RESUMO
In this article, it is shown experimentally that a planar laser-generated ultrasound source with a hard reflective backing will generate higher acoustic pressures than a comparable source with an acoustically matched backing when the stress confinement condition is not met. Furthermore, while the source with an acoustically matched backing will have a broader bandwidth when the laser pulse is short enough to ensure stress confinement, the bandwidths of both source types will converge as the laser pulse duration increases beyond stress confinement. The explanation of the results is supported by numerical simulations.
RESUMO
A custom fibre laser designed as an excitation source for biomedical photoacoustic tomography has been developed. It is based on a custom-drawn large core diameter fibre (200 µm) that enables high pulse energies (â¼10 mJ) to be achieved. The system can provide variable pulse durations (10 - 500 ns) and pulse repetition frequencies (100 Hz - 1 kHz), as well as arbitrary pulse bursts according to specific user defined sequences. The system is also compact and does not require external water cooling. This, along with the flexibility in the temporal characteristics of its output that it offers, will aid the translation of photoacoustic imaging to practical application in medicine and biology.
