Disordered, strongly scattering porous materials as miniature multipass gas cells

TL;DR

This paper demonstrates that highly scattering porous zirconia materials can serve as miniature, alignment-free gas cells by providing an effective optical pathlength equivalent to over 750 passes, enabling compact and low-cost spectroscopic sensors.

Contribution

It introduces a novel approach using disordered porous materials for multipass gas sensing, significantly reducing size and complexity compared to traditional methods.

Findings

Effective pathlength over 5 meters achieved in a 7 mm zirconia sample

Porosity and pore structure enable high scattering and pathlength enhancement

Potential for compact, low-cost, alignment-free optical gas sensors

Abstract

Spectroscopic gas sensing is both a commercial success and a rapidly advancing scientific field. Throughout the years, massive efforts have been directed towards improving detection limits by achieving long interaction pathlengths. Prominent examples include the use of conventional multipass gas cells, sophisticated high-finesse cavities, gas-filled holey fibers, integrating spheres, and diffusive reflectors. Despite this rich flora of approaches, there is a continuous struggle to reduce size, gas volume, cost and alignment complexity. Here, we show that extreme light scattering in porous materials can be used to realise miniature gas cells. Near-infrared transmission through a 7 mm zirconia (ZrO2) sample with a 49% porosity and subwavelength pore structure (on the order of 100 nm) gives rise to an effective gas interaction pathlength above 5 meters, an enhancement corresponding to 750 passes through a conventional multipass cell. This essentially different approach to pathlength enhancement opens a new route to compact, alignment-free and low-cost optical sensor systems.