and the 1064nm oscillating laser are frequency-converted into a 589nm frequency-converted laser by the nonlinear crystal 11. The laser device has a compact structure, combines the advantages of intra-cavity sum frequency and extra-cavity sum frequency, has the advantages of high sum frequency efficiency, easy adjustment of laser collinearity and good laser mode matching, and can generate frequency-converted laser with high conversion efficiency, high power and high beam quality.

[0069] In the description of the present invention, it should be noted that the terms "upper", "lower", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0070] It should also be noted that, in the description of the present invention, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0071] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A composite cavity nonlinear laser frequency conversion device, characterized in that: The device comprises a laser gain module, a first resonant cavity, a second resonant cavity and a nonlinear crystal, wherein the nonlinear crystal is arranged in the first resonant cavity; The laser gain module is used to radiate laser light of a first wavelength and laser light of a second wavelength; The first resonant cavity is used to generate a first oscillating laser, the wavelength of the first oscillating laser is a first wavelength, and the first oscillating laser does not output the first resonant cavity; The second resonant cavity is used to generate a second oscillating laser, and the second oscillating laser is injected into the first resonant cavity, and the wavelength of the second oscillating laser is a second wavelength; The nonlinear crystal is used to perform frequency conversion on the first oscillating laser and the second oscillating laser to generate frequency-converted laser, and the frequency-converted laser is output by the first resonant cavity.

2. The device according to claim 1, characterized in that The first resonant cavity comprises a first reflector, a first beam splitter and a second beam splitter, the second resonant cavity comprises a first reflector and a first output mirror, the laser gain module is arranged between the first reflector and the first beam splitter, and the nonlinear crystal is arranged between the first beam splitter and the second beam splitter; The first reflector is used to reflect the laser light of the first wavelength and the laser light of the second wavelength, the first beam splitter is used to reflect the laser light of the first wavelength to the second beam splitter and transmit it through the nonlinear crystal, the first beam splitter is also used to transmit the laser light of the second wavelength and output frequency-converted laser light; the second beam splitter is used to reflect the laser light of the first wavelength back to the first beam splitter and the first reflector, the laser light of the first wavelength oscillates in the first resonant cavity to generate a first oscillated laser light, and the second beam splitter is also used to transmit the second oscillated laser light; The first output mirror is used to reflect the laser light of the second wavelength back to the first reflector to generate a second oscillating laser light, transmit the second oscillating laser light to output the second resonant cavity, and inject the second oscillating laser light into the first resonant cavity through the second beam splitter.

3. The device according to claim 2, characterized in that The device further comprises a birefringent filter disposed between the laser gain module and the first reflector, wherein the birefringent filter is placed in a Brewster angle manner and is used to convert the laser light of the first wavelength into the laser light of the first wavelength in a horizontal polarization state, and convert the laser light of the second wavelength into the laser light of the second wavelength in a horizontal polarization state; The birefringent filter is also used to adjust the intensities of the first oscillation laser light and the second oscillation laser light.

4. The device according to claim 1, characterized in that The laser gain module includes a first laser gain module for outputting laser light of a first wavelength and a second laser gain module for outputting laser light of a second wavelength.

5. The device according to claim 4, characterized in that The first resonant cavity comprises a second reflector, a second beam splitter and a third beam splitter, the second resonant cavity comprises a third reflector and a second output mirror, the first laser gain module is arranged between the second reflector and the third beam splitter, the nonlinear crystal is arranged between the third beam splitter and the second beam splitter, and the second laser gain module is arranged between the third reflector and the second output mirror; The second reflector is used to reflect the laser light of the first wavelength, the third beam splitter is used to reflect the laser light of the first wavelength to the second beam splitter and transmit the laser light through the nonlinear crystal, and is also used to output frequency-converted laser light; the second beam splitter is used to reflect the laser light of the first wavelength back to the third beam splitter and the second reflector, and the laser light of the first wavelength oscillates in the first resonant cavity to generate a first oscillated laser light; The third reflector is used to reflect the laser of the second wavelength back to the second output mirror to generate a second oscillating laser, and the second oscillating laser is output through the second output mirror. The second output mirror is also used to inject the second oscillating laser into the first resonant cavity through the second beam splitter.

6. The device according to claim 5, characterized in that The device also includes a birefringent filter disposed between the first laser gain module and the second reflector. The birefringent filter is placed in a Brewster angle manner and is used to convert the first wavelength laser into a first wavelength laser in a horizontal polarization state and to adjust the intensity of the first oscillating laser.

7. The device according to any one of claims 1 to 6, characterized in that: The device also includes a shaping lens for shaping the second oscillating laser output by the second resonant cavity so that the second oscillating laser achieves mode matching with the first oscillating laser.

8. The device according to any one of claims 1 to 6, characterized in that: The device also includes a fourth reflector, which is used to adjust the optical path of the second oscillator laser output by the second resonant cavity so that the second oscillator laser injected into the first resonant cavity is colinear with the first oscillator laser.

9. The device according to any one of claims 1 to 6, characterized in that: The device also includes a temperature regulating module for regulating the temperature of the nonlinear crystal.

10. The device according to any one of claims 1 to 6, characterized in that: The laser gain module comprises a laser gain medium and a pump source, and the device further comprises a cooling module for cooling the laser gain medium.

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