Coherent anti-Stokes Raman scattering due to spin transitions of free
carriers in narrow gap semiconductors is discussed. The basic results
of the electrodynamic theory of optical four-wave mixing and of the qu
antum mechanical calculation of the third-order non-linear susceptibil
ity chi((3)) are briefly reported in the context of the particular pro
perties of narrow gap semiconductors. The enhancement of the Raman-lik
e resonances of chi((3)) for photon energies close to the fundamental
gap is demonstrated and interferences of Raman and one-photon interban
d transitions are discussed. Applications of the method to epitaxial f
ilms of narrow gap semiconductors and to quantum well structures are p
resented.