Pulsed laser diodes may offer a smaller, less expensive alternative to conventional optoacoustic laser sources; however they do not provide pulse rates faster than a few tens of kHz and emit at wavelengths only within the near-infrared region. We investigated whether continuous wave (CW) laser diodes, which are available in visible and near-infrared regions, can be good optoacoustic light sources when overdriven with a peak current >40-fold higher than the CW absolute maximum. We found that overdriven CW diodes provided ∼10 ns pulses of ∼200 nJ/pulse and repetition rates higher than 600 kHz without being damaged, outperforming many pulsed laser diodes. Using this system, we obtained images of phantoms and mouse ear and human arm in vivo, confirming their use in optoacoustic imaging and sensing.
Keywords: CNR, contrast to background ration; COD, catastrophic optical damage; CW, continuous wave; Current drivers; DAQ, data acquisition card; FWHM, full width at half maximum; Light sources; Light-emitting diodes; MIP, maximum intensity projection; NIR, near-infrared; Near-infrared; OPO, optical parametric oscillator; PLD, pulsed laser diode; Photoacoustic; SNR, signal-to-noise ratio; TTL, transistor-transistor-logic; UST, ultrasound transducer; VIS, visible; Visible.