High-efficiency optical parametric oscillator

Abstract

The invention discloses a high-efficiency optical parametric oscillator, and belongs to the technical field of lasers, the high-efficiency optical parametric oscillator comprises a pumping source output assembly, a coupling system, a first resonant cavity mirror and a nonlinear crystal which are sequentially arranged along the direction of an optical path, a dispersion prism is arranged at a light outlet of the nonlinear crystal, and the dispersion prism can divide light into signal light and idler frequency light; the dispersion prism and the light source are transmitted along a first light path and a second light path respectively, a second resonant cavity mirror is arranged on the first light path, an optical parameter adjusting assembly is arranged between the dispersion prism and the second resonant cavity mirror, and a third resonant cavity mirror is arranged on the second light path. According to the high-efficiency optical parametric oscillator provided by the invention, the light-light conversion efficiency and high light beam quality of parametric light can be simultaneously obtained under different power pumps under the conditions of not changing a cavity type structure and not needing to be reassembled and adjusted under the different power pumps.

Description

Technical Field

[0001] The invention belongs to the technical field of lasers, and in particular relates to a high-efficiency optical parametric oscillator. Background Art

[0002] With the rapid development of various laser devices and technologies, the laser field is moving towards compact size, high conversion efficiency and high beam quality. In recent years, mid-infrared lasers have been continuously developed and widely used in medical, ranging, imaging and spectroscopy.

[0003] For optical parametric oscillators, the laser power density in the optical parametric oscillator resonant cavity seriously affects the optical-to-optical conversion efficiency and beam quality of the optical parametric oscillator. Usually, under low pump power conditions, the output mirror of the optical parametric oscillator resonant cavity can be plated with a high reflectivity of the signal light to obtain higher optical-to-optical conversion efficiency and beam quality under low-power pumping; under high-power pumping, an output mirror with a signal light transmittance of about 30% is usually used as the optical parametric oscillator cavity mirror to suppress the reverse transformation effect under high-power pumping to obtain higher optical-to-optical conversion efficiency and beam quality. It can be seen that under different power pumping conditions, in order to achieve higher optical conversion efficiency and high beam quality parametric light output, it is necessary to select output mirrors with different transmittances for different pump powers. In actual applications, the transmittance of the output mirror is often difficult to change directly, and it is necessary to select output mirrors with different transmittances to adapt to different power pumping conditions, which makes the adjustment of the optical parametric oscillator cumbersome and affects the application efficiency of the optical parametric oscillator. Summary of the invention

[0004] In view of one or more of the above defects or improvement requirements of the prior art, the present invention provides a high-efficiency optical parametric oscillator to solve the problem that the existing optical parametric oscillator is difficult to adjust under different power pumping conditions.

[0005] To achieve the above object, the present invention provides a high-efficiency optical parametric oscillator, comprising: A pump source output component, a coupling system, a first resonant cavity mirror and a nonlinear crystal are sequentially arranged along the optical path direction, a dispersion prism is provided at the light outlet of the nonlinear crystal, the dispersion prism can separate the light output by the nonlinear crystal into signal light and idler light, and the signal light and the idler light are transmitted along the first optical path and the second optical path respectively; A second resonant cavity mirror is provided on the first optical path, and an optical parameter adjustment component is also provided between the dispersion prism and the second resonant cavity mirror. The optical parameter adjustment component can adjust the optical power density of the signal light between the dispersion prism and the second resonant cavity mirror. A third resonant cavity mirror is provided on the second optical path.

[0006] As a further improvement of the present invention, the optical parameter adjustment component includes a half-wave plate and a polarization splitter prism arranged along the second optical path, the angle of the half-wave plate is adjustable, the polarization splitter prism can split the light emitted by the dispersion prism into a third optical path and a fourth optical path, the third optical path and the fourth optical path are not colinear, and the second resonant cavity mirror is colinearly arranged with the third optical path, and an absorption pool is provided on the fourth optical path, and the absorption pool is used to absorb the signal light.

[0007] As a further improvement of the present invention, the pump source output component includes a fourth resonant cavity mirror, a laser module, a polarizer, a Q switch and a fifth resonant cavity mirror which are sequentially arranged along the optical path direction.

