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HL: Fachverband Halbleiterphysik

HL 43: Optical Properties II

HL 43.3: Vortrag

Donnerstag, 21. März 2024, 10:00–10:15, EW 561

Coherence of magnetic-field-coupled 1S excitons in Cu₂O — •Andreas Farenbruch¹, Nikita V. Siverin¹, Gülistan Uca¹, Dietmar Fröhlich¹, Heinrich Stolz², Dmitri R. Yakovlev¹, and Manfred Bayer¹ — ¹TU Dortmund, Dortmund, Germany — ²Universität Rostock, Rostock, Germany

The coherence of the 1S exciton state in cuprous oxide (Cu₂O) is investigated using difference frequency generation with two-photon excitation (2P-DFG) for varying temperatures and excitation powers. The pulses of the first laser induce a coherent exciton population via a two-photon excitation process. The pulses of the second laser stimulate the emission of photons with the energy difference between the excitons and the stimulating photons. By delaying the pulses of the second laser, the 2P-DFG signal is measured as a function of time. This technique is used to measure the coherence times of the magnetic-field coupled 1S exciton states at magnetic fields of up to 10 T in Voigt configuration.

Characteristic polarization selection rules for this process are derived through group theoretical considerations and experimentally confirmed by measuring the full polarization dependence. Chosen linear polarization settings allow for a selective measurement of the decay of a single exciton state or additional two- or three-level quantum beats. The dependence of the coherence times is investigated for temperatures in the range of 1.4 to 2 K and excitation powers between 3 and 30 mW.

Keywords: Exciton; Nonlinear optics; Four-wave mixing; Semiconductor; Coherence