Hybrid nonlinear photoacoustic and reflectance confocal microscopy for label-free subcellular imaging with a single light source.

Nonlinear photoacoustic microscopy is capable of achieving subcellular optically resolved absorption contrast in three dimensions but cannot provide structural context for the acquired images. We have developed a dual-modality imaging system that combines the optical absorption contrast of a nonlinear photoacoustic microscope with the optical scattering contrast of a reflectance confocal microscope. By integrating the confocal detection optics into the optical setup of the nonlinear photoacoustic microscope, the two systems were co-registered and may be acquired at the same time and with the same light source. Simultaneous images of fixed erythrocytes and fibroblasts were measured to demonstrate the complementary information that is provided by the two modalities.