Ultracompact oxygen sensor using nanoporous materials as strongly-scattering multipass cell for tunable diode laser absorption spectroscopy

In this work, a variety of disordered strongly-scattering nanoporous ceramic materials was systematically investigated to study the influence of the material and processing parameters on their performance. To use these materials as miniature multipass cell it is necessary to achieve the highest possible optical absorption path length (OPL). On the other hand, an increased mean OPL is associated with an increased scattering. This negatively impacts on the signal obtained from the photodiode due to the increase in the solid angle of the transmitted light and to the consequently lower collected light intensity. For practical purposes, therefore, the choice of the optimal material should be a compromise between these two aspects. The material with most promising properties proved to be ZrO
₂
with porosity from 50% to 55%. With samples of 6 mm thickness it is possible to realize mean OPL above 6 m.