WO2018112752A1 - 一种可调谐双波长超快光参量振荡器 - Google Patents

一种可调谐双波长超快光参量振荡器 Download PDF

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WO2018112752A1
WO2018112752A1 PCT/CN2016/111069 CN2016111069W WO2018112752A1 WO 2018112752 A1 WO2018112752 A1 WO 2018112752A1 CN 2016111069 W CN2016111069 W CN 2016111069W WO 2018112752 A1 WO2018112752 A1 WO 2018112752A1
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light
optical parametric
wavelength
crystal
parametric oscillator
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French (fr)
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钟亥哲
李瑛�
杨建龙
章礼富
梁宇海
范滇元
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Shenzhen University
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Shenzhen University
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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
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • 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
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering

Definitions

  • the present invention relates to the field of laser technology, and more particularly to a tunable dual wavelength ultrafast optical parametric oscillator.
  • the energy level structure of the laser medium and the fluorescence emission line play a decisive role in the wavelength of laser light that can be generated.
  • Different laser media can produce lasers of different wavelengths, but in most cases, a laser using a single laser medium can usually only output a laser of a specific wavelength.
  • more and more research or application fields require the use of two different wavelengths of laser light.
  • the pump-probe technique which is widely used in ultrafast kinetic process research, requires an ultrafast laser to excite the sample and another ultrafast laser with a different wavelength to detect the excited signal. To determine the state of the sample being tested.
  • a non-linear difference frequency is used to generate a mid-infrared or even a terahertz (THz) band of radiation sources; a differential absorption type laser radar based on the difference in absorption of lasers of different wavelengths based on the measured gas; CARS (coherent anti-Stokes la Mann scattering) microscopic imaging techniques and the like all require the simultaneous use of lasers of different wavelengths.
  • THz terahertz
  • OPO optical parametric oscillators
  • the embodiment of the invention provides a tunable dual-wavelength ultrafast optical parametric oscillator, which aims to solve the problem that the dual-wavelength optical parametric oscillator in the prior art cannot effectively generate a two-wavelength femtosecond pulse laser without distortion of the pulse waveform. .
  • Embodiments of the present invention provide a tunable dual-wavelength ultrafast optical parametric oscillator including: a pulsed laser pump source placed in sequence, an input coupling mirror, a periodically polarized crystal with a sector structure, an output coupling mirror, and a beam splitter ;
  • the pump light outputted by the pulsed laser pump source enters the periodically polarized crystal with a fan structure through the input coupling mirror, and generates a signal light oscillating back and forth in the periodically polarized crystal with a sector structure And idle frequency light, and output mixed light from the output coupling mirror, and the mixed light is separated by the beam splitter to obtain a signal light pulse laser and an idle frequency light pulse laser respectively;
  • the periodically polarized crystal with a fan-shaped structure is a periodically polarized crystal that satisfies a class II alignment, and the signal light and the idler light are at a preset temperature at a periodic pole of the fan-shaped structure.
  • the group velocity in the crystal is matched, and the mixed light includes the signal light, the idler light, and the residual pump light.
  • the tunable dual-wavelength ultrafast optical parametric oscillator further includes:
  • a crystal temperature control device for regulating the temperature of the periodically polarized crystal with the sector structure.
  • the polarization period of the periodically polarized crystal with a sector structure can be continuously tuned.
  • the temperature of the periodically polarized crystal with the fan structure and the polarization period are tuned together to make the tuning range
  • the signal light of any wavelength within is always matched to the group velocity of the idler light in the periodically polarized crystal with the sector structure.
  • the tunable dual-wavelength ultrafast optical parametric oscillator further includes:
  • a dispersion compensation device disposed on an optical path between the periodically polarized crystal and the output coupling mirror for compensating for a group velocity of the signal light accumulated in the periodically polarized crystal Dispersion.
  • the signal light oscillates back and forth between the input coupling mirror and the output coupling mirror
  • the input coupling mirror is highly reflective to the signal light, and highly transmissive to the pump light
  • the output coupling The mirror partially transmits the signal light and is highly transmissive to the pump light and the idler light.
  • the present invention provides a tunable dual-wavelength ultrafast optical parametric oscillator comprising: a pulsed laser pump source placed in sequence, an input coupling mirror, a periodically polarized crystal with a sector structure, A dispersion compensation device, an output coupling mirror, a beam splitter, and a crystal temperature control device.
  • the present invention utilizes the dispersion relationship between the group velocity of the pulsed laser and the crystal temperature to regulate the operation of the periodically polarized crystal.
