30 research outputs found
Pulse propagation, population transfer and light storage in five-level media
We consider adiabatic interaction of five-level atomic systems and their
media with four short laser pulses under the condition of all two-photon
detunings being zero. We derive analytical expressions for eigenvalues of the
system's Hamiltonian and determine conditions of adiabaticity for both the atom
and the medium. We analyse, in detail, the system's behaviour when the
eigenvalue with non-vanishing energy is realized. As distinct from the usual
dark state of a five-level system (corresponding to zero eigenvalue), which is
a superposition of three states, in our case the superposition of four states
does work. This seemingly unfavourable case is nevertheless demonstrated to
imitate completely a three-level system not only for a single atom but also in
the medium, since the propagation equations are also split into those for
three- and two-level media separately. We show that, under certain conditions,
all the coherent effects observed in three-level media, such as population
transfer, light slowing, light storage, and so on, may efficiently be realized
in five-level media. This has an important advantage that the light storage can
be performed twice in the same medium, i.e., the second pulse can be stored
without retrieving the first one, and then the two pulses can be retrieved in
any desired sequence
Short Pulse Propagation in an Inverted Two-Level Medium
We consider propagation of a pulse carrying optical information in a resonant medium of
twolevel atoms and revisit the concept of the group velocity. We obtain conditions when this concept
may be used and show that in a population inverted medium the possible superluminal propagation
may result in advance times much shorter than the pulse duration because of lethargic amplification
following from the complete exact solution of the problem
Short Pulse Propagation in an Inverted Two-Level Medium
We consider propagation of a pulse carrying optical information in a resonant medium of
twolevel atoms and revisit the concept of the group velocity. We obtain conditions when this concept
may be used and show that in a population inverted medium the possible superluminal propagation
may result in advance times much shorter than the pulse duration because of lethargic amplification
following from the complete exact solution of the problem
Short Pulse Propagation in an Inverted Two-Level Medium
We consider propagation of a pulse carrying optical information in a resonant medium of
twolevel atoms and revisit the concept of the group velocity. We obtain conditions when this concept
may be used and show that in a population inverted medium the possible superluminal propagation
may result in advance times much shorter than the pulse duration because of lethargic amplification
following from the complete exact solution of the problem
Coherent control of interference processes in radiative decays
Possibility of coherent control of spontaneous emission from four- and five-level system
in the laser radiation field is studied. The four-level system consists of two levels
resonantly driven by laser radiation where either of levels may decay to a separate level.
For such a system, we show that the presence of the second decay channel may deteriorate
the destructive interference occurring in case of one decay channel because of
Autler-Townes effect. The five-level diagram represents two two-level resonantly driven
systems with the upper levels decaying to a common level. For this diagram, interference
between the two decay channels takes place and it is partially or completely destructive
or constructive depending on the initial conditions and on the mutual orientation of the
transition dipole moments. It is shown that population transfer takes place by the
same quantum vacuum via spontaneous emission. The populations are shown
to have damping oscillatory nature
Selective reflection by atomic vapor: experiments and self-consistent theory
Selective reflection of laser radiation from the interface between atomic
vapor and a dielectric is studied for a wide range of vapor density. A
self-consistent model is developed, some analytical results are obtained, as
well as a number of curves are computed that are in good agreement with
experimental spectra measured in cesium and rubidium vapor cells.