Carrier-induced changes of the phase of reflected light at a pumped ZnSe layer
2005; American Physical Society; Volume: 72; Issue: 7 Linguagem: Inglês
10.1103/physrevb.72.075204
ISSN1550-235X
AutoresM. Seemann, F. Kieseling, H. Stolz, Robert Franz, G. Manzke, K. Henneberger, T. Passow, D. Hommel,
Tópico(s)Spectroscopy and Quantum Chemical Studies
ResumoThe optical properties of semiconductors are strongly influenced by carriers, which have been injected by a pump pulse. We investigate this effect by studying the amplitude and phase of the light field reflected from a ZnSe layer, applying the method of phase-resolved spectral interferometry. While there are only weak changes in the amplitude with increasing excitation, the phase changes drastically. In the case of the nonexcited sample the phase exhibits a global change at the heavy hole-exciton resonance by $2\ensuremath{\pi}$ towards the band edge. A detailed analysis shows that it can be decomposed into an abrupt, nearly steplike jump by $\ensuremath{\pi}$ and a smooth increase to higher energies up to $2\ensuremath{\pi}$. This behavior can be described by interfering polariton waves including their spatial dispersion. Increasing the intensity of the pump, the steplike jump changes its direction to $\ensuremath{-}\ensuremath{\pi}$, whereby the global jump by $2\ensuremath{\pi}$ vanishes. We explain this behavior within a quantum-kinetic many-body theory by a subtle increase of the excitonic linewidth, which results from (i) a counterbalance of diagonal and off-diagonal dephasing and (ii) memory effects in the scattering between excited carriers and the laser-induced polarization.
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