Ultra-High-Capacity Optical Communications and Networking: Advanced GaAs-based Waveguide Integration for 1.3/1.55 micron Wavelength Division Multiplexing

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This proposal was submitted in response to the solicitation NSF 01-65 on "Ultra-High Capacity Optical Communications and Networking." The present state-of-the-art in wavelength-division multiplexing (WDM), ~100 signal transmission channels in the fiber C-band (1525-1565 nm), employs only a small fraction of available fiber bandwidth. While erbium-doped fiber amplifiers (EDFAs) for the L-band (1565-1605 nm) are presently being developed and deployed, there is a widely-recognized need to develop systems for other portions of silica glass fiber's low-loss transmission "spectral window" (1200-1700 nm). Present C-band systems utilize various approaches for hybrid integration of both active InP-based optoelectronic devices (photon laser sources, amplifiers, and detectors) and passive InP or silica-on-silicon planar lightwave circuits (or PLCs, for multiplexing, demultiplexing, and add/drop functions). Greater functional and/or monolithic integration of the active and passive components used in WDM systems will reduce their costs and accelerate deployment.Researchers have recently demonstrated GalnNAs quantum well heterostructure semiconductor lasers operating at 1310 nm (cw, 300 K) and 1520 nm (pulsed, 300 K). These devices overcome the performance limitations inherent to lnP-based heterostructures due to weak carrier confinement by low potential barriers. This exciting development also has enabled GaAs-based heterostructures to access optical fiber communication system wavelengths for the first time. The potential for complex lightwave circuitry with monolithic integration of active and passive components for optical communications is much greater than exists in the InP material system due to the much larger range of material parameters afforded by GaAs-based 111-V alloys. In particular, the compatibility with A1GaAs and InAlP alloys, which can be converted through wet thermal oxidation to insulating and transparent low refractive index oxides, provides a significant advantage for advanced waveguide integration techniques.In this project, the development of new approaches for the fabrication of GaAs-based photonic integrated circuits for WDM applications in optical communications will be explored. Wet thermal oxidation of A1GaAs and InA1P alloys will be applied to low-loss waveguide fabrication for both active and passive waveguide devices. Novel structure designs and processing approaches will be combined to realize fully-oxidized A1GaAs heterostructures as broadband passive ridge waveguides for monolithic integration with active components. Rare-earth doping of native oxide waveguides will be explored using both Pr3+- and Er3+-doping for 1.3 um and 1.55 um band amplifiers, respectively. Phased-array (PHASAR) based WDM devices will be designed, fabricated and characterized in native-oxide based waveguides. This will lead to curriculum enhancement in the Department of Electrical Engineering at the University of Notre Dame.