A monolithic optical phase-shift detector on silicon

A novel monolithically integrated device used as an optical phase-shift detector is presented. It consists of a diffraction grating etched at the surface of a p-n photodiode fabricated by a process compatible with a standard silicon CMOS technology. When two coherent light beams are collimated toward the surface of the device, the detected optical power generates a current depending on the relative phase between the two incident beams. The operating principle of this detector and the results obtained by finite-difference time-domain modeling are presented. The fabrication process of the first devices is described and the experimental validation of the concept is demonstrated.