High-order pulse front tilt caused by high-order angular dispersion

We have found general expressions relating the high- order pulse front tilt and the high- order angular dispersion in an ultrashort pulse, for the first time to our knowledge. The general formulae based on Fermat's principle are applicable for any ultrashort pulse with angular dispersion in the limit of geometrical optics. By virtue of these formulae, we can calculate the high- order pulse front tilt in the sub- 20- fs UV pulse generated in a novel scheme of sum- frequency mixing in a nonlinear crystal accompanied by angular dispersion. It is also demonstrated how the high- order angular dispersion can be eliminated in the calculation. (C) 2003 Optical Society of America.