WO2024001392A1 - 一种基于非线性放大环形镜的固体激光器 - Google Patents

一种基于非线性放大环形镜的固体激光器 Download PDF

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WO2024001392A1
WO2024001392A1 PCT/CN2023/086568 CN2023086568W WO2024001392A1 WO 2024001392 A1 WO2024001392 A1 WO 2024001392A1 CN 2023086568 W CN2023086568 W CN 2023086568W WO 2024001392 A1 WO2024001392 A1 WO 2024001392A1
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laser
mirror
grating
nonlinear
module
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PCT/CN2023/086568
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English (en)
French (fr)
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玄洪文
衡小波
张志韬
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广东大湾区空天信息研究院
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Publication of WO2024001392A1 publication Critical patent/WO2024001392A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1106—Mode locking
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10053—Phase control
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/10—Nuclear fusion reactors

Definitions

  • Embodiments of the present application relate to the field of laser technology, for example, to a solid laser based on a nonlinear amplifying ring mirror.
  • Solid-state lasers are lasers that use solid materials such as laser crystals, laser glass, laser ceramics, etc. as their working materials. They have the characteristics of high output power, good beam quality, stable performance, long life, wide output band, and diverse working methods. Due to the above advantages, solid-state lasers occupy an important share in the laser application market. They have always been a research hotspot in the field of laser technology and are widely used in laser fine processing, laser communications, remote sensing ranging, biomedicine, and atmosphere. detection and controllable nuclear fusion and many other fields.
  • solid-state lasers can output nanosecond, picosecond or even femtosecond pulse lasers.
  • fiber lasers which have developed rapidly in recent years, solid-state lasers have the advantages of small optical nonlinearity in ultra-short pulses, and can easily achieve high power and narrow pulse width output. Therefore, solid-state lasers are still an important way to obtain high-power and high-beam quality pulse lasers.
  • mode locking technology can be divided into active mode locking and passive mode locking. In active mode-locking technology, the response time of the modulator is relatively slow and its ability to compress pulses is limited. Therefore, its output pulse width is limited, generally on the order of picoseconds.
  • Passive mode locking technology mainly uses saturable absorbers to achieve loss modulation of intra-cavity optical pulses.
  • saturable absorbers When passing through the saturable absorber, pulses with high energy pass through and pulses with low energy are absorbed, causing the edge loss of the optical pulse to be much greater than the middle. Therefore, the optical pulse is narrowed and sub-picosecond and femtosecond mode-locked pulses can be achieved.
  • Common passive mode-locking technologies in solid-state lasers include Semiconductor Saturable Absorber Mirror (SESAM) and Nonlinear Polarization Rotation (NPR). Among them, SESAM is often used in the field of mode-locked lasers due to its good stability and modulation characteristics.
  • SESAM has a small response bandwidth to laser, usually only a few tens of nanometers of spectral response bandwidth, and the production process is complicated.
  • the NPR mode-locking mechanism has a large modulation depth and short response time, and can produce excellent low-noise femtosecond pulses.
  • the NPR mode-locked laser is very sensitive to environmental disturbances, making it difficult to maintain the self-starting function for a long time.
  • This application provides a solid-state laser based on a nonlinear amplifying ring mirror.
  • the mode-locking threshold can be optimized and has a self-starting function by adjusting the phase bias unit.
  • Medium-output pulsed laser has the advantages of high pulse energy, low noise and good long-term stability.
  • the embodiment of the present application provides a solid laser based on a nonlinear amplifying ring mirror, including a pump source, a pump optical coupling module, a nonlinear amplifying ring mirror module and a linear arm module;
  • the nonlinear amplifying ring mirror module includes a first dichroic mirror, a laser crystal, a second dichroic mirror, a plano-concave lens, a first Faraday rotator, a quarter-wave plate, a second Faraday rotator, and a first total reflection Mirrors, highly nonlinear waveguides and polarizing beamsplitters;
  • the linear arm module includes a first grating, a second grating and an output coupling mirror;
  • the axial direction of the laser crystal is located on the transmission central axis of the pump light and laser beam; the axial direction of the highly nonlinear waveguide is located on the transmission central axis of the laser beam;
  • the first Faraday rotator, the quarter-wave plate, the second Faraday rotator and the highly nonlinear waveguide are arranged in sequence to form a phase bias unit; the first grating and the second grating Arranged in parallel and at an acute angle with the transmission central axis of the laser beam, the first grating and the second grating constitute a dispersion compensation unit;
  • the nonlinear amplifying ring mirror module and the linear arm module form a 9-shaped resonant cavity
  • the pump light emitted by the pump source is injected into the pump light coupling module. After being collimated and focused by the pump light coupling module, part of the pump light is injected into the laser by the first dichroic mirror. excitation in the crystal A laser beam is generated, and the residual pump light is reflected back to the laser crystal by the plano-concave lens after passing through the second dichroic mirror; the laser beam passes through the phase bias unit and is reflected by the polarization beam splitting prism. Injected into the dispersion compensation unit, part of the laser beam is reflected back to the polarization beam splitting prism by the output coupling mirror and then split into a first beam and a second beam with different transmission directions.
