Reanalysis of experimental determinations of polariton-polariton interactions in microcavities

Inside solids, photons can become strongly interacting, which allows the possibility of optical transistors, in a which one light beam controls the transmission of another light beam. The strength of this interaction can be greatly increased in specially designed structures in which the photon frequency is near an electronic resonance known as an exciton. The exact value of this interaction strength has been much debated, ranging over orders of magnitude. This paper reviews a set of experiments and argues for a number well below some earlier estimates, but still large compared to the predictions of standard theory calculations.