High dynamic range autocorrelation studies of a femtosecond Ti: sapphire oscillator and its relevance to the optimisation of chirped pulse amplification systems

Abstract We report on background-free intensity autocorrelation studies of sub-50 fs pulses from a Kerr lens mode-locked (KLM) Ti: sapphire laser over an intensity dynamic range of approximately 7 orders of magnitude. Results reveal the presence of a low intensity pedestal, at the 10 −5 level, which can be improved by incorporating a hard aperture in the cavity. We also present the results derived from a ray tracing code used to investigate the propagatin of pulses through a cylindrical mirror stretcher/compressor. The strong dependence of the residual pedestal level with initial pulse bandwidth and spectral clipping is discussed. The various limiting effects of both the seed oscillator and the stretcher/compressor on the final pedestal intensity level in the linear amplification regime are discussed.