Fibre-optic hydrophones (FOHs) are widely used to detect high-intensity focused ultrasound (HIFU) fields.
The most common type consists of an uncoated singlemode fibre with a perpendicularly cleaved end face. The
main disadvantage of these hydrophones is their low
signal-to-noise ratio (SNR). To increase the SNR, signal
averaging is performed, but the associated increased
acquisition times hinder ultrasound field scans. In this
study, with a view to increase SNR whilst withstanding
HIFU pressures, the bare FOH paradigm is extended
to include a partially-reflective coating on the fibre end
face. Here, a numerical model based on the general
transfer-matrix method was implemented. Based on the
simulation results, a single-layer, 172 nm TiO2-coated
FOH was fabricated. The frequency range of the hydrophone was verified from 1 to 30 MHz. The SNR of
the acoustic measurement with the coated sensor was 21
dB higher than of the uncoated one. The coated sensor
successfully withstood a peak-positive pressure of 35
MPa for 6000 pulses