[0008] As a further improvement of the present invention, the surface of the fifth resonant cavity mirror is coated with a partial reflection film for light with a wavelength of 1064 nm, and the transmittance of the fifth resonant cavity mirror to light with a wavelength of 1064 nm is 20%.

[0009] As a further improvement of the present invention, the surface of the fourth resonant cavity mirror is coated with a high-reflection film for 1064nm wavelength light; the laser module includes a Nd:YAG crystal and an 808nm pump source; the polarizer is used to polarize the 1064nm wavelength light, and the Q switch is used to adjust the quality factor of the optical resonant cavity and generate nanosecond pulse laser.

[0010] As a further improvement of the present invention, the coupling system is used to increase the transmittance of 1064nm wavelength laser, and the coupling system has a reduced beam diameter of 500μm for 1064nm wavelength light; the nonlinear crystal is a MgO:PPLN crystal, wherein the doping concentration of MgO is 5%, and the end face of the nonlinear crystal is coated with an anti-reflection film for 1064nm wavelength light, an anti-reflection film for 3~5μm wavelength light, and an anti-reflection film for 1.4~1.7μm wavelength light.

[0011] As a further improvement of the present invention, the signal light and idler light generated by the nonlinear crystal are both linearly polarized lights.

[0012] As a further improvement of the present invention, the surface of the first resonant cavity mirror is coated with an anti-reflection film for pump light and a high-reflection film for signal light and idler light wavelengths.

[0013] As a further improvement of the present invention, the working wavelength of the half-wave plate is designed to be the signal light wavelength, the working wavelength of the polarization beam splitter prism is designed to be the signal light wavelength, and the surface of the second resonant cavity mirror is coated with a high-reflection film for signal light.

[0014] The above-mentioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0015] In general, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects: (1) The high-efficiency optical parametric oscillator of the present invention can increase the signal light power density in the cavity under low-power pumping to improve the light-to-light conversion efficiency under low-power pumping; under high-power pumping, the signal light power density in the cavity is reduced by the optical parametric component, thereby increasing the pump reverse transformation threshold under high power density, and improving the light-to-light conversion efficiency and beam quality under high-power pumping. It solves the problem of achieving light-to-light conversion efficiency and high beam quality of parametric light under different power pumping levels without changing the cavity structure or reinstalling and adjusting.

[0016] (2) The high-efficiency optical parametric oscillator of the present invention is provided with a rotatable half-wave plate and a polarization beam splitter prism, and an absorption pool is provided on one of the transmission paths of the polarization beam splitter prism. When pumping at low power, since the pump power has not reached the reverse transformation threshold, the signal light power density in the cavity can be increased by rotating the half-wave plate, which greatly reduces the parametric light output threshold and improves the light-to-light conversion efficiency when pumping at low power; when pumping at high power, the half-wave plate is rotated so that part of the signal light is transmitted to the absorption pool for absorption, which reduces the energy reflux phenomenon in the cavity, reduces the reverse transformation effect, and greatly increases the reverse transformation threshold, thereby improving the light-to-light conversion efficiency and beam quality under high power pumping. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of a high-efficiency optical parametric oscillator in an embodiment of the present invention.

[0018] In all the drawings, the same reference numerals represent the same technical features, specifically: 1. Coupling system; 2. First resonant cavity mirror; 3. Nonlinear crystal; 4. Dispersion prism; 5. Second resonant cavity mirror; 6. Third resonant cavity mirror; 7. Half-wave plate; 8. Polarization beam splitter prism; 9. Absorption cell; 10. Fourth resonant cavity mirror; 11. Laser module; 12. Polarizer; 13. Q switch; 14. Fifth resonant cavity mirror. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0020] In the description of the present invention, it should be understood that, unless otherwise specified, terms such as “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0021] In addition, unless otherwise specified, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0022] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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 an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0024] Example: See also Figure 1The high-efficiency optical parametric oscillator in the preferred embodiment of the present invention comprises a pump source output component, a coupling system 1, a first resonant cavity mirror 2 and a nonlinear crystal 3 arranged in sequence along the optical path direction, wherein a dispersion prism 4 is provided at the light outlet of the nonlinear crystal 3, and the dispersion prism 4 can divide the light output by the nonlinear crystal 3 into signal light and idler light, and the signal light and the idler light are transmitted along the first optical path and the second optical path respectively, a second resonant cavity mirror 5 is provided on the first optical path, and an optical parameter adjustment component is also provided between the dispersion prism 4 and the second resonant cavity mirror 5, and the optical parameter adjustment component can adjust the optical power density of the signal light between the dispersion prism 4 and the second resonant cavity mirror 5; and a third resonant cavity mirror 6 is correspondingly provided on the second optical path.

