Continuous Wavelength-Sweeping of a Narrow-Linewidth Hybrid-Integrated Extended-Cavity Laser

Chip-level hybrid integration of semiconductor optical amplifiers with low-loss waveguide-based extended cavities, enables lasers with outstanding properties. Especially, ring-resonator based filters enable sub-kHz intrinsic linewidths and wide tunability across the entire gain bandwidth [1]. Nevertheless, wide wavelength tuning is usually done in discrete steps, accompanied by ring and cavity mode hops. Continuous tuning would be desired, to ensure that all wavelengths are covered, and a full optical spectrum can be acquired. This is essential for applications in high-resolution sensing, for example in structural health monitoring using Fiber Bragg gratings (FBG), optical frequency domain reflectometry (OFDR), and LiDAR. As a first step, mode-hop free tuning was demonstrated over a sub-nm range [2], and, recently, with a dedicated laser, over more than 3 nm [3].