Subpicosecond excitonic optical nonlinearities in quantum wells
Résumé
Excitonic resonances in semiconductors are very sensitive to applied optical fields. We present here a comparison between the effects of resonant and non resonant optical excitation, creating respectively real or virtual excitons. A blue shift of the exciton line and a reduction of the oscillator strength are simultaneously observed in multiple-quantum-well-structures for the two following cases : presence of a population of real excitons in very thin wells (two-dimensional systems), or presence of an intense offresonance non absorbed optical field (virtual excitons) independently of the well thickness. The latter configuration (optical Stark effect) has been studied as a function of pump intensity, determining in particular how the saturation of the blue shift is related to the exciton bleaching.
Mots clés
- pump intensity
- exciton bleaching
- optical Stark effect
- well thickness
- multiple quantum well structures
- virtual excitons
- resonant optical excitation
- quantum wells
- nonabsorbed optical field
- oscillator strength reduction
- exciton line blue shift
- nonresonant optical excitation
- real excitons
- excitonic resonances
- subpicosecond excitonic optical nonlinearities
- Stark effect
- spectral line shift
- semiconductor superlattices
- oscillator strengths
- nonlinear optics
- excitons
Domaines
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