Tunable Fabry-Perot sensors with homogenised optical thickness for parallelised photoacoustic signal acquisition

Abstract

Photoacoustic tomography is a hybrid biomedical imaging modality that combines strong optical absorption contrast with the spatial resolution and imaging depth of ultrasound imaging. Fabry–Perot ultrasound sensors enable high-resolution 3D imaging but conventional raster scan-based readout schemes are limited by low speed due to sequential, spatially resolved optical interrogation of the sensor. Camera-based readout schemes, in which the entire detection aperture is illuminated with an expanded, collimated interrogation beam, require a constant interrogation wavelength across the detection aperture and thus a uniform optical thickness of the spacer. In this work, a method for the location-dependent correction of the optical thickness of the photopolymer spacer was developed, reducing fringe position variations by a factor of 50. In addition, electro-optical and thermo-optical effects were investigated to actively tune and stabilise the sensor bias point.