WO2019148353A1 - 一种光参量激光放大器制备方法及光参量激光放大器 - Google Patents

一种光参量激光放大器制备方法及光参量激光放大器 Download PDF

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WO2019148353A1
WO2019148353A1 PCT/CN2018/074695 CN2018074695W WO2019148353A1 WO 2019148353 A1 WO2019148353 A1 WO 2019148353A1 CN 2018074695 W CN2018074695 W CN 2018074695W WO 2019148353 A1 WO2019148353 A1 WO 2019148353A1
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angle
collinear
optical parametric
laser amplifier
light
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PCT/CN2018/074695
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English (en)
French (fr)
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钟亥哲
戴达华
李瑛�
杨建龙
王世伟
范滇元
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深圳大学
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Priority to PCT/CN2018/074695 priority Critical patent/WO2019148353A1/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
    • H01S3/106—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

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  • the invention relates to the field of laser technology, in particular to a method for preparing an optical parametric laser amplifier and an optical parametric laser amplifier.
  • OPA Optical Parametric Amplification
  • the nonlinear crystal absorbs the energy of the laser, thereby generating a thermal effect.
  • the thermal effect has become a core factor that restricts its development, and the thermal effect causes a nonlinear crystal.
  • the change of temperature deviates from the originally set phase matching temperature to destroy the phase matching of the optical parametric laser amplifier, thereby reducing the energy conversion efficiency of the pump light to the signal light, and limiting the performance of the optical parametric laser amplifier.
  • the main object of the present invention is to provide a method for preparing an optical parametric laser amplifier and an optical parametric laser amplifier, which aim to solve the problem that the nonlinear crystal temperature changes in the prior art, and deviates from the originally set phase matching temperature, thereby destroying the light.
  • the phase matching of the parametric laser amplifier results in a decrease in the efficiency of pump light energy conversion to the signal light, which limits the performance of the optical parametric laser amplifier.
  • a first aspect of the present invention provides a method for fabricating an optical parametric laser amplifier, the method comprising:
  • the optical parametric laser amplifier is prepared based on the first target non-collinear angle and the second target non-collinear angle.
  • the determining, by using a preset non-collinear phase matching formula, a mapping relationship between the first non-collinear angle and the second non-collinear angle including:
  • the non-collinear phase matching formula is:
  • ⁇ represents the first non-collinear angle, which is an angle between the pump light and the signal light in the transmission direction
  • ⁇ represents the second non-collinear angle, which is the pump light and An angle in the transmission direction of the idler light
  • T 0 represents a phase matching temperature of the nonlinear crystal in the optical parametric laser amplifier
  • k s (T 0 ) represents a wave vector of the signal light when the temperature is T 0
  • the magnitude of k p (T 0 ) represents the magnitude of the wave vector of the pump light when the temperature is T 0
  • k i (T 0 ) represents the magnitude of the wave vector of the idler light when the temperature is T 0 .
  • the determining the first target non-collinear angle and the second target non-collinear angle based on the preset temperature partial deviation formula and the mapping relationship including:
  • the temperature biasing formula is:
  • ⁇ represents the first non-collinear angle, which is an angle between the pump light and the signal light in the transmission direction
  • ⁇ represents the second non-collinear angle, which is the pump light and An angle in the transmission direction of the idler light
  • T 0 represents a phase matching temperature of the nonlinear crystal in the optical parametric laser amplifier
  • T represents an operating temperature of the nonlinear crystal
  • k s (T) represents The magnitude of the wave vector of the signal light
  • k p (T) represents the magnitude of the wave vector of the pump light
  • k i (T) represents the magnitude of the wave vector of the idler light.
  • a second aspect of the present invention provides an optical parametric laser amplifier prepared by the method of the first aspect, the optical parametric laser amplifier comprising: a laser device, a signal light generator, Optical coupling element and nonlinear crystal;
  • the laser device is configured to output pump light
  • the signal light generator is configured to output signal light
  • the optical coupling element is configured to spatially couple the pump light and the signal light into the nonlinear crystal
  • the nonlinear crystal is configured to amplify the signal light by using the pump light and generate idler light.
  • the invention provides a method for preparing an optical parametric laser amplifier, which uses a preset non-collinear phase matching formula to determine a mapping relationship between a first non-collinear angle and a second non-collinear angle, wherein the first non-collinear angle is a pump
  • the angle between the transmission direction of the pump and the signal light, and the second non-collinear angle is the angle between the direction of transmission of the pump light and the idler light
  • the first is determined based on the preset temperature deflection formula and the mapping relationship.
  • the target non-collinear angle and the second target non-collinear angle, the optical parametric laser amplifier is prepared based on the first target non-collinear angle and the second target non-collinear angle.
  • the first non-collinear angle and the second non-collinear angle may be The first target non-collinear angle and the second target non-collinear angle are determined in the mapping relationship, and the performance of the optical parametric laser amplifier prepared by using the first target non-collinear angle and the second target non-collinear angle is subject to temperature change The influence is small.
  • the second target non-collinear angle automatically adjusts the angle for phase compensation, so as not to destroy the phase matching of the optical parametric laser amplifier. In turn, the energy conversion efficiency of the optical parametric laser amplifier under high average power operating conditions is improved.
