Infrared electric-field sampled frequency comb spectroscopy

TL;DR

This paper introduces a compact broadband infrared frequency comb spectroscopy system capable of high-resolution, electric-field measurement of mid-infrared pulses, enabling detailed molecular and biological sample analysis.

Contribution

It develops a unified apparatus for broadband laser frequency combs and electric-field measurement across 3-27 um, advancing infrared spectroscopy capabilities.

Findings

Spectra of atmospheric compounds like ammonia and CO2 were obtained.

Broadband spectrum of a monoclonal antibody revealed protein secondary structures.

The system operates at the intersection of ultrafast physics and precision spectroscopy.

Abstract

Molecular spectroscopy in the mid-infrared portion of the electromagnetic spectrum (3--25 um) has been a cornerstone interdisciplinary analytical technique widely adapted across the biological, chemical, and physical sciences. Applications range from understanding mesoscale trends in climate science via atmospheric monitoring to microscopic investigations of cellular biological systems via protein characterization. Here, we present a compact and comprehensive approach to infrared spectroscopy incorporating the development of broadband laser frequency combs across 3--27 um, encompassing the entire mid-infrared, and direct electric-field measurement of the corresponding near single-cycle infrared pulses of light. Utilizing this unified apparatus for high-resolution and accurate frequency comb spectroscopy, we present the infrared spectra of important atmospheric compounds such as ammonia and carbon dioxide in the molecular fingerprint region. To further highlight the ability to study complex biological systems, we present a broadband spectrum of a monoclonal antibody reference material consisting of more than 20,000 atoms. The absorption signature resolves the amide I and II vibrations, providing a means to study secondary structures of proteins. The approach described here, operating at the boundary of ultrafast physics and precision spectroscopy, provides a table-top solution and a widely adaptable technique impacting both applied and fundamental scientific studies.