  Photon-echo based quantum memories use inhomogeneously broadened, optically
thick ensembles of absorbers to store a weak optical signal and employ various
protocols to rephase the atomic coherences for information retrieval. We study
the application of two consecutive, frequency-chirped control pulses for
coherence rephasing in an ensemble with a 'natural' inhomogeneous broadening.
Although propagation effects distort the two control pulses differently,
chirped pulses that drive adiabatic passage can rephase atomic coherences in an
optically thick storage medium. Combined with spatial phase mismatching
techniques to prevent primary echo emission, coherences can be rephased around
the ground state to achieve secondary echo emission with close to unit
efficiency. Potential advantages over similar schemes working with $\pi$-pulses
include greater potential signal fidelity, reduced noise due to spontaneous
emission and better capability for the storage of multiple memory channels.
