An angular chirp compensation device and method

Abstract

The application discloses an angular chirp compensation device, which comprises an angular chirp compensation system, a fiber coupling injection mirror, a hollow optical fiber and a fiber output coupling collimating mirror. The angular chirp light first passes through the angular chirp compensation system to compensate the input angular chirp, the spatial chirp is focused to the hollow optical fiber through the fiber coupling injection mirror to eliminate, and the fiber output light beam is collimated through the fiber output coupling collimating mirror. The application can compensate the angular chirp generated by the non-collinear optical parametric amplification process, idle light and self-diffraction nonlinear process, and the compensated light beam has no angular chirp and good beam quality.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser, and particularly relates to a prism, grating and optical fiber-based angular chirp compensation device and method applied to a laser system. BACKGROUND

[0002] Nonlinear effects of laser are very important in the field of basic physics research today. Among them, optical parametric amplification has very wide application in ultrafast laser systems due to its high gain bandwidth and low heat effect, and is the most powerful technical scheme for obtaining next-generation ultrastrong ultra-short laser systems. Generally, the bandwidth of optical parametric broadband amplification can be realized by introducing a certain non-collinear angle to signal light and pump light. The main purpose of the non-collinear angle is to make the projection group velocity of idler light in the signal light transmission direction the same. The disadvantage is that a certain amount of angular chirp is introduced to the idler light, so that the idler light cannot be directly compressed to obtain near-limit transform pulse width, which causes energy waste of the idler light. Moreover, the idler light itself has the advantage of CEP stability, but the existence of angular chirp makes this advantage cannot be utilized. In addition, the angular chirp problem also exists in the nonlinear processes such as four-wave mixing and self-diffraction. At present, researchers and technicians have proposed to use grating to compensate the angular chirp introduced by the nonlinear process. However, the high-order components cannot be well compensated and the efficiency is low. SUMMARY

[0003] In order to overcome the defects such as large energy loss and high-order angular dispersion that cannot be eliminated in the compensation of angular chirp of idler light and self-diffraction light in the existing optical parametric amplification, the application provides an angular chirp compensation device and method. The angular dispersion compensation device uses the dispersion characteristics of the prism or grating to compensate the incident light with angular chirp, and combines the hollow optical fiber to compensate the high-order residual angular dispersion, so as to finally obtain laser output without angular chirp and with excellent spot quality. The method has the advantages of high efficiency and good spot quality.

[0004] The application is implemented by the following technical scheme:

[0005] An angular chirp compensation device, characterized in that it comprises an angular chirp compensation system, a fiber-coupled injection mirror, a hollow optical fiber and a fiber output coupling collimating mirror.

[0006] The angular chirp compensation system is used for compensating the angular chirp of the incident light.

[0007] The fiber-coupled injection mirror is used for receiving the compensated angular chirp light and focusing it into the hollow optical fiber.

[0008] The hollow optical fiber is used for eliminating the spatial chirp and transmitting to the fiber output coupling collimating mirror.

[0009] The optical fiber output coupling collimating mirror outputs the collimated light.

[0010] The angular chirp light is a common light source with near-linear angular chirp, such as non-collinear light of optical parametric amplification, and self-diffraction light generated by four-wave mixing effect.

[0011] The angular chirp compensation system uses a prism or a grating as an angular chirp compensation component.

[0012] The optical fiber coupling injection mirror and the optical fiber output coupling collimating mirror comprise a lens or a concave mirror.

[0013] The angular chirp compensation method using the angular chirp compensation device comprises the following steps:

[0014] Step 1: measuring the angular chirp curve of the angular chirp light by using a suitable waveband spectrometer, and then calculating the linear chirp amount θ of the center wavelength chriped ;

[0015] Step 2: calculating the prism incident angle θ and the vertex angle θ apex of the linear chirp amount θ chriped of the angular chirp light;

[0016] Step 3: focusing the light spot after compensation of the linear angular chirp to the hollow core fiber (4) for spatial chirp compensation through the optical fiber coupling injection mirror (3), and obtaining the laser with no angular chirp and excellent light spot quality by using the optical fiber output coupling collimating mirror (5).

[0017] Compared with the existing angular chirp compensation method, the present application has the following advantages:

[0018] 1) The device of the present application is simple, and the angular chirp compensation can be realized only by using a prism or a grating in cooperation with a hollow core fiber;

[0019] 2) The present application eliminates the angular chirp of the light by using a prism, and has high efficiency;

[0020] 3) The angular chirp compensation method designed in the present application has a wide wavelength range and can be extended to any commonly used waveband;

[0021] 4) The angular chirp compensation device and method designed in the present application support a very wide bandwidth, which can reach more than 300 nm. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 FIG. 1 is a structural schematic diagram of the angular chirp compensation device of the present application.

[0023] Figure 2 FIG. 2 is a structural schematic diagram of the embodiment 1 of the angular chirp compensation device and method of the present application. DETAILED DESCRIPTION

[0024] The application will be further described in detail below with reference to the accompanying drawings and examples, but the protection scope of the application should not be limited thereby.

[0025] Please refer to Figure 1 , Figure 1 It is a structural schematic diagram of the angle chirp compensation device. As shown in the figure, the angle chirp compensation device comprises an angle chirp compensation system 2, a fiber coupling injection mirror 3, a hollow core fiber 4 and a fiber output coupling collimating mirror 5. The angle chirp light 1 is compensated by the angle chirp compensation system 2, the spatial chirp is focused to the hollow core fiber 4 through the fiber coupling injection mirror 3 to eliminate, and finally collimated output through the fiber output coupling collimating mirror 5.

