Abstract

Group velocity dispersion (GVD) is a well-known phenomenon that causes pulse broadening of femtosecond pulses propagating through dispersive materials. Femtosecond spectroscopy is becoming commonplace, and one must consider the effect of GVD in optical components such as mirrors, lenses, prisms, glass plates, glass cells, dielectric-coated mirrors, nonlinear crystals, liquid samples, solid samples, and detectors, each of which shows GVD effects. In this presentation, broadening effects are numerically calculated for GVD in various optical components by means of the Drude refractive-index model. Beam trajectories in various optical components, such as lenses and prisms, are simulated to evaluate the material thickness, which determines the broadening. For example, the ratio of duration times between the incident pulse tin and the output pulse tout through a dispersive plate is calculated from (t_out/t_in)² = 1+(BL/t_in²)², where B is a coefficient that depends on material characteristics and L is the thickness of the plate. For a 1 mm thick BK7 glass plate, a 10 fs laser pulse at 600 nm will broaden to be 22.83 fs with B = 2.052 × 10^–25. Even a 100 µm thick KDP nonlinear crystal broadens a 10 fs pulse to 10.21 fs. Details of femtosecond pulse broadening will be presented for lenses, prisms, water, and air.

© 1990 Optical Society of America