Multispectral Laser‐Scanning Photoacoustic Microscopy With SRS ‐Generated Wavelengths for Skin Chromophore Characterization

ABSTRACT We present a single pump‐source, multispectral laser‐scanning photoacoustic microscopy (MS‐LS‐PAM) platform that integrates stimulated Raman scattering (SRS)‐based wavelength generation for high‐resolution, label‐free skin imaging. The system uses a compact, fiber‐based light source to produce tunable excitation wavelengths from 532 to 571 nm, enabling precise spectral discrimination of key endogenous chromophores, oxyhemoglobin (HbO 2 ), deoxyhemoglobin (Hb), melanin, and collagen, without external contrast agents. Spectral unmixing is performed using non‐negative least squares (NNLS), facilitating quantitative analysis of chromophore distributions. In vivo experiments on B6 (pigmented) and SKH1 hairless (melanin deficient) mice demonstrated accurate chromophore separation, spatially resolved oxygen saturation (sO 2 ) mapping, and clear visualization of collagen and melanin architectures.