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Proceedings Paper

Fresnel lenses: study and fabrication in silicon technology for medium-IR applications
Author(s): Jordi Fonollosa; Rafael Rubio; Jürgen Hildenbrand; Mauricio Moreno; Santiago Marco; Joaquín Santander; Luis Fonseca; Susanne Hartwig; Jürgen Wöllenstein
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Paper Abstract

Diffractive Fresnel Lenses (FL) were designed, fabricated and tested. The lens aims for increasing the sensitivity of a Non-Dispersive InfraRed (NDIR) silicon based optical gas system, focusing as much radiation as possible onto the detector. The studied wavelengths are 10.6μm and 3.4μm, which are the main absorption lines for ethylene and ethanol respectively. The lens diameter (5mm) and the focal length (4mm) are fixed by the detector package. Those diffractive lenses are compatible with the planar nature of silicon microtechnology. A theoretical study about the global lens efficiency as a function of the technological constrains and the process complexity has been carried out. Using only three photolithographic masks, eight quantization steps can be etched and a theoretical lens efficiency of 95% can be achieved. Once the devices were fabricated, the focal length and the spot size have been measured.

Paper Details

Date Published: 21 April 2006
PDF: 11 pages
Proc. SPIE 6186, MEMS, MOEMS, and Micromachining II, 61860R (21 April 2006); doi: 10.1117/12.662793
Show Author Affiliations
Jordi Fonollosa, Univ. de Barcelona (Spain)
Rafael Rubio, Univ. Autònoma de Barcelona (Spain)
Jürgen Hildenbrand, Fraunhofer Institute Physical Measurement Techniques (Germany)
Mauricio Moreno, Univ. de Barcelona (Spain)
Santiago Marco, Univ. de Barcelona (Spain)
Joaquín Santander, Univ. Autònoma de Barcelona (Spain)
Luis Fonseca, Univ. Autònoma de Barcelona (Spain)
Susanne Hartwig, Fraunhofer Institute Physical Measurement Techniques (Germany)
Jürgen Wöllenstein, Fraunhofer Institute Physical Measurement Techniques (Germany)

Published in SPIE Proceedings Vol. 6186:
MEMS, MOEMS, and Micromachining II
Hakan Ürey; Ayman El-Fatatry, Editor(s)

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