MAGNETIC-FIELD ENHANCEMENT OF THE EXCITON-POLARITON SPLITTING IN A SEMICONDUCTOR QUANTUM-WELL MICROCAVITY - THE STRONG-COUPLING THRESHOLD

We investigate the influence of strong magnetic confinement on an exci ton coupled to the resonant mode of a semiconductor microcavity. Cavit y mode coupling to a variety of discrete exciton resonances is describ ed in direct relation to the quantum-well magnetoabsorption spectra. W e show that the magnetic-field-enhanced vacuum Rabi splitting and time -resolved oscillation frequency obey the predicted square-root depende nce on the exciton oscillator strength computed directly from the inte grated absorption spectra. Anticrossing curves measured in zero field and in 11.25 T evidence an interesting three-oscillator coupling obser vable only at high fields due to enhanced higher-order light-hole-exci ton transitions. The data an in excellent agreement with a theoretical model which deduces magnetic-field-dependent oscillator strengths and corresponding reflectance spectra from a variational calculation comb ined with a transfer matrix method.