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HL: Fachverband Halbleiterphysik

HL 45: Optical properties II

HL 45.1: Vortrag

Dienstag, 1. April 2014, 11:15–11:30, POT 006

Photon Echoes from CdTe Quantum Wells in a Magnetic-Field — •Matthias Salewski¹, Lukas Langer¹, Sergey V. Poltavtsev^1,2, Irina A. Yugova², Dmitri R. Yakovlev^1,3, Grzegorz Karczewski⁴, Tomasz Wojtowicz⁴, Ilya A. Akimov^1,3, and Manfred Bayer¹ — ¹Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany — ²Spin Optics Laboratory, St. Petersburg State University, 198504 St. Petersburg, Russia — ³A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia — ⁴Institute of Physics, Polish Academy of Sciences, PL-02668 Warsaw, Poland

The interaction with a short laser-pulse excites negatively charged excitons (trions) from an ensemble of localized electrons in a n-type CdTe/(Cd,Mg)Te semiconductor quantum well. The resulting polarization undergoes a fast dephasing due to inhomogeneous broadening in the sample. It can be reversed by a delayed laser-pulse that creates a photon echo at exactly twice the delay-time. It is possible to split the second pulse into two single pulses to create a stimulated photon echo. With the different methods one can determine the optical T₁ and T₂ times of the system.

The application of a transverse magnetic-field allows to control the amplitude of the photon echo. Exploiting the Larmor precession of electron spins about the transverse magnetic field we demonstrate transfer of coherence between optically accessible and inaccessible pairs of states. The results are explained in terms of the optical Bloch equations accounting for the spin level structure of electrons and trions.