Ring-segment piezopolymer sensor optimized for cylindrical-wave detection in optical-resolution optoacoustic
Alexey Kurnikov1, Maxim Prudnikov1, Daria Voitovich1
1Laboratory of Ultrasound and Optoacoustic Diagnostics, Division of Radiophysics Methods in Medicine, Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603005, Russia.
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Optical resolution optoacoustic (or photoacoustic) microscopy (OR-OAM) utilizing a 532 nm laser wavelength represents a promising approach for non-invasive visualization of superficial hemoglobin-rich structures. However, clinical translation of OR-OAM angiography typically faces a trade-off between achieving high contrast and resolution versus maintaining an extended depth-of-field at safe laser exposure levels. Gradient refractive index (GRIN) fiber lenses can provide an elongated optical focus preserved over a millimeter-scale length. However, developing coaxially aligned wideband acoustic detectors with high sensitivity remains challenging. Here, we introduce a piezopolymer PVDF-TrFE detector featuring a spherically-focused thin (100 μm) ring geometry with a 4.6 mm aperture and 1.5 mm working distance (NA = 0.84). Numerical modeling reveals not only an extended depth of field, but also an improvement in sensitivity compared to conventional full-aperture detectors. In vitro experiments using whole human blood demonstrated a 14 dB signal-to-noise ratio at a safe laser irradiance of 20 mJ/cm2. In vivo angiographic imaging of neonatal mouse cerebral vasculature and human cuticle confirmed the detector's capability to achieve a depth-of-field exceeding 1 mm, highlighting its potential for a broad range of biomedical applications.
