Compact Metasurface Terahertz Spectrometer

TL;DR

This paper introduces a compact, metasurface-based terahertz spectrometer capable of high resolution within a broad frequency band, addressing size and complexity issues of current devices for space applications.

Contribution

The paper presents the design, fabrication, and validation of a novel metasurface terahertz spectrometer with improved miniaturization and performance over existing solutions.

Findings

Achieved a spectral resolution of at least 273.

Successfully demonstrated a miniaturized spectrometer in the 1.7-2.5 THz band.

Validated performance using quantum cascade laser array.

Abstract

The electromagnetic spectrum in the terahertz frequency region is of significant importance for understanding the formation and evolution of galaxies and stars throughout the history of the universe and the process of planet formation. Within the star forming clouds the constituent atoms and molecules are excited to produce characteristic emission and absorption lines, many of which happen at the terahertz frequencies. Thus, detecting the spectral signatures as unique fingerprints of molecules and atoms require terahertz spectrometers, which need to be operated in a space observatory because of the water vapor absorption in the earth atmosphere. However, current terahertz spectrometers face several challenges that limit their performances and applications, including a low resolution, limited bandwidth, large volume, and complexity. In this paper, we address the last two issues by demonstrating a concept of a compact terahertz spectrometer using metasurface. We start by modelling, designing, and fabricating a metasurface, aiming to optimize its performance within a band from 1.7 to 2.5 THz. Next, we make use of an array of quantum cascade lasers that operate at slightly different frequencies around 2.1 THz to validate the performance of the spectrometer. Finally, we apply the spectrum inversion method to analyse the measured data to confirm a resolution R of at least 273. Our results demonstrated a miniaturized terahertz spectrometer concept successfully.