OCT-guided wavefront shaping for non-invasive depth-selective focusing

Imaging in turbid media remains a challenge in modern optics due to strong scattering of light. In recent studies wavefront shaping techniques were shown to be capable of creating a focal spot deep inside of a turbid sample, which subsequently can be used for imaging. By iteratively optimizing the optical wavefront incident at the sample, the light’s intensity at a spatially confined target is maximized and a focal spot arises at this position. We demonstrate the implementation of wavefront shaping in spectral domain optical coherence tomography (SD-OCT). OCT allows, due to the combination of confocal- and coherence gating, for selective detection of light backscattered from a confined volume inside of the medium. While in typical OCT applications this capability is exploited for 3D-imaging of the sample, we use the approach to provide a feedback signal for the wavefront optimization algorithm. We investigate OCT signal increase by means of wavefront shaping and, thus, focusing of light to the OCT detection volume. This approach opens up the way for depth-selective focusing of light inside arbitrary turbid media as well as for new ways of OCT contrast enhancement and imaging.