Optical parametric oscillator

Abstract

The invention discloses an optical parametric oscillator, which relates to the technical field of all-solid-state lasers and vortex light and comprises a pump light source, a first dichroic mirror, a nonlinear crystal, a first reflecting mirror, a partial reflecting mirror, a second dichroic mirror, a rear cavity mirror, an optical rotator, a polarization beam splitter prism, a second reflecting mirror, a third reflecting mirror, a fourth reflecting mirror and a half-wave plate. By designing a special optical path structure, the idler frequency light and the signal light oscillate in two independent paths, so that the mode of the output vortex light is accurately regulated and controlled. In the resonant cavity, the polarization direction of the signal light is adjusted by adopting elements such as an optical rotator, a polarization beam splitter prism and a half-wave plate, and the adjustment mechanism further controls the optical loss in the cavity. According to the invention, the single-state laser can be utilized to realize the output of the superposed-state vortex laser, and the flexible regulation and control of the topological charge carried by a single vortex light in the superposed-state vortex laser can be realized. The regulation and control capability provides a more accurate and controllable means for generation and application of vortex light.

Description

Technical Field

[0001] The invention relates to the technical field of all-solid-state lasers and vortex light, in particular to an optical parametric oscillator. Background Art

[0002] In underwater environments, the propagation of light faces strong attenuation and scattering effects, and traditional optical communication and detection technologies are often limited. As a special light beam with orbital angular momentum, vortex light has a unique rotating wavefront and dark spot characteristics at the center of the beam, which give it significant advantages in underwater applications. Compared with traditional Gaussian beams, vortex light has stronger anti-interference ability and higher focusing performance in underwater environments. It can effectively resist the attenuation caused by inhomogeneous media in water and improve signal transmission distance and detection accuracy. Vortex light shows unique potential, especially in the fields of underwater laser communication, target detection and precision manipulation.

[0003] However, the common methods of generating vortex light currently usually rely on external optical modulators or spatial light modulators. These devices increase the complexity and cost of the system and may affect the stability and efficiency of the laser beam. The traditional method of generating vortex light inside / outside the cavity is difficult to meet the needs of underwater laser detection, imaging and communication for the emission light source due to problems such as low conversion efficiency and single mode. Therefore, how to directly generate superposition state vortex light lasers in the laser cavity has become the key to improving system performance. At present, there is also the problem that the output pulse energy of the blue-green vortex light emission source is low and the mode is single. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an optical parametric oscillator. The present invention can not only simplify the optical system and reduce costs, but also improve the power, stability and beam quality of the laser output, thereby providing more efficient light source support for underwater applications by directly generating superposition state vortex light in the resonant cavity.

[0005] The present invention adopts the following technical solutions to solve the above technical problems:

[0006] An optical parametric oscillator according to the present invention comprises a pump light source, a first dichroic mirror, a nonlinear crystal, a first reflector, a partial reflector, a second dichroic mirror, a rear cavity mirror, an optical rotator, a polarization beam splitter prism, a second reflector, a third reflector, a fourth reflector, and a half-wave plate; wherein,

[0007] The partial reflector, the first dichroic mirror, the nonlinear crystal, the first reflector, and the back cavity mirror constitute a resonant cavity of idler optical parametric oscillation;

[0008] The partial reflector, the first dichroic mirror, the nonlinear crystal, the first reflector, the second dichroic mirror, the optical rotator, the polarization beam splitter prism, the second reflector, the third reflector, the fourth reflector and the half-wave plate constitute a resonant cavity of the signal light parametric oscillation; wherein,

[0009] A pump light source for outputting single-state vortex laser;

[0010] The single-state vortex laser enters the nonlinear crystal after being separated by the first dichroic mirror, and undergoes frequency conversion through an optical parametric oscillation process under the nonlinear effect to generate signal light and idler light;

[0011] The signal light and the idler light are reflected by the first reflector, and the reflected signal light and the idler light are separated into the idler light and the intra-cavity signal light by the second dichroic mirror; the intra-cavity signal light is polarized by the optical rotator, and then enters the polarization beam splitter prism to be separated into two beams with mutually perpendicular polarization directions, and the two beams with mutually perpendicular polarization directions respectively pass through the second reflector, the third reflector, the fourth reflector and the half-wave plate to generate superposition state vortex light, which is output from the polarization beam splitter prism;

[0012] The idler light transmitted through the second dichroic mirror is reflected by the rear cavity mirror and then oscillates again in the resonant cavity of the idler light parametric oscillation, and is output from the partial reflection mirror.

