A Ⅲ-Ⅴ-on-Si ultra-dense comb laser

摘要

Optical frequency combs emerge as a promising technology that enables highly sensitive,near-real-time spectroscopy with a high resolution.The currently available comb generators are mostly based on bulky and high-cost femtosecond lasers for dense comb generation(line spacing in the range of 100 MHz to 1 GHz).However,their integrated and low-cost counterparts,which are integrated semiconductor mode-locked lasers,are limited by their large comb spacing,small number of lines and broad optical linewidth.In this study,we report a demonstration of a Ⅲ-Ⅴ-on-Si comb laser that can function as a compact,low-cost frequency comb generator after frequency stabilization.The use of low-loss passive silicon waveguides enables the integration of a long laser cavity,which enables the laser to be locked in the passive mode at a record-low 1 GHz repetition rate.The 12-nm 10-dB output optical spectrum and the notably small optical mode spacing results in a dense optical comb that consists of over 1400 equally spaced optical lines.The sub-kHz 10-dB radio frequency linewidth and the narrow longitudinal mode linewidth(o400 kHz)indicate notably stable mode-locking.Such integrated dense comb lasers are very promising,for example,for highresolution and real-time spectroscopy applications.