Comments on directional photoionization model of second-harmonic generation in doped glass fibers

Abstract The multiphoton-ionization-interference model of self-organized second-harmonic generation by Anderson et al. (Optics Lett. 16 (1991) 796; SPIE Proc. 1516 (1992) 154) is discussed in the view of recent experiments. It is shown that the inconsistency of the directional photoionization model with some experimental results is a consequence of the fact that the model is based on the instantaneous response of the medium. A new phenomenological model including memory is proposed which removes the difficulties of the Anderson et al. model. The saturation of second-order susceptibility predicted by either model is found to be in a good agreement with all experimental results.