Optical gas detection in microsystems is limited by the short micron scale optical path length available. Recently, the concept of slow-light enhanced absorption has been proposed as a route to compensate for the short path length in miniaturized absorption cells. We extend the previous perturbation theory to the case of a Bragg stack infiltrated by a spectrally strongly dispersive gas with a narrow and distinct absorption peak. We show that considerable signal enhancement is possible. As an example, we consider a Bragg stack consisting of PMMA infiltrated by O2. Here, the required optical path length for visible to near-infrared detection (760 nm) can be reduced by at least a factor of 102, making a path length of 1 mm feasible. By using this technique, optical gas detection can potentially be made possible in microsystems.
Jensen, K. H., Zainal Alam, M. N. H., Scherer, B., Lambrecht, A., & Mortensen, N. A. (2008). Slow-light enhanced light-matter interactions with applications to gas sensing. Optics Communications, 281, 5335-5339. https://doi.org/10.1016/j.optcom.2008.07.073