Real-time wavefront shaping through scattering media by all-optical feedback

Controlling light through dynamically varying heterogeneous media is a sought-after goal with important applications ranging from free-space communication to nanosurgery. The underlying challenge is to control a large number of degrees of freedom of the optical wavefront, at timescales shorter than the medium dynamics. Many advances have been reported recently following the demonstration of focusing through turbid samples by wavefront shaping, where spatial light modulators with more than 1,000 degrees of freedom were used. Unfortunately, spatial light modulator-based wavefront shaping requires feedback from a detector or camera and is currently limited to slowly varying samples. Here, we demonstrate a novel approach for wavefront shaping utilizing all-optical feedback. We show that the complex wavefront required to focus light scattered by turbid samples (including thin biological tissues) can be generated at submicrosecond timescales by the process of field self-organization inside a multimode laser cavity, without requiring electronic feedback, spatial light modulators or phase-conjugation crystals. The self-organization of many laser modes in phase and frequency realized by minimizing radiation losses in a cavity enables the complex wavefront required to focus light scattered by turbid samples to be generated on sub-microsecond timescales without employing electronic feedback, spatial light modulators or phase-conjugation crystals.