  • 1 is an angle diagram of signal light, idler light, and pump light of an optical parametric laser amplifier
  • FIG. 2 is a schematic flow chart of a method for preparing an optical parametric laser amplifier according to a first embodiment of the present invention
  • FIG. 3 is a graph showing a variation of a non-collinear angle ⁇ of an LBO crystal according to the wavelength of a signal light according to the present invention
  • FIG. 4 is a graph showing a variation of a non-collinear angle ⁇ of a YCOB crystal according to a wavelength of a signal light according to the present invention
  • FIG. 5 is a schematic structural diagram of an optical parametric laser amplifier according to a second embodiment and a third embodiment of the present invention.
  • FIG. 6 is a graph showing changes in pump light conversion efficiency with pump power of the optical parametric laser amplifier of the second embodiment under different pump power conditions
  • Fig. 7 is a graph showing another variation of pump light conversion efficiency with pump power of the optical parametric laser amplifier of the third embodiment under different pump power conditions.
  • FIG. 1 is an angle diagram of signal light, idler light and pump light of an optical parametric laser amplifier
  • FIG. 2 is an optical parametric laser amplifier according to a first embodiment of the present invention.
  • Schematic diagram of the preparation method including:
  • Step 201 Determine a mapping relationship between the first non-collinear angle and a second non-collinear angle by using a preset non-collinear phase matching formula, where the first non-collinear angle is pump light ⁇ p and signal light ⁇ s An angle in a transmission direction, the second non-collinear angle being an angle between a pumping light ⁇ p and a direction of transmission of the idler light ⁇ i;
  • the non-collinear phase matching formula is:
  • ⁇ represents the first non-collinear angle, which is an angle between the pump light ⁇ p and the signal light ⁇ s in the transmission direction, and ⁇ represents the second non-collinear angle
  • T 0 represents a phase matching temperature of the nonlinear crystal in the optical parametric laser amplifier
  • k s (T 0 ) represents a temperature of T 0
  • the magnitude of the wave vector of the signal light ⁇ s, k p (T 0 ) represents the magnitude of the wave vector of the pump light ⁇ p when the temperature is T 0
  • k i (T 0 ) represents the idler light when the temperature is T 0 .
  • Step 202 Determine, according to a preset temperature partial deviation formula and the mapping relationship, a first target non-collinear angle and a second target non-collinear angle;
  • the temperature biasing formula is:
  • ⁇ represents the first non-collinear angle, which is an angle between the pump light ⁇ p and the signal light ⁇ s in the transmission direction
  • ⁇ represents the second non-collinear angle, which is the pump An angle between the light ⁇ p and the transmission direction of the idler light ⁇ i
  • T 0 represents a phase matching temperature of the nonlinear crystal in the optical parametric laser amplifier
  • T represents an operating temperature of the nonlinear crystal
  • k s ( T) represents the magnitude of the wave vector of the signal light ⁇ s
  • k p (T) represents the magnitude of the wave vector of the pumping light ⁇ p
  • k i (T) represents the magnitude of the wave vector of the idler light ⁇ i.
  • the wave vector ks(T) of the signal light ⁇ s, the wave vector kp(T) of the pump light ⁇ p, and the wave of the idler light ⁇ i are combined with the phase matching.
  • the vector ki(T) and the angles ⁇ and ⁇ between them need to form a wave-vector triangle, namely:
  • the wave vector ks(T) of the signal light ⁇ s, the wave vector kp(T) of the pump light ⁇ p, and the wave vector ki(T) of the idler light ⁇ i are determined by the temperature of the nonlinear crystal, with the nonlinear crystal temperature The change has changed.
  • the angle ⁇ between the signal light ⁇ s and the pump light ⁇ p is determined by the incident angle of the signal light ⁇ s and the pump light ⁇ p, and the angle ⁇ does not change with the temperature change.
  • phase matching is no longer valid, phase mismatch occurs, and phase mismatch is the root cause of temperature sensitivity of the optical parametric laser amplifier.
  • the idle frequency ⁇ i will automatically select the appropriate non-collinear angle ⁇ , so that the phase mismatch is as small as possible, even 0.
  • the above formula (3) can be obtained by adding the formula (6) ⁇ sin ⁇ to the formula (7) ⁇ cos ⁇ .
  • the phase matching of the optical parametric laser amplifier will no longer be affected by the wave
  • the effect of the loss on the first-order partial conductance of the temperature is only limited by the remaining high-order partial conductance of the wave loss versus temperature. This significantly increases the temperature bandwidth of the optical parametric laser amplifier, making the optical parametric laser amplifier insensitive to temperature variations.
  • the formula (3) is substituted into the mapping relationship obtained by step 201, and the unique target non-collinear angle and the second target non-collinear angle can be determined.
  • Step 203 Prepare the optical parametric laser amplifier based on the first target non-collinear angle and the second target non-collinear angle.
  • a non-collinear phase matching structure that is insensitive to temperature changes may be determined based on the first target non-collinear angle and the second target non-collinear angle, and further, based on the non-collinear phase matching
  • the energy conversion efficiency of the structured optical parametric laser amplifier is also affected by temperature changes.
