Tuning Kerr-Soliton Frequency Combs to Atomic Resonances

TL;DR

This paper presents a robust method for tuning silicon-nitride Kerr-soliton frequency combs across a wide wavelength range, enabling applications in atomic spectroscopy with integrated photonics.

Contribution

It introduces a chip-scale, thermo-optically tunable frequency comb source with consistent soliton generation across multiple resonators for atomic spectroscopy.

Findings

Achieved octave-bandwidth soliton combs at 1064 nm

Demonstrated thermo-optic tuning of 75 resonators over 50°C

Enabled access to wavelengths for rubidium, potassium, and cesium spectroscopy

Abstract

Frequency combs based on nonlinear-optical phenomena in integrated photonics are a versatile light source that can explore new applications, including frequency metrology, optical communications, and sensing. We demonstrate robust frequency-control strategies for near-infrared, octave-bandwidth soliton frequency combs, created with nanofabricated silicon-nitride ring resonators. Group-velocity-dispersion engineering allows operation with a 1064 nm pump laser and generation of dual-dispersive-wave frequency combs linking wavelengths between approximately 767 nm and 1556 nm. To tune the mode frequencies of the comb, which are spaced by 1 THz, we design a photonic chip containing 75 ring resonators with systematically varying dimensions and we use 50 $^\circ$C of thermo-optic tuning. This single-chip frequency comb source provides access to every wavelength including those critical for near-infrared atomic spectroscopy of rubidium, potassium, and cesium. To make this possible, solitons are generated consistently from device-to-device across a single chip, using rapid pump frequency sweeps that are provided by an optical modulator.