An optical parametric oscillator

Abstract

The application discloses an optical parametric oscillator, relates to the field of all-solid-state lasers and vortex light technology, and comprises a pump light source, a first dichroic mirror, a nonlinear crystal, a first reflector, a partially reflecting mirror, a second dichroic mirror, a back cavity mirror, a rotator, a polarization beam splitter prism, a second reflector, a third reflector, a fourth reflector and a half wave plate. Through the design of a special optical path structure, idler light and signal light oscillate in two independent paths, so that the precise regulation and control of output vortex light modes are realized. In the resonant cavity, the rotator, the polarization beam splitter prism and the half wave plate and other elements are used to adjust the polarization direction of the signal light, and the adjustment mechanism further controls the light loss in the cavity. The application can realize the output of superposition state vortex laser by using a single state laser, and realizes the flexible regulation and control of the topological charge number carried by a single vortex light in the superposition state vortex light. The regulation and control capacity provides a more accurate and controllable means for the generation and application of vortex light.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of all-solid-state lasers and vortex light, and particularly relates to an optical parametric oscillator. BACKGROUND

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

[0003] However, the common vortex light generation methods currently rely on external optical modulators or spatial light modulators, which increase the complexity and cost of the system and may affect the stability and efficiency of the laser beam. The traditional intracavity / extracavity vortex light generation method has low conversion efficiency and single mode, which is difficult to meet the demand of underwater laser detection, imaging and communication for the emission source. Therefore, how to directly generate superposition state vortex light laser in the laser cavity has become the key to improve the system performance. The current blue-green vortex light emission source also has the problems of low pulse energy and single mode. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide an optical parametric oscillator. The present application directly generates superposition state vortex light in the resonant cavity, which not only simplifies the optical system and reduces the cost, but also improves the power, stability and beam quality of the laser output, providing more efficient light source support for underwater applications.

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

[0006] According to the optical parametric oscillator provided by the present application, the pump light source, the first dichroic mirror, the nonlinear crystal, the first mirror, the partial mirror, the second dichroic mirror, the back cavity mirror, the optical rotator, the polarization beam splitter prism, the second mirror, the third mirror, the fourth mirror and the half wave plate are provided.

[0007] The partial mirror, the first dichroic mirror, the nonlinear crystal, the first mirror and the back cavity mirror constitute the resonant cavity of the idler light parametric oscillation.

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

[0009] A pump light source is used for outputting single-mode vortex laser;

[0010] The single-mode vortex laser enters the nonlinear crystal after being separated by the first dichroic mirror, and frequency conversion is generated by the 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 mirror, the reflected signal light and the idler light are separated into idler light and intracavity signal light by the second dichroic mirror, the intracavity signal light enters the polarization beam splitting prism after the polarization direction is adjusted by the rotator, and the polarization beam splitting prism is divided into two beams with perpendicular polarization directions, the two beams with perpendicular polarization directions pass through the second mirror, the third mirror, the fourth mirror and the half wave plate respectively, and superposition state vortex light is generated and output from the polarization beam splitting prism;

[0012] The idler light transmitted from the second dichroic mirror is reflected by the rear mirror and re-oscillates in the resonant cavity of the idler light parametric oscillation and is output from the partial mirror.

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

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

[0015] As a further optimization scheme of the optical parametric oscillator, the polarization beam splitting prism has transmittance greater than 99% to the laser with p polarization direction in the signal light wave band, and has reflectivity greater than 99% to the light with s direction polarization, so as to realize polarization selection and optical path separation.

[0016] As a further optimization scheme of the optical parametric oscillator, the rotator is used to adjust the polarization direction of the signal light to linearly polarized light including s polarization and p polarization components, so as to adjust the loss ratio of the intracavity s polarization and p polarization component signal light by the joint action of the half wave plate, and ensure that the polarization direction of the signal light returns to the initial state after passing through the rotator again.