  • the temperature eliminates the group velocity mismatch between the signal light and the idler light in the periodically polarized crystal.
  • Synchronous amplification of signal light and idler light can not only improve the matching bandwidth of the optical parametric oscillator, but also avoid the pulse distortion caused by time deviation, enabling the optical parametric oscillator to simultaneously output two high-quality ultrashort pulses. laser.
  • Figure 1 shows the wavelength of the pulsed laser pump source at 1064.
  • the 3.5-mm-2.9 ⁇ m e-polarized light signal light in the periodically polarized crystal and the corresponding 1.5- ⁇ m-1.7 ⁇ m o-polarized idler light satisfy the variation of the operating temperature and the wavelength required for group velocity matching;
  • Figure 2 shows a period of 3.1 ⁇ m in a periodically polarized crystal when the pulsed laser pump source has a wavelength of 790 nm. -1.7 ⁇ m e-polarized signal light and corresponding 1 ⁇ m-1.5 ⁇ m o-polarized idler light satisfy the variation of the operating temperature required for group velocity matching with wavelength;
  • FIG. 3 is a schematic structural diagram of a tunable dual-wavelength ultrafast optical parametric oscillator according to an embodiment of the present invention
  • a conversion efficiency of a dual-wavelength ultrafast optical parametric oscillator according to an embodiment of the present invention and a spectral curve of a spectral bandwidth of a mid-infrared signal light and a near-infrared idler light with a pump intensity, wherein a wavelength of the pump light 1064nm, the signal light wavelength is 3.2 ⁇ m, corresponding, the idler light wavelength is 1.59 ⁇ m;
  • FIG. 5 is a time waveform diagram of signal light and idler light output by a dual-wavelength ultrafast optical parametric oscillator according to an embodiment of the present invention, wherein The wavelength of the pump light is 1064 nm, the wavelength of the signal light is 3.2 ⁇ m, and the wavelength of the idler light is 1.59 ⁇ m;
  • FIG. 6 is a graph showing the spectral bandwidth of the signal light and the idler light outputted by the dual-wavelength ultrafast optical parametric oscillator according to the wavelength of the signal light/idle frequency light in the embodiment of the present invention. among them, The pump light has a wavelength of 1064 nm.
  • the laser wavelengths of the pump source are 1064 nm and 790, respectively.
  • the periodically polarized crystal's e-polarized signal light and the corresponding o-polarized idler light satisfy the group temperature matching required operating temperature as a function of wavelength.
  • the periodically polarized crystal is selected in this embodiment. It is an 8% doped MgO:PPLN crystal.
  • the output laser wavelength can be from 1 ⁇ m to 3.5. ⁇ m, full coverage from near infrared to mid-infrared. If combined with other wavelengths of pump source, its application range can be extended to 5 ⁇ m (MgO: PPLN crystal limit transmission wavelength).
  • FIG. 3 is a schematic structural diagram of a tunable dual-wavelength ultrafast optical parametric oscillator according to an embodiment of the present invention. For convenience of description, only parts related to the embodiments of the present invention are shown.
  • the tunable dual-wavelength ultrafast optical parametric oscillator illustrated in FIG. 3 mainly includes: a pulsed laser pump source 101, an input coupling mirror 102, a periodically polarized crystal 103 with a sector structure, an output coupling mirror 104, and a beam splitter 105.
  • the crystal temperature control device 106 and the dispersion compensation device 107 The crystal temperature control device 106 and the dispersion compensation device 107.
  • the pulsed laser pump source 101 can be, but is not limited to, a 1064 nm femtosecond pulsed laser, which outputs 1064 of its output.
  • the nm pulse laser is used as pump light, and the pump light enters the optical cavity through the input coupling mirror 102, and generates oscillations between the input coupling mirror 102 and the output coupling mirror 104 in the periodically polarized crystal 103 with a sector structure.
  • Signal light, as well as idle frequency light The signal light is the same as the group velocity of the idler light in the periodically polarized crystal 103 having the sector structure.
  • the signal light extracts energy from the pump light and outputs mixed light from the output coupling mirror 104, which includes partial signal light, idler light, and residual pump light.
  • the mixed light is separated by the beam splitter 105, two ultrashort pulse lasers of different wavelengths are output, which are a signal light pulse laser and an idle frequency light pulse laser.
  • the beam splitter 105 may include, but is not limited to, an optical element that can separate the mixed lights of different wavelengths from each other such as a dichroic prism or a dichroic mirror.
