Optica 1, 276–280 (2014)

Credit: OSA

Although strong light–matter interactions leading to the formation of polaritons are widely studied in a variety of systems, the detailed dynamics are poorly understood. Now, Andrew D. Jameson and colleagues at Oregon State University and the University of Arizona in the USA, and the Philipps-Universität in Marburg, Germany have proposed a so-called pump–reset technique for probing the time evolution of light–matter interaction in a semiconductor microcavity containing quantum wells. In this scheme, a pump pulse creates the polariton and a subsequent single-cycle THz reset pulse is used to switch off the coupling. The perturbation caused by the reset pulse is revealed in modulations of the pump-reflection spectrum and in pronounced polariton oscillations with increasing pump–reset delay. The observed oscillation period is 0.66 ps, as expected, which corresponds to the 6.3 meV energy splitting between the two polaritons. The observed spectrotemporal interference pattern provides direct proof of the coherent character of the light–matter interaction dynamics. The authors anticipate that their scheme will be of considerable value in the field of plasmonic and organic devices, where light–matter coupling has attracted significant research interest.