Berlin 2005 – wissenschaftliches Programm

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DF: Dielektrische Festkörper

DF 10: Elektrische, elektromechanische und optische Eigenschaften

DF 10.11: Vortrag

Dienstag, 8. März 2005, 17:50–18:10, TU EMH225

Integrated optical sensors based on photorefractive LiNbO₃ channel waveguides — •Christian E. Rüter, Florian Werunsky, and Detlef Kip — Clausthal University of Technology, Institute of Physics and Physical Technologies, Leibnizstr. 4, 38678 Clausthal-Zellerfeld

We present results of simulations and preliminary measurements of an integrated interferometric optical sensor based on singlemode LiNbO₃:Ti:Fe channel waveguides. The sensor is designed to work in the near infrared wavelength region around λ = 1.55 µm. The evanescent field of the guided mode senses changes in the refractive index of the layer covering the waveguide. This changes the effective refractive index of the guided mode which alters the transfer function of the interferometer in dependence of the light wavelength. Phase change of the interferometer can be compensated by applying an electric field and utilizing the electro-optic effect. Thus the applied field is the measurement signal of the sensor. Covering the waveguide with a thin layer of higher refractive index than the refractive index of the waveguide region (e.g. TiO₂) leads to an increase of the evanescent field and therefore to higher sensitivity. In combination with an additional functional layer that is sensitive only to, e.g., specific molecules a highly sensitive sensor with a resolution in the ppb range may be realized.