Differential high-resolution stimulated CW Raman spectroscopy of hydrogen in a hollow-core fiber

TL;DR

This paper demonstrates high-resolution stimulated Raman spectroscopy of hydrogen in a hollow-core fiber using narrow linewidth lasers, achieving excellent spectral resolution and sensitivity for molecular identification.

Contribution

The work introduces a novel setup combining narrow linewidth CW lasers and differential measurement for high-resolution, sensitive Raman spectroscopy in a hollow-core fiber.

Findings

Achieved spectral resolution of approximately 10^-4 cm^(-1)

Detected Raman signals with only a few milliwatts of optical power

Enabled high-resolution molecular identification and quantification

Abstract

We demonstrate sensitive high-resolution stimulated Raman measurements of hydrogen using a hollow-core photonic crystal fiber (HC-PCF). The Raman transition is pumped by a narrow linewidth (<50 kHz) 1064 nm continuous-wave (CW) fiber laser. The probe light is produced by a homebuilt CW optical parametric oscillator (OPO), tunable from around 800 nm to 1300 nm (linewidth ~ 5 MHz). These narrow linewidth lasers allow for an excellent spectral resolution of approximately 10^-4 cm^(-1). The setup employs a differential measurement technique for noise rejection in the probe beam, which also eliminates background signals from the fiber. With the high sensitivity obtained, Raman signals were observed with only a few mW of optical power in both the pump and probe beams. This demonstration allows for high resolution Raman identification of molecules and quantification of Raman signal strengths.