The combined use of a wavefront modulator and a scattering medium forms an "opaque lens" which forces the light to focus tightly. The adaptive focus has the same shape as the correlation function of the original speckle pattern and it can be generated at defined positions with resolution up to hundreds of nanometers. We have demonstrated that manipulating the speckle pattern spatial components can structure the shape of the focus. Exploiting selectively spatial-frequencies from the speckle components we realized opaque lenses able to produce sub-correlation foci and Bessel beams.
Diego Di Battista, Daniele Ancora, Haisu Zhang, Krystalia Lemonaki, Stella Avtzi, Stelios Tzortzakis, Marco Leonetti, and Giannis Zacharakis, "Structured adaptive focusing through scattering media," Proc. SPIE 9717, Adaptive Optics and Wavefront Control for Biological Systems II, 971719 (Presented at SPIE BiOS: February 15, 2016; Published: 15 March 2016); https://doi.org/10.1117/12.2211594.
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