Enabling Arbitrary Wavelength Optical Frequency Combs on Chip

TL;DR

This paper introduces a novel approach to generate arbitrary wavelength optical frequency combs on chip by using photonic compound ring resonators with engineered dispersion properties, enabling applications like chip-scale optical clocks.

Contribution

It demonstrates that compound ring resonators can achieve large anomalous GVD at any wavelength, overcoming material limitations in visible and UV regions.

Findings

Successfully designed a mode-locked frequency comb near 794.6nm

Showed compound resonators can have large anomalous GVD despite normal GVD in individual resonators

Proposed application as a flywheel for chip-scale optical clocks

Abstract

A necessary condition for generation of bright soliton Kerr frequency combs in microresonators is to achieve anomalous group velocity dispersion (GVD) for the resonator modes. This condition is hard to implement in visible as well as ultraviolet since the majority of optical materials are characterized with large normal GVD in these wavelength regions. We overcome this challenge by borrowing ideas from strongly dispersive coupled systems in solid state physics and optics. We show that photonic compound ring resonators can possess large anomalous GVD at any desirable wavelength, even if each individual resonator is characterized with normal GVD. Based on this concept we design a mode locked frequency comb with thin-film silicon nitride compound ring resonators in the vicinity of Rubidium D1 line (794.6nm) and propose to use this optical comb as a flywheel for chip-scale optical clocks.