[0013] As a further optimization scheme of the optical parametric oscillator described in the present invention, the nonlinear crystal is phosphate, borate, potassium phosphate, or aluminate.

[0014] As a further optimization scheme of an optical parametric oscillator described in the present invention, the wavelength reflectivity of the first dichroic mirror and the first reflecting mirror to the signal light and the idler light is greater than 99%, the reflectivity of the rear cavity mirror to the idler light is greater than 99%, the transmittance of the second dichroic mirror to the idler light is greater than 99%, and the reflectivity to the signal light is greater than 99%; the partial reflecting mirror has partial transmittance to the idler light.

[0015] As a further optimization scheme of an optical parametric oscillator described in the present invention, the polarization beam splitter prism has a transmittance greater than 99% for laser light in the p-polarization direction of the signal light band, and a reflectivity greater than 99% for light polarized in the s-direction, thereby realizing polarization selection and optical path separation.

[0016] As a further optimization scheme of an optical parametric oscillator described in the present invention, an optical rotator is used to adjust the polarization direction of the signal light to a linearly polarized light including both s-polarization and p-polarization components, thereby adjusting the loss ratio of the s-polarization and p-polarization component signal lights in the cavity through the combined action with the half wave plate, and ensuring that the polarization direction of the signal light is restored to the initial state after passing through the optical rotator again.

[0017] As a further optimization solution of the optical parametric oscillator described in the present invention, the reflectivity of the second reflector, the third reflector, and the fourth reflector to the signal light is greater than 99%.

[0018] As a further optimization solution of an optical parametric oscillator described in the present invention, a half wave plate is used to adjust the polarization direction of the signal light.

[0019] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0020] (1) By making the idler light and the signal light perform optical parametric oscillation in two different optical paths and adjusting the intracavity loss of the vortex light of each mode, the topological charge carried by the vortex light of each mode can be flexibly controlled, thereby realizing superposition state and controllable vortex light laser pulse output in one laser;

[0021] (2) The method provided by the present invention uses a single-state vortex pulse laser as a pump light source to achieve superposition state vortex laser output through a single laser. The optical path structure is simple and compact, and each mode of the superposition state vortex light can be independently controlled, which has high flexibility.

[0022] (3) The present invention adjusts the polarization directions of vortex light of different modes to make them perpendicular to each other, thereby effectively avoiding crosstalk caused by phase distortion when transmitting in a complex underwater environment, thereby improving the stability and transmission performance of the system in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention provides an optical path diagram of a superposition state vortex optical parametric oscillator.

[0024] Figure 2 An intensity distribution diagram of a single-state vortex pump spot and an output superposition state signal spot is provided as an example; wherein (a) is the spot distribution and (b) is the modal diagram.

[0025] The reference numerals in the figure are explained as follows: 1-pump light source, 2-first dichroic mirror, 3-nonlinear crystal, 4-first reflector, 5-partial reflector, 6-second dichroic mirror, 7-back cavity mirror, 8-optical rotator, 9-polarization beam splitter prism, 10-second reflector, 11-third reflector, 12-fourth reflector, 13-half wave plate. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0027] The present invention provides a superposition state vortex optical parametric oscillator, such as Figure 1As shown, it includes a pump light source 1, a dichroic mirror 2, a nonlinear crystal 3, a first reflector 4, a partial reflector 5, a second dichroic mirror 6, a rear cavity mirror 7, an optical rotator 8, a polarization beam splitter prism 9, a second reflector 10, a third reflector 11, a fourth reflector 12, and a half-wave plate 13.

