Mid-infrared supercontinuum generation in tapered chalcogenide fiber for producing octave-spanning frequency comb around 3 {\mu}m

TL;DR

This paper demonstrates a method for generating a broad, coherent mid-infrared supercontinuum in tapered chalcogenide fiber, enabling stable, octave-spanning frequency combs suitable for molecular spectroscopy.

Contribution

It introduces a novel tapered fiber design and in-situ tapering process to produce stable, coherent mid-IR supercontinuum from near-IR frequency combs without additional stabilization.

Findings

Achieved supercontinuum from 2.2 to 5 μm with 40 dB bandwidth

Maintained coherence of the frequency comb through nonlinear processes

Produced stable mid-IR frequency combs from near-IR sources

Abstract

We demonstrate mid-infrared (mid-IR) supercontinuum generation (SCG) with instantaneous bandwidth from 2.2 to 5 {\mu}m at 40 dB below the peak, covering the wavelength range desirable for molecular spectroscopy and numerous other applications. The SCG occurs in a tapered As2S3 fiber prepared by in-situ tapering and is pumped by femtosecond pulses from the subharmonic of a mode-locked Er-doped fiber laser. Interference with a narrow linewidth c.w. laser verifies that the coherence properties of the near-IR frequency comb have been preserved through these cascaded nonlinear processes. With this approach stable broad mid-IR frequency combs can be derived from commercially available near-IR frequency combs without an extra stabilization mechanism.