Fourier transform infrared spectroscopy with visible light

TL;DR

This paper introduces a novel Fourier-transform infrared spectroscopy method utilizing nonlinear interferometers with visible light detection, enabling broadband spectral analysis in the mid-infrared range without spectrally selective detectors.

Contribution

It combines nonlinear interferometry with Fourier-transform spectroscopy using broadband non-collinear SPDC, achieving high spectral coverage and resolution in the mid-infrared range.

Findings

Achieved over 100 cm$^{-1}$ spectral bandwidth without spectrally selective detection.

Demonstrated transmission spectra of polypropylene with 6 cm$^{-1}$ resolution.

Spectral range covered from 3.2 μm to 3.9 μm.

Abstract

Nonlinear interferometers allow spectroscopy in the mid-infrared range by detecting correlated visible light, for which non-cooled detectors with higher specific detectivity and lower dark count rates are available. We present a new approach for the registration of spectral information, which combines a nonlinear interferometer using non-degenerate spontaneous parametric down-conversion (SPDC) with a Fourier-transform spectroscopy concept. In order to increase the spectral coverage, we use broadband non-collinear SPDC in periodically poled LiNbO$_3$. Without the need for spectrally selective detection, continuous spectra with a spectral bandwidth of more than 100$\,$cm$^{-1}$ are achieved. We demonstrate transmission spectra of a polypropylene sample measured with ~ 6$\,$cm$^{-1}$ resolution in the spectral range between 3.2$\,\mu$m to 3.9$\,\mu$m.