Measurement of the enhanced evanescent fields of integrated waveguides for optical near-field sensing

Abstract

The sensitivity of an integrated optical sensing device can be enhanced by coating it with a high refractive index layer, while both incoupled intensity and spatial resolution are maintained. The potential for enhanced sensing is demonstrated using titanium indiffused waveguiding structures in ${\mathrm{LiNbO}}_3$ coated with a ${\mathrm{TiO}}_2$ film. To the best of our knowledge, it could be measured for the first time that the outcoupled intensity at the surface was enhanced by a factor of 12–15 while keeping the penetration depth of the evanescent field constant of the order of only a few tens of nanometers. The evanescent fields of the guided modes were measured and characterized with a scanning near-field optical microscope and are in accordance with the numerical simulations.

© 2008 Optical Society of America

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