  • the mapping relationship between the first non-collinear angle and the second non-collinear angle is determined by using a preset non-collinear phase matching formula, wherein the first non-collinear angle is the pump light ⁇ p and the signal The angle between the transmission direction of the light ⁇ s, the second non-collinear angle is the angle between the pumping light ⁇ p and the idler light ⁇ i, and the first target is determined based on the preset temperature deflection formula and the mapping relationship.
  • the non-collinear angle and the second target non-collinear angle, the optical parametric laser amplifier is prepared based on the first target non-collinear angle and the second target non-collinear angle.
  • the first non-collinear angle and the second non-collinear angle may be The first target non-collinear angle and the second target non-collinear angle are determined in the mapping relationship, and the optical parametric laser amplifier prepared by using the first target non-collinear angle and the second target non-collinear angle is affected by temperature change Very small, when the nonlinear crystal temperature changes and deviates from the originally set phase matching temperature, the second target non-collinear angle automatically adjusts the angle for phase compensation, so as not to destroy the phase matching of the optical parametric laser amplifier.
  • the phase matching of the optical parametric laser amplifier is not affected by the wave loss on the first-order partial derivative of the temperature, and is only subject to the remaining high-order partial derivative of the wave loss to the temperature, realizing the phase matching pair.
  • the temperature change is not sensitive, which in turn increases the energy conversion efficiency of the optical parametric laser amplifier under high average power operating conditions.
  • the optical parametric laser amplifier manufacturing method designs a non-collinear phase matching structure that is insensitive to temperature changes in a simple manner. It should be noted that not any nonlinear crystal or any laser wavelength can achieve non-collinear phase matching that is insensitive to temperature changes, which is manifested by the fact that the optical parametric laser amplifier preparation method has no solution, which is determined by a nonlinear crystal. Nature determines.
  • FIG. 3 and FIG. 4 respectively show the variation of the non-collinear angle ⁇ with the wavelength of the signal light ⁇ s when the LBO crystal and the YCOB crystal are nonlinear media. It should be noted that both the LBO crystal in FIG. 3 and the YCOB crystal in FIG. 4 use the xy plane. It can be seen that by selecting a suitable pumping source, there is a non-collinear phase matching structure that is insensitive to temperature changes in the range of visible to medium to far infrared light, and optical parameter amplification that is insensitive to temperature changes is realized.
  • FIG. 5 is a schematic structural diagram of an optical parametric laser amplifier according to a second embodiment of the present invention.
  • the optical parametric laser amplifier is prepared by the method according to the first embodiment of the present invention, and is characterized in that The optical parametric laser amplifier comprises: a laser device 10, a signal light generator 20, an optical coupling element 30 and a nonlinear crystal 40;
  • the laser device 10 is configured to output pump light ⁇ p;
  • the signal light generator 20 is configured to output signal light ⁇ s;
  • the optical coupling element 30 is configured to spatially couple the pump light ⁇ p and the signal light ⁇ s into the nonlinear crystal 40;
  • the nonlinear crystal 40 is configured to amplify the signal light ⁇ s by using the pump light ⁇ p and generate idler light ⁇ i.
  • an LBO crystal is selected as the nonlinear crystal 40.
  • the laser device 10 is a 790 nm pulse laser and outputs a 790 nm pulsed laser.
  • the signal light generator 20 is a 1030 nm near-infrared pulsed laser.
  • the 790 nm pulsed laser light output from the laser device 10 passes through the optical coupling element 30, enters the nonlinear crystal 40 together with the near-infrared signal light ⁇ s of 1030 nm, and uses the pulsed laser light having a wavelength of 790 nm as the pumping light ⁇ p for the near-infrared signal light of 1030 nm. ⁇ s is amplified.
  • Figure 6 shows the pump light conversion efficiency as a function of pump power for the optical parametric laser amplifier of the second embodiment under different pump power conditions. It can be seen from the figure that the conversion efficiency of the optical parametric laser amplifier does not change with the increase of the pump power without considering the thermal effect of the crystal; however, after adding the crystal thermal effect and the resulting phase mismatch, As the pump power increases, the conversion efficiency of the optical parametric laser amplifier gradually decreases. Compared to the general collinear phase matching, the conversion efficiency of the optical parametric laser amplifier that is insensitive to temperature changes is the same at the same pump power. Significantly higher conversion efficiency than collinear phase matching.
  • the conversion efficiency of the collinear phase matching decreases from ⁇ 50% to ⁇ 10.8%, and the conversion efficiency of the optical parametric laser amplifier that is insensitive to temperature change is still 22.5%, which is collinear. More than twice the phase match.
  • FIG. 5 is also a schematic structural diagram of an optical parametric laser amplifier according to a third embodiment of the present invention.
  • the optical parametric laser amplifier is prepared by the method according to the first embodiment of the present invention, and is characterized in that:
  • the optical parametric laser amplifier comprises: a laser device 10, a signal light generator 20, an optical coupling element 30 and a nonlinear crystal 40;
  • the laser device 10 is configured to output pump light ⁇ p;
  • the signal light generator 20 is configured to output signal light ⁇ s;
  • the optical coupling element 30 is configured to spatially couple the pump light ⁇ p and the signal light ⁇ s into the nonlinear crystal 40;
  • the nonlinear crystal 40 is configured to amplify the signal light ⁇ s by using the pump light ⁇ p and generate idler light ⁇ i.
