Pulse crest surface curvature in some types of compressor

In this work we demonstrate the appearance of a pulse crest curvature which differs from wave-front curvature in certain chirped pulse compressors within the femtosecond range. This happens because the spectrum is made to focus on a grating or a holographic optical element, and this cannot be achieved for all wavelengths. The phenomenon is analysed from the viewpoint of geometric diffraction, as a function of chromatism, and is tested by ray tracing.