Ultrabroadband Supercontinuum Generation and Frequency-Comb Stabilization Using On-Chip Waveguides with Both Cubic and Quadratic Nonlinearities
Daniel D. Hickstein, Hojoong Jung, David R. Carlson, Alexander J. Lind, Ian R. Coddington, Kartik A. Srinivasan, Gabriel G. Ycas, Daniel C. Cole, Abijith S. Kowligy, Stefan Droste, Erin S. Lamb, Nathan R. Newbury, Hong X. Tang, Scott A. Diddams, Scott B. Papp
Using aluminum-nitride photonic-chip waveguides, we generate optical frequency comb supercontinuum spanning 500~nm to 4000~nm, and show that the spectrum can be widely tailored by changing the geometry of the waveguide. Since aluminum nitride exhibits both quadratic and cubic nonlinearities, we observe simultaneous supercontinuum generation, difference frequency generation, second harmonic generation, and third harmonic generation in the same waveguide. By photodetecting the generated light, we measure and stabilize the carrier-envelope-offset frequency of a compact laser comb without the need for an interferometer. This combination of broadband light from the visible through the mid-infrared, combined with simplified self- referencing, provides a path towards inexpensive and robust systems for field-based spectroscopy and metrology.