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Diffractive optical elements based on subwavelength high-contrast gratings

: Kroker, Stefanie; Käsebier, Thomas; Weber, Thomas; Steiner, Stefan; Fuchs, Frank; Kley, Ernst-Bernhard; Tünnermann, Andreas


Chang-Hasnain, C.J. (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
High Contrast Metastructures : San Francisco, California, USA, January 2012
Bellingham, WA: SPIE, 2012 (Proceedings of SPIE 8270)
ISBN: 978-0-8194-8913-5
Paper 82700P
Conference "High Contrast Metastructures" <2012, San Francisco/Calif.>
Conference Paper
Fraunhofer IOF ()
high-contrast gratings; diffraction grating; broadband reflectors

We report on novel concepts for reflective diffractive elements based on high-contrast gratings. To demonstrate the possibilities for such devices reflective cavity couplers with three output ports are investigated. A diffracting period is superposed to a highly reflective subwavelength grating in order to realize diffractive elements. This superposition can be realized with a periodic depth, fill factor or period modulation of the reflector. Further, to limit the total transmission of the device it is necessary to enhance its angular tolerance. We discuss different approaches in order to realize this increased reflectivity in broad range of the angular spectrum. The contribution focuses on the material combination silicon-silica, but the presented concepts also hold for other material combinations with large index contrast and even for monolithic silicon structures.