  • a YCOB crystal is selected as the nonlinear crystal 40.
  • the laser device 10 is a 532 nm pulsed laser and outputs a 532 nm pulsed laser.
  • the signal light generator 20 is a 800 nm near-infrared pulse laser.
  • the 532 nm pulsed laser light output from the laser device 10 passes through the optical coupling element 30, enters the nonlinear crystal 40 together with the near-infrared signal light of 800 nm, and uses the pulsed laser light having a wavelength of 532 nm as the pumping light ⁇ p to perform the near-infrared signal light of 800 nm. amplification.
  • FIG. 7 is a graph showing the pump light conversion efficiency of the optical parametric laser amplifier according to the third embodiment as a function of pump power under different pump power conditions.
  • the conversion efficiency of the optical parametric laser amplifier does not change as the pump power increases, ideally without considering the crystal thermal effect.
  • the conversion efficiency of the optical parametric laser amplifier gradually decreases, as can be seen from Figure 7, compared to the general collinear phase matching.
  • the conversion efficiency of an optical parametric laser amplifier that is insensitive to temperature changes at the same pump power is significantly higher than that under collinear phase matching.
  • the conversion efficiency of collinear phase matching is less than ⁇ 10%, and the optical parametric laser amplifier that is insensitive to temperature change is hardly affected by thermal efficiency, given the pump optical power. Within the range, it is always above 50%.
  • the optical parametric laser amplifier provided by the embodiment of the invention can significantly improve the deterioration of the conversion efficiency caused by the uneven distribution of the crystal temperature during the high-average power optical parametric amplification process.
  • the nonlinear crystal absorbs the laser energy to generate a thermal effect.
  • a non-uniform temperature distribution occurs inside the nonlinear crystal. Since the phase matching of the optical parametric laser amplifier is not sensitive to temperature changes, the effect of thermal effect on its conversion efficiency can be significantly reduced, and the energy conversion efficiency of the optical parametric laser amplifier under high average power operating conditions can be improved.
