Spectrally Flexible Terahertz Frequency Comb Platform for Molecular Fingerprinting

Abstract

We introduce a robust platform tailored for molecular gas detection within the terahertz domain. Our approach integrates near-infrared electro-optic modulation and difference frequency conversion techniques to construct a spectrally adaptable terahertz frequency comb source and combines this novel system with a new generation of substrate-integrated hollow waveguides (iHWGs), offering flexibility in the design of optical absorption paths. Our experimental findings demonstrate the synthesis of flexible terahertz (dual) frequency combs, enabling the precise matching of molecular fingerprints, and low propagation losses that qualify iHWGs for proper THz waveguiding. Measurements of various rotational transitions of nitrous oxide and ammonia further highlight the potential of this sensing platform.