Research

Terahertz (THz) spectroscopy holds significant importance owing to the abundance of molecular and atomic fingerprint lines within this frequency range. In astronomy, THz spectroscopy provides a powerful probe of rotational and vibrational transitions of molecules, offering insights into star and planet formation as well as the physical and chemical processes in galactic and interstellar environments.
Conventional THz spectrometers typically rely on multiple free-space optical elements or moving parts, which makes them bulky and challenge to integrate into compact systems. Metasurfaces – planar optical components composed of subwavelength nanostructures, have recently emerged as a powerful new approach for controlling the polarization, phase, and amplitude of light with unprecedented flexibility. These advances open the door to the design of highly compact and versatile spectroscopic instruments.
Ren et al. (2024) demonstrated multi-wavelength phase gratings composed of segmented metasurface elements incorporating multiple nanostructures. The resulting transmissive grating produced highly uniform diffraction beams while maintaining identical diffraction angles at two distinct frequencies, enabling efficient multi-frequency wavefront control.
Luo et al. (2026) demonstrated a compact terahertz spectrometer that integrates a phase grating and two transmissive metasurfaces on a single platform. The system achieved a frequency resolution better than 21 GHz while occupying less than 1% of the footprint of a conventional terahertz time-domain spectroscopy (THz-TDS) system, providing a highly compact solution for high-resolution terahertz spectral analysis.