[0025] Specifically, the high-efficiency optical parametric oscillator of the present invention can increase the signal light power density in the cavity under low-power pumping to improve the light-to-light conversion efficiency under low-power pumping; under high-power pumping, the signal light power density in the cavity is reduced by an optical parametric component, thereby increasing the pump reverse transformation threshold under high power density, and improving the light-to-light conversion efficiency and beam quality under high-power pumping, thereby solving the problem of obtaining the light-to-light conversion efficiency and high beam quality of parametric light under different power pumping levels without changing the cavity structure or reinstalling and adjusting.

[0026] Furthermore, each resonant cavity mirror in the present application is used to realize feedback and oscillation of light, and reflection or output of light of different wavelengths is realized by selecting films with different wavelength light transmittance on the surface of the resonant cavity mirror.

[0027] Further, as an optional embodiment of the present invention, the optical parameter adjustment component in the present application includes a half-wave plate 7 and a polarization beam splitter prism 8 arranged along the above-mentioned second optical path, the angle of the half-wave plate 7 is adjustable, the polarization beam splitter prism 8 can split the light emitted by the dispersion prism 4 into a third optical path and a fourth optical path, and the third optical path and the fourth optical path are not collinear, the second resonant cavity mirror 5 is collinearly arranged with the third optical path, and an absorption pool 9 is arranged on the fourth optical path, and the absorption pool 9 is used to absorb the signal light. Specifically, the present application uses a half-wave plate 7 and a polarization beam splitter prism 8, and an absorption pool 9 is arranged on the fourth optical path of the polarization beam splitter prism 8. During low-power pumping, since the pump power has not reached the reverse transformation threshold, the signal light power density in the cavity can be increased by rotating the half-wave plate 7, and the light emission threshold of the parametric light can be greatly reduced, so as to improve the light-to-light conversion efficiency during low-power pumping; during high-power pumping, by rotating the half-wave plate 7, part of the signal light is transmitted to the absorption cell 9 through the polarization beam splitter prism 8 for absorption, so as to reduce the energy reflux phenomenon in the optical parametric oscillator cavity, reduce the reverse transformation effect, and greatly increase the reverse transformation threshold, so as to improve the light-to-light conversion efficiency and beam quality under high-power pumping.

[0028] Further, as an optional embodiment of the present invention, the pump source output component in the present application includes a fourth resonant cavity mirror 10, a laser module 11, a polarizer 12, a Q switch 13 and a fifth resonant cavity mirror 14 arranged in sequence along the optical path. Specifically, the pump source output component in the present application is mainly used to realize the output of a high repetition rate Q-switched nanosecond laser with a central wavelength of 1064nm, and then the light beam is narrowed or focused to the center of the nonlinear crystal 3 through the coupling system 1, and then the first resonant cavity mirror 2, the second resonant cavity mirror 5, the third resonant cavity mirror 6 and the optical parameter adjustment component together constitute an optical parametric oscillation resonant cavity.

[0029] Furthermore, the surface of the fourth resonant cavity mirror 10 in the present application is coated with a high-reflection film of a wavelength of 1064nm, and the surface of the fifth resonant cavity mirror 14 is coated with a partial reflection film of a 1064nm laser, so that the pump light generated in the fourth resonant cavity mirror 10 and the fifth resonant cavity mirror 14 is emitted from the light outlet of the fifth resonant cavity mirror 14; the laser module 11 includes a Nd:YAG crystal and an 808nm pump source, which are used to generate gain in the cavity; at the same time, the polarizer 12 is used to polarize the 1064nm wavelength light, and the Q switch 13 is mainly used to adjust the quality factor of the optical resonant cavity and generate nanosecond pulsed laser.

