FEMTOSECOND PULSE FRONT TILT CAUSED BY ANGULAR-DISPERSION

Femtosecond pulse fronts suffer a time delay across the beam when propagating through diffraction gratings or dispersive prisms. A general relation was found describing the tilt angle gamma of the pulse front as, tangamma = lambdadepsilon/dlambda where depsilon/dlambda is the angular dispersion of the grating or prism and lambda is the central wavelength of the pulse. The expression is valid for any spectral device having angular dispersion (e.g., Fabry-Perot interferometer, Lummer-Gehrcke plate, and Michelson echelon). The tilt angle is shown to have a close relation to the classical uncertainty principle.