Tilted combiners/decombiners and photonic integrated circuits (pics) employing the same

Abstract

A monolithic optical transmitter photonic integrated circuit (TxPIC) comprises a plurality of integrated modulated sources which, when all operated at constant current, display a power output that varies as a function of array position similar to a quadratic-shaped curve and, further, forming an array of signal channels each having a different wavelength output. An optical combiner/decombiner is integrated in the circuit and has at least one free space region with a plurality of ordered bands along its edge where the zero order band is substantially at a longitudinal centerline of the free space region and where, on either side of this band, is a first order band followed by additional higher order bands. The ends of the output waveguides from the modulated sources are coupled approximate to the free space region edge along a region of the zero order band between one of the adjacent first order bands and a longitudinal centerline of the zero order band so that the inputs of the signal channels to the combiner of are titled or offset with respect to the longitudinal centerline of the combiner free space region so the combined outputs from the optical combiner will be aligned along the slope of the quadric-shaped curve of the combiner output passband envelope. The tilted combiner/decombiner may also be deployed in a receiver photonic integrated circuit (RxPIC) or other circuit employing such a device.