Application of the low finesse frequency comb for high resolution spectroscopy

TL;DR

This paper introduces a high-resolution spectroscopy method using low finesse frequency combs, leveraging time domain measurements and Fourier analysis to detect resonance with absorbers more sensitively than traditional high finesse combs.

Contribution

It presents a novel approach employing low finesse frequency combs and time domain analysis for enhanced spectral resolution in gamma-photon absorption.

Findings

Low finesse combs are more sensitive to resonance conditions.

Fourier analysis of intensity oscillations reveals spectral content.

Method achieves resolution beyond natural linewidth.

Abstract

High finesse frequency combs (HFC) with large ratio of the frequency spacing to the width of the spectral components have demonstrated remarkable results in many applications such as precision spectroscopy and metrology. We found that low finesse frequency combs having very small ratio of the frequency spacing to the width of the spectral components are more sensitive to the exact resonance with absorber than HFC. Our method is based on time domain measurements reviling oscillations of the radiation intensity after passing through an optically thick absorber. Fourier analysis of the oscillations allows to reconstruct the spectral content of the comb. If the central component of the incident comb is in exact resonance with the single line absorber, the contribution of the first sideband frequency into oscillations is exactly zero. We demonstrate this technique with gamma-photon absorbtion by M\"{o}ssbauer nuclei providing the spectral resolution beyond the natural broadening.