[0028] The laser output from the pump light source generates optical parametric oscillation after passing through the nonlinear crystal, wherein the partial reflector 5, the first dichroic mirror 2, the nonlinear crystal 3, the first reflector 4, and the back cavity mirror 7 constitute a resonant cavity of the idler optical parametric oscillation.

[0029] The partial reflector 5 has a high reflectivity at the signal light wavelength and a certain transmittance at the idle light wavelength band.

[0030] The partial reflector 5, the first dichroic mirror 2, the nonlinear crystal 3, the first reflector 4, the second dichroic mirror 6, the optical rotator 8, the polarization beam splitter prism 9, the second reflector 10, the third reflector 11, the fourth reflector 12 and the half wave plate 13 constitute a resonant cavity for parametric oscillation of the signal light.

[0031] The signal light passing through the nonlinear crystal is p-polarized linear polarized light. After passing through the optical rotator 8, it has polarization components in both the p direction and the s direction. After passing through the polarization beam splitter prism 9, it is split into two beams. After passing through the half-wave plate 13, the polarization direction is changed. Part of it is output after passing through the polarization beam splitter prism 9, and part of it continues to oscillate in the resonant cavity.

[0032] The idle light transmitted through the second dichroic mirror 6 is reflected by the back cavity mirror 7 and oscillates again in the resonant cavity of the idle light parametric oscillation, and passes through the second dichroic mirror 6 again, is reflected by the first reflecting mirror, passes through the nonlinear mirror body 3 again, and is reflected by the dichroic mirror 2 before being output from the partial reflecting mirror 5.

[0033] The optical rotator 8 and the polarization beam splitter prism 9 are used to control the intracavity loss of the vortex light of each mode to achieve independent regulation of its topological charge.

[0034] The optical rotator 8 and the polarization beam splitter prism 9 are used to adjust the polarization direction of the vortex light of each mode in the superposition state vortex light, so that the polarization direction remains unchanged after passing through the optical rotator 8 again, and it is still p-direction linear polarized light.

[0035] The following are parameters of an embodiment of the present invention:

[0036] The present invention provides a superposition state vortex optical parametric oscillator, wherein the pump light source 1 is a 355nm vortex optical laser realized by triple frequency of a 1064nm laser, and the topological charge number l carried by the pump light source 1 is 3, and the light spot distribution is as follows: Figure 2 As shown in (a) in the figure. After passing through the first dichroic mirror 2, it passes through a beryllium aluminate (BBO) crystal with a size of 4*4*10mm 3, the end face is coated with 355nm and 480-520nm band anti-reflection film, the first dichroic mirror 2 and the first reflector 4 have anti-reflection for 355nm wavelength, and have high reflectivity for 480-520nm & 1118-1323nm band. The rear cavity mirror 7 has high reflectivity in the 480-520nm & 1118-1323nm band, and the partial reflector 5 has a transmittance of about 20% in the 1118-1323nm band. Therefore, the rear cavity mirror 7, the first dichroic mirror 2, the nonlinear crystal, the first reflector 4 and the partial reflector 5 form a resonant cavity of the idler optical parametric oscillation.

[0037] The dichroic mirror 6 has high transmittance for 1118-1323nm laser and high reflectivity for 480-520nm laser, and the optical rotator has a rotation angle of 30° for 480nm laser. The polarization beam splitter prism 9 has high transmittance for 480nm laser in the p-polarization direction and high reflectivity for 480nm laser in the s-polarization direction. The second reflector 10, the third reflector 11, and the fourth reflector 12 all have high transmittance for 480-520nm laser, and the wavelength of the half-wave plate is 486nm.