[0017] As a further optimization scheme of the optical parametric oscillator, the reflectivity of the second mirror, the third mirror and the fourth mirror to the signal light is greater than 99%.

[0018] As a further optimization scheme of the optical parametric oscillator, the half-wave plate is used to adjust the polarization direction of the signal light.

[0019] Compared with the prior art, the technical scheme 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 intra-cavity loss of the vortex light of each mode, the topological charge carried by the vortex light of each mode can be flexibly regulated, so that superposition state and adjustable vortex light laser pulse output can be realized in one laser.

[0021] (2) The method provided by the application uses single-mode vortex pulse laser as a pump light source, realizes superposition state vortex laser output through a single laser, has a simple and compact optical path structure, and can independently regulate each mode of the superposition state vortex light, so that high flexibility is achieved.

[0022] (3) By adjusting the polarization direction of the vortex light of different modes to be perpendicular to each other, the application effectively avoids crosstalk caused by phase distortion when the vortex light is transmitted in a complex underwater environment, and improves the stability and transmission performance of the system in actual application. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is an optical path diagram of a superposition state vortex optical parametric oscillator provided by the application;

[0024] Figure 2 The application provides an intensity distribution diagram of a single-mode vortex pump light spot and an output superposition state signal light spot; wherein (a) is a light spot distribution, and (b) is a mode diagram.

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

[0026] The technical scheme of the application will be further described in detail in combination with the drawings:

[0027] The application provides a superposition state vortex optical parametric oscillator, which comprises a pump light source, a first dichroic mirror, a nonlinear crystal, a first mirror, a partial mirror, a second dichroic mirror, a back cavity mirror, a rotary optical device, a polarization beam splitter prism, a second mirror, a third mirror, a fourth mirror and a half-wave plate. Figure 1As shown, including pump light source 1, dichroic mirror 2, nonlinear crystal 3, first mirror 4, partially reflecting mirror 5, second dichroic mirror 6, back cavity mirror 7, optical rotator 8, polarization beam splitter prism 9, second mirror 10, third mirror 11, fourth mirror 12, half wave plate 13.

[0028] The laser output from the pump light source passes through the nonlinear crystal to generate optical parametric oscillation, wherein the partially reflecting mirror 5, the first dichroic mirror 2, the nonlinear crystal 3, the first mirror 4, and the back cavity mirror 7 constitute the resonant cavity of the idler light parametric oscillation.

[0029] The partially reflecting mirror 5 has high reflectivity at the signal light wavelength and certain transmittance at the idler light wavelength.

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

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

[0032] The idler light transmitted through the second dichroic mirror 6 is reflected by the back cavity mirror 7 and re-oscillates in the resonant cavity of the idler light parametric oscillation, and after passing through the second dichroic mirror 6 again, it is reflected by the first mirror, passes through the nonlinear mirror 3 again, and is reflected by the dichroic mirror 2, and is output from the partially reflecting mirror 5.

[0033] The optical rotator 8 and the polarization beam splitter prism 9 are used to control the in-cavity loss of the vortex light of each mode to realize independent regulation of the topological charge number.

[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 after passing through the optical rotator 8 again, the polarization direction remains unchanged and is still linearly polarized light with p direction.

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

[0036] The superposition state vortex light parametric oscillator of the present application, the pump light source 1 is a 355nm vortex light laser realized by tripling 1064nm laser, which carries a topological charge number l=3, and the spot distribution is as shown in Figure 2 (a). After passing through the first dichroic mirror 2, it passes through the beryllium aluminum (BBO) crystal, and the crystal size is 4*4*10mm 3The end face is coated with 355nm and 480-520nm band antireflection film, the first dichroic mirror 2 and the first mirror 4 are antireflection to 355nm wavelength and have high reflectivity to 480-520nm&1118-1323nm band. The rear cavity mirror 7 has high reflectivity to 480-520nm&1118-1323nm band, and the partial mirror 5 has a transmittance of about 20% to 1118-1323nm band. Therefore, the rear cavity mirror 7, the first dichroic mirror 2, the nonlinear crystal, the first mirror 4 and the partial mirror 5 form the resonant cavity of the idler light parametric oscillation.