  • the first beam is in the The nonlinear amplification ring mirror module is transmitted in a clockwise direction
  • the second beam is transmitted in a counterclockwise direction in the nonlinear amplification ring mirror module
  • the first beam and the second beam pass through the laser crystal
  • the phase difference is generated in the opposite order of the phase bias unit.
  • the interference occurs nonlinear phase shift mode locking, forming a mode-locked laser.
  • Part of the mode-locked laser passes through the first step in turn.
  • the grating, the second grating and the output coupling mirror are output.
  • Figure 1 is a schematic structural diagram of a solid laser based on a nonlinear amplifying ring mirror module provided by an embodiment of the present application;
  • FIG. 2 is a schematic structural diagram of another solid-state laser based on a nonlinear amplifying ring mirror module provided by an embodiment of the present application.
  • FIG. 1 is a schematic structural diagram of a solid-state laser based on a nonlinear amplifying ring mirror module provided by an embodiment of the present application.
  • the embodiment of the present application provides a nonlinear amplification ring-based
  • the solid laser of the mirror module includes a pump source 1, a pump optical coupling module 3, a nonlinear amplifying ring mirror module 4 and a linear arm module 5.
  • the nonlinear amplification ring mirror module 4 includes a first dichroic mirror 40, a laser crystal 41, a second dichroic mirror 42, a plano-concave lens 43, a first Faraday rotator 44, a quarter wave plate 45, and a second Faraday rotator. 46.
  • the linear waveguide 48 is arranged in sequence to form the phase bias unit 01; the first grating 50 and the second grating 51 are arranged in parallel and have an acute angle with the transmission central axis of the laser beam, and the first grating 50 and the second grating 51 form the dispersion compensation unit 02;
  • the nonlinear amplifying ring mirror module 4 and the linear arm module 5 form a 9-shaped resonant cavity.
  • the pump light S0 emitted by the pump source 1 is injected into the pump optical coupling module 3. After being collimated and focused by the pump optical coupling module 3, part of the pump light S0 is injected into the laser crystal 41 by the first dichroic mirror 40 to excite laser light. Beam S1 and residual pump light S0 pass through the second dichroic mirror 42 and are reflected back to the laser crystal 41 by the plano-concave lens 43; the laser beam S1 passes through the first Faraday rotator 44 and the quarter in the phase offset unit 01 in sequence.
  • the wave plate 45, the second Faraday rotator 46 and the high nonlinear waveguide 48 are then injected into the dispersion compensation unit 02 through the polarizing beam splitter prism 49, where the first total reflection mirror 47 is located between the second Faraday rotator 46 and the high nonlinear waveguide 48.
  • the first total reflection mirror 47 is set to adjust the propagation direction of the laser beam S1.
  • the mode locking threshold can be optimized, so that the solid-state laser has a self-starting function; a small part
  • the laser beam S1 is output by the output coupling mirror 52.
  • the laser beam S1 is reflected back to the polarizing beam splitter prism 49 by the output coupling mirror 52 and is split into a first beam S11 and a second beam S12 with different transmission directions.
  • the first beam S11 The second light beam S12 is transmitted in the nonlinear amplifying ring mirror module 4 in the clockwise direction (shown in the direction of the arrow P2 in the figure), and the second light beam S12 is transmitted in the nonlinear amplifying ring mirror module 4 in the counterclockwise direction (shown in the direction of the arrow P1 in the figure). ) transmission, the first beam S11 and the second beam S11 pass through the laser crystal 41 and the phase bias unit 01 in reverse order to generate a phase difference.
  • nonlinear phase shift mode locking occurs due to interference, forming mode locking.
  • Laser S2 part mode-locked laser S2 is directly output to the outside of the cavity through the polarizing beam splitter prism 49. Another part of the mode-locked laser S2 is output after passing through the first grating 50, the second grating 51 and the output coupling mirror 52. Most of the mode-locking laser S2 is reflected back by the output coupling mirror 52.
  • the polarizing beam splitting prism 49 is then split again and enters the nonlinear amplifying ring mirror module 4 to undergo the same process as the first beam S11 and the second beam S12 , and the interference cycle occurs again in the polarizing beam splitting prism 49 .
