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Physics

Physics Department Current Events



Tuesday, October 28, 2014
Physics Party
12:30 p.m., Marshak Science Building, Room 418N
 


Wednesday, October 29, 2014
Physics Colloquium
4:00 p.m., Marshak Science Building, Room 418N

Pallab Bhattacharya

Charles M. Vest Distinguished University Professor; James R. Mellor Professor of Engineering
Department of Electrical Engineering and Computer Science
University of Michigan, Ann Arbor, MI

"Strong Coupling Phenomena in Semiconductor Microcavities"

The study of light-matter interaction in a solid-state microcavity has been of considerable interest for some time.  Under conditions of strong coupling, the irreversible spontaneous emission process changes to a reversible and periodic exchange of energy between emitter and cavity mode in the form of Rabi oscillations.  The degeneracy between emitter and photon is lifted, giving rise to two light-matter entangled eigenstates spectrally separated by a characteristic interaction energy, or Rabi splitting, ΩVRS.  Elementary excitations in a strongly coupled exciton-photon system are quasiparticles called polaritons, which are bosons.  A polariton laser, proposed in 1996, exploits the strong coupling regime of exciton-photon interaction in a microcavity.  A degenerate and coherent state of polaritons is created near k// ~0 in the polariton dispersion by a combination of polariton-phonon, polariton-polariton, and eventually stimulated polariton-polariton scattering.  The last process, which is phase coherent, is the principle gain mechanism.  The coherent polariton state at k// ~0 generates coherent light by spontaneous radiative recombination.  The separation of stimulation and emission results in coherent emission without the requirements of population inversion and with a much smaller level of excitation than in a conventional photon laser.  The concept therefore represents a new paradigm in the history of coherent emission.  The exciton binding energy and ΩVRS are important factors which determine the choice of materials.  In this talk I will describe ultralow threshold optically excited room temperature polariton lasing with a single and array of GaN nanowires and electrically pumped polariton lasers with GaAs-and GaN-based microcavities.



Thursday, October 20, 2014
Majors Jamboree
12:00 noon- 2:00 p.m., Great Hall, 2nd Floor, Shepard Hall
"Connection to a Major and/or Minor"

 

 

 

 

Pallab Bhattacharya

Pallab Bhattacharya, Charles M. Vest Distinguished University Professor; James R. Mellor Professor of Engineering, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI