Ultrabroadband supercontinuum generation and frequency-comb stabilization using on-chip waveguides with both cubic and quadratic nonlinearities

摘要

Using aluminum-nitride photonic-chip waveguides, we generateoptical-frequency-comb supercontinuum spanning from 500 nm to 4000 nm with a0.8 nJ seed pulse, and show that the spectrum can be tailored by changing thewaveguide geometry. Since aluminum nitride exhibits both quadratic and cubicnonlinearities, the spectra feature simultaneous contributions from numerousnonlinear mechanisms: supercontinuum generation, difference-frequencygeneration, second-harmonic generation, and third-harmonic generation. As oneapplication of integrating multiple nonlinear processes, we measure andstabilize the carrier-envelope-offset frequency of a laser comb by directphotodetection of the output light. Additionally, we generate ~0.3 mW in the3000 nm to 4000 nm region, which is potentially useful for molecularspectroscopy. The combination of broadband light generation from the visiblethrough the mid-infrared, combined with simplified self-referencing, provides apath towards robust comb systems for spectroscopy and metrology in the field.