Integrated optical Young interferometer.

The integrated optical configuration of a Young interferometer is proposed for refractometry and chemical sensing. We coupled light into an integrated optical Ybranch by fixing a laser diode directly at the input of the optical device. We solved the problem of ambiguity in the interference order by operating the laser diode at currents below threshold, resulting in visibility modulation of the interference fringes caused by the low coherence length of the emitted light. A very compact device results that measures the refractive index of liquids or gases. An electronic scanning technique by means of a CCD array provides a fast readout without the need for moving parts.