Supercontinuum generation from nanojoule femtosecond lasers is well known in photonic-crystal fibers, channel waveguides, and micro-resonators, in which strong confinement shapes their dispersion and provides sufficient intensity for self-phase modulation, four-wave mixing, and Raman scattering to cause substantial spectral broadening. Until now, supercontinuum generation in bulk media has not been observed at equivalent energies, but here we introduce a new mechanism combining second- and third-order nonlinearities to produce broadband visible light in orientation-patterned gallium phosphide. A supercontinuum from the blue/green to the red is produced from 32 nJ 1040 nm femtosecond pulses, and a nonlinear-envelope-equation model including ${\chi ^{(2)}}$ and $ {\chi ^{(3)}} $ nonlinearities implies that high-order parametric gain pumped by the second-harmonic light of the laser and seeded by self-phase-modulated sidebands is responsible.

中文翻译：

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取向图案的磷化镓中产生超连续谱

纳焦飞秒激光器产生的超连续谱在光子晶体光纤，通道波导和微谐振器中是众所周知的，其中强约束限制了它们的色散，并为自相位调制，四波混合和拉曼散射提供了足够的强度，从而引起实质性光谱展宽。到现在为止，还没有观察到在等效能量下在大体积介质中产生超连续谱的现象，但是在这里，我们介绍了一种结合二阶和三阶非线性在定向图案化的磷化镓中产生宽带可见光的新机制。从32 nJ 1040 nm飞秒脉冲产生一个从蓝色/绿色到红色的超连续谱，并建立了一个非线性包络方程模型，其中包括$ {\ chi ^ {（2）}} $和$ {\ chi ^ {（3 ）}} $ 非线性意味着由激光的二次谐波光泵浦并由自相位调制边带播种的高阶参数增益是负责任的。