Title :
Coupled Bloch-phonon modes in superlattices
Author :
Ghosh, Avik W. ; Jonsson, L. ; Wilkins, J.W. ; Dekorsy, T. ; Bartels, A. ; Kurz, H. ; Kohler, Klaus ; Hey, Roger ; Ploog, K.
Author_Institution :
Dept. of Phys., Ohio State Univ., Columbus, OH, USA
Abstract :
Summary form only given. Electrons in an electrically biased superlattice execute Bloch oscillations (BO) at THz frequencies. The BOs can be tuned into resonance with other THz modes, such as plasmons and coherent longitudinal optical (LO) phonons. The coupling of BOs to such modes strongly affects the dephasing dynamics and thus the associated THz emission.Contrary to conventional mode-coupling theory, the experimental oobservation of the direct coupling of BOs with LO phonons in GaAs/AlGaAs superlattices reveals that there is no gap in the coupled spectrum at resonance. However, there is a substantial transfer of coherence from BOs to LO phonons at resonance, leading to an enhancement of the phonon amplitude. Starting from a microscopic Hamiltonian with polar (Frohlich) coupled LO phonons and superlattice electrons in an external field, we explain the non-existence of the gap and the resonant transfer of coherence.
Keywords :
III-V semiconductors; aluminium compounds; gallium arsenide; high-speed optical techniques; optical pumping; optical tuning; phonons; resonant states; semiconductor superlattices; submillimetre wave generation; Bloch oscillations; GaAs-AlGaAs; GaAs/AlGaAs superlattices; LO phonons; THz emission; THz frequencies; THz modes; coherence resonant transfer; coupled Bloch-phonon modes; coupled spectrum; dephasing dynamics; electrically biased superlattice; external field; microscopic Hamiltonian; mode-coupling theory; phonon amplitude; polar coupled LO phonons; resonance tuned; superlattice electrons; Coherence; Electron microscopy; Electron optics; Frequency; Gallium arsenide; Optical superlattices; Phonons; Plasmons; Resonance; Stimulated emission;
Conference_Titel :
Quantum Electronics and Laser Science Conference, 2001. QELS '01. Technical Digest. Summaries of Papers Presented at the
Conference_Location :
Baltimore, MD, USA
Print_ISBN :
1-55752-663-X
DOI :
10.1109/QELS.2001.961981