  • the optical parametric laser amplifier has a simple structure, does not require a complicated optical path, and is easy to operate.

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Abstract

本发明公开一种光参量激光放大器制备方法及光参量激光放大器，包括：利用预设非共线相位匹配公式确定第一非共线角与第二非共线角的映射关系，其中，第一非共线角为泵浦光与信号光传输方向上的夹角，第二非共线角为泵浦光与闲频光传输方向上的夹角，基于预设的温度偏导公式及映射关系，确定第一目标非共线角及第二目标非共线角，基于第一目标非共线角及第二目标非共线角制备光参量激光放大器。以上述方法制备的光参量激光放大器的性能受温度变化的影响很小，在非线性晶体温度发生变化、偏离原设的相位匹配温度时，第二目标非共线角自动调整角度进行相位补偿，从而不会破坏光参量激光放大器的相位匹配，进而提高光参量激光放大器在高平均功率运行条件下的能量转换效率。

Description

一种光参量激光放大器制备方法及光参量激光放大器 技术领域
本发明涉及激光技术领域，尤其涉及一种光参量激光放大器制备方法及光参量激光放大器。
背景技术
光参量激光放大器(Optical Parametric Amplification，OPA)是激光领域的重要光学系统，广泛应用于科研、医学、工业等领域。OPA的基本工作原理是将一束高频率激光ωp和一束低频率激光ωs同时射入非线性晶体中，由于两者之间的差频效应，高频率激光ωp的能量转移到低频率激光ωs上，从而使低频率激光ωs的能量得到放大，同时会得到第三种频率为ωi的闲频光，其中，ωp>ωs，ωp＝ωs+ωi，ωp一般为泵浦光，ωs一般为信号光。但是，在光参量放大过程中，非线性晶体会吸收激光的能量，从而产生热效应，对于高平均功率的光参量激光放大器来说，热效应已成为制约其发展的核心因素，热效应会引发非线性晶体温度的变化，使其偏离原先设定的相位匹配温度从而破坏光参量激光放大器的相位匹配，从而降低了泵浦光向信号光能量转换效率，限制了光参量激光放大器的性能。
因此，现有技术中存在着因非线性晶体温度发生变化，偏离原先设定的相位匹配温度，从而破坏光参量激光放大器的相位匹配，导致泵浦光向信号光能量转换效率降低，限制了光参量激光放大器性能的问题。
发明内容
本发明的主要目的在于提供一种光参量激光放大器制备方法及光参量激光 放大器，旨在解决现有技术中存在的因非线性晶体温度发生变化，偏离原先设定的相位匹配温度，从而破坏光参量激光放大器的相位匹配，导致泵浦光向信号光能量转换效率降低，限制了光参量激光放大器性能的问题。
为实现上述目的，本发明第一方面提供一种光参量激光放大器制备方法，所述方法包括：
利用预设的非共线相位匹配公式确定第一非共线角与第二非共线角的映射关系，其中，所述第一非共线角为泵浦光与信号光的传输方向上的夹角，所述第二非共线角为泵浦光与闲频光的传输方向上的夹角；
基于预设的温度偏导公式及所述映射关系，确定第一目标非共线角及第二目标非共线角；
基于所述第一目标非共线角及所述第二目标非共线角制备所述光参量激光放大器。
进一步的，所述利用预设的非共线相位匹配公式确定第一非共线角与第二非共线角的映射关系，包括：
利用所述非共线相位匹配公式确定第一非共线角与第二非共线角的映射关系；
所述非共线相位匹配公式为：
k s(T 0)sinα＝k i(T 0)sinθ
k p(T 0)＝k s(T 0)cosα+k i(T 0)cosθ
其中，α表示所述第一非共线角，为所述泵浦光与所述信号光的传输方向上的夹角，θ表示所述第二非共线角，为所述泵浦光与所述闲频光的传输方向上的夹角，T 0表示所述光参量激光放大器中的非线性晶体的相位匹配温度，k s(T 0)表示温度为T 0时的信号光的波矢的大小，k p(T 0)表示温度为T 0时的泵浦光的波矢的大小，k i(T 0)表示温度为T 0时的闲频光的波矢的大小。
进一步的，所述基于预设的温度偏导公式及所述映射关系，确定第一目标 非共线角及第二目标非共线角，包括：
基于所述温度偏导公式及所述映射关系，确定所述第一目标非共线角及所述第二目标非共线角；
所述温度偏导公式为：
Figure PCTCN2018074695-appb-000001
其中，α表示所述第一非共线角，为所述泵浦光与所述信号光的传输方向上的夹角，θ表示所述第二非共线角，为所述泵浦光与所述闲频光的传输方向上的夹角，T 0表示所述光参量激光放大器中的非线性晶体的相位匹配温度，T表示所述非线性晶体的工作温度，k s(T)表示所述信号光的波矢的大小，k p(T)表示所述泵浦光的波矢的大小，k i(T)表示所述闲频光的波矢的大小。
为实现上述目的，本发明第二方面提供一种光参量激光放大器，所述光参量激光放大器由第一方面所述的方法制备，所述光参量激光放大器包括：激光装置、信号光发生器、光学耦合元件及非线性晶体；
所述激光装置，用于输出泵浦光；
所述信号光发生器，用于输出信号光；
所述光学耦合元件，用于将所述泵浦光及所述信号光空间耦合并入射至所述非线性晶体中；
所述非线性晶体，用于利用所述泵浦光对所述信号光进行放大，并生成闲频光。
