Double-end pumping optical parametric amplification system

Abstract

The invention discloses a double-end pumping optical parametric amplification system which comprises a seed laser, a dichroscope, a first pumping laser, a half-wave plate, a first plano-concave mirror, a periodic lithium niobate crystal, a second plano-concave mirror, a second pumping laser, a first plane mirror and a second plane mirror. According to the system, through the design of a double-end pumping structure and a circulating light path, the problems that a traditional single-end pumping optical parametric amplification system is low in light field compression efficiency and remarkable in heat effect are solved. The method is suitable for application fields with strict requirements on low-noise light fields, such as continuous variable quantum key distribution and high-precision interference measurement.

Description

Technical Field

[0001] This invention relates to the field of fiber optics and laser technology, and in particular to a dual-ended pumped optical parametric amplification system. Background Technology

[0002] Optical parametric amplification (OPA), as an important nonlinear optical gain mechanism, is widely used in ultrafast laser systems, spectral detection, and quantum information processing. By leveraging the interaction between the pump light and signal light in a nonlinear crystal, optical field compression of the signal light can be achieved. However, in practical applications, traditional PPA systems often employ a single-end pump structure, where the pump light is injected from one end of the nonlinear crystal. While this approach is relatively simple, it suffers from low pump efficiency, insufficient nonlinear interaction, and poor output stability, thus limiting the compression degree. Furthermore, single-end pump structures tend to generate non-uniform thermal distributions in the nonlinear crystal, introducing additional phase noise and further reducing the quality of optical field compression. Therefore, designing a compact and optically stable optical parametric amplification system is of significant engineering value and research importance for improving PPA efficiency and enhancing system stability. Summary of the Invention

[0003] To address the aforementioned issues, this invention provides a dual-pumped optical parametric amplification system. Through bidirectional pumping and a four-mirror ring cavity structure, it achieves efficient optical field compression of signal light, improves the overall system performance, and solves the technical problems of low compression efficiency, limited amplification gain, and unstable optical path in existing solutions.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A dual-pumped optical parametric amplification system includes a seed laser, a dichroic mirror, a first pump laser, a half-wave plate, a first plano-concave mirror, a periodic lithium niobate crystal, a second plano-concave mirror, a second pump laser, a first plane mirror, and a second plane mirror, wherein...

[0006] The signal light output from the seed laser is incident on the incident end of the dichroic mirror. The pump light output from the first pump laser is polarized by a half-wave plate and then incident on the dichroic mirror to be combined with the signal light. The combined light is focused by the first plano-concave mirror and enters the first end of the periodic lithium niobate crystal. At the same time, the pump light output from the second pump laser is focused by the second plano-concave mirror and injected in the opposite direction from the second end of the periodic lithium niobate crystal. It interacts parametrically with the combined light in the periodic lithium niobate crystal. The resulting amplified signal light is reflected by the second plano-concave mirror and then passes through the first and second plane mirrors in sequence before being output. The unconsumed first and second pump lights circulate in the four-mirror ring cavity, realizing parametric amplification in the periodic lithium niobate crystal.

[0007] Furthermore, the first plano-concave mirror, the periodic lithium niobate crystal, the second plano-concave mirror, the first plane mirror, and the second plane mirror constitute a four-mirror annular cavity. The central optical axes of each optical element are located in the same plane, and the concave surfaces of the first and second plano-concave mirrors are arranged opposite each other. The first and second plane mirrors are symmetrically distributed and form an angle of 45±1° with the horizontal optical path. The first plano-concave mirror, the periodic lithium niobate crystal, and the second plano-concave mirror are located on a first horizontal line, and the first and second plane mirrors are located on a second horizontal line. The first horizontal line is parallel to the second horizontal line.

[0008] Furthermore, the seed laser is a fiber laser or a solid-state laser, with an output dual wavelength range of 770-795nm.

[0009] Furthermore, the dichroic mirror has a reflectivity of not less than 96% at a wavelength of 532nm and a transmittance of not less than 98% in the wavelength range of 770-795nm.

