# Integrated tunable green light source on silicon nitride

## TL;DR

This paper introduces a new on-chip green light source with high power and wide tunability for telecommunications and quantum applications.

## Contribution

The work presents a novel method for generating tunable green light using photo-induced nonlinearities in silicon nitride microresonators.

## Key findings

- Green light generation reaches up to 3.5 mW via second-harmonic generation and is tunable over 29 nm.
- Milliwatt-level all-optical poling threshold is achieved without amplifiers.
- Comb-assisted all-optical poling enables 11 nm tunability of green light while maintaining pump resonance.

## Abstract

Integrated green light sources are essential for telecommunications and quantum applications, while the performance of current on-chip green light generation is still limited in power and tunability. In this work, we demonstrate green light generation in silicon nitride microresonators using photo-induced second-order nonlinearities, achieving up to 3.5 mW green power via second-harmonic generation and densely tunable over a 29 nm range. In addition, we report milliwatt-level all-optical poling (AOP) threshold, allowing for amplifier-free continuous-wave AOP. Furthermore, we demonstrate non-cascaded sum-frequency generation, leveraging the combination of AOP and simultaneous coherent frequency combs generation at 1 μm. Such comb-assisted AOP enables switching of the green light generation over an 11 nm range while maintaining the pump within a single resonance. The combination of such highly efficient photo-induced nonlinearity and multi-wavelength AOP enables the realization of low-threshold, high-power, widely-tunable on-chip green sources.