Interferometric microphone for optoacoustic spectroscopy

A Fabry–Perot interferometer constructed with a pellicle beam splitter can be used as a sensitive microphone. Pressure disturbances inside the interferometer cavity alter the mirror separation, thereby changing the optical interference pattern. The optoacoustic effect can be detected in a cell attached to the Fabry–Perot interferometer by monitoring the change in intensity of the central interference fringe.