Dependence of nonlinear hot-images of intense laser beams on the thickness of Kerr medium with gain and loss

Abstract

Based on the angular spectrum theory of light propagation and the mean-field approximation, an expression for intensity of hot image of the intense laser beam through a thick Kerr medium with gain and loss is obtained, beyond the thin-medium approximation. Thereby the dependence of intensity of hot image on the thickness and gain/loss of medium and the property of obscuration are identified analytically and numerically. It is shown that, for a given obscuration, the intensity of hot image decreases as the medium thickness increases for definite B integral and increases monotonously with the medium thickness for definite input power of laser beam. For definite output power of laser beam and gain/loss of medium, the intensity of hot image firstly increases and subsequently decreases as the medium thickness increases. Furthermore, it is shown that hot image from obscuration of phase modulation is more intense than that from obscuration of pure amplitude modulation, even in the presence of medium gain and loss. As the size of obscuration increases, the intensity of hot image first increases gradually, after reaching a maximum value, it decreases rapidly to a minimum value.