Two-layer waveguiding structure in LiNbO/sub 3/ with birefringence reversal for refractive-index sensors with large measurement range

A two-layer structure in LiNbO/sub 3/ fabricated by Ti-indiffusion and proton exchange has been developed and studied. This structure is especially suitable for constructing refractive-index sensors with a large measurement range. Besides its high sensitivity this structure offers some additional advantages, including the possibility of optimizing the sensitivity for a given measurand and the elimination of the necessity for buffer layers. The largely different sensitivities of the fundamental TE/sub 0/- and TM/sub 0/-modes achieved allows the measurement and the reference channel to be incorporated in the same waveguide. This allows a new type of polarization interferometry that increases the flexibility of the refractive-index sensor design.<
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