BALANCED DUAL PHOTODIODES INTEGRATED WITH A 3 DB DIRECTIONAL COUPLER FOR COHERENT LIGHTWAVE RECEIVERS

A photonic integrated circuit consisting of a 3 db directional coupler and two GaInAs pin photodiodes connected in series at the output of the coupler has been fabricated. The photodiodes have typical dark currents of approximately 3 nA at a reverse bias of 8 v, with more than 1MΩ isolation. Symmetrical operating characteristics with respect to the launching direction have been achieved.