Optical parametric oscillator and laser generating device

Abstract

This application discloses an optical parametric oscillator and a laser generating device, relating to the field of laser technology. The optical parametric oscillator includes a first optical fiber, a mirror assembly, a nonlinear crystal, and a second optical fiber. The first optical fiber has a first receiving end and a first output end. The first receiving end is used to receive pump light. The second optical fiber has a second receiving end and a second output end. Light output from the first output end can be transmitted to the second receiving end via the mirror assembly and the nonlinear crystal. The second output end is used to output signal light. The mirror assembly includes multiple mirrors. The nonlinear crystal is located in the optical path between two mirrors. A first grating is disposed on the first optical fiber, and a second grating is disposed on the second optical fiber. Both the first and second gratings are fiber Bragg gratings. Because this application uses a first optical fiber and a second optical fiber to define the light transmission path, compared to a free-space optical path, the optical fiber can be coiled, which is beneficial for reducing the overall size and improving integration.

Description

Technical Field

[0001] This application relates to the field of laser technology, and more specifically, to an optical parametric oscillator and a laser generating device. Background Technology

[0002] An optical parametric oscillator (OPO) is a technique that generates light of other frequencies by the interaction of a laser of a certain frequency with a nonlinear crystal. Because the output light frequency (or wavelength) can be adjusted almost arbitrarily according to the type of crystal, phase matching angle, and temperature design, it is an effective means of achieving mid- and far-infrared output and has important applications in the laser field.

[0003] Based on the temporal characteristics of the fundamental frequency light, optical parametric oscillators (OPOs) can be classified into continuous-wave, nanosecond, picosecond, and femtosecond types. For continuous-wave and nanosecond devices, the signal light can consistently extract energy from the pump light during its multiple round trips within the cavity. However, for picosecond and femtosecond lasers, due to the shorter pulse length, the newly generated signal light at a new frequency does not have enough time to oscillate and extract energy within the duration of a single pump pulse. Therefore, synchronous pumping technology is required. This technology involves designing the resonant cavity length so that the signal light coincides with the next pump pulse after one round trip, achieving continuous energy conversion between the signal and pump light.

[0004] Because the cavity length must be matched to the repetition frequency, the volume of picosecond mid-infrared parametric oscillators is usually large. For example, for an 80 MHz 1064 nm fundamental pump light, the cavity length needs to reach 1.8737 m, which will occupy a large volume and is not conducive to the integrated use of the device. Utility Model Content

[0005] The purpose of this application is to provide an optical parametric oscillator and a laser generator that have high integration and small size.

[0006] The embodiments of this application can be implemented as follows:

[0007] In a first aspect, this application provides an optical parametric oscillator, including a first optical fiber, a mirror group, a nonlinear crystal, and a second optical fiber. The first optical fiber has a first receiving end and a first output end. The first receiving end is used to receive pump light. The second optical fiber has a second receiving end and a second output end. The light output from the first output end can be transmitted to the second receiving end through the mirror group and the nonlinear crystal. The second output end is used to output signal light. The mirror group includes multiple mirrors. The nonlinear crystal is located in the optical path between two mirrors. A first grating is disposed on the first optical fiber, and a second grating is disposed on the second optical fiber. Both the first grating and the second grating are fiber Bragg gratings.

[0008] In an optional embodiment, the reflector group includes a first reflector, a second reflector, a third reflector, and a fourth reflector, with a first output terminal, a first reflector, a second reflector, a nonlinear crystal, a third reflector, a fourth reflector, and a second receiver arranged sequentially along the optical path.

[0009] In an optional implementation, the first, second, third, and fourth reflectors are all parabolic reflectors.

[0010] In an optional implementation, the equivalent focal length of the first, second, third, and fourth reflecting mirrors is 10-50 mm.

[0011] In an optional implementation, the first, second, third, and fourth reflectors are arranged in a rectangular array.

