Optofluidic adaptive optics in multi-photon microscopy.

Adaptive optics, in combination with multi-photon techniques, is a powerful approach to image deep into a specimen. Remarkably, virtually all adaptive optics schemes today rely on wavefront modulators that are reflective, diffractive or both. This, however, can pose a severe limitation for applications. Here, we present a fast and robust sensorless adaptive optics scheme adapted for transmissive wavefront modulators. We study our scheme in numerical simulations and in experiments with a novel, optofluidic wavefront shaping device that is transmissive, refractive, polarisation-independent, and broadband. We demonstrate scatter correction of two-photon-excited fluorescence images of microbeads as well as brain cells and benchmark our device against a liquid-crystal spatial light modulator. Our method and technology could open new routes for adaptive optics in scenarios where previously, the restriction to reflective and diffractive devices may have staggered innovation and progress.