Ultra fast decay of enhanced degenerate-four-wave mixing of multiple GaAs thin layers

By means of the nonlocal theory of the pulse response and the analysis of the exciton–radiation coupled modes, it is elucidated that a nondipole type excitonic state confined in a thin film strongly couples with a radiation field in a particular thickness region, which leads to a large nonlinear response combined with the ultra fast radiative decay in the case of GaAs. Such strong coupling can be further enhanced by the multiple layered structure, where the radiative width concentrates in a particular collective mode keeping the optimum condition for the enhanced nonlinear response.