[0030] Further, as an optional embodiment of the present invention, the Q switch 13 in the present application is an optical device for a laser, which can control the loss in the laser cavity, thereby generating a high-energy short-pulse laser, and Q represents the quality factor, which represents the relationship between the ability of the laser cavity to store energy and the loss. Further, the Q switch 13 is an acousto-optic Q-switched switch 13, which includes an acousto-optic Q-switched crystal, an acousto-optic driver, and a signal source, and is used to generate nanosecond pulse lasers.

[0031] Furthermore, the coupling system 1 in the present application is mainly used to increase the transmittance of 1064nm light and to focus the 1064nm light, and the size of the focused light spot is smaller than the aperture of the nonlinear crystal 3; and a half-wave plate 7 is also provided inside the coupling system 1 to adjust the polarization direction of the 1064nm laser to meet the phase matching condition.

[0032] Furthermore, the nonlinear crystal 3 in the present application is a MgO:PPLN crystal, wherein the doping concentration of MgO is 5%. When the pump light is injected into the crystal of the nonlinear crystal 3, due to the feedback of the first resonant cavity mirror 2, the second resonant cavity mirror 5 and the third resonant cavity mirror 6, signal light and idler light are formed in the cavity. And the signal light and idler light in the present application are polarized light. After passing through the half-wave plate 7 and the polarization beam splitter prism 8, the angle of the half-wave plate 7 is rotated so that the polarization direction of the signal light cannot be completely matched with the polarization beam splitter prism 8, so that part of the signal light is output from one side of the polarization beam splitter prism 8 and absorbed by the absorption pool 9, so as to achieve the power ratio of the signal light power in the resonant cavity by adjusting the rotation angle of the half-wave plate 7. Furthermore, the light output end face of the nonlinear crystal 3 is coated with an anti-reflection film for 1064nm wavelength light, an anti-reflection film for 3~5μm wavelength light and an anti-reflection film for 1.4~1.7μm wavelength light. Among them, 1064nm wavelength light corresponds to the near-infrared band, 3~5μm wavelength light corresponds to idler light, and 1.4~1.7μm wavelength light corresponds to signal light.

[0033] Furthermore, the surface of the first resonant cavity mirror 2 in the present application is coated with an anti-reflection film for pump light and a high-reflection film for signal light and idler light, the surface of the second resonant cavity mirror 5 is coated with a high-reflection film for signal light, and the surface of the third resonant cavity mirror 6 is coated with a high-reflection film for signal light.

[0034] Further, as an optional embodiment of the present invention, the third prism in the present application can enhance the transmittance of light with a wavelength of 3 to 5 μm and light with a wavelength of 1.4 to 1.7 μm; the third resonant cavity in the present application is coated with an anti-reflection film for light with a wavelength of 3 to 5 μm; the operating wavelength of the half-wave plate 7 in the present application is 1.47 μm, the operating wavelength of the polarization splitter prism 8 is 1.7 μm, and the absorption band of the absorption cell 9 is 1.4 to 1.7 μm.

[0035] Further, as an optional embodiment of the present invention, when the low-power 1064nm pump laser power of the present application is 10w, the 1064nm laser is beam-contracted to the MgO:PPLN crystal through the coupling system 1, and the MgO:PPLN crystal receives the pump light, and the half-wave plate 7 inside the coupling system 1 is rotated to meet the quasi-phase matching, and generates 1.47μm signal light and 3.82μm idler light. Among them, the 1.47μm signal light is transmitted along the half-wave plate 7, the polarization beam splitter prism 8 and the second resonant cavity mirror 5, and the 3.82μm idler light is transmitted along the third resonant cavity mirror 6. Then the angle of the half-wave plate 7 is rotated so that the polarization direction of the 1.47μm signal light is completely matched with the polarization beam splitter prism 8. At this time, the entire resonant cavity is highly reflective to the 1.47μm signal light, and there is a high 1.47μm laser power density in the cavity of the optical parametric oscillator, which greatly improves the light-to-light conversion efficiency of the parametric light under low-power pumping.

