Role of intensity fluctuations in laser-beam apodization with a graded random phase window.
Analysis indicates that a transparent window with graded random surface modulation will apodize a laser beam. Following the apodizer the laser beam consists of a scattered component of mean intensity I(s) and an apodized component of mean intensity I(a). The apodizer intensity transmission is exp[-k(2)(n-1)(2)t( 2)(r)], where t( 2)(r)is the window surface modulation mean-squared amplitude, k is the radiation wave number, and n is the window refractive index. Interference between the scattered and unscattered radiation produces intensity fluctuations similar to laser speckle. For high-power applications, minimization of the probability of optical damage due to intensity fluctuations requires that I(a)/I(s) greater, similar 10(2).
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