  • a crystal temperature control device 106 for regulating the temperature of the periodically polarized crystal 103 having a sector structure includes a crystal temperature control furnace disposed below the periodically polarized crystal 103 having a sector structure.
  • a dispersion compensating element 107 is further disposed between the periodically polarized crystal 103 having a sector structure and the output coupling mirror 104, and the dispersion compensating element 107 is for eliminating group velocity accumulated in the periodically polarized crystal 103 by the signal light oscillated back and forth. Dispersion.
  • the periodically polarized crystal 103 with a fan-shaped structure is a periodically polarized crystal that satisfies the class II alignment matching.
  • an 8% doped MgO:PPLN crystal is used.
  • the refractive index (n) of the crystal changes with temperature, and the group velocity (v) of the pulsed laser in the crystal is also a physical quantity related to temperature.
  • Periodically polarized crystals generally need to satisfy the quasi-phase matching condition (e+e- ⁇ e) of class 0, requiring that the pump light, the signal light, and the idler light are both e-polarized light.
  • the two pulsed lasers in the same polarization state have a large difference in group velocity, and this difference cannot be simply eliminated by changing the operating temperature of the periodically polarized crystal.
  • the two laser beams propagate in the crystal in an orthogonal manner (for example, the signal light is o-polarized light, the idler light is e-polarized light; or the signal light is e-polarized light, and the idler light is o-polarized light)
  • Their group speeds may be equal at a certain temperature.
  • the signal light and the idler light need to have the same group velocity.
  • the dual-wavelength optical parametric oscillator in this embodiment uses a class II quasi-phase matching technique, and uses the group velocity of the pulsed laser.
  • Synchronous amplification of signal light and idler light can not only improve the matching bandwidth of the optical parametric oscillator, but also avoid the pulse distortion caused by time deviation, enabling the optical parametric oscillator to simultaneously output high-quality dual-wavelength ultrashort pulses. laser.
  • the simultaneous implementation of group velocity matching and phase velocity matching requires that the periodically polarized crystal operate at a specific temperature, and that the polarization period of the periodically polarized crystal is also specific. For the different wavelengths of signal light and idler light, the preset temperature required for group velocity matching and the polarization period required for phase velocity matching are different.
  • the embodiment of the present invention employs a periodically polarized crystal 103 having a sector structure, and the periodically polarized crystal 103 having a sector structure satisfies the class II level match.
  • the periodically polarized crystal 103 with a sector structure can change the transverse dimension of the signal light, the idler light and the pump light in the periodically polarized crystal 103 with the sector structure, compared to the conventional periodically polarized crystal.
  • Position continuously tuning its polarization period.
  • the crystal temperature control device 106 is for regulating the temperature of the periodically polarized crystal 103 having a sector structure.
  • the tunable output wavelength of the tunable dual-wavelength ultrafast optical parametric oscillator is achieved by the coordinated operation of the operating temperature of the periodically polarized crystal 103 with the sector structure and the polarization period. For any laser wavelength within the tuning range, the group speed of the signal light and the idler light is always equal.
  • the pulsed laser pump source 101 uses a 1064 nm femtosecond pulse laser, and its output is 1064.
  • the nm pulsed laser is used as the pump light.
  • the sector-shaped periodically polarized crystal 5 is selected from 8% doped MgO:PPLN crystals satisfying the class II alignment. Its polarization period is 36 ⁇ m - 46 Continuously adjustable in the ⁇ m range.
  • the signal light and idler light of the tunable dual-wavelength ultrafast optical parametric oscillator are in the mid-infrared and near-infrared bands, respectively.
  • the output signal light can be continuously tuned from 2.9 ⁇ m to 3.5 ⁇ m.
  • the idler light has a wavelength of ⁇ 1.7 ⁇ m to 1.5 ⁇ m.
  • the 1064 nm pump pulsed laser has a pulse width of 100 fs. Tune the signal light to 3.2 Mid-infrared pulsed laser of ⁇ m.
  • the wavelengths of the pump light, signal light, and idler light are 1064 nm, 3.2 ⁇ m, and 1.59 ⁇ m, respectively.
  • the ⁇ m idler light satisfies the group velocity matching, and the temperature of the 8% doped MgO:PPLN crystal needs to be controlled at 145 oC. At such operating temperatures, the polarization period required to satisfy phase velocity matching is 40. Mm.
  • the optical parametric oscillator Based on the nonlinear coupled wave equations, we numerically simulate the operation of the optical parametric oscillator.
