Collecting back-reflected photons in photoacoustic microscopy.

Since the photoacoustic effect relies only on the absorbed optical energy, the back-reflected photons from samples in optical-resolution photoacoustic microscopy are usually discarded. By employing a 2 x 2 single-mode fiber optical coupler in a laser-scanning optical-resolution photoacoustic microscope for delivering the illuminating laser light and collecting the back reflected photons, a fiber-optic confocal microscope is integrated with the photoacoustic microscope. Thus, simultaneous multimodal imaging can be achieved with a single light source and images from the two modalities are intrinsically registered. Such capabilities are demonstrated in imaging both phantoms and small animals in vivo.