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Ultrafast coherent carrier control in quantum wells

Kontrolle ultraschneller kohärenter Ladungsträger in Quantum Wells


Physica status solidi. B 204 (1997), No.9, pp.9-15 : Ill., Lit.
ISSN: 0031-8957
ISSN: 0370-1972
Journal Article
Fraunhofer IAF ()
III-V Halbleiter; III-V semiconductor; optical measurement; optische Messung; quantum wells

A fast scanning ultrafast phase-dependent reflectivity technique is used to measure the coherent properties of multiple quantum wells at carrier densities below 108 cm (exp -2). Signal to noise ratios in the reflected intensity >80 dB can be achieved allowing underlying coherences to be measured at time delays beyond 30 ps. An unexpected 1.5 ps rise time of the coherence is resolved before a non-exponential decay and ascribed to interference of polaritons. By time-resolving the pair of pulses reflected off the sample, a complete history of energy flow in the quantum wells can be identified. Both spontaneous and stimulated coherent reemission are observed in good agreement with models based on the Bloch equations.