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Periodic silicon nanostructures for spectroscopic microsensors

 
: Wehrspohn, R.; Gesemann, B.; Pergande, D.; Geppert, T.; Schweizer, S.; Moretton, S.; Lambrecht, A.

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Subramania, G.S. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Active photonic materials IV : 22 - 25 August 2011, San Diego, California, United States; Part of SPIE optics + photonics
Bellingham, WA: SPIE, 2011 (Proceedings of SPIE 8095)
ISBN: 978-0-8194-8705-6
Paper 809508
Active Photonic Materials Conference <4, 2011, San Diego/Calif.>
Englisch
Konferenzbeitrag
Fraunhofer IPM ()
Fraunhofer IWM ()
silicon; photonic crystals; gas sensing; infrared; ion mobility microspectrometer

Abstract
Periodic silicon nanostructures can be used for different kinds of gas sensors depending on the analyte concentration. First we present an optical gas sensor based on the classical non-dispersive infrared technique for ppm-concentration using ultra-compact photonic crystal gas cells. It is conceptually based on low group velocities inside a photonic crystal gas cell and anti-reflection layers coupling light into the device. Experimentally, an enhancement of the CO2 infrared absorption by a factor of 2.6 to 3.5 as compared to an empty cell, due to slow light inside a 2D silicon photonic crystal gas cell, was observed; this is in excellent agreement with numerical simulations. In addition we report on silicon nanotip arrays, suitable for gas ionization in ion mobility microspectrometers (mic ro-IMS) having detection ranges in principle down to the ppt-range. Such instruments allow the detection of explosives, chemical warfare agents, and illicit drugs, e.g., at airports. We describe the fabrication process of large-scale-ordered nanotips with different tip shapes. Both silicon microstructures have been fabricated by photoelectrochemical etching of silicon.

: http://publica.fraunhofer.de/dokumente/N-185767.html