[0012] In an optional implementation, the optical path length between the first and second reflectors is equal to the optical path length between the third and fourth reflectors; the distance between the second reflector and the center of the nonlinear crystal is equal to the distance between the third reflector and the center of the nonlinear crystal.

[0013] In an optional embodiment, a first optical fiber is wound between a first receiving end and a first output end to form a first winding structure, and a first grating is located between the first winding structure and the first receiving end.

[0014] The second optical fiber between the second receiving end and the second output end forms a second winding structure, and the second grating is located between the second winding structure and the second output end.

[0015] In an optional implementation, the nonlinear crystal is a periodically polarized lithium niobate crystal.

[0016] In an optional embodiment, the first grating is used to reflect light with a wavelength of 2μm and has a reflectivity of more than 99%, while the second grating has a reflectivity of 20% to 80% for light with a wavelength of 2μm.

[0017] Secondly, this application provides a laser generating device, including a pump laser and an optical parametric oscillator according to any of the foregoing embodiments, wherein the pump laser is used to output pump light to a first receiving end of a first optical fiber.

[0018] The beneficial effects of the optical parametric oscillator and laser generator provided in this application embodiment include:

[0019] This application provides an optical parametric oscillator, including a first optical fiber, a mirror assembly, a nonlinear crystal, and a second optical fiber. The first optical fiber has a first receiving end and a first output end. The first receiving end is used to receive pump light. The second optical fiber has a second receiving end and a second output end. Light output from the first output end can be transmitted to the second receiving end through the mirror assembly and the nonlinear crystal. The second output end is used to output signal light. The mirror assembly includes multiple mirrors. The nonlinear crystal is located in the optical path between two mirrors. A first grating is disposed on the first optical fiber, and a second grating is disposed on the second optical fiber. Both the first and second gratings are fiber Bragg gratings. Because this application uses the first and second optical fibers to define the light transmission path, compared to a free-space optical path, the optical fiber can be coiled, which is beneficial for reducing the overall size and improving integration. Furthermore, by using the first and second gratings (both fiber Bragg gratings) as partial cavity mirrors of the oscillator, reflection within a narrow spectral range can be achieved, thereby realizing the output of narrow-linewidth signal light.

[0020] The laser generating device provided in this application includes a pump laser and the aforementioned optical parametric oscillator, thus featuring high integration and small size. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a laser generating device in one embodiment of this application.

[0023] Icons: 100 - Optical parametric oscillator; 110 - First optical fiber; 110a - First receiver; 110b - First output; 111 - First grating; 112 - First winding structure; 120 - Second optical fiber; 120a - Second receiver; 120b - Second output; 121 - Second grating; 122 - Second winding structure; 130 - Nonlinear crystal; 140 - First mirror; 150 - Second mirror; 160 - Third mirror; 170 - Fourth mirror; 200 - Pump laser. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0026] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0027] In the description of this application, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0028] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0029] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0030] For picosecond optical parametric oscillators (OPOs), synchronous pumping technology is generally used to stabilize the signal light and achieve gain. For a standing wave cavity (SWR), the relationship between the cavity length and the fundamental frequency repetition rate is: l = c / 2f; where l is the cavity length, c is the speed of light, and f is the fundamental frequency repetition rate. For the mid-infrared band, including 2 μm, a 1 μm band fundamental frequency light is often used for pumping. To compress the linewidth, a volume Bragg grating (VBG) can be used as one of the cavity mirrors. Because the cavity length must be matched with the repetition frequency, the picosecond mid-infrared OPO is usually quite large. For example, for an 80 MHz 1064 nm fundamental frequency pump light, the cavity length needs to reach 1.8737 m, which will occupy a large volume and is not conducive to the integrated use of the device. In addition, the VBG used to shorten the cavity length, as one of the cavity mirrors, has wavelength sensitivity that makes angle adjustment difficult. Its efficiency variation at high power is also one of the factors affecting the ease of use of the device.

