Integriert-optischer Sensor

An on-chip optical sensor for the detection of refractive index changes has a substrate body made of lithium niobate in which a monomode birefringent waveguide is provided along the X or Y kerf axis of the sliced lithium niobate crystal. Said crystal stretches between two end faces of the substrate body and along its surface, whereby a lateral boundary surface of the waveguide is brought into contact with a measuring fluid. Laser radiation is applied to a coupling surface and a light detector is applied with the measuring signal received by reflection or transmission from a corresponding coupling surface. The impinging laser radiation is linear polarized by a first polarizer twisted in the plane of the end face by a predefined angle, preferably by 45 degrees, in relation to the Z axis, and the emerging laser radiation applied to the coupling surface is linear polarized by a second polarizer twisted in the plane of the end face also by a predefined angle, preferably by 55 degrees, in re lation to the Z axis. The TE mode and TM mode propagating in the waveguide change their phase positions relative to each other as a result of a change in the refractive index of the measuring fluid.