  We theoretically investigate a scheme in which backward coherent anti-Stokes
Raman scattering (CARS) is significantly enhanced by using slow light.
Specifically, we reduce the group velocity of the Stokes excitation pulse by
introducing a coupling laser that causes electromagnetically induced
transparency (EIT). When the Stokes pulse has a spatial length shorter than the
CARS wavelength, the backward CARS emission is significantly enhanced. We also
investigated the possibility of applying this scheme as a CARS lidar with O2 or
N2 as the EIT medium. We found that if nanosecond laser with large pulse energy
(>1 J) and a telescope with large aperture (~10 m) are equipped in the lidar
system, a CARS lidar could become much more sensitive than a spontaneous Raman
lidar.
