Ultra-High-Capacity Optical Communications and Networking: Integrated Guided Wave Devices for Terabit per Second Optical Communications

Northwestern University, Evanston IL

Investigators

Abstract

This proposal was submitted in response to the solicitation NSF 01-65 on "Ultra-High Capacity Optical Communications and Networking." Future systems for optical signal processing and communications will require large scale integration of photonic devices. Ferroelectric oxides have long been recognized as highly non-linear optical materials with significant advantages, especially when used as optical waveguides. In the form of high-index-contrast, thin film structures, high-density integrated optics can be potentially achieved. The intrinsic confinement of the electromagnetic field in the thin film guide leads to high power densities and strong optical nonlinearities. Their utilization in thin film waveguide structures, however, has been limited because of difficulties in preparing low loss materials with bulk-like non-linear optical properties. Recent advances in the epitaxy of ferroelectrics, however, indicate that thin-film guided -wave devices are now realizable. In the proposed program epitaxial ferroelectric oxide thin film waveguide structures for microphotonic devices and integrated optical systems will be investigated. The proposed work builds upon our demonstration of low loss epitaxial ferroelectric thin films prepared by metalorganic vapor phase epitaxy (MOVPE) and the demonstration of large band width guided wave electro-optic modulators. MOVPE enables the preparation of ferroelectric oxides with high electro-optic coefficients that are not available as large single crystals. Specific systems to be investigated include BaTiO3, and other ferroelectrics. Thin film guided wave electro-optic devices will be fabricated including Mach-Zehnder electro-optic modulators and beam steering devices. Thin film modulators with bandwidths of 20-100 GHz will be designed and fabricated. By using highly nonlinear ferroelectric thin films, significant improvements in bandwidth, and operating voltage are anticipated compared to conventional bulk ferroelectric devices. The feasibility of integrating epitaxial ferroelectrics with silicon will be investigated. Metalorganic molecular beam epitaxy (MOMBE) will be used to form low index, epitaxial buffer layers that act as a stable interfacial layer between the ferroelectric oxide and the silicon substrate. Devices will be fabricated using both conventional and e-beam lithography. Potential applications for microphotonic devices and systems are in terabit per second optical communications, local area networks, and optical interconnects.