1 February 1994 Diffractive microlenses with antireflection coatings fabricated by thin film deposition
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Optical Engineering, 33(2), (1994). doi:10.1117/12.153180
Abstract
Two-dimensional arrays of Fresnel zone microlenses were fabricated and coated with antireflection layers by an ion beam sputter deposition technique. The reflection of these lenses was analyzed on the basis of an angular spectrum approach for different substrate materials. A minimum reflectivity as low as 2 x 10-4 was realized by means of in situ controlled multilayers of TiO2 and SiO2. The lenses have a circular aperture of 2 mm and different focal lengths for the wavelengths of 1.52 and 0.63 μm, respectively. The kinoform profile in each zone of the Fresnel zone lenses was approximated by an eight-level profile. Such stepped profiles were realized with several masks written with an electron beam and transferred by photolithographic technology. Our measurements reveal that the spot sizes of the fabricated microlenses are close to the diffraction-limited values, and the highest measured diffraction efficiencies for the eight-level structures are greater than 80%.
Edgar Pawlowski, Herbert Engel, Margit Ferstl, Walther Fuerst, Berndt Kuhlow, "Diffractive microlenses with antireflection coatings fabricated by thin film deposition," Optical Engineering 33(2), (1 February 1994). http://dx.doi.org/10.1117/12.153180
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KEYWORDS
Lenses

Antireflective coatings

Reflection

Microlens

Refractive index

Silicon

Diffraction

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