Abstract

The cladding mode reorganization in high refractive-index (HRI)-coated long period gratings (LPGs) is theoretically analyzed and experimentally observed with the aim of exploring the sensitivity of the resonance wavelength to the change of the refractive index in a nanoscale overlay. Experimental results show that the transition between cladding modes and overlay modes occurs when the refractive index of the liquid crystal (LC) overlay is changed from 1.477 to 1.515 by increasing its temperature from $20°\mathrm{C}$ to $65°\mathrm{C}$. The spectral tuning ability of LPGs coated with a HRI LC layer by electro-optic modulation on a LC layer is also demonstrated, and the maximum tuning range can reach approximately $10\mathrm{nm}$ by choosing a highly sensitive operating point in the transition region.

© 2009 Optical Society of America

Mode transition in high refractive index coated long period gratings

A. Cusano, A. Iadicicco, P. Pilla, L. Contessa, S. Campopiano, A. Cutolo, and M. Giordano
Opt. Express 14(1) 19-34 (2006)

Long period grating working in transition mode as promising technological platform for label-free biosensing

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Transition mode long period grating biosensor with functional multilayer coatings

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Long-period grating refractive index sensor with a modified cladding structure for large operational range and high sensitivity

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