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

## TL;DR

This paper demonstrates a novel on-chip silicon nitride waveguide technique to generate a broadband visible frequency comb spanning from below 400 nm to above 600 nm at a 10 GHz repetition rate, linking telecom and visible wavelengths.

## Contribution

It introduces a new method combining spectral broadening and triple-sum frequency generation in silicon nitride waveguides for visible frequency combs.

## Key findings

- Achieved broadband visible frequency comb from 400 nm to 600 nm.
- Generated 150 pJ pulses via electro-optic modulation.
- Linked telecom and visible wavelength bands for applications.

## Abstract

A broadband visible 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, are coupled to a silicon nitride waveguide giving rise to a broadband near-infrared supercontinuum. Modal phase matching inside the waveguide allows direct triple-sum frequency transfer of the near-infrared supercontinuum into the visible wavelength range covering more than 250 THz from below 400 nm to above 600 nm wavelength. This scheme directly links the mature optical telecommunication band technology to the visible wavelength band and can find application in astronomical spectrograph calibration as well as referencing of continuous-wave lasers.