[0031] To address at least one deficiency in the aforementioned related technologies, this application provides an optical parametric oscillator that uses optical fiber to define the light transmission path. Compared to free-space optical paths, optical fiber can be coiled, which helps reduce the overall size and improve integration.

[0032] Figure 1 This is a schematic diagram of a laser generating device in one embodiment of this application. Figure 1 As shown, the laser generating device provided in this application embodiment includes a pump laser 200 and an optical parametric oscillator 100. The optical parametric oscillator 100 includes a first optical fiber 110, a mirror group, a nonlinear crystal 130, and a second optical fiber 120. The first optical fiber 110 has a first receiving end 110a and a first output end 110b. The first receiving end 110a is used to receive pump light from the pump laser 200, and the first output end 110b is used to output light to the mirror group. The second optical fiber 120 has a second receiving end 120a and a second output end 120b. The light output from the first output end 110b can be transmitted to the second receiving end 120a through the mirror group and the nonlinear crystal 130, and the second output end 120b is used to output signal light. In this application, the mirror group includes multiple mirrors, and the nonlinear crystal 130 is located in the optical path between two mirrors. A first grating 111 is provided on the first optical fiber 110, and a second grating 121 is provided on the second optical fiber 120. Both the first grating 111 and the second grating 121 are fiber Bragg gratings.

[0033] Optionally, the optical parametric oscillator 100 provided in this embodiment can be used to convert the shorter wavelength pump light output by the pump laser 200 into a longer wavelength mid- or far-infrared laser and output it. Optionally, the pump light output by the pump laser 200 has a center wavelength of 1064 nm, a repetition frequency of 80 MHz, and a pulse width of 20 ps, ​​and the optical parametric oscillator 100 can convert the pump light into a 2 μm wavelength mid-infrared laser.

[0034] Optionally, both the first grating 111 and the second grating 121 are fiber Bragg gratings (FBGs). A fiber Bragg grating is an optical device in which a periodic refractive index modulation structure is written into the core of an optical fiber using ultraviolet laser. It can be used for wavelength selection, feedback control, or frequency stabilization of pump lasers to improve the stability and output efficiency of the optical parametric oscillator 100. FBGs are advantageous for achieving narrow linewidths; the narrower the linewidth, the better the monochromaticity of the output laser. Optionally, the first grating 111 is used to reflect light with a wavelength of 2μm and has a reflectivity of over 99%, while the second grating 121 has a reflectivity of 2μm light of 20% to 80%, for example, 40%.

[0035] In this embodiment, since the first optical fiber 110 and the second optical fiber 120 are flexible, their length can be reduced by winding, thus improving compactness. In this embodiment, the first optical fiber 110 between the first receiving end 110a and the first output end 110b is wound to form a first winding structure 112, and a first grating 111 is located between the first winding structure 112 and the first receiving end 110a; the second optical fiber 120 between the second receiving end 120a and the second output end 120b is wound to form a second winding structure 122, and a second grating 121 is located between the second winding structure 122 and the second output end 120b.

[0036] In this embodiment, the reflector group includes a first reflector 140, a second reflector 150, a third reflector 160, and a fourth reflector 170. The first output terminal 110b, the first reflector 140, the second reflector 150, the nonlinear crystal 130, the third reflector 160, the fourth reflector 170, and the second receiving terminal 120a are sequentially arranged along the optical path. In this embodiment, the laser output from the first output terminal 110b is transmitted to the first reflector 140, where its transmission direction is changed by 90° before being transmitted to the second reflector 150. The second reflector 150 changes the transmission direction by 90°, and the laser beam then passes through the nonlinear crystal 130 to reach the third reflector 160. The beam direction is changed by 90° by the third reflector 160 before being transmitted to the fourth reflector 170. The fourth reflector 170 changes the beam direction by another 90° before transmitting it to the second receiving terminal 120a of the second optical fiber 120.

