Femtosecond THz Studies of Intra-Excitonic Transitions

Journal Article · Tue Oct 02 04:00:00 EDT 2007 · Physica Status Solidi (b)

OSTI ID:951100

Huber, Rupert; Schmid, Ben A; Kaindl, Robert A; Chemla, Daniel S

Few-cycle THz pulses are employed to resonantly access the internal fine structure of photogenerated excitons in semiconductors, on the femtosecond time scale. This technique allows us to gain novel insight into many-body effects of excitons and reveal key quantum optical processes. We discuss experiments that monitor the density-dependent re?normalization of the binding energy of a high-density exciton gas in GaAs/AlGaAs quantum wells close to the Mott transition. In a dilute ensemble of 3p excitons in Cu2O, stimulated THz emission from internal transitions to the energetically lower 2s state is observed at a photon energy of 6.6 meV, with a cross section of 10-14 cm2. Simultaneous interband excitation of both exciton levels drives quantum beats, which cause efficient THz emission at the difference frequency. By extending this principle to various other exciton resonances, we develop a novel way of mapping the fine structure by two-dimensional THz emission spectroscopy.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Materials Sciences Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 951100
• Report Number(s): LBNL-598E
• Journal Information: Physica Status Solidi (b), Journal Name: Physica Status Solidi (b) Journal Issue: 6 Vol. 245; ISSN 0370-1972
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BINDING ENERGY
CROSS SECTIONS
EMISSION SPECTROSCOPY
EXCITATION
EXCITONS
FINE STRUCTURE
MONITORS
PHOTONS
QUANTUM WELLS
RENORMALIZATION
excitons
quantum wells
ultrafast dynamics