MIT Department of Electrical Engineering & Computer Science
Microcavity Polariton Laser: Coherent Matter and Light
Rajeev J. Ram
University of California, Santa Barbara
Monday, March 18, 1996
2:15 PM (2:00 refreshments)
Grier Room, 34-401B
EECS Special Seminar
Abstract
All lasers rely on stimulated emission of photons to establish coherence.
This stimulation is a particular manifestation of the quantum mechanical
cooperation between identical bosons. Since photons are only one of the many
bosons, e.g. excitons and polaritons, that exist in semiconductors, we can
exploit the bosonic nature of these massive particles to generate coherent
matter. This coherent matter can be used to generate coherent light without
gain, without population inversion, and even without resonators. In this
talk, we discuss the analogous inversion and threshold conditions for
semiconductor matter lasers as well as the dynamics of coherent matter states.
We then discuss recent experiments with a microcavity-polariton laser.
Microcavity polaritons are generated by placing quantum well excitons in a
high finesse microcavity. Since these particles are constructed, their
properties--including their masses and scattering rates--are "user-defined."
We demonstrate a laser-type threshold in a system of massive polaritons;
this is a strong indication of large, coherent polariton populations.
This system is the first source of coherent radiation in GaAs that preserves
excitonic populations; gain in a conventional semiconductor laser occurs only
after all the excitons are destroyed by ionization. Time-resolved femtosecond
and picosecond spectroscopy is used to study the dynamics of these polaritons.
URL of this page:
http://www-eecs.mit.edu/AY95-96/events/24.html
Created: Feb 29, 1996
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Modified: Jun 25, 1997
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