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Proceedings Paper • Open Access

Grism manufacturing by low temperature mineral bonding
Author(s): G. Kalkowski; K. Grabowski; G. Harnisch; T. Flügel-Paul; U. Zeitner; S. Risse

Paper Abstract

By uniting a grating with a prism to a GRISM compound, the optical characteristics of diffractive and refractive elements can be favorably combined to achieve outstanding spectral resolution features. Ruling the grating structure into the prism surface is common for wavelengths around 1 μm and beyond, while adhesive bonding of two separate parts is generally used for shorter wavelengths and finer structures. We report on a manufacturing approach for joining the corresponding glass elements by the technology of hydrophilic direct bonding. This allows to manufacture the individual parts separately and subsequently combine them quasimonolithically by generating stiff and durable bonds of vanishing thickness, high strength and excellent transmission. With this approach for GRISM bonding, standard direct-write- or mask-lithography equipment may be used for the fabrication of the grating structure and the drawbacks of adhesive bonding (thermal mismatch, creep, aging) are avoided. The technology of hydrophilic bonding originates from “classical” optical contacting [1], but has been much improved and perfected during the last decades in the context of 3-dimensinal stacking Si-wafers for microelectronic applications [2]. It provides joins through covalent bonds of the Si-O-Si type at the nanometer scale, i.e. the elementary bond type in many minerals and glasses. The mineral nature of the bond is perfectly adapted to most optical materials and the extremely thin bonding layers generated with this technology are well suited for transmission optics. Creeping under mechanical load, as commonly observed with adhesive bonding, is not an issue. With respect to diffusion bonding, which operates at rather high temperatures close to the glass transition or crystal melting point, hydrophilic bonding is a low temperature process that needs only moderate heating. This facilitates provision of handling and alignment means for the individual parts during the set-up stages and greatly eases joining optical materials of different thermal expansion. The technology has been successfully used in the past for bonding various glasses as well as crystalline optical materials [3, 4]. Here we will focus on bonding prisms elements and binary gratings of fused silica with and without coatings at the bonding interface. Further, preliminary results on bonding prism-grating-prism (PGP) combinations will be presented.

Paper Details

Date Published: 25 September 2017
PDF: 7 pages
Proc. SPIE 10562, International Conference on Space Optics — ICSO 2016, 1056204 (25 September 2017); doi: 10.1117/12.2296039
Show Author Affiliations
G. Kalkowski, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
K. Grabowski, Fraunhofer Institut für Angewandte Optik und Feinmechanik (Germany)
G. Harnisch, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
T. Flügel-Paul, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
U. Zeitner, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
S. Risse, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)


Published in SPIE Proceedings Vol. 10562:
International Conference on Space Optics — ICSO 2016
Bruno Cugny; Nikos Karafolas; Zoran Sodnik, Editor(s)

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