Four-photon absorption cross section in potassium bromide at 532 nm

Abstract
We exploit recombination luminescence of self-trapped excitons for the measurement of the four-photon absorption cross section in KBr at 532 nm. The value is found to be σ(4)=(2±1)×10112 cm8 sec3. The validity of this method is verified by comparison with a four-photon absorption model describing the interaction process.