  • the length of the 8% doped MgO:PPLN crystal is 2 Mm.
  • the conversion efficiency of the optical parametric oscillator is shown, 3.2 ⁇ m mid-infrared signal light and 1.59
  • the spectral bandwidth of the ⁇ m near-infrared idler light varies with the pump intensity. As the intensity of the pump increases, the optical parametric oscillator gradually enters the saturation region, and the spectral bandwidths of the signal light and the idler light also decrease due to "reflow".
  • FIG. 5 is a quantum conversion efficiency of the optical parametric oscillator of ⁇ 30 At the time of %, the time waveform of the signal light and the idler light after the dispersion compensation is output. As shown in the figure, neither the signal light nor the idler light has any pulse distortion, and their pulse widths are basically the same, about 50.
  • Fs corresponds to two different wavelength ultrashort pulse lasers output by the optical parametric oscillator.
  • Fig. 6 is a graph showing the spectral bandwidth of the signal light and the idler light outputted by the dual-wavelength optical parametric oscillator as a function of the signal light/idle frequency wavelength.
  • the spectral bandwidths of the signal light and the idler light are both shown when the quantum conversion efficiency of the optical parametric oscillator is ⁇ 30. The result at %.
  • the signal light tuning range of 2.9 ⁇ m - 3.4 ⁇ m corresponding to the idler light wavelength of 1.63 ⁇ m - 1.58 ⁇ m
  • the spectral bandwidth of the output signal light and the idler light remain stable. It exhibits superior wavelength tuning capability for ultrashort pulsed lasers.
  • the tunable dual-wavelength ultrafast optical parametric oscillator comprises: a pulsed laser pump source placed in sequence, an input coupling mirror, a periodically polarized crystal with a sector structure, a dispersion compensation device, an output coupling mirror, a beam splitter And the crystal temperature control device, compared with the prior art, the invention utilizes the dispersion relationship between the group velocity of the pulsed laser and the crystal temperature, and eliminates the signal in the periodically polarized crystal by regulating the operating temperature of the periodically polarized crystal. The group velocity mismatch between light and idle frequency.
