FOCUSING COHERENT Light PIONEERING EXPERIMENT
Faster modulation methods using, among others, micromechanics and photonic integrated circuits [ 11 ], have now reached a pixel rate that is a full million times faster than our first experiment. Another route to very high-speed wavefront shaping is the use of( digital) optical phase conjugation, or by using a-priori information about the sample to reduce the number of required measurements. These developments have made wavefront shaping in dynamic materials – once inconceivable – a reality. Wavefront shaping experiments require only some standard optics and a spatial light modulator or digital micromirror device, of which low-cost varieties have become available. Hence the equipment is within reach of undergraduate labs worldwide and the experiment has been replicated by many students, often sparking their interest in working with scattered light [ 12 ].
Conclusion
The first demonstration of focusing through scattering materials sparked the enthusiasm of an open scientific community. It helped convince people that light scattering can be a resource instead of an obstacle, inspired sophisticated theoretical advances and enabled increasingly powerful new methods to be developed, such as measurements of the transmission and reflection matrices. Thanks to scientific and technological developments in many labs worldwide, applications in tissue microscopy, quantum optics, computing and semiconductor metrology have been realized. Finally, perhaps the deepest insight into the meaning of the paper was reflected to us by the late professor Yaron Silberberg: because a high enhancement can be reached already with incomplete and imperfect wavefronts, you do not need to be perfect to make a difference.
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