[0037] In this embodiment, the first reflector 140, the second reflector 150, the third reflector 160, and the fourth reflector 170 are arranged in a rectangular array. The optical path length between the first reflector 140 and the second reflector 150 is equal to the optical path length between the third reflector 160 and the fourth reflector 170. Optionally, the first reflector 140 and the second reflector 150 are spaced 40-60 mm apart (e.g., 50 mm), and the third reflector 160 and the fourth reflector 170 are spaced 40-60 mm apart (e.g., 50 mm). Further, the distance between the second reflector 150 and the center of the nonlinear crystal 130 is equal to the distance between the third reflector 160 and the center of the nonlinear crystal 130, both being 20-40 mm (e.g., both being 30 mm).

[0038] Furthermore, the optical path length between the first output terminal 110b and the first reflector 140 can be 20~40mm, such as 30mm; the optical path length between the second receiving terminal 120a and the fourth reflector 170 can be 20~40mm, such as 30mm.

[0039] Furthermore, the optical path length between the first grating 111 and the first output end 110b is 800~850mm, for example, 826.9mm; since the first optical fiber 110 forms the first winding structure 112, the spatial distance between the first grating 111 and the first output end 110b can be much smaller than the aforementioned optical path length.

[0040] Furthermore, the optical path length between the second grating 121 and the second receiving end 120a is 800~850mm, for example, 826.9mm (which can be equal to the optical path length between the first grating 111 and the first output end 110b). Since the second optical fiber 120 forms a second wound structure 122, the spatial distance between the second grating 121 and the second receiving end 120a can be much smaller than the aforementioned optical path length. It is evident that defining the optical path using optical fiber can reduce the overall length of the device.

[0041] Optionally, the first reflecting mirror 140, the second reflecting mirror 150, the third reflecting mirror 160, and the fourth reflecting mirror 170 are all parabolic reflecting mirrors, specifically high-reflectivity off-axis parabolic mirrors. Optionally, the equivalent focal length of the first reflecting mirror 140, the second reflecting mirror 150, the third reflecting mirror 160, and the fourth reflecting mirror 170 is 10~50mm. In one specific embodiment, the equivalent focal length of the first reflecting mirror 140, the second reflecting mirror 150, the third reflecting mirror 160, and the fourth reflecting mirror 170 is 30mm.

[0042] In this embodiment, the nonlinear crystal 130 is a periodically polarized lithium niobate (PPLN) crystal, which can significantly improve the optical parametric conversion efficiency through quasi-phase matching (QPM) technology.

[0043] Secondly, this application provides a laser generating device, including a pump laser 200 and an optical parametric oscillator 100 of any of the foregoing embodiments, wherein the pump laser 200 is used to output pump light to the first receiving end 110a of the first optical fiber 110.

[0044] Pump light (e.g., light with a wavelength of 1 μm) emitted by pump laser 200 enters the first optical fiber 110 from the first receiving end 110a. The first grating 111 reflects only light of a specific wavelength, such as 2 μm. Therefore, the pump light can pass through the first grating 111 and is subsequently reflected by the first mirror 140 and the second mirror 150, then converged to reach the nonlinear crystal 130. The nonlinear crystal 130 converts the pump light into a longer wavelength signal light and an idler light, which are then transmitted sequentially through the third mirror 160, the fourth mirror 170, and the second optical fiber 120. The 2 μm signal light, due to reflection from the first grating 111 and the second grating 121, will oscillate and propagate in the optical fiber and free space. Light of wavelengths other than the target wavelength (e.g., 2μm) can be transmitted through the first grating 111 and the second grating 121, preventing other light of wavelengths other than the target wavelength from oscillating and amplifying in the cavity. Ultimately, the light of the target wavelength is left to oscillate and amplify in the optical fiber and free space. The second grating 121 can partially transmit the light of the target wavelength. Therefore, the enhanced signal light of the target wavelength can be output through the second output end 120b of the second optical fiber 120.

