Terahertz asynchronous twin-comb for prefiguring hypersensitivity beyond spectrum domain.

Ma, Liang; Fan, Fei; Feng, Jixin; Shen, Peng; Song, Chengwei; Ji, Yunyun; Wang, Xianghui; Chang, Shengjiang · Nat Commun · 2025

basic_science · Level V

Where this comes from

Abstract

Lower-frequency characteristics of the terahertz regime confer advantageous low photon energy for biochemical sensing while imposing inherent sensitivity constraints. Here, we demonstrate a terahertz asynchronous twin-comb sensor and an extra-spectrum sensing mechanism through cascading microchannel architecture within a metallic waveguide. The extra-spectrum sensing prefigures an enhanced sensitivity of 4 orders of magnitude compared to existing terahertz biosensing and surpasses its counterpart in the optical band. Hypersensitivities of 0.398 GHz mm<sup>2</sup> pg<sup>-1</sup> in trace detection manifest through the located characteristic resonance frequency beyond the spectrum domain. Additionally, we observed the photoisomerization of azo dye in the terahertz band with a photoresponse sensitivity of 0.91 GHz cm<sup>2</sup> mW<sup>-1</sup>, opening possibilities for photoactive material-assisted terahertz sensors. In summary, we instantiate an asynchronous twin-comb sensing beyond the spectrum domain, offering a perspective for ultrasensitive sensing, and promising applications in optical frequency comb precision metrology, artificial intelligence photonics, and integrated sensing and communications.