  A possibility to greatly enhance frequency-conversion efficiency of
stimulated Raman scattering is shown by making use of extraordinary properties
of three-wave mixing of ordinary and backward waves. Such processes are
commonly attributed to negative-index plasmonic metamaterials. This work
demonstrates the possibility to replace such metamaterials that are very
challenging to engineer by readily available crystals which support elastic
waves with contra-directed phase and group velocities. The main goal of this
work is to investigate specific properties of indicated nonlinear optical
process in short pulse regime and to show that it enables elimination of
fundamental detrimental effect of fast damping of optical phonons on the
process concerned. Among the applications is the possibility of creation of a
family of unique photonic devices such as unidirectional Raman amplifiers and
femtosecond pulse shapers with greatly improved operational properties.
