Continuous wave laser diodes enable fast optoacoustic imaging

Abstract

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.

Sensitivity Enhanced Photoacoustic Imaging Using a High-Frequency PZT Transducer with an Integrated Front-End Amplifier

“…It is possible to further improve the imaging depth by increasing the laser energy within the ANSI limits. The size of the transducer used in this work was not comparable to that reported previously [12,15,16], which also limits the imaging depth range. The axial resolution achieved in this work was 104 µm.…”

“…Different from the conventional pulse-echo based US imaging, PA imaging is typically performed by illuminating the target with a nanosecond laser pulse and then detecting the ultrasonic signals using a mechanically scanned single-element ultrasonic transducer or an array probe [6][7][8]. PA imaging has been demonstrated to be capable of high resolution structural imaging such as mapping of subcutaneous micro-vessels [9][10][11][12][13], anatomic features discrimination [14][15][16], and detection of atherosclerotic plaques based on the lipid-specific contrast [17][18][19]. Meanwhile, PA imaging also shows the potential for physiological information measurements such as hemoglobin oxygen saturation (sO2) [20][21][22], metabolic oxygen rate [23], and tissue temperature distribution [24][25][26].…”

Design of photoacoustic microscope system based on labVIEW platform

“…It combines the advantages of high contrast of pure optical imaging and high penetration depth of pure blood imaging [9][10]. As one of the important branches of photoacoustic imaging, photoacoustic microscopy also has the above advantages, which can realize the imaging image of millimeter-scale detection depth and micron-level imaging accuracy [11][12][13], but the existing photoacoustic microscopy system usually uses volume. A large solid-state laser or an OPO laser is used as an excitation source for the system and is constrained in practical applications [13][14][15].…”

A cost-efficient open source laser engine for microscopy

“…As a substitute for scientific-grade lasers, inexpensive laser diodes can deliver comparable laser power at a fraction of the cost (<100 euros/dollars). Such laser diodes have already been successfully used for low cost illumination in photoacoustic microscopy [6][7][8][9], pump-probe microscopy [10], stimulated emission-depletion (STED) microscopy [11] and SMLM [12]. Due to their high divergence and asymmetrical intensity profile, they are challenging to couple into single-mode optical fibers with a decent efficiency.…”