  We propose a ``channelization'' architecture to achieve wide-band
electromagnetically induced transparency (EIT) and ultra-slow light propagation
in atomic Rb-87 vapors. EIT and slow light are achieved by shining a strong,
resonant ``pump'' laser on the atomic medium, which allows slow and
unattenuated propagation of a weaker ``signal'' beam, but only when a
two-photon resonance condition is satisfied. Our wideband architecture is
accomplished by dispersing a wideband signal spatially, transverse to the
propagation direction, prior to entering the atomic cell. When particular
Zeeman sub-levels are used in the EIT system, then one can introduce a magnetic
field with a linear gradient such that the two-photon resonance condition is
satisfied for each individual frequency component. Because slow light is a
group velocity effect, utilizing differential phase shifts across the spectrum
of a light pulse, one must then introduce a slight mismatch from perfect
resonance to induce a delay. We present a model which accounts for diffusion of
the atoms in the varying magnetic field as well as interaction with levels
outside the ideal three-level system on which EIT is based. We find the maximum
delay-bandwidth product decreases with bandwidth, and that delay-bandwidth
product ~1 should be achievable with bandwidth ~50 MHz (~5 ns delay). This is a
large improvement over the ~1 MHz bandwidths in conventional slow light systems
and could be of use in signal processing applications.
