Flexible terahertz gas sensing platform based on substrate-integrated hollow waveguides and an opto-electronic light source

We report on a flexible platform for molecular sensing in the terahertz range. Merging the well-established technologies of near-infrared electro-optic modulation and photomixing realizes a spectrally adaptable terahertz source, which is combined with a new generation of compact gas cells, so-called substrate-integrated hollow waveguides (iHWGs). iHWGs have been developed in the mid-infrared and provide flexibility in the design of the optical absorption path. Here, we demonstrate its suitability for the terahertz domain by presenting its low propagation losses and by measuring rotational transitions of nitrious oxide (N2O). A fast frequency sideband modulation technique results in substantially reduced measurement times and increased accuracy compared to a standard wavelength tuning method.

Automated summary

We present a flexible molecular sensing platform in the terahertz range, achieved by merging near-infrared electro-optic modulation and photomixing technologies. The platform utilizes a new generation of compact gas cells called substrate-integrated hollow waveguides (iHWGs), which have been developed for the mid-infrared. We demonstrate the suitability of iHWGs for the terahertz domain by showcasing their low propagation losses and measuring rotational transitions of nitrous oxide (N2O). A fast frequency sideband modulation technique is employed, resulting in significantly reduced measurement times and increased accuracy compared to a standard wavelength tuning method.