Spectral responsitivity and efficiency of metal-based femtosecond autocorrelation technique

We have studied, for the first time experimentally, the efficiency and spectral responsivity of an autocorrelation technique that is based on second harmonic generation from metal surfaces. High-quality autocorrelation traces are obtained with pulse energies as small as only 64 pJ (intensity 6.5 MW/cm), resulting in an efficiency that is comparable with existing nonlinear-crystal-based autocorrelation techniques. Our scheme, however, has a number of significant advantages over most existing autocorrelation techniques because it is dispersion-free and provides automatic phase matching over an extremely wide spectral range. This technique has potential for temporally characterizing any light source with a super-broad spectrum, a task that cannot be accomplished with existing techniques. 2004 Elsevier B.V. All rights reserved. PACS: 42.65.Ky; 42.62.Eh