Monolithic 1550 nm Narrow Linewidth Laser by Optical Injection Locking

Lasers with high-frequency spectral purity are critical for numerous applications, including sensing and spectroscopy [1] and microwave photonic devices [2]. Prior research has demonstrated that coupling a distributed feedback (DFB) semiconductor laser with a high-Q external optical cavity can create a self-injection-locked (SIL) system. However, effective hybrid SOI- or <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Si}_{3}\mathrm{N}_{4}$</tex> -based SIL and external cavity laser (ECL) designs require highly efficient coupling components between the 111- V and silicon platforms. In addition, heterogeneous integration complicates the testing of individual components before their integration into complex systems. This requires stringent process control to ensure high yield, while also increasing fabrication complexity and cost.