在非线性频率变换中, 常用级联晶体补偿走离角。然而在KTiOPO4晶体级联倍频实验中发现, 当其中一块晶体沿通光轴旋转180°时, 倍频转换效率急剧降低。理论分析表明, 当一块晶体旋转180°后, 其有效非线性系数正负号发生改变, 等效于在级联晶体之间产生了大小为π的相位失配量, 使倍频转换效率降低。提出了利用空气色散补偿该相位失配量的方法, 相较于使用波片的相位失配量补偿方法, 具有结构简单、温度稳定性好、无插入损耗和成本低等特点。实验结果表明, 利用空气色散可以补偿相位失配量, 消除单块晶体旋转对晶体级联倍频效率的影响, 验证了理论分析的正确性以及空气色散补偿方法的可行性。

The optical parametric chirped pulse amplification (OPCPA) near the 800 nm wavelength has gained significant popularity in the recent years. This can be attributed to the development of laboratory-scale Ndglass lasers with their associated second harmonic generation (SHG), the mature nonlinear crystal growth technology, and the commercialized mode-locked Tisapphire oscillator. In this study, the characteristics of the 808-nm centered broad bandwidth signal OPCPA based on potassium dideuterium phosphate (DKDP) crystals are investigated. The phase mismatch in DKDP crystals for different deuteration levels of 0~99% is studied and a numerical simulation of the high energy optical parameric amplification (OPA) process with the considerations of absorption and several high deuteration levels is presented. Results show that the broadband bandwidth OPCPA at 808 nm can be obtained when the deuteration level is more than 90%.

The optical parametric chirped pulse amplification (OPCPA) near the 800 nm wavelength has gained significant popularity in the recent years. This can be attributed to the development of laboratory-scale Ndglass lasers with their associated second harmonic generation (SHG), the mature nonlinear crystal growth technology, and the commercialized mode-locked Tisapphire oscillator. In this study, the characteristics of the 808-nm centered broad bandwidth signal OPCPA based on potassium dideuterium phosphate (DKDP) crystals are investigated. The phase mismatch in DKDP crystals for different deuteration levels of 0~99% is studied and a numerical simulation of the high energy optical parameric amplification (OPA) process with the considerations of absorption and several high deuteration levels is presented. Results show that the broadband bandwidth OPCPA at 808 nm can be obtained when the deuteration level is more than 90%.

给出了适用于多波长再生的数据抽运简并四波混频(FWM)耦合模方程组，提出了时隙交织波长信道再生的准相位匹配均衡方法。从优化设计简并FWM相位失配因子入手，针对实验室已有的光纤，实现了4个固定波长信道的均衡再生；通过设计光纤参数，在一定带宽范围内可实现任意4个波长的均衡再生。计算结果表明，再生输出信号的脉冲峰值功率、消光比(ER)和Q值之间的差异分别不超过0.25 dB、0.42 dB和1.5。

为了研究热致相位失配对中红外连续波单谐振光学参量振荡器(CW-SRO)输出效率的影响, 结合CW-SRO计算模型和热传导方程, 利用有限元分析方法, 重点对输出3.3 μm波长闲频光的CW-SRO进行了分析。计算了不同信号光输出耦合率及不同泵浦功率下CW-SRO晶体输出截面上热致相位失配量的分布。由计算结果可以看出：晶体吸收腔中振荡信号光是导致晶体热效应的主要因素；在相同的输入条件下, 泵浦功率在30 W以上时CW-SRO的热致相位失配将会大大降低其泵浦损耗率；通过增加信号光输出耦合率的方法, 可以减少热致相位失配对CW-SRO输出效率的影响, 但CW-SRO的振荡阈值会增加。

以波动方程和受激拉曼散射（SRS）物质方程为基础，采用光种子法，建立了固体相干反斯托克斯拉曼频移器的归一化耦合波方程，研究了晶体中反斯托克斯光转换效率。在脉冲抽运条件下分析了归一化增益系数G、归一化相位失配系数ΔK以及一阶斯托克斯光种子的归一化光场振幅ψs0三个变量对固体相干反斯托克斯拉曼频移器的影响，并作出了一系列相应曲线，由所得曲线估算了各归一化变量的合理取值范围。分析结果表明，在ΔK=0时，通过增大ψs0来打破拉曼增益抑制的影响，其转换效率峰值可达到44%。而当ψs0较弱时，可选取合适的相位失配系数，反斯托克斯光转换效率可达40%。

We present a spiral phase filtering system with a large tolerance for edge enhancement of both phase and amplitude objects in optical microscopy. The method is based on a Fourier 4-f spatial filtering system. A phase mismatched spiral phase plate (SPP) fabricated by electron beam lithography is employed as the radial Hilbert transform for image edge enhancement. Compared with holography, SPP is simple, economical, reliable, and easy to integrate.

Phase mismatching for third-harmonic generation (THG) in barium metaborate (BBO) crystal is investigated in detail. Upon using BBO crystal in the Type I (oo→e) scheme, in the two independent planes (principal section of the crystal and the plane normal to principal section), when the input second-harmonic beam deviates from the expected direction, phase mismatching occurs and the angle deviation produces different effects on the conversion efficiency. We numerically simulate these two cases of phase mismatching and identify the relation between the conversion efficiency and the deviation angle in the air. The computational results indicate that the phase matching tolerance in the principal section is 0.2° (in the air), while the phase matching tolerance in the plane normal to principal section is 4.5° (in the air). After conducting a lab experiment, the results agree perfectly with the computational results, indicating that the deviation angle in the principal section has a greater effect on the conversion efficiency.

利用分步快速傅里叶变换和四阶龙格-库塔法,对具有一定温升分布的倍频晶体的二次谐波转换过程进行了研究。综合考虑了谐波转换过程中的离散、衍射、二阶、三阶非线性等效应,着重讨论了倍频晶体吸收光能后,晶体内温升分布对晶体内o光和e光的折射率分布的影响,定量分析了温度分布引起的相位失配量、输出光场分布、二次谐波转换效率随倍频晶体温度分布变化的规律。结果表明:在高功率倍频系统中,倍频晶体温升分布引起基频光、倍频光的相位失配,相位失配导致输出光场光强分布的变化以及谐波转换效率的降低。

研究了同向泵浦分布式拉曼放大器(DRA)中泵浦－信号间的四波混频(FWM)效应。基于分段求和法，导出了不同零色散波长光纤组成的前向泵浦DRA中FWM功率的计算公式。考虑受激拉曼放大的情况下，数值模拟了DRA中FWM引起的信道串扰随光纤传输距离的演变，以及FWM与光纤零色散波长之间的关系。理论分析了色散补偿光纤(DCF)对FWM串扰的抑制效应。计算结果表明，在采用非零色散位移光纤(NZDSF)作为传输介质的DRA中，泵浦－信号间存在着较强的FWM效应，严重影响了密集波分复用(DWDM)系统的传输性能。引入适量DCF，不仅能降低DRA中FWM引起的信道串扰，还可有效消除色散导致的波形失真。