Berlin 2005 – scientific programme
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HL: Halbleiterphysik
HL 37: Photonische Kristalle I
HL 37.5: Talk
Monday, March 7, 2005, 11:00–11:15, TU P270
Photonic Crystal Based Spectroscopic Gas Sensors — •Torsten M. Geppert1,2, Daniel Pergande2, Andreas v. Rhein2, Stefan L. Schweizer2, Ralf B. Wehrspohn2 und Armin Lambrecht3 — 1Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle — 2Universität Paderborn, Dept. Physik, Warburgerstr. 100, D-33098 Paderborn — 3Fraunhofer-Institut für Physikalische Messtechnik, Heidenhofstr. 8, D-79110 Freiburg
Gas sensors are important for a broad range of technical fields. Among other types, spectroscopic gas sensors are a very general approach, applicable for the detection of a variety of different gases due to their high selectivity to specific absorption lines for each gas. A drawback of such systems is their relatively large size caused by the necessary size of the interaction volume of the dilute gas medium and the light. The use of 2D photonic crystals (PhCs), e.g. made of macroporous silicon, allows a dramatic decrease in size of of the interaction volume by exploitation of certain features of the PhC bandstructure such as a very low group velocity vg. However, a low vg leads to high reflection at the PhC interface, resulting in low transmission and therefore an unfavorable signal-to-noise-ratio. Investigations of different strategies to improve the transmission led to the development of a novel taper concept, the so-called Anti-Reflection-Layer. Its working principle is different from classical anti-reflection-coatings and based on mode-matching of the incoming plane wave and the Bloch-modes in the photonic crystal.