[0010] Furthermore, the first pump laser and the second pump laser have an output wavelength of 532nm and an output power of 50W.

[0011] Furthermore, the periodic lithium niobate crystal is a quasi-phase-matched crystal.

[0012] Furthermore, both the first and second plano-concave mirrors are coated with a 770-795nm high-reflection film and a 532nm anti-reflection film on their concave surfaces.

[0013] Furthermore, the first and second planar reflectors are coated with a 770-795nm high-reflectivity film, with the second planar reflector serving as the output coupling mirror.

[0014] Furthermore, both the pump light and the signal light propagate along an "8"-shaped optical path within the four-mirror annular cavity. This "8"-shaped optical path includes a first pump light that is focused by a first plano-concave mirror and enters the periodic lithium niobate crystal to undergo a parametric process. The unconsumed first pump light is then reflected by a second plano-concave mirror, a first plane mirror, a second plane mirror, and a second plano-concave mirror before re-entering the periodic lithium niobate crystal. The "8"-shaped optical path also includes a second pump light that is focused by a second plano-concave mirror onto the periodic lithium niobate crystal. The unconsumed second pump light is then reflected by a first plano-concave mirror, a second plane mirror, a first plane mirror, and a second plano-concave mirror before re-entering the periodic lithium niobate crystal, ultimately achieving dual-end pumping of the periodic lithium niobate crystal and generating a compressed state light source.

[0015] Furthermore, the optical parametric amplification system controls the pump power ratio injected into the four-mirror ring cavity at both ends by adjusting the output power of the first pump laser and the second pump laser, thereby changing the compression of the signal light.

[0016] The beneficial effects of this invention are as follows:

[0017] A dual-pump structure is employed, allowing pump light to be injected simultaneously from both ends of a periodic lithium niobate crystal, effectively enhancing the efficiency of nonlinear interactions. The symmetrical pump configuration not only improves the signal light gain but also significantly enhances the optical field compression, contributing to higher-quality quantum state manipulation and low-noise signal transmission. A four-mirror ring cavity structure is introduced, enabling multiple cyclic interactions between the signal and pump light within the cavity, further enhancing the parametric amplification effect. This closed-loop structure not only improves compression efficiency but also enhances system stability and optical path consistency, overcoming problems such as optical path drift and low coupling efficiency found in existing schemes. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a dual-ended pumped optical parametric amplification system according to the present invention;

[0019] Figure 2 This is a schematic diagram of the structural parameters of the figure-eight ring laser resonator of the present invention;

[0020] Figure label:

[0021] 1. Seed laser; 2. Dichroic mirror; 3. First pump laser; 4. Half-wave plate; 5. First plano-concave mirror; 6. Periodic lithium niobate crystal; 7. Second plano-concave mirror; 8. Second pump laser; 9. First plane mirror; 10. Second plane mirror. Detailed Implementation

[0022] To make the objectives and technical solutions of this application clearer, the present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention, but should not be used to limit the scope of protection of the present invention.

[0023] In the description of this invention, the use of "first" and "second" is only for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or implicitly indicating the order of the technical features indicated.

[0024] like Figure 1 As shown, the present invention provides a dual-pumped optical parametric amplification system, comprising the following components: a seed laser 1, a dichroic mirror 2, a first pump laser 3, a half-wave plate 4, a first plano-concave mirror 5, a periodic lithium niobate crystal 6, a second plano-concave mirror 7, a second pump laser 8, a first plane mirror 9, and a second plane mirror 10.