[0038] The partial reflector 5, the first dichroic mirror 2, the nonlinear crystal 3, the first reflector 4, the second dichroic mirror 6, the optical rotator 8, the polarization beam splitter prism 9, the second reflector 10, the third reflector 11, the fourth reflector 12, and the half-wave plate 13 constitute a resonant cavity for parametric oscillation of the signal light. The superposition state vortex light is output from the polarization beam splitter prism 9, and the mode is as follows: Figure 2 As shown in (b) in the figure, the polarization direction of the signal light is changed by using an optical rotator to adjust the intracavity loss separately, thereby achieving separate control of the vortex light of each mode in the superposition state vortex light.

[0039] The optical rotator 8 and the polarization beam splitter prism 9 are used to adjust the polarization direction of the vortex light of each mode in the superposition state vortex light, so that the polarization direction remains unchanged after passing through the optical rotator 8 again, and it is still p-direction linear polarized light.

[0040] The above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. An optical parametric oscillator, characterized in that: It includes a pump light source, a first dichroic mirror, a nonlinear crystal, a first reflector, a partial reflector, a second dichroic mirror, a rear cavity mirror, an optical rotator, a polarization beam splitter prism, a second reflector, a third reflector, a fourth reflector, and a half-wave plate; wherein, The partial reflector, the first dichroic mirror, the nonlinear crystal, the first reflector, and the back cavity mirror constitute a resonant cavity of idler optical parametric oscillation; The partial reflector, the first dichroic mirror, the nonlinear crystal, the first reflector, the second dichroic mirror, the optical rotator, the polarization beam splitter prism, the second reflector, the third reflector, the fourth reflector and the half-wave plate constitute a resonant cavity of the signal light parametric oscillation; wherein, A pump light source for outputting single-state vortex laser; The single-state vortex laser enters the nonlinear crystal after being separated by the first dichroic mirror, and undergoes frequency conversion through an optical parametric oscillation process under the nonlinear effect to generate signal light and idler light; The signal light and the idler light are reflected by the first reflector, and the reflected signal light and the idler light are separated into the idler light and the intra-cavity signal light by the second dichroic mirror; the intra-cavity signal light is polarized by the optical rotator, and then enters the polarization beam splitter prism to be separated into two beams with mutually perpendicular polarization directions, and the two beams with mutually perpendicular polarization directions respectively pass through the second reflector, the third reflector, the fourth reflector and the half-wave plate to generate superposition state vortex light, which is output from the polarization beam splitter prism; The idler light transmitted through the second dichroic mirror is reflected by the rear cavity mirror and then oscillates again in the resonant cavity of the idler light parametric oscillation, and is output from the partial reflection mirror.

2. An optical parametric oscillator according to claim 1, characterized in that: The nonlinear crystal is phosphate, borate, potassium phosphate, or aluminate.

3. An optical parametric oscillator according to claim 1, characterized in that: The wavelength reflectivity of the first dichroic mirror and the first reflector to the signal light and the idle light is greater than 99%, the reflectivity of the rear cavity mirror to the idle light is greater than 99%, the transmittance of the second dichroic mirror to the idle light is greater than 99%, and the reflectivity to the signal light is greater than 99%; the partial reflector has partial transmittance to the idle light.

4. An optical parametric oscillator according to claim 1, characterized in that: The polarization beam splitter prism has a transmittance greater than 99% for laser light in the p-polarization direction of the signal light band, and a reflectivity greater than 99% for light polarized in the s-direction, thereby realizing polarization selection and optical path separation.

5. The optical parametric oscillator according to claim 1, characterized in that: The optical rotator is used to adjust the polarization direction of the signal light to linearly polarized light including both s-polarization and p-polarization components, thereby adjusting the loss ratio of the s-polarization and p-polarization component signal light in the cavity through the combined action with the half wave plate, and ensuring that the polarization direction of the signal light is restored to the initial state after passing through the optical rotator again.

6. The optical parametric oscillator according to claim 1, characterized in that: The reflectivity of the second reflector, the third reflector and the fourth reflector to the signal light is greater than 99%.

7. An optical parametric oscillator according to claim 1, characterized in that: The half wave plate is used to adjust the polarization direction of the signal light.

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