Observation of huge nonlinear absorption enhancement near exciton resonance in GaN

Huge excitonic enhancement of two-photon absorption near the exciton-transition energy was observed in the GaN system. The peak value of the nonlinear absorption coefficient is at least 1500 cm/GW, corresponding to an enhancement factor of >100. The room temperature exciton dephasing time is also obtained based on a spectral analysis to be similar to150 fs in bulk GaN, which is close to the exciton ionization time. (C) 2003 American Institute of Physics.