We demonstrate a novel technique for in situ 3D spatial light patterning using ultrasound. By employing a customdesigned ultrasonic phased array, we form standing pressure waves that modulate the refractive index of the target medium in which light patterns are to be formed. Ultrasound pressure waves change the density of the medium locally and as a result, the refractive index is changed. Therefore, the phase front of the traveling optical waves in the medium is modulated. The interaction of light and ultrasound through the medium can be designed such that a collimated beam of light is gradually focused to multiple points deep into the medium to form arbitrary patterns of light illumination, as well as multipoint parallel imaging. These patterns can be reconfigured by changing the ultrasound interference patterns by controlling the frequency and phase of the ultrasound array elements. In this work, we demonstrate experimentally that this technique can be used to perform multi-point imaging in turbid media.
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