Visible blue-to-red 10 GHz frequency comb via on-chip triple-sum-frequency generation

Abstract

A broadband visible (VIS) blue-to-red, 10 GHz repetition rate frequency comb is generated by combined spectral broadening and triple-sum-frequency generation in an on-chip silicon nitride waveguide. Ultra-short pulses of 150 pJ pulse energy, generated via electro-optic modulation of a 1560 nm continuous-wave laser (CW), are coupled to a silicon nitride waveguide giving rise to a broadband near-infrared (NIR) supercontinuum. Modal phase matching inside the waveguide allows direct triple-sum-frequency transfer of the NIR supercontinuum into the VIS wavelength range covering more than 250 THz from below 400 to above 600 nm wavelength. This scheme directly links the mature optical telecommunication band technology to the VIS wavelength band and can find application in astronomical spectrograph calibration, as well as referencing of CW lasers.