Previous Research Projects (Selected)
Wave Acoustooptic Interactions and Devices in Compound Semiconductor
Investigator: C.S. Tsai
Research Assistants: S. Nguyen, A. Roy, and B. Sun
Support: Amerasia Technology Corp.; Statek, Inc.; University of California MICRO Program
Despite the maturity of guided-wave acoustooptic (AO) Bragg cell technology on LiNbO3 substrate, it suffers from one inherent disadvantage: presently only a partial or hybrid integration can be realized on the same substrate. In contrast, devices modules based on gallium arsenide (GaAs) and indium phosphide (InP) potentially are capable of total or monolithic integration because both the laser sources and the photodetectors, as well as the associated electronic circuits, can be integrated in the same substrate. Researchers have studied extensively the guided-wave AO interaction on GaAs; for InP, however, work on these interactions has not been reported. The latter is the material of choice for realizing monolithic AO circuits at the optical wavelengths widely used in optical fiber communication systems, namely, at 1.3?|m and 1.5?|m. This new project is concerned with the theoretical and experimental studies on guided-wave AO interactions and the resulting monolithic integrated optic devices on the optical waveguide that consists of a lattice matched InP/InGaAsP guiding layer and an InP cladding layer on <001> InP substrate.
Integrated Acoustooptic Space Switch Modules and Applications
Investigator: C.S. Tsai
Research Assistants: S.Calciu, S. Nguyen and A. Roy
Support: Advanced Research Projects Agency; Amerasia Technology Corp.; Rockwell internations Science Center, Statek, Inc.; University of California MICRO Program
Most of the existing optical waveguide space switch matrices utilize electrooptic effects in LiNbO3- and GaAs-based substrates and may be characterized into two types: those utilizing parallel channel waveguide switches and those utilizing intersecting channel waveguide switches. However, these switch matrices are configured in stages (or tandem), and require a large number of basic cross-point switches as the size of the matrix or the number of ports increase. As a result, the real estate of the substrate and the resulting optical propagation losses and crosstalks, as well as the complexity in both electrode layouts and electronic driver circuits, greatly increase with the size of the switch matrix. Optical space switches that utilize acoustooptic (AO) Bragg diffraction can alleviate significantly these undesirable characteristics. Four-by-four and eight-by-eight integrated AO space switches have been realized to demonstrate their applications to nonblocking multicast and broadcast switchings, as well as matrix-matrix multiplication. Future research efforts are focused on the realization of space switch modules with larger sizes than eight-by-eight and with fiber couplings at the input and output ports.
Low-Sidelobe Level Integrated Acoutooptic Tunable Filters and Applications
Investigator: C.S. Tsai
Research Assistants: J. Lan, A. Roy, and B. Sun
Support: Advanced Research Projects Agency; Amerasia Technology Corp.; Northrop Corp.; Technology Corp.; Statek, Inc.; University of California MICRO Program
Guided-wave acoustooptic (AO) tunable filters possess the potential to be used as tunable wavelength filters and switches in fiber optic wavelength-division multiplexing systems. To improve filter sidelobe suppression, the researchers have conceived coupling-weighting techniques that are capable of increasing suppression by as much as 20 to 35 decibels over that obtainable with conventional coupling. The researchers are conducting further theoretical and experimental studies, and fabricating integrated AO tunable filters to demonstrate their applications to wavelength- multiplexed fiber optic communication networks.
Waves-Based Integrated Optic Bragg Cell Module with Applications to RF Signal Processing and Optical Switching
Investigator: C.S. Tsai
Research Assistants: S. Calciu, Y. Pu, W. Ren, and B. Sun
Support: Advanced Research Projects Agency; General Instrument, Inc.; New Focus, Inc.; Office of Naval Research; University of California MICRO Program
This research on the interaction between magnetostatic waves and guided optical waves in ferromagnetic thin-films has resulted in GHz bandwidth magnetooptic (MO) Bragg cells in pure YIG waveguides and bismuth-doped YIG waveguides. Wideband light beam deflection/scanning, high-speed light beam switching, and RF spectral analysis have been demonstrated using such MO Bragg cells with encouraging performance characteristics. Of particular importance is the successful demonstration of very wideband RF spectral analysis. Theobjective is to realize devices that can provide superior performance characteristics even at higher and electronically tunable carrier frequencies and higher modulation and switching speed. Integrated MO Bragg cells have been realized recently and used to demonstrate applications to spectral analysis for RF signals and light beam scanning. Future research is aimed at the realization of MO device modules having the MO Bragg cell and the collimation-focusing lens pair formed in the same wave guide substrate and demonstration of applications to light beam switching, RF spectral analysis, and frequency modulation.
Optically Activated Integrated optic Modulators and Switches in GaAs Waveguides
Investigator: C.S. Tsai
Research Assistants: J. Lan and W. Ren
Support: IT&T Corp.; University of California MICRO Program
Optically activated devices based on optical-optical interaction currently are of great interest. This project is concerned with the realization of novel devices such as modulators and switches with applications to communications and computing. Specifically, an optically activated guided wave Mach-Zehnder interferometric modulator and switch has been constructed in gallium arsenide channel waveguides. A ?? radian phase shift at the optical wavelength of 1.15 ?|m has been achieved with modulating pulse energy of 320 PJ at an interaction length as short as 22 ?|m. A directional-coupler modulator and switch also are being studied.
Manufacturing and Packaging of Integrated Acoustooptic and Magnetooptic Device Modules
Investigators: C.S. Tsai and C.C. Lee
Support: Office of Naval Research; University of California MICRO Program; Western Digital, Inc.
A cost-effective packaging approach for integrated acoustooptic and magnetooptic device modules must begin with concurrent engineering of the following aspects: packaging materials, bonding media and techniques, mechanical and thermal design, electrical connection, and optical interface. In this research, these five technical aspects will be integrated in the packaging design and manufacturing process.
Ultrasonic Characterization of Fiber-Reinforced Composites and Biomedical Tissue
Investigators: C.S. Tsai and J. Jones
Support: Rohr Industries
The objective of this project is to carry out theoretical and experimental studies on back-scattered ultrasound in porous fiber-reinforced composites and biological tissues. The methods of statistical moment and Monte Carlo are being explored and employed.
(Joie Jones is Professor of Radiological Sciences at UCI.)