Fig. 5: Multispectral Raster Scanning Optoacoustic Mesoscopy system using four laser diodes.

a The schematic of the system developed showing the electrical and optical connections of the different parts of the system. b The laser diode illumination system. Each laser diode is attached to a separate laser diode driver and focused into a multimode fiber with a 2-lens system. The four laser diodes are coupled in a 4 × 4 fiber power combiner and each output of the combiner has ~25% of the power of each input, combining all the wavelengths. c The scanning head of the RSOM system consisting of the x–y scanning stages (i), the 3D printed holder (ii), the Ultrasound Transducer (iii) and the four output fibers of the fiber power combiner (iv) arranged in a circular pattern around the UST. Image components adapted with permission from the copyright holders; the optomechanical components in b are retrieved from Thorlabs Inc. and the scanning stages (U-723 XY) in c from Physik Instrumente GmbH (https://www.physikinstrumente.com/en/products/xy-stages/u-723-piline-xy-stage-1000583/#downloads).