MIT Department of Electrical Engineering & Computer Science

E E C S

Creation of Optimized Quantum Well Optoelectronic Switches

Dr. John Alfred Trezza
Stanford University

Monday, February 26, 1996
2:15 PM (2:00 refreshments)
Grier Room, Room 34-401A
EECS Special Seminar

Abstract

External optical modulation can have many advantages over direct laser switching. Some of the desirable characteristics of efficient optical switches are low chirp, low power, large contrast ratio, and high speed. In addition, modulators should ideally have desirable optical bandwidth, and be photon conserving and reversible. MBE grown quantum well optoelectronic modulators in the GaAs/AlGaAs/InGaAs materials system are examined from both the electronic and optical viewpoints and are optimized to meet the above criteria. The design, growth, fabrication, and testing aspects of device development will be covered as will electrical and optical control and the integration of these devices into systems.

Experimental results and theoretical analysis of quantum well opto-electroabsorption utilizing either the quantum-confined Stark effect or field induced carrier separation are discussed. These two techniques provide the framework for creating large absorption changes with little or no refractive index changes. Tradeoffs between band to band transitions in single quantum wells versus more complex coupled quantum well architectures are described.

These quantum well elements are then used in several types of experimental optical modulator structures to further enhance optical switching. Zero chirp reflection modulators (which use increasing absorption to either increase or decrease reflectivity), vertical cavity phase flip modulators (which encode information by changing reflected phase by 180 degrees, while keeping intensity constant), and vertical cavity X-modulators (which are reversible switches that route optical beams rather than absorbing in one of the switched states) will be explained. Explanations of combinations of devices for crossbar switches, beam routers and optical logic and imaging applications will also be made, and directions for future research will be discussed.

URL of this page: http://www-eecs.mit.edu/AY95-96/events/17.html
Created: Jan 26, 1996 | Modified: Jun 25, 1997
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