We investigate and model a picosecond synchronously pumped optical parametric oscillator (OPO) based on an aperiodically poled lithium niobate (APPLN) nonlinear crystal with a chirped quasi-phase matching (QPM) grating. We observe remarkable spectral features with an asymmetric OPO spectrum consisting of a main peak with lower sidelobes. Depending on the sign of the QPM chirp rate, the sidelobes are located either on the red or on the blue side of the main peak. Meanwhile, sidebands develop in the depleted pump spectrum. We attribute these features to cascaded sum-/difference-frequency generation processes, which are quasi-phase matched at different positions in the APPLN crystal. A terahertz-generation cascading effect is also observed and characterized at high pump power.

中文翻译：

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基于chi准相位匹配的皮秒同步泵浦光参量振荡器

我们调查和建模基于second线性准相位匹配（QPM）光栅的非周期性极化铌酸锂（APPLN）非线性晶体的皮秒同步泵浦光参量振荡器（OPO）。我们观察到非对称OPO光谱具有非凡的光谱特征，该光谱由主峰和较低的旁瓣组成。取决于QPM线性调频率的符号，旁瓣位于主峰的红色或蓝色侧。同时，在耗尽的泵浦频谱中会出现边带。我们将这些特征归因于级联的和/差频生成过程，这些过程在APPLN晶体的不同位置处是准相位匹配的。还在高泵浦功率下观察到并表征了太赫兹级联效应。