  We report new aspects of temporal dispersion in Fourier pulse shapers which
contain spectral dispersers with a nonlinear frequency to space mapping. These
effects are particularly important in high resolution operation since high
resolution dispersers typically exhibit pronounced nonlinear angular dispersion
over relatively small bandwidths. In this paper we present a general discussion
of the new effects followed by quantitative analysis and experimental
verification for pulse shapers which utilize a virtually imaged phased array
(VIPA) as the spectral disperser. Compared to the well known 4f configuration,
our results demonstrate a substantial modification to the placement of the
optical components required to obtain zero temporal dispersion. Furthermore,
spectral phase variations associated with nonzero dispersion coupled with
contributions from multiple diffraction orders are shown to give rise to a
dramatic new spectral interference effect, which can be used to monitor
temporal dispersion purely in the spectral domain. We expect the effects we
present in this paper to become prominent even for more conventional
diffraction grating based pulse shapers for bandwidths sufficiently large that
nonlinear spectral mapping becomes strong.