本发明提供一种光参量激光放大器制备方法，利用预设的非共线相位匹配公式确定第一非共线角与第二非共线角的映射关系，其中，第一非共线角为泵浦光与信号光的传输方向上的夹角，第二非共线角为泵浦光与闲频光的传输方向上的夹角，基于预设的温度偏导公式及映射关系，确定第一目标非共线角及第二目标非共线角，基于第一目标非共线角及第二目标非共线角制备光参量激 光放大器。与现有技术相比，通过将预设的温度偏导公式代入第一非共线角与第二非共线角的映射关系中，可以从第一非共线角与第二非共线角的映射关系中确定出第一目标非共线角及第二目标非共线角，利用该第一目标非共线角及第二目标非共线角制备的光参量激光放大器的性能受温度变化的影响很小，在非线性晶体温度发生变化、偏离原先设定的相位匹配温度的时候，第二目标非共线角会自动调整角度进行相位补偿，从而不会破坏光参量激光放大器的相位匹配，进而提高光参量激光放大器在高平均功率运行条件下的能量转换效率。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为光参量激光放大器的信号光、闲频光以及泵浦光之间的角度关系图；
图2为本发明第一实施例提供的一种光参量激光放大器制备方法的流程示意图；
图3为本发明提供的LBO晶体的非共线角α随信号光波长的变化曲线图；
图4为本发明提供的YCOB晶体的非共线角α随信号光波长的变化曲线图；
图5为本发明第二实施例、第三实施例提供的光参量激光放大器的结构示意图；
图6为不同泵浦功率条件下，第二实施例所述光参量激光放大器的泵浦光转换效率随泵浦功率的变化曲线图；
图7为不同泵浦功率条件下，第三实施例所述光参量激光放大器的泵浦光转换效率随泵浦功率的另一变化曲线图。
具体实施方式
为使得本发明的发明目的、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。
为了说明本发明所述的技术方案，下面通过具体实施例来进行说明。
请参阅图1及图2，图1为光参量激光放大器的信号光、闲频光以及泵浦光之间的角度关系图，图2为本发明第一实施例提供的一种光参量激光放大器制备方法的流程示意图，包括：
步骤201、利用预设的非共线相位匹配公式确定第一非共线角与第二非共线角的映射关系，其中，所述第一非共线角为泵浦光ωp与信号光ωs的传输方向上的夹角，所述第二非共线角为泵浦光ωp与闲频光ωi的传输方向上的夹角；
其中，非共线相位匹配公式为：
k s(T 0)sinα＝k i(T 0)sinθ                                   (1)
k p(T 0)＝k s(T 0)cosα+k i(T 0)cosθ
(2)其中，α表示所述第一非共线角，为所述泵浦光ωp与所述信号光ωs的传输方向上的夹角，θ表示所述第二非共线角，为所述泵浦光ωp与所述闲频光ωi的传输方向上的夹角，T 0表示所述光参量激光放大器中的非线性晶体的相位匹配温度，k s(T 0)表示温度为T 0时的信号光ωs的波矢的大小，k p(T 0)表示温度为T 0时的泵浦光ωp的波矢的大小，k i(T 0)表示温度为T 0时的闲频光ωi的波矢的大小。
步骤202、基于预设的温度偏导公式及所述映射关系，确定第一目标非共线角及第二目标非共线角；
所述温度偏导公式为：
Figure PCTCN2018074695-appb-000002
其中，α表示所述第一非共线角，为所述泵浦光ωp与所述信号光ωs的传输方向上的夹角，θ表示所述第二非共线角，为所述泵浦光ωp与所述闲频光ωi的传输方向上的夹角，T 0表示所述光参量激光放大器中的非线性晶体的相位匹配温度，T表示所述非线性晶体的工作温度，k s(T)表示所述信号光ωs的波矢的大小，k p(T)表示所述泵浦光ωp的波矢的大小，k i(T)表示所述闲频光ωi的波矢的大小。
在本发明实施例中，结合图1所示的，在相位匹配的前提下，信号光ωs的波矢ks(T)、泵浦光ωp的波矢kp(T)、闲频光ωi的波矢ki(T)以及它们之间的夹角α和θ，需构成波矢三角形，即：
k s(T)sinα＝k i(T)sinθ                                      (4)
k p(T)＝k s(T)cosα+k i(T)cosθ
(5)
其中，信号光ωs的波矢ks(T)、泵浦光ωp的波矢kp(T)及闲频光ωi的波矢ki(T)是由非线性晶体的温度决定，随非线性晶体温度的变化而变化。信号光ωs和泵浦光ωp之间的夹角α由信号光ωs和泵浦光ωp的入射角度决定，夹角α不会随温度的变化而改变，当非线性晶体的工作温度偏离原先设定的相位匹配温度T 0的时候，信号光ωs的波矢ks(T)、泵浦光ωp的波矢kp(T)及闲频光ωi的波矢ki(T)均会相应发生变化，使相位匹配不再成立，出现相位失配，而相位失配是造成光参量激光放大器的能量转换效率对温度敏感的根本原因，但是，需要说明的是，当非线性晶体的工作温度出现变化时，闲频光ωi会自动选择合适的非共线角θ，使相位失配量尽可能小，甚至为0。因此，若要实现光参量激光放大器的能量转换效率对温度变化不敏感，需要公式(4)和公式(5)能够在任意温度下始终成立。因此，对公式(4)和公式(5)的两 侧，分别对温度T一阶求导，对公式(4)一阶求导得到公式(6)，对公式(5)一阶求导得到公式(7)，具体的：
Figure PCTCN2018074695-appb-000003
Figure PCTCN2018074695-appb-000004
由公式(6)×sinθ与公式(7)×cosθ相加，即可得到上述的公式(3)。
在本发明实施例中，只要相互作用的泵浦光ωp、信号光ωs及闲频光ωi非共线的传输方向满足上述关系式(3)，光参量激光放大器的相位匹配将不再受波失对温度一阶偏导量的影响，仅仅受制于波失对温度的其余高阶偏导量。由此显著的提高了光参量激光放大器的温度带宽，使光参量激光放大器具有对温度变化不敏感的特性。
在本发明实施例中，将公式(3)代入利用步骤201求出的映射关系中，可以确定具有唯一性的第一目标非共线角及第二目标非共线角。
步骤203、基于所述第一目标非共线角及所述第二目标非共线角制备所述光参量激光放大器。
在本发明实施例中，基于第一目标非共线角及第二目标非共线角可确定一种对温度变化不敏感的非共线相位匹配结构，进而，基于这种非共线相位匹配结构制备的光参量激光放大器的能量转换效率受温度变化的影响也很小。
