We present simultaneous photoacoustic and fluorescence microscopy using a modulated laser diode. Photoacoustic waves and modulated fluorescence are generated by using a laser diode with a wavelength of 405nm at modulation frequencies in the Megahertz range. Additionally, a continuous wave offset radiation can be superposed. The excitation light is focused to the sample using a high NA objective. Luminescence is collected by the same objective in a confocal configuration and measured by an avalanche photo diode. Photoacoustic waves are recorded on the opposite site of the sample using a hydrophone. Acoustic and luminescence signals are recorded using a lock-in technique. We present photoacoustic imaging on red blood cells and multimodal imaging on fluorescent microspheres. Nonlinear photoacoustic and luminescence effects were introduced with the help of a superposed continuous wave laser.

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G. Langer and T. Berer, "Non-linear photoacoustic and fluorescence microscopy using a modulated laser diode," Proc. SPIE 9708, Photons Plus Ultrasound: Imaging and Sensing 2016, 97082K (Presented at SPIE BiOS: February 17, 2016; Published: 15 March 2016); https://doi.org/10.1117/12.2213027.