Electromagnetically induced coherent backscattering

We demonstrate a strong coherent backward wave oscillation using forward propagating fields only. This is achieved by applying laser fields to an ultra-dispersive medium with proper chosen detunings to excite a molecular vibrational coherence that corresponds to a backward propagating wave. The physics then has much in common with propagation of ultra-slow light. Applications to coherent scattering and remote sensing are discussed

From Laser Induced Line Narrowing To Electromagnetically Induced Transparency: Closed System Analysis

Laser induced line narrowing effect, discovered more than thirty years ago, can also be applied to recent studies in high resolution spectroscopy based on electromagnetically induced transparency. In this paper we first present a general form of the transmission width of electromagnetically induced transparency in a homogeneously broadened medium. We then analyze a Doppler broadened medium by using a Lorentzian function as the atomic velocity distribution. The dependence of the transmission linewidth on the driving field intensity is discussed and compared to the laser induced line narrowing effect. This dependence can be characterized by a parameter which can be regarded as ``the degree of optical pumping''.Comment: 8 pages, 5 figure

A resonant single frequency molecular detector with high sensitivity and selectivity for gas mixtures

Air quality control is an important task in prevention of human exposure to toxic and harmful gases and requires reliable gas sensors. During last decades many gas sensing mechanisms, based on different physical or chemical interactions with sensitive materials, have been developed, but the problem of precise analysis of gas mixtures still remains. The problem can be solved by introducing new sensing mechanism based on an adiabatically changing electric field interacting with the rotational structure of the molecules with dipole moments. We have theoretically demonstrated a single low frequency gas detector that can be used for sensing of gas mixtures with high selectivity, accuracy, and sensitivity. The enhancement of the population difference between corresponding molecular levels and reached the theoretical maximum of absorption have been shown

Group velocity study in hot Rb vapor with buffer gas

We study the behavior of the group velocity of light under conditions of electromagnetically induced transparency (EIT) in a Doppler broadened medium. Specifically, we show how the group delay (or group velocity) of probe and generated Stokes fields depends on the one-photon detuning of drive and probe fields. We find that for atoms in a buffer gas the group velocity decreases with positive one-photon detuning of the drive fields, and increases when the fields are red detuned. This dependence is counter-intuitive to what would be expected if the one-photon detuning resulted in an interaction of the light with the resonant velocity subgroup.Comment: 6 pages, 7 figure

Coherent control of atomic excitation using off-resonant strong few-cycle pulses

We study the dynamics of a two-level system driven by an off-resonant few-cycle pulse which has a phase jump $\phi$ at $t=t_{0}$, in contrast to many cycle pulses, under non rotating-wave approximation (NRWA). We give a closed form analytical solution for the evolution of the probability amplitude $|C_{a} (t)|$ for the upper level. Using the appropriate pulse parameters like phase-jump $\phi$, jump time $t_{0}$, pulse width $\tau$, frequency $\nu$ and Rabi frequency $\Omega_{0}$ the population transfer, after the pulse is gone, can be optimized and for the pulse considered here, enhancement of $10^{6}-10^{8}$ factor was obtained.Comment: 5 Pages, 7 Figure