Simulation analysis of the restraining effect of a spatial filter on a hot image

Abstract

Based on the restraining effect that spatial filtering has on the frequency spectrum of a beam, from the small-scale focusing theory of Bespalov and Talanov (B-T theory) we derive an expression for the pinhole diameter of the spatial filter corresponding to the fastest growing frequency. Then, compared with the theoretical pinhole diameter of the spatial filter, the restraining effect of the spatial filter on a hot image with different pinhole diameters is numerically investigated. The numerical results show that, if the pinhole diameter is larger than the theoretical one, the hot-image intensity will remain steady; once the pinhole diameter becomes smaller than the theoretical one, the hot-image intensity will begin to decrease. Moreover, as the pinhole diameter decreases, a more prominent restraining effect can be obtained. But reducing the diameter of the spatial filter would lead to greater beam energy loss. The parameters of the spatial filter must be chosen to guarantee that the scheme fulfills the demand for low beam energy loss and a satisfactory restraining effect simultaneously.

Hot images induced by arrayed mechanical defects in high-power laser system with cascaded medium

“…Researchers have established the diffraction theory model and analytical methods for the hot image, with which the analytical expression for the intensity and the location of the hot image based on the thinsheet approximation has been obtained, [7][8][9] and the evolution of the hot image in a system with a thick medium and the restraining effects of the spatial filters on the hot image have been also analyzed. 10,11 The majority of the papers just mentioned focused on the evolution of the hot images induced by a single scatterer and in a high-power laser system with a single nonlinear medium. It is well known that the hot image should be derived from the localized perturbation of the laser beam in the nonlinear medium.…”

Study on impact of spatial filter on a hot image through medium with gain

“…In addition, some researchers extended studies of the hot image in complicated systems comprising the cascaded nonlinear medium and in special conditions in which the multiple obscurations and arrayed mechanical defects [8][9][10] are introduced. Peng et al [11] analyzed the restraining effect of spatial filters on hot image with nonlinear medium of no gain, as we know, in high power systems spatial filters are most commonly used between amplifying chains for filtering out high frequency, so it is required to discuss the impacts of spatial filter on a hot image through medium with gain, in this paper, we present theoretical and numerical treatment for hot image formation considering the spatial filter effect. It may be helpful for designing the high power systems and minimizing the damage risks coming from the hot image.…”

Investigation on the formation of second-order-hot-image-like fringes

“…Some research work has been done on the propagation of nonlinear imaging and the properties of hot image induced by attenuation scatterer and phase scatterer [3][4][5][6][7][8][9][10][11][12][13]. Moreover, bandwidth [14,15] and spatial filter [16] methods have been developed to suppress the nonlinear imaging. It has been shown by experiments [3] that image fringe of a pure phase-typed scatterer is generally worse than that of a pure attenuation-typed one.…”