Investigation of mixed‐mode polariton dispersion in AgGas2

Abstract
The observation of mixed‐mode exciton polaritons is reported in high quality AgGaS2 crystals grown by a Bridgman technique. By changing the magnitude of the total K‐vector and its direction with respect to the crystalline axis in the two‐photon experiments it is possible to excite resonances on the upper polariton and on the pure longitudinal exciton. The results are quantitatively explained by the polariton theory for uniaxial crystals.