Focusing light through turbid media by binary amplitude modulation

Materials such as white paint, paper, milk, tissue appear opaque because they strongly scatter the incident light. It is impossible to focus light through such turbid media using conventional optics. However, it has been shown that it is possible to focus light through or inside such materials using a feedback based algorithm that spatially modifies the phase of the wavefront. When the incident wavefront is optimized in order to match the configuration of the sample a bright spot is created in the desired position [1,2]. Optical phase conjugation based methods have also been successfully utilized for the purpose of focusing light through turbid media [3-5]. Spatial phase modulation of the incident wave is central for all of these experiments. The slow response time of spatial phase modulators is a major obstacle to the in vivo use of these methods.