Magnetic-field interaction of spatially confined quantum-well exciton-polaritons

We report on pronounced magneto-optical effects of trapped polariton modes in a single InGaAs quantum well microresonator with a lithographically defined modulation of the cavity length. In our optical polariton traps with diameters ranging from 1 to 10 mu m, a confinement potential of 7.5 meV is achieved. In magnetic-field dependent experiments, a diamagnetic shift and a Zeeman splitting of the trap-modes are observed which confirms that the polaritonic nature of the quantized emission modes are preserved even for traps as small as 1 mu m. Furthermore, focusing on theoretical estimates using a simple model, we have identified a clear correlation between the polaritons' magnetic response and their excitonic fraction, corresponding to the Hopfield coefficients of the composite particles.