Tight focus of light using micropolarizer and microlens
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Using a binary microlens of diameter 14 μm and focal length 532 nm (NA = 0.997) in resist, we focus a 633 nm laser beam into a near-circular focal spot with dimensions (0.35 ± 0.02)λ and (0.38 ± 0.02)λ (λ is incident wavelength) at full width half-maximum intensity. The area of the focal spot is 0.105λ2. The incident light is a mixture of linearly and radially polarized beams generated by reflecting a linearly polarized Gaussian beam at a 100 μm 100 μm four-sector subwavelength diffractive optical microelement with a gold coating. The focusing of a linearly polarized laser beam (the other conditions being the same) is found to produce an elliptical focal spot measuring (0.40 ± 0.02)λ and (0.50 ± 0.02)λ. To our knowledge, this is the first implementation of subwavelength focusing of light using a pair of micro-optic elements (a binary microlens and a micropolarizer).
Stafeev , S S , O'Faolain , L , Kotlyar , V V & Nalimov , A G 2015 , ' Tight focus of light using micropolarizer and microlens ' Applied Optics , vol 54 , no. 14 , pp. 4388-4394 . DOI: 10.1364/AO.54.004388
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Funding: European Research Council (ERC) (337508); Ministry of Education and Science of the Russian Federation (MK-4816.2014.2, NSh-3970.2014.9); Russian Foundation for Basic Research (14-07-31092, 14-07-97039, 14-29-07133, 15-07-01174).
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