Field-resolved spectroscopy in the molecular fingerprint region

Abstract

Vibrational spectroscopy in the mid-infrared (MIR) molecular fingerprint region (∼2–25 μm) provides information on the molecular composition, structure and conformation, affording tremendous potential for advances in fields ranging from fundamental research over security and environmental applications to biology and medicine. Traditionally, broadband measurements in this spectral region are carried out in the frequency domain. For each spectral element, the absorption of a sample is determined from the attenuation of the source intensity when placing the sample in the beam path. This brings about two severe limitations for the detection of small absorptions (and of small absorption differences). First, intensity noise of the source directly affects the ability of the spectrometer to detect intensity changes induced by small changes in the absorption. Second, the detection dynamic range necessary to simultaneously resolve the full power of the source and small absorption changes restricts power scaling and ultimately limits the smallest detectable change induced by an absorption.