[0025] The connections between the various components are as follows:

[0026] The signal light emitted by the seed laser 1 is first incident on the dichroic mirror 2. The pump light generated by the first pump laser 3 is polarized by the half-wave plate 4 and then combined with the signal light at the dichroic mirror 2. The combined beam is focused by the first plano-concave mirror 5 and enters the periodically polarized lithium niobate crystal 6 from the first end. Simultaneously, the pump light output from the second pump laser 8 is focused by the second plano-concave mirror 7 and injected in reverse from the other end (i.e., the second end) of the periodic lithium niobate crystal 6, achieving efficient nonlinear parametric interaction with the combined beam incident from the first end of the periodic lithium niobate crystal 6 within the crystal. In the periodic lithium niobate crystal 6, an optical parametric amplification process occurs, enhancing the signal light and accompanied by a certain degree of optical field compression. After the compressed signal light is output from the periodic lithium niobate crystal 6, it is reflected by the second plano-concave mirror 7 and propagates sequentially to the first plane mirror 9 and the second plane mirror 10, finally exiting the system from the second plane mirror 10. The unconsumed pump light (i.e. the unconsumed first and second pump light) continues to propagate in a loop within the annular cavity formed by the four mirrors (first plano-concave mirror 5, second plano-concave mirror 7, first plane mirror 9, and second plane mirror 10), achieving efficient multiplexing and cyclic parametric amplification of the pump light.

[0027] In one embodiment, the seed laser 1 can be a fiber laser or a solid-state laser, with an output wavelength range covering 770-795nm. The laser has good wavelength stability (better than ±0.1nm) and power stability (better than ±1%), and can provide a high-quality, low-noise signal source for the optical parametric amplification process.

[0028] The dichroic mirror 2 exhibits excellent spectral selectivity, with a reflectivity of no less than 96% at a wavelength of 532 nm and a transmittance of no less than 98% in the wavelength range of 770-795 nm. This dichroic mirror 2 is used to achieve the recombination of pump light and signal light, ensuring high-efficiency optical path coupling of the two lights at different wavelengths while avoiding unnecessary energy loss.

[0029] Both the first pump laser 3 and the second pump laser 8 are high-power green lasers with a working wavelength of 532 nm and a single unit output power of up to 50W. They have high stability, are suitable for long-term continuous operation, and provide sufficient pump energy for nonlinear crystals.

[0030] The half-wave plate 4 is a zero-order half-wave plate in the 532 nm band with a transmittance of ≥99.5%, used to precisely control the polarization state of the pump light.

[0031] The periodic lithium niobate crystal 6 is a nonlinear optical crystal employing quasi-phase-matching technology. It utilizes a periodic polarization structure to achieve efficient optical parametric conversion under set temperature conditions. This periodic lithium niobate crystal 6 supports efficient parametric amplification between 770-795nm signal light and 532nm pump light, exhibiting a wide phase-matching bandwidth and a high nonlinear coefficient.

[0032] Both the first plano-concave mirror 5 and the second plano-concave mirror 7 have concave surfaces coated with a dual-band thin-film coating: high reflectivity (≥99.5%) in the 770-795 nm band and high transmittance (≥98%) in the 532 nm band. This design ensures that the signal light can form a stable reflection circuit within the cavity, while the pump light can be smoothly injected into the periodic lithium niobate crystal 6. Furthermore, the radius of curvature of the first plano-concave mirror 5... The second plano-concave mirror has a radius of curvature of 7. .

[0033] The first plane mirror 9 has a high reflectivity (99%) in the signal band (770-795 nm), while the second plane mirror 10 has a reflectivity (90-95%) in the signal band (770-795 nm). As an output coupling mirror, it couples part of the signal light to the outside of the cavity. Both are coated with a 770-795 nm high reflectivity film.

[0034] The first plano-concave mirror 5, the periodic lithium niobate crystal 6, the second plano-concave mirror 7, the first plane mirror 9, and the second plane mirror 10 constitute a four-mirror annular cavity.

[0035] The first plano-concave mirror 5, the periodic lithium niobate crystal 6, the second plano-concave mirror 7, the first plane mirror 9, and the second plane mirror 10 constitute a coplanar four-mirror annular cavity. The central optical axes of each optical element are located in the same plane, and the concave surfaces of the first plano-concave mirror 5 and the second plano-concave mirror 7 are arranged opposite each other with their radii of curvature matching the laser mode. The first plane mirror 9 and the second plane mirror 10 are symmetrically distributed, forming an angle of 45±1° with the horizontal optical path to ensure the precise intersection of the figure-eight optical path. The first plano-concave mirror 5, the periodic lithium niobate crystal 6, and the second plano-concave mirror 7 are located on a first horizontal line, and the first plane mirror 9 and the second plane mirror 10 are located on a second horizontal line. The first horizontal line is parallel to the second horizontal line.

