Holographic phase conjugation is used to focus light onto sub-wavelength holes in a gold film directly on top of a photorefractive lithium niobate crystal. This could lead to a high-numerical-aperture-focusing system.
© 2008 Optical Society of America
F. Kalkum, S. Broch, and K. Buse, "Volume Holographic Phase Conjugation through a Sub-Wavelength Hole," in Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies, OSA Technical Digest (CD) (Optical Society of America, 2008), paper JThA121.
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