In situ 3D reconfigurable ultrasonically sculpted optical beam paths.

We demonstrate that optical beams can be spatially and temporally shaped in situ by forming 3D reconfigurable interference patterns of ultrasound waves in the medium. In this technique, ultrasonic pressure waves induce a modulated refractive index pattern that shapes the optical beam as it propagates through the medium. Using custom-designed cylindrical ultrasonic arrays, we demonstrate that complex patterns of light can be sculpted in the medium, including dipole and quadrupole shapes. Additionally, through a combination of theory and experiment, we demonstrate that these optical patterns can be scanned in radial and azimuthal directions. Moreover, we show that light can be selectively confined to different extrema of the spatial ultrasound pressure profile by temporally synchronizing lightwave and ultrasound. Finally, we demonstrate that this technique can also be used to define spatial patterns of light in turbid media. The notion of in situ 3D sculpting of optical beam paths using ultrasound interference patterns can find intriguing applications in biological imaging and manipulation, holography, and microscopy.