A simple integrated Young interferometer sensor was prepared on a glass substrate with a pair of single-mode straight channel waveguides apart. A tapered thin film of was locally deposited on one channel to form a composite waveguide sensing arm with a greatly enhanced evanescent field. With the prism-coupling method a single beam of laser light was simultaneously launched into the two channels to yield a high-contrast interference pattern. Refractive-index sensitivity of the interferometer and its response to protein adsorption were investigated by using a slit-photodetector assembly to interrogate the sensor signal. The factors affecting the fringe contrast were analyzed.
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