  • Synchronous amplification of signal light and idler light can not only improve the matching bandwidth of the optical parametric oscillator, but also avoid the pulse distortion caused by the time deviation, so that the optical parametric oscillator can simultaneously output two high-quality ultra-short Pulsed laser.

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Abstract

涉及激光技术领域，提供了一种可调谐双波长超快光参量振荡器，包括：依次放置的脉冲激光泵浦源（101）、输入耦合镜（102）、带扇形结构的周期性极化晶体（103）、色散补偿装置（107）、输出耦合镜（104）、分光镜（105），以及晶体控温装置（106），相较于现有技术，这种振荡器利用脉冲激光的群速度与晶体温度之间的色散关系，通过调控周期性极化晶体（103）的工作温度，消除周期性极化晶体（103）内信号光与闲频光间的群速度失配。信号光与闲频光的同步放大，不但可以提升光参量振荡器的匹配带宽，更是避免了由于时间走离造成的脉冲畸变，使光参量振荡器能够同时输出两路高质量的超短脉冲激光。

Description

一种可调谐双波长超快光参量振荡器 技术领域
本发明涉及激光技术领域，尤其涉及 一种可调谐双波长超快光参量振荡器。
背景技术
激光介质的能级结构和荧光发射谱线对能够产生何种波长的激光起着决定性的作用。不同激光介质可以产生不同波长的激光，但是，大多数情况下，使用单一激光介质的激光器，通常也只能输出一种特定波长的激光。然而，从物理、化学学科的基础研究到医学，甚至工业应用，越来越多的研究或者应用领域需要同时用到两束不同波长的激光。比如广泛应用于超快动力学过程研究的泵浦探测（pump-probe）技术，就需要用一束超快激光激发样品，再用另一束波长不同的超快激光探测其发出的受激信号，以此确定被测样品的状态。此外，通过非线性差频产生中红外，甚至太赫兹（THz）波段的辐射源；基于被测气体对不同波长的激光存在吸收差异的差分吸收式激光雷达；CARS（相干反斯托克斯喇曼散射）显微成像技术等都需要同时使用不同波长的激光。
人们已经在固体激光系统，例如钛宝石激光器，利用分裂（self-spectrum splitting），受激粒子的能级分裂以及布里渊散射等方法实现了双波长的激光输出。但是，基于非线性频率转换的光参量振荡器（OPO），仍是目前获得双波长激光最有效的途径之一。利用二阶非线性效应，OPO能够将入射激光（称为泵浦光）转变为两束波长各异的出射激光，对于单谐振的OPO，一般将在谐振腔内来回振荡的激光称为信号光，将与信号光共存的另一束激光称为闲频光。信号光、闲频光与泵浦光之间始终满足能量守恒。OPO天然具有双波长激光输出的特点，因此被广泛用作双波长激光器。
随着科技的进步，人们对医学、生物、物理等学科的研究已进入纳米、原子尺度，无论是泵浦探测，还是CARS，都需要借助超短脉冲激光来获得更高的分辨率，这对双波长激光器的输出脉宽以及光束质量均提出了更高的要求。但是，通常情况下，在光参量振荡过程中，相互作用的泵浦光、信号光和闲频光在晶体中的速度（即群速度）并不相同，一般称之为群速度失配（GVM）。当OPO工作在超快时间尺度（例如飞秒，即10-15秒）的时候，由于会在光参量振荡过程中相互走离，信号光与闲频光都会出现不同程度的脉冲畸变，尤其是闲频光。泵浦光的脉宽越短，群速度失配的影响越显著。这极大限制了飞秒OPO输出的信号光与闲频光的脉宽，以及光束质量。
 技术问题
本发明实施例提供了一种可调谐双波长超快光参量振荡器，旨在解决现有技术中的双波长光参量振荡器无法有效地产生脉冲波形无畸变的双波长飞秒脉冲激光的问题。
 技术解决方案
本发明实施例提供了一种可调谐双波长超快光参量振荡器，包括：依次放置的脉冲激光泵浦源、输入耦合镜、带扇形结构的周期性极化晶体、输出耦合镜及分光镜；
