Yu. V. Rostovtsev

Gain-swept superradiance applied to the stand-off detection of trace impurities in the atmosphere.

We show that gain-swept superradiance can be used to detect low (parts per million) concentrations of various gases at distances on the order of kilometers, which is done by using pulse timing to create small regions of gain at positions that sweep toward a detector. The technique is far more sensitive than previous methods such as light detection and ranging or differential absorption light detection and ranging.

New analytic solution of Schrödinger's equation

We obtain an analytic solution beyond adiabatic approximation by transferring the 1D Schrodinger equation into the Ricatti equation. Then we show that our solution is more accurate than JWKB approximation. The generalizations of the approach to 3D are suggested, and possible applications of obtained solutions are discussed.

Fast optical switching via stimulated Raman adiabatic passage

We demonstrate a new approach to fast optical switching with a technique based on stimulated Raman adiabatic passage in which a laser pulse switches the probe field on and off via another coupling pulse. This new kind of optical switching is not limited by the decay rate of an excited state and can operate in the subnanosecond time domain. The experimental observation in Rb atomic vapor is in good agreement with numerical simulations.

Quantum interference in atomic vapor controlled by a magnetic field

We have shown that quantum interference in a driven quasi-degenerate two-level atomic system can be controlled by an externally applied magnetic field. We demonstrate that the mechanism of optical control is based on quantum interference, which allows one to implement both electromagnetically induced transparency and electromagnetically induced absorption (EIA) in one atomic system. The experimental realization is suggested.

Three-photon electromagnetically induced absorption and transparency in an inhomogeneously broadened atomic vapour

We study both theoretically and experimentally three-photon electromagnetically induced transparency and electromagnetically induced absorption resonances in inhomogeneously broadened 85 Rb atomic vapour driven by probe and drive laser radiations. We observe narrow Doppler-free absorption as well as transmission resonances for the probe field when the driving laser field is redshifted from the D1 or D2 lines of 85Rb; the frequency difference between the drive and probe fields is equal to the hyperfine splitting of the ground state of the atoms, and the probe field is tuned to the centre of the Doppler broadened atomic transition. We theoretically study the spectroscopic effect in both homogeneously and inhomogeneously broadened media. Our numerical simulations are in good agreement with the experimental results.

Observation of electromagnetically induced transparency in cesium molecules

We have studied electromagnetically induced transparency (EIT) in diatomic cesium molecules in a vapor cell by using tunable diode lasers. We have observed a sub-natural Λ-resonance in absorption molecular band B1Πu − X1Σg+ at different cesium vapor pressures. The width of the EIT resonance shows a linear dependence on a cesium vapor pressure.We have studied electromagnetically induced transparency (EIT) in diatomic cesium molecules in a vapor cell by using tunable diode lasers. We have observed a sub-natural Lambda-resonance in an absorption molecular band at different cesium vapor pressures. The width of the EIT resonance shows a linear dependence on cesium vapor pressure. Narrow Lambda-resonances in molecules can be used as frequency references for femtosecond laser frequency combs.

Dynamic control of EIT by changing optical phase

We have studied phase dynamics in EIT in a dense rubidium vapor. We have observed a very fast growth of the absorption when the phase of the optical field was abruptly changed, followed by a slow return to the steady state absorption. Then the transmission was slowly restored to stationary magnitude. The recovery time is on the order of the transit time of the atom flying through the laser beam and decreases with increasing optical power. The fast variation of the transparency is proportional to the phase deviation. The obtained result can be used for the fast control of EIT, for example, in an optical switch.

Spatial amplification of a laser wave and the transverse spread of electrons in an undulator with a noncollinear configuration

The spatial amplification of a wave in a magnetostatic undulator with noncollinear electron and laser beams is studied in the framework of the dispersion relation for single-frequency and collective regimes. The dependence of the gain on the electron beam width is estimated with regard to the spatial boundedness of the beams. The laser power threshold at which the selection with respect to the transverse velocity is possible is obtained for a free-electron laser without inversion.

Absorption and emission in defective cholesteric liquid crystal cells

We investigated peculiarities of absorption, emission and photonic density of states of a cholesteric liquid crystal with an isotropic defect layer inside. The influence of the defect layer position on absorption and emission in the system was studied. It was shown that for non-diffracting circularly polarized incident light absorption/emission is maximum if the defect is in the centre of the system; and for diffracting circularly polarized incident light absorption/emission is maximum if the defect is shifted from the centre of the system to its left border from where light is incident. We also investigated influence of the defect layer thickness and those parameters which characterize loss and gain on absorption and emission. The influence of anisotropic absorption in the cholesteric liquid crystal layer on photonic density states was investigated, too.

Using phase dynamics in EIT to probe ground state relaxation in rubidium vapor

We have studied a time response of electromagnetically induced transparency (EIT) in a rubidium vapor to a rapid variation of optical phase. We have observed a very fast growth of the absorption when the phase of the optical field has been abruptly changed, followed by a slow return to the level of steady-state absorption. The recovery time decreases with increasing optical power. A simple theoretical analysis shows that under our experimental conditions the low power limit of the recovery time is determined by the ground relaxation time. In our case it is defined by a time-of-flight of rubidium atoms through laser beam. The obtained value of the ground state relaxation time is in a good agreement with result of direct measurements by ‘relaxation in the dark’ method. Our technique based on phase dynamics in EIT can be used for investigation of the ground state relaxation and the fast control of EIT.