Abstract

We present a theoretical study of the ambient refractive index sensing characteristics of long period gratings in bare and metal-coated D-shaped fibers. An equivalent rectangular core waveguide method based on the first-order perturbation theory has been used to study the modal behavior of the waveguide. Power coupling corresponding to dual resonance in both cases has been investigated, and an optimum metal thickness giving maximum sensitivity has been found to exist. The study shows that the dual resonances can be shifted to lower wavelengths by increasing (decreasing) the metal thickness (core to flat surface separation). Further, an optimum combination of metal thickness and core to flat surface separation, corresponding to maximum sensitivity, has been presented for different cladding modes and their relative performance has been discussed. It has been shown theoretically that detection of refractive index changes as small as 1.67×10⁻⁷ RIU in the ambient region is possible using the optimized parameters. The study should find application in realizing highly sensitive biochemical sensors.

© 2009 Optical Society of America

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History
Original Manuscript: April 2, 2009
Manuscript Accepted: July 31, 2009
Revised Manuscript: July 28, 2009
Published: August 20, 2009

References

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Author Affiliations

Saurabh Mani Tripathi, Arun Kumar

Indian Institute of Technology Delhi

Emmanuel Marin, Jean-Pierre Meunier

Université de Saint-Etienne

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