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"Ultrafast phenomena and superfluorescence in
a dense semiconductor plasma

Alexey Belyanin


Superfluorescence is one of very few quantum phenomena in which a macroscopic ensemble of initially incoherent quantum oscillators demonstrates cooperative, coherent behavior due to an efficient self‐phasing. Superfluorescence places a fundamental upper limit on the rate of radiative decay in any excited system. It has been observed in gases and crystals doped with active impurities. In semiconductors, an analog of superfluorescence would be a cooperative recombination of nonequilibrium carriers. However, ultrafast carrier scattering tends to destroy optical coherence. As a result, superfluorescence in semiconductors remained elusive for many years, despite a significant amount of experimental effort. In this talk I will overview general properties of ultrafast radiative dynamics of carriers in semiconductors and then present our theoretical and experimental studies of dense semiconductor plasmas created in semiconductor quantum wells via intense femtosecond excitation. We show that in this system strong quantum confinement and carrier degeneracy imposed by quantum well potential and an external magnetic field can suppress decoherence processes and enable superfluorescence. In recent experiments conducted at Rice University and the National High Magnetic Field Lab in Tallahassee, several key signatures of superfluorescence were observed, in agreement with our predictions. These include ultrafast depopulation of Landau levels accompanied by picosecond bursts of radiation and the transition from omnidirectional amplified spontaneous emission to a randomly directed but highly collimated output. I will also discuss some peculiar properties of emission from the excitonic many‐body state.

Tuesday, November 15, 2011
IQSE 578, 11:30 a.m.
Mitchell Physics Building

Institute for Quantum Science and Engineering
Texas A&M University

(Sandwiches, salad, and soda to be served at 11:00 a.m.)