Integrated optical sensor for refractive index measurement esp. of liq. - has Mach-Zehnder interferometer formed from two arms of optical waveguide, and acousto=optical mode converter with continuously variable frequency

摘要

The integrated optical sensor determines the absolute index of refraction of a substance, esp. a liq., with a substrate body of lithium niobate. A single mode doubly refracting optical wave conductor is provided which extends along its surface between the two endfaces (7,10) of the substrate body (2). At a part of its length it is split into two arms of equal length. One arm on part of its length has a layer (19) of proton exchanged lithium niobate, insufficient for leading to a mode, and across a specified length makes optical contact with the substance, and these arms form a Mach Zehnder interferometer. The inlet face of the wave conductor is radiated with polarised light from a light source, and a light detector is acted upon with the measurement light radiated from the outlet endface of the wave conductor. The part of the optical wave conductor (6) split into the two arms (8,9) forming the Mach Zehnder interferometer is placed in the region (4) facing the outlet endface (10) of the surface of the substrate body (2). An acoustic-optical TM/TE mode converter (13) is integrated in the interferometer w.r.t. the transmission direction of the light, in a region (3) of the surface of the substrate body (2) connected to the inlet endface (7). The acoustic frequency of the TM/TE mode converter (13) is continuously alterable in a specified range. USE/ADVANTAGE - Integrated optical sensor allows determn. of absolute index of refraction of substances esp. of liquids with greater accuracy. Dispersion can be detected with help of this sensor.