5 January 1993 Synthetic phase holograms written by laser lithography
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Proceedings Volume 1718, Workshop on Digital Holography; (1993); doi: 10.1117/12.138557
Event: Workshop on Digital Holography, 1992, Prague, Czech Republic
Abstract
Computer generated holograms (CGH) consist of patterns which have been calculated numerically starting from the desired function of the optical component and the known physical laws of diffraction. The real fabrication of such holograms poses two different tasks. First the computed pattern has to be converted into one mask or a set of masks. Thereby submicron resolution is required for CGHs that are to be used for visible light. This means that one has to use microlithographic techniques such as electron-beam or laser lithography. The second task is to achieve the necessary groove depth and profile. Wet etching techniques have been quite common for this purpose but they have two disadvantages: it is difficult to obtain a precise etch stop particularly with very fine structures due to capillary effects and mostly one is constrained to certain crystallographic orientations. This makes it hardly possible to achieve directional anisotropic etching in glass. Dry etching techniques overcome both of these problems. The foundry for micro-optical elements in Erlangen makes use of laser lithography and reactive-ion etching. Both technologies are discussed in some detail. The scope of computer generated holograms ranges from the well known Dammann-gratings, gratings which produce arrays of light spots of equal intensity, to very complex two- dimensional structures for example for the correction of aberrations or for three-dimensional displays. In his paper we also describe some results with the production of microlenses that can be realized using our technologies.
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Stefan Haselbeck, M. Heissmeier, Walter P. Hofmann, Ulrich W. Krackhardt, Bernd Manzke, Pekka Savander, M. Schrader, Johannes Schwider, Martin Sperl, Norbert Streibl, "Synthetic phase holograms written by laser lithography", Proc. SPIE 1718, Workshop on Digital Holography, (5 January 1993); doi: 10.1117/12.138557; https://doi.org/10.1117/12.138557
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