Super-resolution discrete-Fourier-transform spectroscopy using precisely periodic radiation beyond time window size limitation

TL;DR

This paper introduces a novel discrete Fourier transform spectroscopy method using precisely periodic pulsed terahertz radiation, achieving ultra-high spectral resolution beyond traditional time window limitations, enabling detailed molecular analysis.

Contribution

The study demonstrates a new spectroscopic technique that overcomes time window constraints by matching the repetition period, allowing resolution limited only by spectral interleaving, with potential broad applications.

Findings

Achieved linewidths narrower than 1/50T, resolving low-pressure molecular gas lines.

Spectral resolution limited only by interleaving interval, not time window size.

Enhanced spectrometer performance for practical applications.

Abstract

Fourier transform spectroscopy (FTS) has been widely used in a variety of fields in research, industry, and medicine due to its high signal-to-noise ratio, simultaneous acquisition of signals in a broad spectrum, and versatility for different radiation sources. Further improvement of the spectroscopic performance will widen its scope of applications. Here, we demonstrate improved spectral resolution by overcoming the time window limitation using discrete Fourier transform spectroscopy (dFTS) with precisely periodic pulsed terahertz (THz) radiation. Since infinitesimal resolution can be achieved at periodically discrete frequencies when the time window size is exactly matched to the repetition period T, a combination of THz-dFTS with a spectral interleaving technique achieves a spectral resolution only limited by the spectral interleaving interval. Linewidths narrower than 1/(50T) are fully resolved allowing the attribution of rotational-transition absorption lines of low-pressure molecular gases within a 1.25 MHz band. The proposed method represents a powerful tool to improve spectrometer performance and accelerate the practical use of various types of FTS.