[0045] In summary, this application discloses an optical parametric oscillator 100, including a first optical fiber 110, a mirror group, a nonlinear crystal 130, and a second optical fiber 120. The first optical fiber 110 has a first receiving end 110a and a first output end 110b. The first receiving end 110a is used to receive pump light. The second optical fiber 120 has a second receiving end 120a and a second output end 120b. The light output from the first output end 110b can be transmitted to the second receiving end 120a through the mirror group and the nonlinear crystal 130. The second output end 120b is used to output signal light. The mirror group includes multiple mirrors. The nonlinear crystal 130 is located in the optical path between two mirrors. A first grating 111 is disposed on the first optical fiber 110, and a second grating 121 is disposed on the second optical fiber 120. Both the first grating 111 and the second grating 121 are fiber Bragg gratings. Because this application uses a first optical fiber 110 and a second optical fiber 120 to define the light transmission path, the optical fiber can be coiled, which is beneficial for reducing the overall size and improving the integration density compared to a free-space optical path. Furthermore, by using a first grating 111 and a second grating 121 (both fiber Bragg gratings) as partial cavity mirrors of the oscillator, reflection within a narrow spectral range can be achieved, thereby realizing the output of narrow linewidth signal light.

[0046] This application also discloses a laser generating device, including a pump laser 200 and the aforementioned optical parametric oscillator 100, thus featuring high integration and small size.

[0047] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. An optical parametric oscillator, characterized by, The device includes a first optical fiber, a mirror assembly, a nonlinear crystal, and a second optical fiber. The first optical fiber has a first receiving end and a first output end. The first receiving end is used to receive pump light. The second optical fiber has a second receiving end and a second output end. The light output from the first output end can be transmitted to the second receiving end through the mirror assembly and the nonlinear crystal. The second output end is used to output signal light. The mirror assembly includes multiple mirrors. The nonlinear crystal is located in the optical path between two mirrors. A first grating is disposed on the first optical fiber, and a second grating is disposed on the second optical fiber. Both the first grating and the second grating are fiber Bragg gratings.

2. The optical parametric oscillator of claim 1, wherein, The reflector group includes a first reflector, a second reflector, a third reflector, and a fourth reflector, and the first output terminal, the first reflector, the second reflector, the nonlinear crystal, the third reflector, the fourth reflector, and the second receiving terminal are arranged sequentially along the optical path.

3. The optical parametric oscillator of claim 2, wherein, The first reflector, the second reflector, the third reflector, and the fourth reflector are all parabolic reflectors.

4. The optical parametric oscillator of claim 3, wherein, The equivalent focal length of the first reflector, the second reflector, the third reflector, and the fourth reflector is 10~50mm.

5. The optical parametric oscillator of claim 2, wherein, The first reflector, the second reflector, the third reflector, and the fourth reflector are arranged in a rectangular array.

6. The optical parametric oscillator of claim 5, wherein, The optical path length between the first and second reflectors is equal to the optical path length between the third and fourth reflectors; the distance between the second reflector and the center of the nonlinear crystal is equal to the distance between the third reflector and the center of the nonlinear crystal.

7. The optical parametric oscillator of claim 1, wherein, The first optical fiber between the first receiving end and the first output end is wound to form a first winding structure, and the first grating is located between the first winding structure and the first receiving end. The second optical fiber between the second receiving end and the second output end is wound to form a second winding structure, and the second grating is located between the second winding structure and the second output end.

8. The optical parametric oscillator of claim 1, wherein, The nonlinear crystal is a periodically polarized lithium niobate crystal.

9. The optical parametric oscillator of claim 1, wherein, The first grating is used to reflect light with a wavelength of 2μm and has a reflectivity of over 99%, while the second grating has a reflectivity of 20% to 80% for light with a wavelength of 2μm.

10. A laser generating apparatus, characterized by comprising: It includes a pump laser and an optical parametric oscillator as described in any one of claims 1-9, wherein the pump laser is used to output pump light to the first receiving end of the first optical fiber.

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