HIGH DYNAMIC-RANGE AUTOCORRELATION STUDIES OF A FEMTOSECOND TI-SAPPHIRE OSCILLATOR AND ITS RELEVANCE TO THE OPTIMIZATION OF CHIRPED PULSE AMPLIFICATION SYSTEMS

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. Re sults reveal the presence of a low intensity pedestal, at the 10(-5) l evel, which can be improved by incorporating a hard aperture in the ca vity. We also present the results derived from a ray tracing code used to investigate the propagation 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 stre tcher/compressor on the final pedestal intensity level in the linear a mplification regime are discussed.