Laser Diode Beam Shaping and Homogenization with a Multimode Fiber applied to Optical Resolution Photoacoustic Microscopy based on Linear Phased Array Ultrasound Probe

Pulsed Laser diodes stacks (PLD) are a promising low cost option as laser sources for Optical Resolution Photo acoustic Microscopes (ORPAM). Nevertheless, their multimode beams with wide divergences and non-uniform light distributions, imposes limitations to the lateral resolution that can be achieved at a long laser focusing distance needed for clinical applications. Here, it is devised a new strategy to attain high lateral resolutions at a centimeter-long working distance, based on coupling the PLD power into a square core multimode optical fiber. An ORPAM system with an ultrasound linear phased-array in reflection confocal mode was built to test its performance.