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30 April 1993 Refractive-index sensors based on coupling to high-index multimode overlays
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The evanescent coupling between a side polished fiber and a high index multi-mode slab waveguide produces resonances in the wavelength response of the device. The position of these resonances is sensitive to the thickness/index of the superstrate layer. This structure could then provide either film growth monitors or refractive index sensors. The sensitivity of the device is dependent upon the parameters of the slab waveguide and we present here both theoretical and experimental results for a selection of slab indices and thicknesses. The device is capable of detecting index changes of < 4 X 10-5 and with the use of an active material, such as lithium niobate, in the role of the overlay it offers the potential for a closed loop sensor.
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
David G. Moodie, Walter Johnstone, Graham Thursby, and Kevin J. McCallion "Refractive-index sensors based on coupling to high-index multimode overlays", Proc. SPIE 1796, Chemical, Biochemical, and Environmental Fiber Sensors IV, (30 April 1993);

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