在本发明实施例中，利用预设的非共线相位匹配公式确定第一非共线角与第二非共线角的映射关系，其中，第一非共线角为泵浦光ωp与信号光ωs的传输方向上的夹角，第二非共线角为泵浦光ωp与闲频光ωi的传输方向上的夹角，基于预设的温度偏导公式及映射关系，确定第一目标非共线角及第二目标非共线角，基于第一目标非共线角及第二目标非共线角制备光参量激光放大器。与 现有技术相比，通过将预设的温度偏导公式代入第一非共线角与第二非共线角的映射关系中，可以从第一非共线角与第二非共线角的映射关系中确定出第一目标非共线角及第二目标非共线角，利用该第一目标非共线角及第二目标非共线角制备的光参量激光放大器受温度变化的影响很小，在非线性晶体温度发生变化、偏离原先设定的相位匹配温度的时候，第二目标非共线角会自动调整角度进行相位补偿，从而不会破坏光参量激光放大器的相位匹配。在这种非共线相位匹配条件下，光参量激光放大器的相位匹配不受波失对温度一阶偏导量的影响，仅受制于波失对温度的其余高阶偏导量，实现相位匹配对温度变化不敏感，进而提高光参量激光放大器在高平均功率运行条件下的能量转换效率。
需要注意的是，在本发明实施例中，上述光参量激光放大器制备方法以一种简便的方式，设计出对温度变化不敏感的非共线相位匹配结构。需要说明的是，并非任意非线性晶体、任意激光波长都可以实现对温度变化不敏感的非共线相位匹配，具体表现为所述光参量激光放大器制备方法无解，这是由非线性晶体的性质决定的。
基于本发明所述的光参量激光放大器制备方法，图3和图4分别给出了以LBO晶体跟YCOB晶体为非线性介质时，非共线角α随信号光ωs波长的变化曲线图。需要注意的是，图3中的LBO晶体与图4中的YCOB晶体均用到xy平面。可见，通过选择合适的泵浦光源，在可见光到中远红外光的波段范围内，均存在对温度变化不敏感的非共线相位匹配结构，实现对温度变化不敏感的光参量放大。
进一步的，请参阅图5，图5为本发明第二实施例提供的光参量激光放大器的结构示意图，所述光参量激光放大器由本发明第一实施例所述的方法制备，其特征在于，所述光参量激光放大器包括：激光装置10、信号光发生器20、光学耦合元件30及非线性晶体40；
所述激光装置10，用于输出泵浦光ωp；
所述信号光发生器20，用于输出信号光ωs；
所述光学耦合元件30，用于将所述泵浦光ωp及所述信号光ωs空间耦合并入射至所述非线性晶体40中；
所述非线性晶体40，用于利用所述泵浦光ωp对所述信号光ωs进行放大，并生成闲频光ωi。
在本发明实施例中，选用LBO晶体作为非线性晶体40。
其中，为了论证由光参量激光放大器制备方法得到的非共线相位匹配结构用于设计对温度变化不敏感的光参量激光放大器的可行性，采用四阶Runge-Kutta和分步傅里叶算法，基于非线性耦合波方程组，对其进行了数值模拟。这种计算方法已成功应用于不同类型光参量放大激光器的数值模拟，并得到与实验数据高度吻合的仿真结果，具体仿真结果如下：
其中，激光装置10为790nm脉冲激光器，输出790nm脉冲激光。信号光发生器20为1030nm的近红外脉冲激光器。激光装置10输出的790nm脉冲激光经过光学耦合元件30，与1030nm的近红外信号光ωs一同进入非线性晶体40，以波长为790nm的脉冲激光做为泵浦光ωp，对1030nm的近红外信号光ωs进行放大。
进一步的，如图3所示，采用LBO晶体xy平面的I类相位匹配时，对温度变化不敏感的光参量激光放大器需要泵浦光ω p与信号光ω s以非共线的方式(非共线角α＝2.44°)，入射至LBO晶体中。具体的，LBO晶体沿θ＝90°，Ф＝45.8°方向切割。
图6给出了不同泵浦功率条件下，第二实施例所述光参量激光放大器的泵浦光转换效率随泵浦功率的变化曲线。从图中可见，在不考虑晶体热效应的理想情况下，光参量激光放大器的转换效率不随泵浦功率的增大而改变；但是，加入晶体热效应，以及由此造成的相位失配之后，随着泵浦功率的增大，光参量激光放大器的转换效率逐渐下降，相比于一般的共线相位匹配，在相同的泵 浦功率下，所述对温度变化不敏感的光参量激光放大器的转换效率明显比共线相位匹配下的转换效率高。当泵浦功率达到350W，共线相位匹配的转换效率由原来的～50％下降至～10.8％，而所述对温度变化不敏感的光参量激光放大器的转换效率仍有22.5％，是共线相位匹配的两倍以上。
进一步的，请参阅图5，图5还为本发明第三实施例提供的光参量激光放大器的结构示意图，所述光参量激光放大器由本发明第一实施例所述的方法制备，其特征在于，所述光参量激光放大器包括：激光装置10、信号光发生器20、光学耦合元件30及非线性晶体40；
所述激光装置10，用于输出泵浦光ωp；
所述信号光发生器20，用于输出信号光ωs；
所述光学耦合元件30，用于将所述泵浦光ωp及所述信号光ωs空间耦合并入射至所述非线性晶体40中；
所述非线性晶体40，用于利用所述泵浦光ωp对所述信号光ωs进行放大，并生成闲频光ωi。
在本发明实施例中，选用YCOB晶体作为非线性晶体40。
其中，激光装置10为532nm脉冲激光器，输出532nm脉冲激光。信号光发生器20为800nm的近红外脉冲激光器。激光装置10输出的532nm脉冲激光经过光学耦合元件30，与800nm的近红外信号光一同进入非线性晶体40，以波长为532nm的脉冲激光做为泵浦光ωp，对800nm的近红外信号光进行放大。
进一步的，如图4所示，采用YCOB晶体xy平面的I类相位匹配时，对温度变化不敏感的光参量激光放大器需要泵浦光ω p与信号光ω s以非共线的方式(非共线角α＝6.02°)，入射至YCOB晶体中。具体的，YCOB晶体沿θ＝90°，Ф＝52.6°方向切割。
