Portable laser ultrasound system by using high power diode lasers for endoscopic biomedical applications

Medical ultrasound is a diagnostic and treatment method that employs ultrasonic signals as carriers of information. It boasts a broad range of applications, including the visualization of internal bodily structures, the detection of underlying diseases and cellular stimulation. Presently, the most employed ultrasound transducer relies on the principles of piezoelectricity. Nonetheless, piezoelectric transducers may encounter limitations in terms of bandwidth. However, the ultrasound generated by laser through the optoacoustic effect has a large bandwidth, and by using high power laser diodes we can reduce the size of the transducer, enabling endoscopy ultrasound applications. We have designed and implemented a portable endoscopic ultrasonic generator using high power diode lasers and ultrasound generating bi-composites (candle soot-PDMS). We have reduced the size of the ultrasound generating system (laser diode, laser driver and composite) to a width of 5.5 mm making it suitable for an endoscopy application. We have designed and manufactured the control instrumentation of the ultrasonic generation system in a single small instrument (generation of electrical pulses and voltage control). The ultrasonic generation system was characterized, obtaining ultrasonic signals with a bandwidth of 40 MHz, pressures of 264.29 kPa and an optoacoustic conversion efficiency of 2.5x10^-3 Pa/(W/m²).