Broad spectra are of interest for a variety of applications, including pulse compression and ultrafast optical signal processing. We report a scheme of a cascaded chirped quasi-phase-matching (QPM) grating with a complementary reciprocal lattice vector bandwidth. The large reciprocal lattice vector bandwidth provided by first- and second-order QPM can simultaneously achieve second and third harmonic generations. Combined the effective nonlinear coefficient model with the transfer function method, it reveals that spectrum width increased with increasing fundamental wave bandwidth, reciprocal lattice vector bandwidth, chirp rate, and crystal length. The two-section cascaded chirped QPM grating can offer a reciprocal lattice vector bandwidth as large as 0.3 to 1.26 μm − 1, which corresponds to a broadband spectrum covering 450 to 820 nm upon illumination with a tunable femtosecond laser. The proposed grating could extend supercontinuum generation toward potential spectroscopic applications.

中文翻译：

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级联线性调频准相位匹配光栅通过互补互易晶格矢量产生广谱

广泛的光谱适用于各种应用，包括脉冲压缩和超快光信号处理。我们报告了一种具有互补互易晶格矢量带宽的级联啁啾准相位匹配 (QPM) 光栅方案。一阶和二阶 QPM 提供的大互易晶格矢量带宽可以同时实现二次和三次谐波生成。将有效非线性系数模型与传递函数方法相结合，揭示了谱宽随着基波带宽、倒易晶格矢量带宽、啁啾率和晶体长度的增加而增加。两段级联线性调频 QPM 光栅可提供大至 0.3 至 1.26 μm − 1 的倒易晶格矢量带宽，这对应于用可调谐飞秒激光器照射时覆盖 450 至 820 nm 的宽带光谱。所提出的光栅可以将超连续谱产生扩展到潜在的光谱应用。