Interlaced Spin Grating is a scheme for the preparation of spectro-spatial
periodic absorption gratings in a inhomogeneously broadened absorption profile.
It relies on the optical pumping of atoms in a nearby long-lived ground state
sublevel. The scheme takes advantage of the sublevel proximity to build large
contrast gratings with unlimited bandwidth and preserved average optical depth.
It is particularly suited to Tm-doped crystals in the context of classical and
quantum signal processing. In this paper, we study the optical pumping dynamics
at play in an Interlaced Spin Grating and describe the corresponding absorption
profile shape in an optically thick atomic ensemble. We show that, in Tm:YAG,
the diffraction efficiency of such a grating can reach 18.3% in the small
angle, and 11.6% in the large angle configuration when the excitation is made
of simple pulse pairs, considerably outperforming conventional gratings.Comment: 11 pages, 13 figures in Physical Review A, 201
The time-reversal (TR) protocol we implement in an erbium-doped YSO crystal is based on photon echoes but avoids the storage of the signal to be processed. Unlike other approaches implying digitizing or highly dispersive optical fibers, the proposed scheme reaches the μs range and potentially offers high bandwidth, both required for RADAR applications. In this Letter, we demonstrate faithful reversal of arbitrary pulse sequences with 6 μs duration and 10 MHz bandwidth. To the best of our knowledge, this is the first demonstration of TR via linear filtering in a programmable material.
Based on the similarity of paraxial diffraction and dispersion mathematical descriptions, the temporal imaging of optical pulses combines linear dispersive filters and quadratic phase modulations operating as time lenses. We consider programming a dispersive filter near atomic resonance in rare earth ion-doped crystals, which leads to unprecedented high values of dispersive power. This filter is used in an approximate imaging scheme, combining a single time lens and a single dispersive section and operating as a time-reversing device, with potential applications in radio-frequency signal processing. This scheme is closely related to a three-pulse photon echo with chirped pulses, but the connection with temporal imaging and dispersive filtering emphasizes new features.
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