  • the embodiment of this application is based on the nonlinear amplifying ring mirror module mode locking technology, adopts a 9-shaped cavity structure, and uses a laser crystal as the gain medium.
  • the mode locking threshold can be optimized, so that the laser has a self-starting function and outputs laser light. It has the advantages of low noise, wide spectrum and good long-term stability, and can easily achieve high power and narrow pulse width output.
  • FIG. 2 is a schematic structural diagram of another solid-state laser based on a nonlinear amplifying ring mirror module provided by an embodiment of the present application.
  • the solid-state laser also includes an optical isolator 2, which is located on the central axis of the pump light S0 transmission.
  • the pump light S0 emitted by the pump source 1 enters the pump optical coupling module 3 through the optical isolator 2 to prevent the pump light S0 from returning and protect the pump source 1.
  • the pump light coupling module 3 includes a first plano-convex lens 30, a second total reflection mirror 31, a third total reflection mirror 32 and a third total reflection mirror 31 located on the central axis of transmission of the pump light S0.
  • Two plano-convex lenses 33; the laser crystal 41 is also located at the common focus of the second plano-convex lens 33 and the plano-concave lens 43.
  • the combination of the first plano-convex lens 30 and the second plano-convex lens 33 is configured to collimate and focus the pump light S0, so that the pump light S0 is injected into the laser crystal 41 by the first dichroic mirror 40 to excite the laser beam S1;
  • the laser crystal 41 is set The axial direction is located on the transmission central axis of the pump light and laser beam and the laser crystal 41 is located at the focus of the second plano-convex lens 33 and the plano-concave lens 43, which can improve the excitation efficiency of the laser crystal 41 and increase the light output power of the laser beam S1;
  • the second total reflection mirror 31 and the third total reflection mirror 32 are configured to change the light path and compress the volume of the solid laser.
  • the pump source 1 includes a semiconductor laser or a fiber laser, and the operating wavelength of the pump source 1 is the same as the pump wavelength of the laser crystal 41 .
  • Pump source 1 includes a semiconductor laser or a fiber laser, and the operating wavelength of the pump source 1 is the same as the pump wavelength of the laser crystal 41 .
  • the working wavelength of the pump source is the same as the pump wavelength of the laser crystal to provide excitation energy to the laser crystal.
  • the surfaces of the first plano-convex lens 30 and the second plano-convex lens 33 are coated with a pump light high transmittance film, and the pump light high transmittance film is configured to improve the transmission of the pump light. pass rate; the concave surface of the plano-concave lens 43 facing the laser crystal 41 is coated with a high-reflective film for pump light, and the high-reflective film for pump light is configured to increase the reflectivity of the pump light.
  • the surfaces of the first dichroic mirror 40 and the second dichroic mirror 42 facing the laser crystal 41 are coated with a pump light high transmittance film and a laser beam high reflection film.
  • the pump light high transmittance film and the laser beam high reflection film are set to ensure that the residual pump light is transmitted and the laser beam is reflected to the first Faraday rotator 44 of the phase bias unit 01; the first dichroic mirror 40 and the second dichroic mirror
  • the surface of the mirror 42 facing away from the laser crystal 41 is coated with a pump light high transmittance film, and the pump light high transmittance film is arranged to increase the transmittance of the pump light.
  • the laser crystal 41 includes an optical crystal doped with rare earth ions or transition metal ions.
  • rare earth ions or transition metal ions such as Yb: YAG, Er: YLF, Ho: YAG, Cr: LiCAF, etc.
  • using laser crystals as gain media their optical nonlinearity is small, and it is easy to achieve high power and narrow pulse width output of solid laser lasers.
  • the first Faraday rotator 44 and the second Faraday rotator 46 include a thin Faraday rotator and a Faraday rotator in which a magneto-optical crystal is inserted into a permanent magnet.
  • the signal light transmitted in the forward direction in the 9-shaped resonant cavity can pass through the system, and the light beam transmitted in the reverse direction can be blocked. Avoid harmful reflected light in the system causing optical device damage and system instability.
  • signal light refers to pump light, laser beam and mode-locked laser.
  • the highly nonlinear waveguide 48 includes a strip waveguide, a ridge waveguide, a photonic crystal fiber (Photonic Crystal Fiber, PCF) or a nonlinear waveguide such as a highly nonlinear fiber, which can be used for signal processing. Optical gain amplification, pulse compression and mode selection, etc.
  • the polarizing beam splitter prism 49 is configured to separate the horizontal polarization component and the vertical polarization component of the laser beam.
  • the first grating 50 and the second grating 51 include chirped volume Bragg grating, chirped fiber Bragg grating or transmission dielectric film grating.
