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Proceedings Paper

Comparison of fabrication methods for microstructured deep UV multimode waveguides based on fused silica
Author(s): Philipp Elmlinger; Martin Schreivogel; Marc Schmid; Myriam Kaiser; Roman Priester; Patrick Sonström; Michael Kneissl
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Paper Abstract

The suitability of materials for deep ultraviolet (DUV) waveguides concerning transmittance, fabrication, and coupling properties is investigated and a fused silica core/ambient air cladding waveguide system is presented. This high refractive index contrast system has far better coupling efficiency especially for divergent light sources like LEDs and also a significantly smaller critical bending radius compared to conventional waveguide systems, as simulated by ray-tracing simulations. For the fabrication of 300-ffm-thick multimode waveguides a hydrouoric (HF) acid based wet etch process is compared to selective laser etching (SLE). In order to fabricate thick waveguides out of 300-ffm-thick silica wafers by HF etching, two masking materials, LPCVD silicon nitride and LPCVD poly silicon, are investigated. Due to thermal stress, the silicon nitride deposited wafers show cracks and even break. Using poly silicon as a masking material, no cracks are observed and deep etching in 50 wt% HF acid up to 180 min is performed. While the masked and unmasked silica surface is almost unchanged in terms of roughness, notching defects occur at the remaining polysilicon edge leading to jagged sidewalls. Using SLE, waveguides with high contour accuracy are fabricated and the DUV guiding properties are successfully demonstrated with propagation losses between 0.6 and 0:8 dB=mm. These values are currently limited by sidewall scattering losses.

Paper Details

Date Published: 27 April 2016
PDF: 12 pages
Proc. SPIE 9888, Micro-Optics 2016, 98880A (27 April 2016); doi: 10.1117/12.2227518
Show Author Affiliations
Philipp Elmlinger, Robert Bosch GmbH (Germany)
Martin Schreivogel, Robert Bosch GmbH (Germany)
Marc Schmid, Robert Bosch GmbH (Germany)
Myriam Kaiser, TRUMPF Laser- und Systemtechnik GmbH (Germany)
Roman Priester, TRUMPF Laser- und Systemtechnik GmbH (Germany)
Patrick Sonström, Robert Bosch GmbH (Germany)
Michael Kneissl, Technische Univ. Berlin (Germany)

Published in SPIE Proceedings Vol. 9888:
Micro-Optics 2016
Hugo Thienpont; Jürgen Mohr; Hans Zappe; Hirochika Nakajima, Editor(s)

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