所述脉冲激光泵浦源输出的泵浦光经过所述输入耦合镜进入所述带扇形结构的周期性极化晶体，在所述带扇形结构的周期性极化晶体中产生来回振荡的信号光，以及闲频光，并从所述输出耦合镜输出混合光，所述混合光经所述分光镜分离后，分别得到信号光脉冲激光和闲频光脉冲激光；
所述带扇形结构的周期性极化晶体为满足II类准位相匹配的周期性极化晶体，所述信号光与所述闲频光在预置温度下在所述带扇形结构的周期性极化晶体中的群速度匹配，所述混合光中包含所述信号光、所述闲频光以及残留的所述泵浦光。
进一步地，所述可调谐双波长超快光参量振荡器，还包括：
晶体控温装置，用于调控所述带扇形结构的周期性极化晶体的温度。
进一步地，所述带扇形结构的周期性极化晶体的极化周期能够连续调谐。
进一步地，根据所述脉冲激光泵浦源输出的泵浦光的波长及预置的调谐规则，对所述带扇形结构的周期性极化晶体的温度以及极化周期联动调谐，以使调谐范围内的任意波长的所述信号光与所述闲频光在所述带扇形结构的周期性极化晶体中的群速度始终匹配。
进一步地，所述可调谐双波长超快光参量振荡器还包括：
色散补偿装置，所述色散补偿装置设置在所述周期性极化晶体与所述输出耦合镜之间的光路上，用于补偿所述信号光在所述周期性极化晶体内累积的群速度色散。
进一步地，所述信号光在所述输入耦合镜和所述输出耦合镜之间来回振荡，所述输入耦合镜对所述信号光高反射，对所述泵浦光高透射，所述输出耦合镜对所述信号光部分透射，对所述泵浦光和所述闲频光高透射。
 有益效果
从上述本发明实施例可知，本发明提供了一种可调谐双波长超快光参量振荡器，包括：依次放置的脉冲激光泵浦源、输入耦合镜、带扇形结构的周期性极化晶体、色散补偿装置、输出耦合镜、分光镜，以及晶体控温装置，相较于现有技术，本发明利用脉冲激光的群速度与晶体温度之间的色散关系，通过调控周期性极化晶体的工作温度，消除周期性极化晶体内信号光与闲频光间的群速度失配。信号光与闲频光的同步放大，不但可以提升光参量振荡器的匹配带宽，更是避免了由于时间走离造成的脉冲畸变，使光参量振荡器能够同时输出两路高质量的超短脉冲激光。
附图说明
图1是当脉冲激光泵浦源的波长为1064 nm时，周期性极化晶体内3.5μm-2.9μm的e偏振光信号光和与之对应的1.5μm-1.7μm的o偏振闲频光满足群速度匹配所需工作温度随波长的变化曲线；
图2是当脉冲激光泵浦源的波长为790 nm时，周期性极化晶体内3.1μm -1.7μm的e偏振信号光和与之对应的1μm-1.5μm的o偏振闲频光满足群速度匹配所需工作温度随波长的变化曲线；
图3是本发明实施例提供的可调谐双波长超快光参量振荡器的结构示意图；
图4是本发明实施例中的双波长超快光参量振荡器的转换效率，以及中红外信号光与近红外闲频光的光谱带宽随泵浦光强的变化曲线，其中,泵浦光波长为1064nm，信号光波长为3.2μm，对应的，闲频光波长为1.59μm；
图5是本发明实施例中的双波长超快光参量振荡器输出的信号光与闲频光的时间波形图，其中, 泵浦光波长为1064nm，信号光波长为3.2μm，对应的，闲频光波长为1.59μm；
图6是本发明实施例中的双波长超快光参量振荡器输出的信号光与闲频光的光谱带宽随信号光/闲频光波长的变化曲线。其中, 泵浦光波长为1064nm。
 本发明的实施方式
为使得本发明实施例的发明目的、特征、优点能够更加的明显和易懂，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而非全部实施例。基于本发明中的实施例，本领域技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
如图1、图2所示，图中给出了当泵浦源的激光波长分别为1064 nm和790 nm的时候，周期性极化晶体内e偏振信号光和与之对应的o偏振闲频光满足群速度匹配所需工作温度随波长的变化曲线，周期性极化晶体在本实施例中选用的是8%掺杂MgO:PPLN晶体。从图中可以看出，仅考虑以1064 nm 和790 nm的脉冲激光器为泵浦源，就可实现输出激光波长从1 μm到3.5 μm，近红外到中红外波段的全覆盖。若再配合其它波长的泵浦源，其应用范围可以扩展到5 μm（MgO:PPLN晶体的极限透射波长）。
请参阅图3，图3是本发明实施例提供的可调谐双波长超快光参量振荡器的结构示意图，为了便于说明，仅示出了与本发明实施例相关的部分。图3示例的可调谐双波长超快光参量振荡器，主要包括：脉冲激光泵浦源101、输入耦合镜102、带扇形结构的周期性极化晶体103、输出耦合镜104以及分光镜105、晶体控温装置106以及色散补偿装置107。
