Silicon is well known for its strong third-order optical nonlinearity, exhibiting efficient supercontinuum and four-wave mixing processes. A strong second-order effect that is naturally inhibited in silicon can also be observed, for example, by electrically breaking the inversion symmetry and quasi-phase matching the pump and the signal. To generate an efficient broadband second-harmonic signal, however, the most promising technique requires matching the group velocities of the pump and the signal. In this work, we utilize dispersion engineering of a silicon waveguide to achieve group velocity matching between the pump and the signal, along with an additional degree of freedom to broaden the second harmonic through the strong third-order nonlinearity. We demonstrate that the strong self-phase modulation and cross-phase modulation in silicon help broaden the second harmonic by 200 nm in the O-band. Furthermore, we show a waveguide design that can be used to generate a second-harmonic signal in the entire near-infrared region. Our work paves the way for various applications, such as efficient and broadband complementary-metal oxide semiconductor based on—chip frequency synthesizers, entangled photon pair generators, and optical parametric oscillators.

硅以其强大的三阶光学非线性而闻名，表现出高效的超连续谱和四波混频过程。还可以观察到在硅中自然抑制的强二阶效应，例如，通过电破坏反转对称性和准相位匹配泵和信号。然而，为了产生有效的宽带二次谐波信号，最有前途的技术需要匹配泵的群速度和信号。在这项工作中，我们利用硅波导的色散工程来实现泵浦和信号之间的群速度匹配，以及通过强三阶非线性加宽二次谐波的额外自由度。我们证明了硅中的强自相位调制和交叉相位调制有助于将 O 波段中的二次谐波加宽 200 nm。此外，我们展示了一种波导设计，可用于在整个近红外区域产生二次谐波信号。我们的工作为各种应用铺平了道路，例如基于芯片频率合成器、纠缠光子对发生器和光学参量振荡器的高效宽带互补金属氧化物半导体。