  • the first light Parameters such as the grating period of the grating 50 and the second grating 51 enable the mode-locked laser that meets the operating wavelength to be output from the output coupling mirror 52 .
  • the surface of the output coupling mirror 52 facing the 9-shaped resonant cavity is coated with a reflective film.
  • the reflectivity of the reflective film to the laser beam is ⁇ , 70% ⁇ ⁇ ⁇ 100%.
  • the laser beam continues to be reflected back to the nonlinear amplifying ring mirror module 4 and is excited by the laser crystal 41 for gain amplification; the surface of the output coupling mirror 52 facing away from the 9-shaped resonant cavity is coated with an anti-reflection film, and the anti-reflection film is set for transmission output mode locking laser.
  • a semiconductor laser with an operating wavelength of 940nm or 969nm is selected as the pump source 1; a rod-shaped Yb:YAG crystal is selected as the laser crystal 41; the surfaces of the first plano-convex lens 30 and the second plano-convex lens 33 are selected Coated with a high-reflective film with a wavelength of 940nm to 969nm; the concave surface of the plano-concave lens 43 facing the laser crystal 41 is coated with a high-reflective film with a wavelength of 940nm to 969nm; the first dichroic mirror 40 and the second dichroic mirror 42 face the laser crystal 41 The surface is coated with a high-transmission film with a wavelength of 940nm ⁇ 969nm and a high-reflection film with a wavelength of 1020nm ⁇ 1100nm, and the other surface is coated with a high-transmittance film with a wavelength of 940nm ⁇ 969nm;
  • the reflective film has a reflectivity of 99% for signal light with a wavelength of 1020nm to 1100nm, and the other surface is coated with an antireflection coating, which increases the transmittance of signal light with a wavelength of 1020nm to 1100nm.
  • the 940nm or 969nm pump light S0 emitted by the pump source 1 enters the pump optical coupling module 3 after passing through the optical isolator 2.
  • the first dichroic mirror 40 injects Yb into the nonlinear amplification ring mirror module 4:
