Optical fiber photoacoustic–photothermal probe

We describe the operation of an all-optical probe that provides an alternative means of implementing photoacoustic and photothermal investigative techniques, particularly those used in biomedical applications. The probe is based on a transparent, acoustically and thermally sensitive Fabry–Perot polymer film sensor mounted at the end of an optical fiber. We demonstrate the ability of the system to make photoacoustic and photothermal measurements simultaneously and evaluate its photothermal response, using a nonscattering liquid target of known and adjustable absorption coefficient. The acoustic and thermal noise floors were 2 kPa and $6\times {10}^{-3}{ }^{°}\mathrm{C}$, respectively, obtained over a 25-MHz measurement bandwidth and 30 signal averages.