Analysis on FM-to-AM conversion of SSD beam induced by etalon effect in a high-power laser system
FM-to-AM conversion based on non-uniform spectral transmission of broadband beam is harmful to high power laser facility. Smoothing by spectral dispersion (SSD) beam as a broadband beam is very special for it is monochromatic at given time and space on near field, and so the method that optical spectral transfer function is used as filters can’t accurately describe its amplitude modulation (AM) characteristics. This letter presents the theories of etalon effect for SSD beam. With low order approximation instead of steady-state approximation, the analytic model of temporal shape of SSD beam is achieved for the first time, which gives the detailed AM characteristics at local and integral aspects, such as the variation of ripples width and amplitude in general situation. We also analyze FM-to-AM conversion on focal plane; in the focusing process, the lens simply acts as an integrator to smooth AM of SSD beam. Note that AM control is required for near field to avoid optics damage and for far field to ensure an optimal interaction of laser-target, the results provide some important phenomena and rules that can be applied for pulse shape control.
Li Ping,Su Jingqin,Feng Bing,Wei Xiaofeng. Analysis on FM-to-AM conversion of SSD beam induced by etalon effect in a high-power laser system[J].High Power Laser Science and Engineering,,():.