  • the YAG crystal is excited to generate a 1030nm band laser beam S1.
  • the residual pump light S0 passes through the second dichroic mirror 42 and is reflected back to the Yb: YAG crystal by the plano-concave lens 43.
  • the laser beam S1 passes through the phase offset unit 01 and is then reflected by the polarizing beam splitter prism 49.
  • the mode-locking threshold can be optimized and has a self-starting function.
  • the pulse laser output from the 9-shaped cavity solid laser has the advantages of high pulse energy, low noise, and good long-term stability.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
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Abstract

本申请公开了一种基于非线性放大环形镜的固体激光器，包括泵浦源、泵浦光耦合模块、非线性放大环形镜模块和线性臂模块；泵浦光耦合模块包括第一平凸透镜、第二全反射镜、第三全反射镜和第二平凸透镜；非线性放大环形镜模块包括第一二色镜、激光晶体、第二二色镜、平凹透镜、第一法拉第旋转器、四分之一波片、第二法拉第旋转器、第一全反射镜、高非线性波导和偏振分光棱镜；线性臂模块包括第一光栅、第二光栅和输出耦合镜；非线性放大环形镜模块中的第一法拉第旋转器、四分之一波片、第二法拉第旋转器和高非线性波导构成相位偏置单元。

Description

一种基于非线性放大环形镜的固体激光器
本申请要求在2022年6月28日提交中国专利局、申请号为202210753522.3的中国专利申请的优先权，该申请的全部内容通过引用结合在本申请中。
技术领域
本申请实施例涉及激光器技术领域，例如涉及一种基于非线性放大环形镜的固体激光器。
背景技术
固体激光器是以固体材料如激光晶体、激光玻璃、激光陶瓷等作为工作物质的激光器，具有输出功率高、光束质量好、性能稳定、寿命长、输出波段广和工作方式多样等特点。由于上述这些优势，固体激光器在激光应用的市场中占有重要份额，其一直以来都是激光技术领域中的一个研究热点，被广泛应用于激光精细加工、激光通信、遥感测距、生物医学、大气探测和可控核聚变等众多领域。
利用调Q或者锁模技术，固体激光器可输出纳秒、皮秒乃至飞秒脉冲激光。相对近年来快速发展的光纤激光器而言，固体激光器在超短脉冲方面具有光学非线性小、容易实现高功率和窄脉宽输出等优点。因此固体激光器依然是获得高功率高光束质量脉冲激光的重要途径。目前根据锁模方式不同，锁模技术可以分为主动锁模和被动锁模。主动锁模技术中调制器响应时间相对较慢，对脉冲的压缩能力有限，因此其输出脉冲宽度受限，一般为皮秒量级。而被动锁模技术主要通过可饱和吸收体实现对腔内光脉冲进行损耗调制，当经过可饱和吸收体时，脉冲能量高的通过，能量低的被吸收，导致光脉冲边缘损耗远大于中间，因此实现光脉冲的窄化，可实现亚皮秒及飞秒锁模脉冲。固体激光器中常见的被动锁模技术包括半导体可饱和吸收镜(Semiconductor Saturable Absorber Mirror，SESAM)和非线性偏振旋转(Nonlinear Polarization Rotation，NPR)。 其中SESAM由于具有较好的稳定性和调制特性，经常被用在锁模激光领域，但是SESAM对激光的响应带宽较小，通常只有几十纳米的光谱响应带宽，并且制作过程比较复杂。NPR锁模机制调制深度大、响应时间短，能产生优良低噪声飞秒脉冲，但NPR锁模激光器对环境扰动非常敏感，导致难以长期保持自启动功能。
发明内容
本申请提供了一种基于非线性放大环形镜的固体激光器，利用非线性放大环形镜锁模技术，通过调节相位偏置单元，可优化锁模阈值并具备自启动功能，在9字腔固体激光器中输出的脉冲激光具有脉冲能量高、噪声低和长期稳定性好等优点。
本申请实施例提供了一种基于非线性放大环形镜的固体激光器，包括泵浦源、泵浦光耦合模块、非线性放大环形镜模块和线性臂模块；
所述非线性放大环形镜模块包括第一二色镜、激光晶体、第二二色镜、平凹透镜、第一法拉第旋转器、四分之一波片、第二法拉第旋转器、第一全反射镜、高非线性波导和偏振分光棱镜；