[0036] Further, as another optional embodiment of the present invention, when the high-power 1064nm pump laser power in the present application is 90w, the 1064nm laser is beam-contracted to the MgO:PPLN crystal through the coupling system 1, and the MgO:PPLN crystal receives the pump light, and the half-wave plate 7 inside the rotating coupling system 1 is used to meet the quasi-phase matching, and generates a 1.47μm signal light and a 3.82μm idler light. Among them, the 1.47μm signal light is transmitted along the half-wave plate 7, the polarization beam splitter prism 8 and the second resonant cavity mirror 5, and the 3.82μm idler light is transmitted along the third resonant cavity mirror 6. Similarly, the angle of the half-wave plate 7 is rotated so that the polarization direction of the 1.47μm signal light is 45° with the polarization beam splitter prism 8, and part of the signal light is reflected to the absorption cell 9 for absorption. The entire resonant cavity has a large loss for the 1.47μm signal light, which suppresses the high parametric light laser power density in the cavity and greatly improves the reverse transformation threshold under high-power pumping, so that it can achieve higher light-to-light conversion efficiency and higher beam quality under high-power pumping.

[0037] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-efficiency optical parametric oscillator, characterized in that: include: A pump source output component, a coupling system, a first resonant cavity mirror and a nonlinear crystal are sequentially arranged along the optical path direction, a dispersion prism is provided at the light outlet of the nonlinear crystal, the dispersion prism can separate the light output by the nonlinear crystal into signal light and idler light, and the signal light and the idler light are transmitted along the first optical path and the second optical path respectively; A second resonant cavity mirror is provided on the first optical path, and an optical parameter adjustment component is also provided between the dispersion prism and the second resonant cavity mirror. The optical parameter adjustment component can adjust the optical power density of the signal light between the dispersion prism and the second resonant cavity mirror. A third resonant cavity mirror is provided on the second optical path.

2. The high efficiency optical parametric oscillator according to claim 1, characterized in that: The optical parameter adjustment component includes a half-wave plate and a polarization splitter prism arranged along the second optical path, the angle of the half-wave plate is adjustable, the polarization splitter prism can split the light emitted by the dispersion prism into a third optical path and a fourth optical path, the third optical path and the fourth optical path are not colinear, and the second resonant cavity mirror is colinearly arranged with the third optical path, and an absorption pool is provided on the fourth optical path, and the absorption pool is used to absorb the signal light.

3. The high efficiency optical parametric oscillator according to claim 1, characterized in that: The pump source output component comprises a fourth resonant cavity mirror, a laser module, a polarizer, a Q switch and a fifth resonant cavity mirror which are sequentially arranged along the optical path direction.

4. The high-efficiency optical parametric oscillator according to claim 3, characterized in that: The surface of the fifth resonant cavity mirror is coated with a partial reflection film for light with a wavelength of 1064 nm, and the transmittance of the fifth resonant cavity mirror to light with a wavelength of 1064 nm is 20%.

5. The high-efficiency optical parametric oscillator according to claim 3, characterized in that: The surface of the fourth resonant cavity mirror is coated with a high-reflection film for 1064nm wavelength light; the laser module includes a Nd:YAG crystal and an 808nm pump source; the polarizer is used to polarize the 1064nm wavelength light, and the Q switch is used to adjust the quality factor of the optical resonant cavity and generate nanosecond pulse laser.

6. The high-efficiency optical parametric oscillator according to claim 5, characterized in that: The coupling system is used for enhancing the transmittance of 1064nm wavelength laser, and the beam reduction diameter of the coupling system for 1064nm wavelength light is 500μm; the nonlinear crystal is MgO:PPLN crystal, wherein the doping concentration of MgO is 5%, and the end face of the nonlinear crystal is coated with an anti-reflection film for 1064nm wavelength light, an anti-reflection film for 3~5μm wavelength light, and an anti-reflection film for 1.4~1.7μm wavelength light.

7. The high-efficiency optical parametric oscillator according to claim 6, characterized in that: The signal light and idler light generated by the nonlinear crystal are both linearly polarized lights.

8. The high efficiency optical parametric oscillator according to claim 1, characterized in that: The surface of the first resonant cavity mirror is coated with an anti-reflection film for pump light and a high-reflection film for signal light and idler light wavelengths.

9. The high-efficiency optical parametric oscillator according to claim 2, characterized in that: The working wavelength of the half-wave plate is designed to be the wavelength of the signal light, the working wavelength of the polarization beam splitter is designed to be the wavelength of the signal light, and the surface of the second resonant cavity mirror is coated with a high reflection film for the signal light.

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