Medical ultrasound is an imaging technique that utilizes ultrasonic signals as information carriers, and has wide applications such as seeing internal body structures and finding the sources of an internal diseases. The most used ultrasonic transducer today is based on piezoelectricity. The piezoelectric transducer, however, may have a limited bandwidth and insufficient sensitivity for reduced element size. In this work we demonstrate the generation of wideband ultrasound pulses using high power diode lasers (HPDLS), short pulsed current sources and composite absorbers. We design and implement the pulsed current sources optimized for the HPDLs. We fabricate candle soot-PDMS composite targets. We have achieved peak pressure of 323 kPa and bandwidths at -6 dB of 34 MHz using a diode laser with an optoacoustics conversion efficiency of 5.3 * 10 -3 Pa/(W/m 2 ). Finally, we present a compact low-cost tunable ultrawideband laser ultrasound emitter.
High Power Diode Laser (HPDLs) can potentially be more suitable laser sources for commercial implementation of short pulse application such as optoacoustic biomedical imaging, compared to the commonly used solid state lasers due to their lower cost, compact size and higher repetition rate. However, the commercially available HPDLs are designed and characterized to operate with much longer pulse durations and lower peak powers compared to what usually is required in optoacoustics applications. In this paper, we study the operation of the HPDL devices, out of the manufacturer datasheet ratings at high current (< 40A) and short pulses (< 100ns). Two short pulse, high current drivers have been used to control the HPLDs. We have obtained optical peak powers of 257 W and energies per pulse of 5.2 µJ at 20 ns optical pulse duration with a single HPDL chip and using a four HPDL chips array, we have achieved optical peak powers of 750 W and energies per pulse of 31.2 µJ at 40 ns optical pulse duration. This new operating regimen improves the performance of HPDL for optoacoustic biomedical imaging techniques.
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