所述线性臂模块包括第一光栅、第二光栅和输出耦合镜；
所述激光晶体的轴向位于泵浦光和激光光束的传输中心轴上；所述高非线性波导的轴向位于激光光束的传输中心轴上；
所述第一法拉第旋转器、所述四分之一波片、所述第二法拉第旋转器和所述高非线性波导依次设置构成相位偏置单元；所述第一光栅和所述第二光栅平行设置且与所述激光光束的传输中心轴的夹角为锐角，所述第一光栅和所述第二光栅构成色散补偿单元；
所述非线性放大环形镜模块和所述线性臂模块构成9字型谐振腔；
所述泵浦源发射的泵浦光注入所述泵浦光耦合模块，经所述泵浦光耦合模块准直聚焦后，部分所述泵浦光由所述第一二色镜注入所述激光晶体中激发产 生激光光束，残余所述泵浦光透过所述第二二色镜后被所述平凹透镜反射回所述激光晶体；所述激光光束经过所述相位偏置单元后由所述偏振分光棱镜注入所述色散补偿单元，部分所述激光光束由所述输出耦合镜反射回所述偏振分光棱镜后被分束成传输方向不同的第一光束和第二光束，所述第一光束在所述非线性放大环形镜模块中沿顺时针方向传输，所述第二光束在所述非线性放大环形镜模块中沿逆时针方向传输，所述第一光束和所述第二光束经过所述激光晶体和所述相位偏置单元的顺序相反而产生相位差，再次传输至所述偏振分光棱镜时干涉发生非线性相移锁模，形成锁模激光，部分所述锁模激光依次经所述第一光栅、所述第二光栅和所述输出耦合镜后输出。
附图说明
图1为本申请实施例提供的一种基于非线性放大环形镜模块的固体激光器的结构示意图；
图2为本申请实施例提供的另一种基于非线性放大环形镜模块的固体激光器的结构示意图。
附图中：1-泵浦源；2-光隔离器；3-泵浦光耦合模块；30-第一平凸透镜；31-第二全反射镜；32-第三全反射镜；33-第二平凸透镜；4-非线性放大环形镜模块；40-第一二色镜；41-激光晶体；42-第二二色镜；43-平凹透镜；44-第一法拉第旋转器；45-四分之一波片；46-第二法拉第旋转器；47-第一全反射镜；48-高非线性波导；49-偏振分光棱镜；5-线性臂模块；50-第一光栅；51-第二光栅；52-输出耦合镜；01-相位偏置单元；02-色散补偿单元。
具体实施方式
下面结合附图和实施例对本申请作详细说明。
图1为本申请实施例提供的一种基于非线性放大环形镜模块的固体激光器的结构示意图。结合图1所示，本申请实施例提供了一种基于非线性放大环形 镜模块的固体激光器，固体激光器包括泵浦源1、泵浦光耦合模块3、非线性放大环形镜模块4和线性臂模块5。非线性放大环形镜模块4包括第一二色镜40、激光晶体41、第二二色镜42、平凹透镜43、第一法拉第旋转器44、四分之一波片45、第二法拉第旋转器46、第一全反射镜47、高非线性波导48和偏振分光棱镜49；线性臂模块5包括第一光栅50、第二光栅51和输出耦合镜52；激光晶体41的轴向位于泵浦光和激光光束的传输中心轴上；高非线性波导48的轴向位于激光光束的传输中心轴上；第一法拉第旋转器44、四分之一波片45、第二法拉第旋转器46和高非线性波导48依次设置构成相位偏置单元01；第一光栅50和第二光栅51平行设置且与激光光束的传输中心轴的夹角为锐角，第一光栅50和第二光栅51构成色散补偿单元02；非线性放大环形镜模块4和线性臂模块5构成9字形谐振腔。
泵浦源1发射的泵浦光S0注入泵浦光耦合模块3，经泵浦光耦合模块3准直聚焦后，部分泵浦光S0由第一二色镜40注入激光晶体41中激发产生激光光束S1，残余泵浦光S0透过第二二色镜42后被平凹透镜43反射回激光晶体41；激光光束S1依次经过相位偏置单元01中的第一法拉第旋转器44、四分之一波片45、第二法拉第旋转器46和高非线性波导48后由偏振分光棱镜49注入色散补偿单元02，其中，第一全反射镜47位于第二法拉第旋转器46和高非线性波导48之间的激光光束S1的传播中心轴上，第一全反射镜47设置为调整激光光束S1的传播方向，通过调节相位偏置单元01可优化锁模阈值，使得固体激光器具备自启动功能；小部分激光光束S1由输出耦合镜52输出，绝大部分激光光束S1被输出耦合镜52反射回偏振分光棱镜49后被分束成传输方向不同的第一光束S11和第二光束S12，第一光束S11在非线性放大环形镜模块4中沿顺时针方向(如图中P2箭头方向所示)传输，第二光束S12在非线性放大环形镜模块4中沿逆时针(如图中P1箭头方向所示)传输，第一光束S11和第二光束S11经过激光晶体41和相位偏置单元01的顺序相反而产生相位差，再次传输至偏振分光棱镜49时干涉发生非线性相移锁模，形成锁模激光S2，一部分锁模激光 S2经由偏振分光棱镜49直接输出至腔外，另一部分锁模激光S2依次经第一光栅50、第二光栅51和输出耦合镜52后输出，大部分锁模激光S2被输出耦合镜52反射回偏振分光棱镜49后再次被分束入射至非线性放大环形镜模块4中进行与第一光束S11和第二S12相同的过程，并再次在偏振分光棱镜49发生干涉循环往复。
