Nonlinear photoacoustic waves for light guiding to deep tissue sites.

Light scattering by tissues limits performance in biological sensing or stimulation. Here we present a photoacoustic technique that increases light transmittance by one order of magnitude and enables light localization in deep tissue. Laser-induced nonlinear acoustic waves are utilized to produce a high refractive index contrast in scattering medium without high-intensity pressure. The size of guiding area is around 60 μm, which is equivalent or smaller than the diameter of multimode fibers. To show potential use in biomedical fields, we performed light guiding and imaging of fluorescence, through swine tissues with thickness more than 1 mm.