进一步的，请参阅图7，图7为不同泵浦功率条件下，第三实施例所述光参量激光放大器的泵浦光转换效率随泵浦功率的变化曲线图。在图7中，在不 考虑晶体热效应的理想情况下，光参量激光放大器的转换效率不随泵浦功率的增大而改变。但是，加入晶体热效应，以及由此造成的相位失配之后，随着泵浦功率的增大，光参量激光放大器的转换效率逐渐下降，从图7中可见，相比于一般的共线相位匹配，在相同的泵浦功率下对温度变化不敏感的光参量激光放大器的转换效率明显比共线相位匹配下的转换效率高。其中，当泵浦功率超过1000W，共线相位匹配的转换效率仅有不到～10％，而对温度变化不敏感的光参量激光放大器几乎不受热效率的影响，在给出的泵浦光功率范围内，始终保持在50％以上。
综上所述，本发明实施例所提供的光参量激光放大器，可显著改善高平均功率光参量放大过程中由于晶体温度分布不均造成的转换效率恶化问题。具体的，在光参量放大的同时，非线性晶体吸收激光能量，产生热效应。使非线性晶体内部出现不均匀的温度分布。由于光参量激光放大器的相位匹配对温度变化不敏感，由此可显著减少热效应对其转换效率的影响，提高光参量激光放大器在高平均功率运行条件下的能量转换效率。并且该光参量激光放大器的结构简单，无需复杂的光路，操作简便。
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一种光参量激光放大器制备方法及光参量激光放大器的描述，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 (4)

  1. 一种光参量激光放大器制备方法，其特征在于，所述方法包括：
    利用预设的非共线相位匹配公式确定第一非共线角与第二非共线角的映射关系，其中，所述第一非共线角为泵浦光与信号光的传输方向上的夹角，所述第二非共线角为泵浦光与闲频光的传输方向上的夹角；
    基于预设的温度偏导公式及所述映射关系，确定第一目标非共线角及第二目标非共线角；
    基于所述第一目标非共线角及所述第二目标非共线角制备所述光参量激光放大器。
  2. 根据权利要求1所述的方法，其特征在于，所述利用预设的非共线相位匹配公式确定第一非共线角与第二非共线角的映射关系，包括：
    利用所述非共线相位匹配公式确定第一非共线角与第二非共线角的映射关系；
    所述非共线相位匹配公式为：
    k s(T 0)sinα＝k i(T 0)sinθ
    k p(T 0)＝k s(T 0)cosα-k i(T 0)cosθ
    其中，α表示所述第一非共线角，为所述泵浦光与所述信号光的传输方向上的夹角，θ表示所述第二非共线角，为所述泵浦光与所述闲频光的传输方向上的夹角，T 0表示所述光参量激光放大器中的非线性晶体的相位匹配温度，k s(T 0)表示温度为T 0时的信号光的波矢的大小，k p(T 0)表示温度为T 0时的泵浦光的波矢的大小，k i(T 0)表示温度为T 0时的闲频光的波矢的大小。
  3. 根据权利要求2所述的方法，其特征在于，所述基于预设的温度偏导公式及所述映射关系，确定第一目标非共线角及第二目标非共线角，包括：
    基于所述温度偏导公式及所述映射关系，确定所述第一目标非共线角及所 述第二目标非共线角；
    所述温度偏导公式为：
    Figure PCTCN2018074695-appb-100001
    其中，α表示所述第一非共线角，为所述泵浦光与所述信号光的传输方向上的夹角，θ表示所述第二非共线角，为所述泵浦光与所述闲频光的传输方向上的夹角，T 0表示所述光参量激光放大器中的非线性晶体的相位匹配温度，T表示所述非线性晶体的工作温度，k s(T)表示所述信号光的波矢，k p(T)表示所述泵浦光的波矢，k i(T)表示所述闲频光的波矢。
  4. 一种光参量激光放大器，所述光参量激光放大器由权利要求1至3任意一项所述的方法制备，其特征在于，所述光参量激光放大器包括：激光装置、信号光发生器、光学耦合元件及非线性晶体；
    所述激光装置，用于输出泵浦光；
    所述信号光发生器，用于输出信号光；
    所述光学耦合元件，用于将所述泵浦光及所述信号光空间耦合并入射至所述非线性晶体中；
    所述非线性晶体，用于利用所述泵浦光对所述信号光进行放大，并生成闲频光。
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20160064891A1 (en) * 2004-03-25 2016-03-03 Imra America, Inc. Optical parametric amplification, optical parametric generation, and optical pumping in optical fibers systems
CN106410577A (zh) * 2016-10-19 2017-02-15 上海交通大学 温度和波长不敏感光参量啁啾脉冲放大器

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20160064891A1 (en) * 2004-03-25 2016-03-03 Imra America, Inc. Optical parametric amplification, optical parametric generation, and optical pumping in optical fibers systems
CN106410577A (zh) * 2016-10-19 2017-02-15 上海交通大学 温度和波长不敏感光参量啁啾脉冲放大器

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