脉冲激光泵浦源101可以但不限于选用1064 nm飞秒脉冲激光器，将其输出的1064 nm脉冲激光作为泵浦光，该泵浦光经输入耦合镜102，进入光学谐振腔，在带扇形结构的周期性极化晶体103中产生在输入耦合镜102和输出耦合镜104之间来回振荡的信号光，以及闲频光。其中该信号光与该闲频光在该带扇形结构的周期性极化晶体103中的群速度相同。通过光参量放大，信号光从泵浦光中获取能量，并从输出耦合镜104中输出混合光，该混合光中包含部分信号光、闲频光以及残留的泵浦光。该混合光经分光镜105分离后，输出两种不同波长的超短脉冲激光，分别是信号光脉冲激光和闲频光脉冲激光。分光镜105可以但不限于包括：分光棱镜、双色镜等可以将不同波长的混合光相互分离的光学元件。
晶体控温装置106，用于调控带扇形结构的周期性极化晶体103的温度，其包括设置于带扇形结构的周期性极化晶体103的下方的晶体控温炉。
带扇形结构的周期性极化晶体103和输出耦合镜104之间还设置有色散补偿元件107，该色散补偿元件107用于消除来回振荡的信号光在周期性极化晶体103内累积的群速度色散。
其中，带扇形结构的周期性极化晶体103是满足II类准位相匹配的周期性极化晶体，在本实施例中选用的是8%掺杂MgO:PPLN晶体。晶体折射率（n）会随温度的不同而变化，晶体内脉冲激光的群速度（v）也是与温度有关的物理量。为了利用非线性晶体最大的非线性系数（d33）， 周期性极化晶体通常都需要满足0类的准相位匹配条件（e+e-›e），要求泵浦光、信号光和闲频光均为e偏振光。处于同一偏振态的两种脉冲激光，其群速度存在比较大的差别，而且，这种差异并不能简单地通过改变周期性极化晶体的工作温度来消除。但是，当这两束激光以正交的方式在晶体中传播（例如，信号光为o偏振光、闲频光为e偏振光；或者信号光为e偏振光、闲频光为o偏振光），它们的群速度有可能在特定温度下相等。为了得到高质量的双波长超短脉冲激光，信号光与闲频光需要有相同的群速度，本实施例中的双波长光参量振荡器采用II类准相位匹配技术，利用脉冲激光的群速度与晶体温度之间的色散关系，通过调控带扇形结构的周期性极化晶体103的工作温度，使信号光与闲频光满足群速度匹配（GVM=0），再在此温度基础上，设计出合适的极化周期，使OPO满足相速度匹配，从而使OPO能够同时满足相速度匹配与群速度匹配。信号光与闲频光的同步放大，不但可以提升光参量振荡器的匹配带宽，更是避免了由于时间走离造成的脉冲畸变，使光参量振荡器能够同时输出高质量的双波长超短脉冲激光。
群速度匹配与相速度匹配的同时实现，要求周期性极化晶体工作在特定的温度，而且，该周期性极化晶体的极化周期也是特定的。对不同波长的信号光与闲频光，其群速度匹配所需要的预置温度，以及相速度匹配所需要的极化周期均各不相同。
为了实现双波长超快光参量振荡器的激光波长的可调谐，本发明实施例采用带扇形结构的周期性极化晶体103，且该带扇形结构的周期性极化晶体103满足II类准位相匹配。带扇形结构的周期性极化晶体103相较于常用的周期性极化晶体，能够通过改变信号光、闲频光与泵浦光在带扇形结构的周期性极化晶体103中的横向维度的位置，对其极化周期进行连续调谐。晶体控温装置106，用于调控带扇形结构的周期性极化晶体103的温度。通过对该带扇形结构的周期性极化晶体103的工作温度以及极化周期的联动调谐，实现所述可调谐双波长超快光参量振荡器输出激光波长的可调谐。对调谐范围内的任意激光波长，信号光与所述闲频光的群速度始终相等。
具体的，脉冲激光泵浦源101选用1064 nm飞秒脉冲激光器，其输出的1064 nm脉冲激光作为泵浦光。所述扇形周期性极化晶体5选用满足II类准位相匹配的8%掺杂MgO:PPLN晶体。其极化周期在36 μm - 46 μm范围内连续可调。所述可调谐双波长超快光参量振荡器的信号光与闲频光正好分别处于中红外与近红外波段。在20 oC – 250 oC的温度区间内，输出的信号光可以在2.9 μm至3.5 μm范围内连续调谐，相应的，闲频光的波长为~1.7 μm至1.5 μm。
采用同步泵浦单谐振设计，该1064 nm泵浦脉冲激光的脉冲宽度为100 fs。将信号光调谐至3.2 μm的中红外脉冲激光。泵浦光、信号光、闲频光的波长分别为1064 nm、3.2 μm和1.59 μm。为了使e偏振的3.2 μm信号光与o偏振的1.59 μm闲频光满足群速度匹配，需要将8%掺杂MgO:PPLN晶体的温度控制在145 oC。在这样的工作温度下，满足相速度匹配所需要的极化周期为40 μm。基于非线性耦合波方程组，我们对所述光参量振荡器的运行情况进行了数值模拟。所述8%掺杂MgO:PPLN晶体的长度为2 mm。如图4所示，图中给出了所述光参量振荡器的转换效率，3.2 μm中红外信号光与1.59 μm近红外闲频光的光谱带宽随泵浦光强的变化曲线。随着泵浦光强的增加，所述光参量振荡器逐渐进入饱和区域，信号光与闲频光的光谱带宽也都因为“回流”，出现了不同程度的下降。即便如此，由于信号光与闲频光的群速度相同，它们的光谱带宽依然保持良好，可以支持小于50 fs的傅氏变换极限的超短脉冲激光。图5为所述光参量振荡器的量子转换效率为~30 %的时候，输出经色散补偿后的信号光与闲频光的时间波形图，如图所示，信号光与闲频光均未出现任何脉冲畸变，它们的脉冲宽度基本相同，约为50 fs，对应所述光参量振荡器输出的两种不同波长的超短脉冲激光。
