Control of Electron Coherences with Coherent Phonons
Abstract
This report focuses on the generation of coherent phonon fields using ultrafast optical pulses and theoretical work on coherent control and Bose-Einstein condensation of excitons. Our results illustrate the concept of phonon field entanglement and establish the relationship between phonon generation in opaque substances and resonant Raman scattering. We consider specifically coherent modes in LaAlO3, squeezed quantum-entangled phonons in KTaO3, and thermally-entangled transverse optical-acoustical modes in SrTiO3. The resonant work covers the E2' - resonance of antimony and the band gap of GaSe. Our work on condensates centers on light emission from optically-active excitons in quantum-well structures. We show that a coherent electromagnetic field is emitted and that condensation in a two-dimensional system can take place at finite temperatures. The bosonic description is extended to consider a weak disorder potential. We find that the collective state is a Glauber coherent state, substantially different from that of few-level models. The theory is used to explain transient linear optical experiments involving resonantly excited excitons in GaAs structures. We consider particularly coherent control of the exciton density and spin and resonant Rayleigh scattering. Our quantum mechanical approach for light emission shows that excitonic secondary emission has a coherent component, in agreement with experiments.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 29, 2000
- Accession Number
- ADA384771
Entities
People
- Roberto Merlin
Organizations
- University of Michigan