Near-Infrared photoacoustic microscopy of lipids based on a nanosecond SRS fiber amplifier

Near-Infrared Photoacoustic Microscopy (NIR-PAM) has a unique potential to label-free image lipids with high-resolution, -sensitivity, and -speed, which constitute essential biohallmarks to investigate biological functionalities and pathophysiological processes. To empower NIR-PAM for accessing the intrinsic vibrational absorption of lipids, we demonstrate a novel stimulated Raman scattering (SRS) fiber amplifier that delivers optical excitation at ~1200 nm, >200 kHz repetition rates, <2 ns pulse durations, and 5 µJ pulse energies. We apply NIR-PAM to resolve intrinsic lipid contrast in biomedical specimens ranging from single-cells to lipid-rich tissue with subcellular resolution.