Mid-infrared optical frequency comb generation from a chi-2 optical superlattice box resonator

TL;DR

This paper introduces a novel chi-2 optical superlattice box resonator that generates mid-infrared optical frequency combs using a near-infrared pump, achieving broad bandwidth, high power, and low noise suitable for sensing and spectroscopy.

Contribution

The development of a chi-2 superlattice resonator for MIR OFC generation using optical parametric down conversion, eliminating the need for MIR pump lasers and improving dispersion control.

Findings

Broadband MIR OFC with 250 nm span around 2060 nm

High output power over 370 mW

Low linewidth of 6.1 kHz indicating low noise

Abstract

Optical frequency combs (OFCs) at Mid-Infrared (MIR) wavelengths are essential for applications in precise spectroscopy, gas sensing and molecular fingerprinting, because of its revolutionary precision in both wavelength and frequency domain. The microresonator-based OFCs make a further step towards practical applications by including such high precision in a compact and cost-effective package. However, dispersion engineering is still a challenge for the conventional chi-3 micro-ring resonators and a MIR pump laser is required. Here we develop a different platform of a chi-2 optical superlattice box resonator to generate MIR OFC by optical parametric down conversion. With near-material-limited quality factor of 2.0*10^7, broadband MIR OFC can be generated with over 250 nm span around 2060 nm, where only a common near-infrared laser is necessary as pump. The fine teeth spacing corresponds to a measurable radio frequency beat note at 1.566 GHz, and also results in a fine spectroscopy resolution. Its linewidth is measured to be 6.1 kHz, which reveals a low comb noise that agrees well with the clean temporal waveforms. With high output power of over 370 mW, such MIR OFC is capable for long distance sensing and ranging applications.