Glass Waveguides on Silicon for Hybrid Optical Packaging.

The first generation of optical integrated circuits are now ready to leave the laboratory and enter into commercial application. There are three elements to these circuits: optically active devices, such as lasers and detectors, optical waveguides to provide interconnection and filtering, and optical packaging to provide a controlled environment and conduit to the external world. This paper reviews our work on deposited glass waveguides on silicon to form the waveguides and filters. The choice of these particular waveguides make sense only as part of a consistent approach to optoelectronic packaging. Our group's direction, hybrid optical packaging on silicon (HOPS), is described and briefly compared with other techniques. For these packages, two waveguides were developed: a "tight mode" waveguide with a silicon nitride rib core for matching a semiconductor laser and a "loose mode" waveguide with a phosphosilicate glass core for matching an optical fiber. The tight mode waveguide was used to make both silicon chip Bragg reflector lasers, which exhibited narrow linewidth and low chirp, and resonant optical reflector lasers, having linewidths as narrow as 26 kHz. The loose mode waveguide was used to fabricate multichannel star couplers, a polarization splitter and a 4 channel Mach-Zender multiplexer. The fabrication of Bragg reflection filters by deep UV photolithography is described.