A photonic integrated circuit technology for coherent optical processing

Abstract

A complete photonic integrated circuit (PIC) technology for coherent homodyne and heterodyne optical signal processing is presented. The GaAs/AlGaAs PIC is based exclusively on integration of waveguide phase modulators with interconnecting waveguides, directional couplers, turning mirrors, and gratings. Emphasis is on simplicity of fabrication and high yield of complex PIC designs achieved through the use of only one or two etch steps to define the PIC followed by conventional isolation and metalization steps. Current progress on critical device and fabrication technologies will be discussed. These include high resolution ridge-waveguide etching for definition of directional coupler waveguide power splitters, fabrication of ridge-waveguide phase modulators, without significant bias-dependent absorption modulation, as well as alignment and etch issues for turning-mirrors and gratings. Finally, all of these elements are designed for integration into a single PIC without epitaxial regrowth. Fully integrated Mach-Zehnder amplitude modulators are demonstrated. Systems applications of this PIC technology, including optical frequency modulation of an input single-frequency source, tunable bandpass optical filters, and complete control of frequency and far field of a phased-array radar antenna, will be presented.