[0036] The distance from the center of the first plano-concave mirror 5 to the center of the periodic lithium niobate crystal 6 is The distance from the center of the periodic lithium niobate crystal 6 to the second plano-concave mirror 7 is The distance from the second plano-concave mirror 7 to the first planar reflecting mirror 9 is The distance from the first plane mirror 9 to the second plane mirror 10 is The distance from the second plane mirror 10 to the first plano-concave mirror 5 is ,like Figure 2 As shown. Further, the wraparound matrix of the periodic lens sequence can be obtained as follows:

[0037] ,

[0038] The stability conditions of the "8" shaped vocal melody: You can select , , , and The stability parameters of the resonant cavity fully meet the design requirements, ensuring the stable operation of the laser system. A, B, C, and D are intermediate parameters.

[0039] When the optical path design within the figure-eight cavity satisfies the resonant cavity stability condition, the combined pump light and signal light undergo multiple parametric downconversions within the periodic lithium niobate crystal 6. Based on the energy conservation principle... ,in The pump light wavelength, The wavelength of the signal light. At the idler wavelength, this process generates idler light of approximately 2 μm. The signal light and idler light form a quantum correlation through nonlinear interaction, achieving optical field compression of the signal light and generating compressed light. After multiple rounds of cyclic amplification, the signal light is highly compressed, and the quantum noise of the signal light is lower than the standard quantum limit, ultimately generating a non-classical light source.

[0040] The optical propagation path within the figure-eight cavity satisfies the following: the first pump light and the signal light are transmitted along the first circular path, sequentially reflected by the first plano-concave mirror 5 → periodic lithium niobate crystal 6 → second plano-concave mirror 7 → first plane mirror 9 → second plane mirror 10 → returning to the first plano-concave mirror 5 and then re-entering the periodic lithium niobate crystal 6; the second pump light is transmitted in the reverse direction along the second circular path, sequentially reflected by the second plano-concave mirror 7 → periodic lithium niobate crystal 6 → first plano-concave mirror 5 → second plane mirror 10 → first plane mirror 9 → returning to the second plano-concave mirror 7 and then re-entering the periodic lithium niobate crystal 6; the signal light is partially transmitted through the second plane mirror 10 to achieve coupling output.

[0041] The dual-pumped optical parametric amplification system can flexibly control the pump power ratio injected into the four-mirror ring cavity at both ends by adjusting the output power of the first pump laser 3 and the second pump laser 8, thereby further improving the compression of the signal light.

[0042] Through the above design, the dual-pumped optical parametric amplification system of this embodiment not only achieves high compression and low noise signal light generation, but also has high structural stability and tunability, providing effective technical support for high-performance quantum light sources.

[0043] The contents of this invention not described in detail are existing technologies known to those skilled in the art.

[0044] The above embodiments are provided merely for the purpose of describing the present invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. Various equivalent substitutions and modifications made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. A dual-end-pumped optical parametric amplification system, characterized by, The application relates to a kind of four-mirror ring cavity dual-wavelength fiber laser, comprising seed laser (1), dichroic mirror (2), first pump laser (3), half-wave plate (4), first plano-concave mirror (5), periodic lithium niobate crystal (6), second plano-concave mirror (7), second pump laser (8), first plane mirror (9) and second plane mirror (10), wherein, Signal light output by the seed laser (1) is incident to the dichroic mirror (2), first pump light output by the first pump laser (3) is incident to the dichroic mirror (2) after polarization adjustment by the half-wave plate (4), and the combined light is focused by the first plano-concave mirror (5) and then enters the first end of the periodic lithium niobate crystal (6); at the same time, second pump light output by the second pump laser (8) is focused by the second plano-concave mirror (7) and then injected from the second end of the periodic lithium niobate crystal (6) in the opposite direction, and the parametric interaction occurs between the combined light and the second pump light in the periodic lithium niobate crystal (6), the amplified signal light is reflected by the second plano-concave mirror (7) and then output by the first plane mirror (9) and the second plane mirror (10) in sequence, and the first and second pump lights not consumed are transmitted in the four-mirror ring cavity to achieve parametric amplification in the periodic lithium niobate crystal (6).

