Development of tunable Fabry-Pérot polymer film sensors for parellelised photoacoustic signal acquisition (Conference Presentation)

Abstract

Fabry-Perot (FP) polymer film sensors exhibit small element sizes, high acoustic sensitivity, transparency and flat frequency response to enable high resolution 3D photoacoustic (PA) imaging in backward mode. However, conventional raster scan interrogation can result in slow data acquisition (several min for 3D images) compared to parallelized piezoelectric detector arrays. To address this limitation, parallelization using a camera-based readout of FP sensors is investigated. This approach requires the optical thickness of the polymer spacer to be sufficiently uniform over the scan area to obtain high acoustic sensitivity for all active elements. Since the deposition of passive polymer layers with sufficient homogeneity of thickness is challenging, the use of electro-optically (EO) or piezoelectric (PE) tunable polymer film spacers is investigated. The spacers are sandwiched between two dielectric mirrors and transparent electrodes to form an FP sensor. In this work, spin coated guest-host systems consisting of EO chromophores (2-methyl-4-nitroaniline) embedded in a PMMA matrix, and thermally evaporated PE film spacers (PVDF) were examined. Both systems were electrically poled using a corona discharge. The optical transfer function, the transmission spectrum of the excitation passband from 600 nm to 1100 nm and the tuning range of the FP sensors were determined. Furthermore, the detection of PA waves was demonstrated. Tunable FP sensors in conjunction with camera-based interrogation techniques have the potential to provide 3D image acquisition times on the order of seconds.