图6为双波长光参量振荡器输出的信号光与闲频光的光谱带宽随信号光/闲频光波长的变化曲线。图中给出的信号光与闲频光的光谱带宽均为当所述光参量振荡器的量子转换效率为~30 %时的结果。在2.9 μm - 3.4 μm的信号光调谐范围内（对应闲频光波长为1.63 μm - 1.58 μm），输出信号光与闲频光的光谱带宽均保持稳定。表现出优越的针对超短脉冲激光的波长调谐能力。
本发明提供的可调谐双波长超快光参量振荡器，包括：依次放置的脉冲激光泵浦源、输入耦合镜、带扇形结构的周期性极化晶体、色散补偿装置、输出耦合镜、分光镜，以及晶体控温装置，相较于现有技术，本发明利用脉冲激光的群速度与晶体温度之间的色散关系，通过调控周期性极化晶体的工作温度，消除周期性极化晶体内信号光与闲频光间的群速度失配。信号光与闲频光的同步放大，不但可以提升光参量振荡器的匹配带宽，更是避免了由于时间走离造成的脉冲畸变，使光参量振荡器能够同时输出两路高质量的的超短脉冲激光。
需要说明的是，对于前述的各方法实施例，为了简便描述，故将其都表述为一系列的动作组合，但是本领域技术人员应该知悉，本发明并不受所描述的动作顺序的限制，因为依据本发明，某些步骤可以采用其它顺序或者同时进行。其次，本领域技术人员也应该知悉，说明书中所描述的实施例均属于优选实施例，所涉及的动作和模块并不一定都是本发明所必须的。
在上述实施例中，对各个实施例的描述都各有侧重，某个实施例中没有详述的部分，可以参见其它实施例的相关描述。
以上为对本发明所提供的可调谐双波长超快光参量振荡器的描述，对于本领域的技术人员，依据本发明实施例的思想，在具体实施方式及应用范围上均会有改变之处，综上，本说明书内容不应理解为对本发明的限制。

Claims (6)

  1. 一种可调谐双波长超快光参量振荡器，包括：依次放置的脉冲激光泵浦源、输入耦合镜、带扇形结构的周期性极化晶体、输出耦合镜及分光镜；
    所述脉冲激光泵浦源输出的泵浦光经过所述输入耦合镜进入所述带扇形结构的周期性极化晶体，在所述带扇形结构的周期性极化晶体中产生来回振荡的信号光，以及闲频光，并从所述输出耦合镜输出混合光，所述混合光经所述分光镜分离后，分别得到信号光脉冲激光和闲频光脉冲激光；
    所述带扇形结构的周期性极化晶体为满足II类准位相匹配的周期性极化晶体，所述信号光与所述闲频光在预置温度下在所述带扇形结构的周期性极化晶体中的群速度匹配，所述混合光中包含所述信号光、所述闲频光以及残留的所述泵浦光。
  2. 根据权利要求1所述的可调谐双波长超快光参量振荡器，其特征在于，所述可调谐双波长超快光参量振荡器，还包括：
    晶体控温装置，用于调控所述带扇形结构的周期性极化晶体的温度。
  3. 根据权利要求2所述的可调谐双波长超快光参量振荡器，其特征在于，所述带扇形结构的周期性极化晶体的极化周期能够连续调谐。
  4. 根据权利要求3所述可调谐双波长超快光参量振荡器，其特征在于，根据所述脉冲激光泵浦源输出的泵浦光的波长及预置的调谐规则，对所述带扇形结构的周期性极化晶体的温度以及极化周期联动调谐，以使调谐范围内的任意波长的所述信号光与所述闲频光在所述带扇形结构的周期性极化晶体中的群速度始终匹配。
  5. 根据权利要求1至4任一项所述可调谐双波长超快光参量振荡器，其特征在于，所述可调谐双波长超快光参量振荡器还包括：
    色散补偿装置，所述色散补偿装置设置在所述周期性极化晶体与所述输出耦合镜之间的光路上，用于补偿所述信号光在所述周期性极化晶体内累积的群速度色散。
  6. 根据权利要求1至4任一项所述可调谐双波长超快光参量振荡器，其特征在于，所述信号光在所述输入耦合镜和所述输出耦合镜之间来回振荡，所述输入耦合镜对所述信号光高反射，对所述泵浦光高透射，所述输出耦合镜对所述信号光部分透射，对所述泵浦光和所述闲频光高透射。
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CN121238315A (zh) * 2025-12-04 2025-12-30 山东大学 Bibo晶体非共线光参量振荡器的光谱拓展装置及方法
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CN117175339B (zh) * 2023-08-25 2024-05-24 中国人民解放军国防科技大学 一种宽调谐范围高分辨率的中远红外激光产生方法
CN120473808A (zh) * 2025-04-08 2025-08-12 浙江大学 一种多波长红外激光输出装置
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