Magneto-Quantum Beats and Coherence in Resonant Light Scattering from Quadrupole Polaritons in Cu ₂ O

Abstract

PACS. 71.35 -Excitons and related phenomena. PACS. 42.50 -Quantum optics. PACS. 78.47 -Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter.

Propagation Beats of Quadrupole Polaritons in Cu2O

“…The oscillations are interpreted as quantum interference between polaritons of the two branches [5]. As was recently shown [6] magneto-quantum beats of quadrupole polaritons in Cu,O can also be detected in light scattering experiments. In this case, however, polariton propagation effects do not lead to an additional beat structure.…”

“…As can be seen from the sharp peaks the Zeeman splitting is still dominating but there are also other contributions within the spectrum of the exciting pulse. From the analysis of the splitting for different values of the magnetic field we determined an effective g-value for the polaritons of geff = 0.95 A 0.06 which is slightly higher than the g-value which was determined by quantum-beat spectroscopy in a light scattering experiment (g,,, = 0.89 k 0.01, [6]). …”

Propagation Hanle effect of quadrupole polaritons in Cu2O

“…4 Just this case will be considered in the present paper, taking into account polariton quantum beats in the presence of a magnetic field. The influence of a magnetic field on the optical orientation of exciton polaritons was studied experimentally in CdSe crystals by Nawrocki et al 9 and Planel et al 10 The Hanle effect based on the interference of polariton wave packets will be the main issue of the present paper and we will take into account the existence of the propagation quantum beats observed experimentally in Cu 2 O crystals and discussed by Frohlich et al, 11,12 Langer et al, 13,14 and Stolz. 15 The quantum beats effect and the Faraday and Hanle effects as well as resonant Raman scattering are closely related, being intrinsically interconnected and originating from quantum interference effects.…”

“…The total energy relaxation time or the population lifetime is usually measured by time-resolved luminescence spectroscopy. [11][12][13][14][15] As was emphasized in Ref. 13 the quantum beat method allows one to distinguish between coherent Raman scattering and incoherent hot luminescence.…”

“…This splitting can be determined with a high resolution, being independent of the inhomogeneous broadening, 15 whereas the phase relaxation times of the excited states can be determined from the damping of the beats. 13 The coherence time, which is also known as the dephasing time, has been measured by intervals of time during which the excited states lose their initial phases. The coherence time coh determines the homogeneous broadening of the excited state ␥ by the relation 2␥ϭប/ coh , where coh is defined by the elastic collisions, which exclusively affect the phases and do not lead to excited-state depopulation.…”