  We show that useful non-instantaneous nonlinear phase shifts can be obtained
from cascaded quadratic processes in the presence of group velocity mismatch.
The two-field nature of the process permits responses that can be effectively
advanced or retarded in time with respect to one of the fields. There is an
analogy to a generalized Raman-scattering effect, permitting both red and blue
shifts of short pulses. We expect this capability to have many applications in
short-pulse generation and propagation, such as the compensation of
Raman-induced effects and high-quality pulse compression, which we discuss.
