30,223 research outputs found
Transmission eigenvalues and the bare conductance in the crossover to Anderson localization
We measure the field transmission matrix t for microwave radiation
propagating through random waveguides in the crossover to Anderson
localization. From these measurements, we determine the dimensionless
conductance, g, and the individual eigenvalues of the transmission
matrix whose sum equals g. In diffusive samples, the highest
eigenvalue, , is close to unity corresponding to a transmission of
nearly 100%, while for localized waves, the average of , is nearly
equal to g. We find that the spacing between average values of is
constant and demonstrate that when surface interactions are taken into account
it is equal to the inverse of the bare conductance.Comment: 5 pages, 5 figure
High-frequency Light Reflector via Low-frequency Light Control
We show that the momentum of light can be reversed via the atomic coherence
created by another light with one or two orders of magnitude lower frequency.
Both the backward retrieval of single photons from a timed Dicke state and the
reflection of continuous waves by high-order photonic band gaps are analysed.
The required control field strength scales linearly with the nonlinearity
order, which is explained by the dynamics of superradiance lattices.
Experiments are proposed with Rb atoms and Be ions. This holds
promise for light-controllable X-ray reflectors.Comment: 5 pages, 5 figure
Superradiance Lattice
We show that the timed Dicke states of a collection of three-level atoms can
form a tight-binding lattice in momentum space. This lattice, coined the
superradiance lattice (SL), can be constructed based on electromagnetically
induced transparency (EIT). For a one-dimensional SL, we need the coupling
field of the EIT system to be a standing wave. The detuning between the two
components of the standing wave introduces an effective uniform force in
momentum space. The quantum lattice dynamics, such as Bloch oscillations,
Wannier-Stark ladders, Bloch band collapsing and dynamic localization can be
observed in the SL. The two-dimensional SL provides a flexible platform for
Dirac physics in graphene. The SL can be extended to three and higher
dimensions where no analogous real space lattices exist with new physics
waiting to be explored.Comment: 6pages, 4 figure
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