本申请实施例基于非线性放大环形镜模块锁模技术，采用9字腔结构，利用激光晶体作为增益介质，通过调节相位偏置单元，可优化锁模阈值，使得激光器具备自启动功能，输出激光具有噪声低、光谱宽、长期稳定性好的优势，容易实现高功率和窄脉宽输出。
图2为本申请实施例提供的另一种基于非线性放大环形镜模块的固体激光器的结构示意图。可选的，如图2所示，固体激光器还包括光隔离器2，光隔离器2位于泵浦光S0传输中心轴上。泵浦源1发射的泵浦光S0经光隔离器2进入泵浦光耦合模块3，避免泵浦光S0回返，起到保护泵浦源1的作用。
可选的，继续参照图2所示，泵浦光耦合模块3包括依次位于泵浦光S0传输中心轴上的第一平凸透镜30、第二全反射镜31、第三全反射镜32和第二平凸透镜33；激光晶体41还位于第二平凸透镜33和平凹透镜43的共同焦点处。第一平凸透镜30和第二平凸透镜33的组合设置为准直聚焦泵浦光S0，以便泵浦光S0由第一二色镜40注入激光晶体41中激发产生激光光束S1；设置激光晶体41的轴向位于泵浦光和激光光束的传输中心轴上以及激光晶体41位于第二平凸透镜33和平凹透镜43的焦点处，可以提高激光晶体41的激发效率，提高激光光束S1的出光功率；第二全反射镜31和第三全反射镜32设置为改变光线路径，压缩固体激光器体积。
可选的，继续参照图1和图2所示，泵浦源1包括半导体激光器或光纤激光器，泵浦源1的工作波长与激光晶体41的泵浦波长相同。泵浦源1
设置为发射泵浦光，采用泵浦源的工作波长与激光晶体的泵浦波长相同，给激光晶体提供激励能源。
可选的，继续参照图1和图2所示，第一平凸透镜30和第二平凸透镜33的表面镀有泵浦光高透膜，泵浦光高透膜设置为提高泵浦光的透过率；平凹透镜43面向激光晶体41的凹面镀有泵浦光高反膜，泵浦光高反膜设置为提高泵浦光的反射率。
可选的，继续参照图1和图2所示，第一二色镜40和第二二色镜42面向激光晶体41的表面同时镀有泵浦光高透膜和激光光束高反膜，泵浦光高透膜和激光光束高反膜设置为保证残余泵浦光透过和激光光束被反射到相位偏置单元01的第一法拉第旋转器44；第一二色镜40和第二二色镜42背向激光晶体41的表面镀有泵浦光高透膜，泵浦光高透膜设置为提高泵浦光的透过率。
可选的，继续参照图1和图2所示，激光晶体41包括掺杂稀土离子或者过渡金属离子的光学晶体。如Yb：YAG、Er：YLF、Ho：YAG、Cr：LiCAF等，利用激光晶体作为增益介质，其光学非线性小，容易实现固体激光器激光的高功率和窄脉宽输出。
可选的，继续参照图1和图2所示，第一法拉第旋转器44和第二法拉第旋转器46包括薄片式法拉第旋转器和磁光晶体插入永磁体中构成的法拉第旋转器。采用第一法拉第旋转器44、四分之一波片45和第二法拉第旋转器46可以使9字形谐振腔内正向传输的信号光通过该系统，而将反向传输的光束阻断，可以避免系统内的有害反射光导致光学器件损伤、系统不稳定等情况。其中，信号光指的是泵浦光、激光光束和锁模激光。
可选的，继续参照图1所示，高非线性波导48包括条形波导、脊型波导、光子晶体光纤(Photonic Crystal Fiber，PCF)或者高非线性光纤在内的非线性波导，可以对信号光增益放大、脉冲压缩和模式选择等。
可选的，继续参照图1和图2所示，偏振分光棱镜49设置为将激光光束的水平偏振分量和垂直偏振分量分开。
可选的，继续参照图1和图2所示，第一光栅50和第二光栅51包括啁啾体布拉格光栅、啁啾光纤布拉格光栅或者透射式介质膜光栅。通过设置第一光 栅50和第二光栅51的光栅周期等参数，使得满足工作波长的锁模激光从输出耦合镜52输出。
可选的，继续参照图1和图2所示，输出耦合镜52面向9字型谐振腔的表面镀有反射膜，反射膜对激光光束的反射率为β，70％＜β＜100％，使得激光光束继续反回非线性放大环形镜模块4中被激光晶体41激发增益放大；输出耦合镜52背向9字型谐振腔的表面镀有增透膜，增透膜设置为透射输出锁模激光。
下面列举一个具体的实施例。
在本实施例中，继续参照图2所示，泵浦源1选用工作波长为940nm或969nm的半导体激光器；激光晶体41选用棒状Yb：YAG晶体；第一平凸透镜30和第二平凸透镜33表面镀有波长为940nm～969nm的高透膜；平凹透镜43面向激光晶体41的凹面镀有波长为940nm～969nm的高反膜；第一二色镜40和第二二色镜42面向激光晶体41的表面同时镀有波长为940nm～969nm的高透膜和1020nm～1100nm的高反膜，另一表面镀有波长为940nm～969nm的高透膜；第一法拉第旋转器44和第二法拉第旋转器46选用薄片式法拉第旋转器；高非线性波导48选用棒状蓝宝石波导；；第一光栅50和第二光栅51选用透射式介质膜光栅；输出耦合镜52面向谐振腔的表面镀有反射膜，该反射膜对波长为1020nm～1100nm的信号光的反射率为99％，另一表面镀有增透膜，该增透膜提高波长为1020nm～1100nm的信号光的透过率。
