Over the past decade, optical frequency combs have been used for a growing number of applications, such as chemical sensing, distance ranging, timekeeping, searching for exoplanets, and optical communication. Frequency comb sources in the visible to mid-infrared wavelength range are commercially available, but they are large and expensive instruments. To enable their widespread use, a fully integrated solution is highly desirable.
The goal of this project is to develop on-chip electrically pumped visible comb lasers for absorption and Raman spectroscopy applications. The availability of fully integrated visible frequency comb sources will open doors to compact, cheap spectroscopic sensors for environmental monitoring and medical diagnostic tools. If the goal is met, this will also be a major step forward in the development of portable, lightweight optical clocks and frequency rulers for astronomical spectrographs.
To reach our goal, we will combine high-quality InGaN optical amplifiers and saturable absorbers with low-loss, CMOS-compatible, passive silicon nitride waveguide cavities. This is expected to result in a drastic performance improvement compared to existing monolithically integrated InGaN mode-locked lasers. By careful design of the extended silicon nitride cavity and innovative dispersion engineering, we will be able to realize efficient mode-locked comb lasers with a wide optical bandwidth, narrow linewidth comb lines, and a variety of repetition rates.