A large and ultra fast nonlinear response of GaAs thin films due to nano-scale spatial structure of the internal field

Summary form only given. How we can overcome the trade-off between the magnitude of nonlinearity and response time of semiconductors is a challenging problem because a resonant excitation for large nonlinearity usually induces a long decay time. Recently, a large enhancement of the degenerate-four-wave mixing (DFWM) for GaAs thin films has been observed for a particular thickness (110 nm). As theoretically predicted, this is due to the resonant enhancement of the internal field with a nano-scale spatial pattern. In this paper, we elucidate that this enhanced response also shows very fast decay, by means of time-resolved measurements of the three beam DFWM and nonlocal transient response theory.