2. A dual-end-pumped optical parametric amplification system according to claim 1, characterized in that, The first plano-concave mirror (5), the periodic lithium niobate crystal (6), the second plano-concave mirror (7), the first plane mirror (9) and the second plane mirror (10) constitute a four-mirror ring cavity, the central optical axes of the optical elements are located in the same plane, the concave surfaces of the first plano-concave mirror (5) and the second plano-concave mirror (7) are oppositely arranged, the first plane mirror (9) and the second plane mirror (10) are symmetrically distributed and form an angle of 45±1° with the horizontal light path, the first plano-concave mirror (5), the periodic lithium niobate crystal (6) and the second plano-concave mirror (7) are located on a first horizontal line, the first plane mirror (9) and the second plane mirror (10) are located on a second horizontal line, and the first horizontal line is parallel to the second horizontal line.

3. A dual-end-pumped optical parametric amplification system according to claim 1, wherein, The seed laser (1) is a fiber laser or a solid-state laser, and outputs dual-wavelength light in the range of 770-795 nm.

4. A dual-end-pumped optical parametric amplification system according to claim 1, wherein, The dichroic mirror (2) has a reflectivity of not less than 96% at a wavelength of 532 nm and a transmittance of not less than 98% in the wavelength range of 770-795 nm.

5. A dual-end-pumped optical parametric amplification system according to claim 1, wherein, The first pump laser (3) and the second pump laser (8) output light at a wavelength of 532 nm and have an output power of 50 W.

6. A dual-end-pumped optical parametric amplification system according to claim 1, wherein, The periodic lithium niobate crystal (6) is a quasi-phase matching crystal.

7. A dual-end-pumped optical parametric amplification system according to claim 1, wherein, The concave surfaces of the first plano-concave mirror (5) and the second plano-concave mirror (7) are coated with high-reflection films for 770-795 nm and antireflection films for 532 nm.

8. A dual-end-pumped optical parametric amplification system according to claim 1, wherein, The first plane mirror (9) and the second plane mirror (10) are coated with high-reflection films for 770-795 nm, and the second plane mirror (10) serves as an output coupling mirror.

9. A dual-end-pumped optical parametric amplification system according to claim 1, wherein, The pump light and the signal light propagate along the "8" shaped light path in the four-mirror ring cavity, the "8" shaped light path comprises that the first pump light is focused by the first plano-concave mirror (5) and enters the periodical lithium niobate crystal (6) to generate the parametric process, the unconsumed first pump light is reflected by the second plano-concave mirror (7), the first plane mirror (9), the second plane mirror (10) and the first plano-concave mirror (5) and re-enters the periodical lithium niobate crystal (6); the "8" shaped light path also comprises that the second pump light is focused by the second plano-concave mirror (7) to the periodical lithium niobate crystal (6), and the unconsumed second pump light is reflected by the first plano-concave mirror (5), the second plane mirror (10), the first plane mirror (9) and the second plano-concave mirror (7) and re-enters the periodical lithium niobate crystal (6), and finally the double-end pump periodical lithium niobate crystal (6) is realized to generate the squeezed state light source.

10. The dual-end-pumped optical parametric amplification system of claim 1, wherein, The optical parametric amplification system controls the pump power ratio of the two ends of the four-mirror ring cavity by adjusting the output power of the first pump laser (3) and the second pump laser (8) to change the squeezing degree of the signal light.

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