[0026] Figure 2 It is a structural schematic diagram of embodiment 1 of the angle chirp compensation device, and specifically comprises: OPA pump light 6, OPA signal light 7, nonlinear crystal 8, OPA idler light 9, angle chirp compensation system 2, fiber coupling injection mirror 3, hollow core fiber 4, output coupling collimating lens 5. The fiber coupling injection mirror 3 in this embodiment adopts a reflective concave mirror.

[0027] The OPA pump light 6 is nonlinearly interacted with the OPA signal light 7 in the nonlinear crystal 8 through a non-collinear way. By properly selecting the phase matching angle of the nonlinear crystal 8 and the non-collinear angle of the OPA pump light 6 and the OPA signal light 7, wideband signal light parametric amplification can be realized while the OPA idler light 9 with angle chirp is output. The OPA idler light 9 is first subjected to angular dispersion compensation by the angle chirp compensation system 2, and then the idler light with low-order angular dispersion eliminated is coupled into the hollow core fiber 4 using a reflective concave mirror. The hollow core fiber 4 further eliminates the high-order angular dispersion of the idler light, and the output idler light without angle chirp is collimated through the coupling collimating lens 5. The device can finally obtain wideband high-efficiency idler light output with angle chirp eliminated.

[0028] The present example uses a LD-pumped Nd:YAG solid laser frequency-doubled output 532 nm laser as the OPA pump light 6, with an energy of 100 mJ, a repetition rate of 100 Hz, and a pulse width of 4 ns. The OPA signal light 7 has a bandwidth of 825-1025 nm, a repetition rate of 1 kHz, and an energy of 20 uJ. The nonlinear crystal 8 uses an LBO crystal, with the working main plane being an “XOY” plane and the cutting angle being (90°, 13.2°), and the crystal thickness being 30 mm. The nonlinear crystal 8 is coated with a film parameter of 532 nm and 820-1500 nm high transmission, which covers the pump light 6, the signal light 7, and the idler light 9. The non-collinear angle of the pump light 6 and the signal light 7 in the nonlinear crystal 8 is 1.3°, which supports the amplification of signal light with a bandwidth of more than 200 nm. After passing through the nonlinear crystal, the energy of the signal light 7 is amplified to 10 mJ, with a gain of 500 times, and the energy of the idler light 9 is 7.11 mJ.

[0029] According to the non-collinear angle value and the crystal refractive index equation, the idler light wavelength range satisfying the momentum conservation is 1300±100 nm, and the angular chirp is 69.95 urad / nm. In order to improve the efficiency of the prism angular chirp compensation device, all the prisms are incident at the Brewster angle, with a top angle of 69°, so that the angular chirp of a single prism is -26 urad / nm. The idler light prism angular chirp compensation system 2 is composed of three Brewster angle prisms. The angular chirp of the idler light 9 can be well compensated, and the efficiency is as high as 98%, which is mainly due to the Brewster angle incidence. After eliminating the low-order linear angular chirp, the idler light is focused into a hollow core fiber 4 with a core diameter of 500 um by a reflective concave mirror 3 with a focal length of 500 mm. The residual high-order angular chirp can be eliminated by the hollow core fiber. After passing through the hollow core fiber, the total efficiency is 66.8%. Finally, a collimating lens 5 is used to collimate the output laser, with a lens focal length of 300 mm. The spectral measurements of the left, right, and middle feature points of the collimated spot show that the spectral components are almost indistinguishable, and the angular chirp of the idler light generated in the OPA process is well eliminated and has a high efficiency.

[0030] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and they should be covered by the claims of the present application.

Claims

1. An angular chirp compensation method based on an angular chirp compensation device, characterized in that, The device comprises: an angular chirp compensation system (2), a fiber-coupled injection mirror (3), a hollow-core fiber (4) and a fiber output coupling collimating mirror (5); The angular chirp compensation system (2) is used for angular chirp compensation of the incident angular chirp light (1); all the prisms are at Brewster angle incidence, and the angular chirp compensation system (2) is composed of three Brewster angle prisms; The fiber-coupled injection mirror (3) is used for receiving the compensated angular chirp light (9) and focusing it to the hollow-core fiber (4); The hollow-core fiber (4) is used for eliminating spatial chirp and transmitting to the fiber output coupling collimating mirror (5); The fiber output coupling collimating mirror (5) is used for collimating the incident light and then outputting; The angular chirp light (1) is a common near-linear angular chirp light source such as non-collinear optical parametric amplification idler light, four-wave mixing effect generated self-diffraction light and the like; The method comprises the following steps: Step one, measure the angular chirp curve of the angular chirped light (1) using a suitable waveband spectrometer, then calculate the linear chirp amount θ of the center wavelength chriped ; Step two, calculate the prism incident angle θ, and the vertex angle θ apex The linear chirp amount θ of the diagonal chirped light (1) chriped Compensation; Step three, the compensated linear angular chirp light spot is focused to the hollow-core fiber (4) by the fiber-coupled injection mirror (3) for spatial chirp compensation, and the fiber output is used for obtaining the laser with no angular chirp and excellent light spot quality by the fiber output coupling collimating mirror (5).

2. The method of claim 1, wherein, The angular chirp compensation system (2) uses a prism or a grating as an angular chirp compensation component.

3. The method of claim 1, wherein, The fiber-coupled injection mirror (3) and the fiber output coupling collimating mirror (5) comprise a lens or a concave mirror.

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