Wavelength Division Multiplexing (WDM) technology provides many options to the design of flexible alloptical networks. To exploit these options to their full potential, Photonic Integrated Circuits (PICs) for wavelength routing and switching will be indispensable. One of the basic building blocks of such PICs is the planar phased-array (PHASAR) wavelength demultiplexer. The monolithic integration of PHASARs with photodetectors, amplifiers, and other waveguide-based (passive) components is discussed.

Butt-joint waveguide couplings are fabricated for use in InP-based photonic integration, and characterized by scanning electron microscopy and optical transmission measurements. Several parameters have been optimized in the characterization study: size and shape of the mask protecting the first waveguide layer during butt-joint regrowth, and the crystallographic direction of the butt-joint interface. The studies show that high-quality butt-joints having negligible optical loss can be made with good fabrication tolerance. Using the optimized butt-joint, DBR-type, gain-clamped SOAs have been fabricated which are free of internal excess reflections. A constant optical gain of 21 dB is obtained up to a signal output power of 25 mW. The devices show CATV grade linearity in a 77 channel CATV linearity test at a distortion level of -55 dB below carrier.