Optical frequency comb Faraday rotation spectroscopy

TL;DR

This paper introduces a broadband, interference-free optical frequency comb Faraday rotation spectroscopy system that detects paramagnetic species using a femtosecond optical parametric oscillator and Fourier transform spectrometer, demonstrating nitric oxide detection.

Contribution

It presents the first implementation of OFC-FRS with background suppression via magnetic field switching, enabling broadband detection of paramagnetic molecules.

Findings

Successful measurement of nitric oxide's fundamental band

Good agreement with theoretical models

Demonstration of long-term averaging capability

Abstract

We demonstrate optical frequency comb Faraday rotation spectroscopy (OFC-FRS) for broadband interference-free detection of paramagnetic species. The system is based on a femtosecond doubly resonant optical parametric oscillator and a fast-scanning Fourier transform spectrometer (FTS). The sample is placed in a DC magnetic field parallel to the light propagation. Efficient background suppression is implemented via switching the direction of the field on consecutive FTS scans and subtracting the consecutive spectra, which enables long term averaging. In this first demonstration, we measure the entire Q- and R-branches of the fundamental band of nitric oxide in the 5.2-5.4 {\mu}m range and achieve good agreement with a theoretical model.