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Strong coupling effects in quantum dot microcavities

We have investigated strong coupling effects between the vacuum field and individual quantum dot excitons in GaAs based semiconductor microcavities. By using dots with large dipole moments we observe a vacuum Rabi splitting of up to 140μeV. Engineering the interaction of light with matter allows one to tune important properties of solids like e.g. the spontaneous emission rate or the spontaneous emission coupling factor into a laser mode. In the frame of cavity quantum electro dynamics light matter interaction phenomena are divided into weak and strong interaction effects. Weak interaction effects result e.g. in an enhancement of the spontaneous emission rate of an emitter in a cavity when on resonance with the cavity modes. Strong interaction effects can be observed when the rate describing the coupling of the emitter and the light becomes stronger than dissipative processes in the system. Then emission becomes a reversible process. We have investigated strong coupling effects in semiconductor microcavities with InGaAs quantum dots. The cavities are based on undoped GaAs/AlAs VCSEL structures from which micropillars with diameters between 1.0 μm and 4 μm are realized by reactive etching. In combination with the vertical optical confinement the etching of pillars allows to obtain discrete photon modes. The microcavities have quality factors Q of about 5.000 to 35.000, which correspond to photon lifetimes in the cavities between 2 and 18 ps. The quantum dot density and emission energy range has been optimized in order to locate only single quantum dot excitons close to the cavity resonance. At low excitation powers these structures can therefore be used to investigate the interaction of a single quantum dot exciton and the vacuum field. By using dots with large dipole moments we observe clear anticrossing effects JTuH4-1-INV