Field-Deployable Ultraviolet Dual-Comb Spectrometer for Mobile Formaldehyde Sensing

We report, to the best of our knowledge, the first field-deployable ultraviolet (UV) dual-comb spectrometer (DCS) for environmental sensing of formaldehyde. By combining broadband UV spectroscopy with sub-second temporal resolution the instrument enables fast, sensitive, and species-selective measurements of trace gas concentrations. Formaldehyde is a significant atmospheric pollutant and photochemical precursor with adverse effects on human and environmental health.

Current observational capabilities are limited by a gap between satellite-based remote sensing, which provides large-scale coverage, but coarse spatial and temporal resolution, and stationary in-situ instruments, which offer high sensitivity but represent only localized sampling volumes with often a bad selectivity. The presented system addresses this gap by enabling measurements with spatial resolutions ranging from hundreds of meters to kilometres, making it well suited for mobile and regional-scale atmospheric studies. Preliminary tests resulted in a resolution of 35 ppb formaldehyde for a total pathlength of 1 km and a measurement time of 1s with potential improvement in sensitivity by one order of magnitude.

Leveraging recent advances in dual-comb laser technology, we developed a compact and mechanically robust spectrometer that generates coherent radiation in the ultraviolet spectral region around 350 nm without any moving optical components. This design ensures high stability and reliability under field conditions and makes the system particularly suitable for mobile deployments. The use of DCS allows for the integration of many measurements, each fast enough to be unimpeded by atmospheric turbulences, via coherent averaging.

These characteristics make UV dual-comb spectrometers especially promising for environmental monitoring and remote sensing applications. The demonstrated system operational in a car represents a significant step toward next-generation atmospheric sensing platforms capable of bridging observational scales and extending DCS environmental sensing to the ultraviolet.