  We introduce the concept of the inverse prism as the dual of the conventional
prism and deduce from this duality an implementation of it based on temporal
discontinuity and spatial dispersion provided by anisotropy. Moreover, we show
that this inverse prism exhibits the following three unique properties:
chromatic refraction birefringence, ordinary-monochromatic and extraordinary-
polychromatic temporal refraction, and linear-to-Lissajous polarization
transformation.
