FOCUSING COHERENT Light PIONEERING EXPERIMENT ensemble-averaged intensity before wavefront shaping. Timewise, it was feasible to measure the phase of a few thousand individual pixel groups, leading to an enhancement of intensity by three orders of magnitude. The experimentally achieved enhancement versus the number of pixel groups, shown in Fig. 3, showed good agreement with this simple formula. Since the model does not depend on properties of the sample, other than that it should be scattering the light randomly, wavefront shaping can focus light through a large variety of materials, illustrated in Fig. 4: titanium dioxide pigment( white paint), eggshells, human teeth, flowers and food items. All were able to focus light, however some of the materials decorrelated or moved before a very bright focus was reached, so that the highest enhancements were only reached for solid materials.
Applications and developments
After the paper appeared, there was an overwhelming interest in our work. It captures the imagination that one can use any turbid object to focus light: an‘ opaque lens’
Figure 3. Measured intensity enhancement vs the number of segments. Squares, sample in focus; triangles, sample 100 μm behind focus; solid curve, theory( ideal); dotted curve: theory( finite decorrelation time). Reprinted with permission from [ 1 ] © Optical Society of America.
as Phillip Schewe put it in Physics Today. Many applications seemed to be just around the corner. However, practical applications were blocked by three seemingly insurmountable barriers. First, our method was about a million times too slow. Our SLM could process only about
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