Frequency comb generation in a quadratic nonlinear waveguide resonator

摘要

We demonstrate a frequency comb generation via a quadratic nonlinear optical waveguide in a resonatoras a monolithic device. In the experiment, we constructed the device by a periodically-poled lithiumniobate waveguide with high reective coatings for 1.5μm light at both ends of the waveguide. Whenwe set a pump frequency at 1540 nm to on-resonance, we observed a wide spectral broadening up to60 nm around the pump frequency due to cascaded processes of second harmonic generation and opticalparametric oscillation. A narrow radio frequency beat spectrum of the frequency comb appeared at3.5 GHz which corresponds to the free spectral range of the resonator. Furthermore, when we use twopump lights, we succeeded in a control of the mode spacing of the frequency comb by adjusting thefrequency difference of the two pump light.