泵浦源1发射的940nm或者969nm泵浦光S0经光隔离器2后进入泵浦光耦合模块3，准直聚焦后由第一二色镜40注入非线性放大环形镜模块4中的Yb：YAG晶体激发产生1030nm波段激光光束S1，残余泵浦光S0透过第二二色镜42后被平凹透镜43反射回Yb：YAG晶体，激光光束S1经过相位偏置单元01后由偏振分光棱镜49注入线性臂模块5的色散补偿单元02，再由输出耦合镜52部分反射回偏振分光棱镜49，分为两束光注入非线性放大环形镜模块4，两束光分别沿逆时针和顺时针方向传输，两束光经过Yb：YAG晶体和相位偏置单元01的顺序相反而产生相位差，在传输至偏振分光棱镜49处干涉发生非线性 相移锁模，1％的锁模激光S2由输出耦合镜52输出。本实施例中，通过调节相位偏置单元01，可优化锁模阈值并具备自启动功能，在9字腔固体激光器中输出的脉冲激光具有脉冲能量高、噪声低和长期稳定性好等优点。

Claims (11)

  1. 一种基于非线性放大环形镜的固体激光器，包括泵浦源、泵浦光耦合模块、非线性放大环形镜模块和线性臂模块；
    所述非线性放大环形镜模块包括第一二色镜、激光晶体、第二二色镜、平凹透镜、第一法拉第旋转器、四分之一波片、第二法拉第旋转器、第一全反射镜、高非线性波导和偏振分光棱镜；
    所述线性臂模块包括第一光栅、第二光栅和输出耦合镜；
    所述激光晶体的轴向位于泵浦光和激光光束的传输中心轴上；所述高非线性波导的轴向位于激光光束的传输中心轴上；
    所述第一法拉第旋转器、所述四分之一波片、所述第二法拉第旋转器和所述高非线性波导依次设置构成相位偏置单元；所述第一光栅和所述第二光栅平行设置且与所述激光光束的传输中心轴的夹角为锐角，所述第一光栅和所述第二光栅构成色散补偿单元；
    所述非线性放大环形镜模块和所述线性臂模块构成9字型谐振腔；
    所述泵浦源发射的泵浦光注入所述泵浦光耦合模块，经所述泵浦光耦合模块准直聚焦后，部分所述泵浦光由所述第一二色镜注入所述非线性放大环形镜模块中的所述激光晶体中激发产生激光光束，残余所述泵浦光透过所述第二二色镜后被所述平凹透镜反射回所述激光晶体；所述激光光束经过所述相位偏置单元后由所述偏振分光棱镜注入所述色散补偿单元，部分所述激光光束由所述输出耦合镜反射回所述偏振分光棱镜后被分束成传输方向不同的第一光束和第二光束，所述第一光束在所述非线性放大环形镜模块中沿顺时针方向传输，所述第二光束在所述非线性放大环形镜模块中沿逆时针方向传输，所述第一光束和所述第二光束经过所述激光晶体和所述相位偏置单元的顺序相反而产生相位差，再次传输至所述偏振分光棱镜时干涉发生非线性相移锁模，形成锁模激光，部分所述锁模激光依次经所述第一光栅、所述第二光栅和所述输出耦合镜后输出。
  2. 根据权利要求1所述的固体激光器，还包括光隔离器，所述光隔离器位 于所述泵浦光传输中心轴上。
  3. 根据权利要求1所述的固体激光器，其中，所述泵浦光耦合模块包括依次位于所述泵浦光传输中心轴上的第一平凸透镜、第二全反射镜、第三全反射镜和第二平凸透镜；
    所述激光晶体位于所述第二平凸透镜和所述平凹透镜的共同焦点处。
  4. 根据权利要求1所述的固体激光器，其中，所述泵浦源包括半导体激光器或光纤激光器，所述泵浦源的工作波长与所述激光晶体的泵浦波长相同。
  5. 根据权利要求3所述的固体激光器，其中，所述第一平凸透镜和所述第二平凸透镜的表面镀有泵浦光高透膜，所述平凹透镜面向所述激光晶体的凹面镀有泵浦光高反膜。
  6. 根据权利要求1所述的固体激光器，其中，所述第一二色镜和所述第二二色镜面向所述激光晶体的表面同时镀有泵浦光高透膜和激光光束高反膜，所述第一二色镜和所述第二二色镜背向所述激光晶体的表面镀有泵浦光高透膜。
  7. 根据权利要求1所述的固体激光器，其中，所述激光晶体包括掺杂稀土离子或者过渡金属离子的光学晶体。
  8. 根据权利要求1所述的固体激光器，其中，所述第一法拉第旋转器和所述第二法拉第旋转器包括薄片式法拉第旋转器或者磁光晶体插入永磁体中构成的法拉第旋转器。
  9. 根据权利要求1所述的固体激光器，其中，所述高非线性波导包括条形波导、脊型波导、光子晶体光纤或者高非线性光纤在内的非线性波导。
  10. 根据权利要求1所述的固体激光器，其中，所述第一光栅和所述第二光栅包括啁啾体布拉格光栅、啁啾光纤布拉格光栅或者透射式介质膜光栅。
  11. 根据权利要求1所述的固体激光器，其中，所述输出耦合镜面向9字型谐振腔的表面镀有反射膜，所述反射膜对所述激光光束的反射率为β，70％＜β＜100％；所述输出耦合镜背向9字型谐振腔的表面镀有增透膜。
PCT/CN2023/086568 2022-06-28 2023-04-06 一种基于非线性放大环形镜的固体激光器 WO2024001392A1 (zh)

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