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

[0038] The partial mirror 5, the first dichroic mirror 2, the nonlinear crystal 3, the first mirror 4, the second dichroic mirror 6, the optical rotator 8, the polarization beam splitter prism 9, the second mirror 10, the third mirror 11, the fourth mirror 12 and the half wave plate 13 form the resonant cavity of the signal light parametric oscillation. The resonant cavity of the signal light parametric oscillation is formed. The superposition state vortex light is output from the polarization beam splitter prism 9, and the mode is shown in (b) of FIG. 4. Figure 2 The polarization direction of the signal light is changed by the optical rotator to adjust the cavity loss respectively, so that the vortex light of each mode of the superposition state vortex light is adjusted respectively.

[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 of the superposition state vortex light, so that the polarization direction is unchanged after the vortex light passes through the optical rotator 8 again, and the polarization direction is still p direction linearly polarized light.

[0040] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered in the protection scope of the present application.

Claims

1. An optical parametric oscillator, characterized in that, It includes a pump source, a first dichroic mirror, a nonlinear crystal, a first reflecting mirror, a partial reflecting mirror, a second dichroic mirror, a rear cavity mirror, a beam rotator, a polarizing beam splitter prism, a second reflecting mirror, a third reflecting mirror, a fourth reflecting mirror, and a half-wave plate; among which, The aforementioned partial reflector, first dichroic mirror, nonlinear crystal, first reflector, and rear cavity mirror constitute a resonant cavity for idler frequency optical parametric oscillation. The aforementioned partial reflector, first dichroic mirror, nonlinear crystal, first reflector, second dichroic mirror, optical rotator, polarizing beam splitter prism, second reflector, third reflector, fourth reflector, and half-wave plate constitute a resonant cavity for parametric oscillation of signal light; wherein, Pump source, used to output single-state vortex laser; The single-state vortex laser is separated into colors by the first dichroic mirror and then enters the nonlinear crystal. Under the nonlinear effect, it undergoes frequency conversion through an optical parametric oscillation process to generate signal light and idler light. The signal light and idler light are reflected by the first mirror. The reflected signal light and idler light are then separated into idler light and cavity signal light by the second dichroic mirror. The cavity signal light is polarized by a rotator and then enters a polarizing beam splitter, where it is split into two beams with mutually perpendicular polarization directions. These two beams with mutually perpendicular polarization directions pass through the second mirror, the third mirror, the fourth mirror, and a half-wave plate, respectively, and generate superimposed vortex light, which is then output from the polarizing beam splitter. The idler light transmitted through the second dichroic mirror is reflected by the rear cavity mirror and then oscillates again in the resonant cavity where the idler light parametrically oscillates before being output from the partial reflector.

2. The optical parametric oscillator according to claim 1, characterized in that, Nonlinear crystals are phosphates, borates, potassium phosphates, or aluminates.

3. The optical parametric oscillator according to claim 1, characterized in that, The first dichroic mirror and the first reflecting mirror have a wavelength reflectivity greater than 99% for the signal light and idler light, the rear cavity mirror has a reflectivity greater than 99% for the idler light, the second dichroic mirror has a transmittance greater than 99% for the idler light and a reflectivity greater than 99% for the signal light; some reflecting mirrors have partial transmittance for the idler light.

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

5. An optical parametric oscillator according to claim 1, characterized in that, A rotator is used to adjust the polarization direction of signal light to linearly polarized light that includes both s-polarization and p-polarization components. In combination with a half-wave plate, it adjusts the loss ratio of the s-polarization and p-polarization components of the signal light in the cavity and ensures that the polarization direction of the signal light returns to its initial state after passing through the rotator again.

6. An optical parametric oscillator according to claim 1, characterized in that, The second, third, and fourth reflecting mirrors have a reflectivity of more than 99% for the signal light.

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

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