The availability of nonlinear parametric processes, such as frequency conversion in photonic integrated circuits is essential. In this contribution, we demonstrate a highly tunable second-harmonic generation in a fully complementary metal–oxide–semiconductor (CMOS)-fabrication-compatible silicon nitride integrated photonic platform. We induce the second-order nonlinearity using an all-optical poling technique with the second-harmonic light generated in the fundamental mode, and a narrow quasi-phase matching (QPM) spectrum by avoiding higher-order mode mixing. We are then able to broadly tune the phase-matched pump wavelength over the entire C-band (1540 nm to 1560 nm) by varying the poling conditions. Fine-tuning of QPM is enabled by thermo-optic effect with the tuning slope $\Delta \lambda /\Delta {T}$ in our device being 113.8 pm/°C. In addition, we exploit the measurable variation of the 3 dB QPM bandwidth to confirm how the length of the all-optically inscribed grating varies with exposure time.

中文翻译：

---

全光极化氮化硅波导中的高度可调谐二次谐波生成

非线性参数过程（例如光子集成电路中的频率转换）的可用性至关重要。在这项贡献中，我们证明了在完全互补的金属氧化物半导体（CMOS）制造兼容的氮化硅集成光子平台中可高度调谐的二次谐波产生。我们使用全光极化技术，通过在基模中生成的第二谐波光，以及避免高阶模混合的窄准相位匹配（QPM）光谱，来诱导二阶非线性。然后，我们可以通过改变极化条件在整个C波段（1540 nm至1560 nm）范围内广泛调谐相位匹配的泵浦波长。QPM的微调是通过热光效应通过调节斜率$ \ Delta \ lambda / \ Delta {T} $来实现的在我们的设备中为113.8 pm /°C。此外，我们利用3 dB QPM带宽的可测量变化来确认全光学刻写光栅的长度如何随曝光时间而变化。