Temporal Contrast Enhancement of Gemini Laser System with a Nonlinear Temporal Filter at the Front End

Ultra-high intensity lasers based on the chirped pulse amplification (CPA) have proved to be a very powerful drive source to accelerate electrons and protons, producing ultrafast coherent X-ray pulses and high-quality bright proton beams. The temporal contrast (TC) of such lasers plays a crucial role in these applications while even a minute level of light would destroy the target before the main pulse [1]. TC enhancement [2] is being an important part of the system development of petawatt class laser systems, such as Gemini which is a CPA system based on Ti:Sapphire active medium. Implementation of transmission gratings in a stretcher design addresses TC improvements at the range of few tens of picoseconds before the main pulse [3]. Reduction of the background level of TC could be achieved by using different strategies one of which is an application of intensity dependent filter before CPA chain. In this paper we present the results of TC enhancement after to inclusion of a nonlinear temporal filtering (TF) device into modified front end.