Kisik Kim

An electromagnetically induced grating by microwave modulation

We study the phenomenon of an electromagnetically induced phase grating in a double-dark state system of 87Rb atoms, the two closely placed lower fold levels of which are coupled by a weak microwave field. Owing to the existence of the weak microwave field, the efficiency of the phase grating is strikingly improved, and an efficiency of approximately 33% can be achieved. Under the action of the weak standing wave field, the high efficiency of the phase grating can be maintained by modulating the strength and detuning of the weak microwave field, increasing the strength of the standing wave field.

A quantum trajectory unraveling of the superradiance master equation

We unravel the superradiance master equation into quantum trajectories whose stochastic wavefunction is conditioned on photon counting records resolved in photon emission time and direction. Numerical results are reported which illustrate the wealth of statistical information made available by simulating the counting records.

Quantum variances in field modes of parametric down converter

Parametric down converter is a device to generate quantum nonclassical states of light. Such states play a key role in studies of new quantum optical effects. Here we present an analysis of output quadrature variances in the signal, idler, and pump modes of the down converter. Our treatment in Schrodinger three-mode representation with quantized pump is based on multi-particle representation of the down converter wave function. This enables to trace behaviour of the wave amplitudes of the multi-particle correlated states with increase of the gain parameter and the input pump intensity. The developed method allows us to calculate minimum quadrature variances in the output modes as functions of the gain parameter and the pump amplitude. Special attention is given to pump output quantum quadrature variances. We show that the pump mode acquires new quantum properties different from input due to action of the down converter. We compare our results related to the separate signal and idler quantum quadrature variances with the ones following from the classical pump approximation.

Approximate method in coherent-mode representation.

An approximate method to find the coherent-mode eigenfunctions and the corresponding eigenvalues for nondegenerate cross spectral densities of a source is presented.

Polarization of completely coherent random electromagnetic beams

It is shown that the spectral degree of polarization rho(r, omega) of a fluctuating electromagnetic beam which is completely coherent throughout a domain D is necessarily the same at every point in D. It can take on any value in the range 0 < or = rho < or = 1. In particular, the fully coherent beam can be completely polarized or completely unpolarized throughout D.

Generation of correlated squeezing in nonlinear coupler

We investigate theoretically the generation of the correlated squeezed state in the nonlinear coupler when the coherent optical fields propagate along the nonlinear coupler. We study the behaviours of the quantum fields generated from vacuum in the optical waveguides of the short-length nonlinear coupler by linearizing the quantum equations of motion around the corresponding classical solutions. The linearized treatment enables us to take into account the depletion of the classical fields and the influence of input conditions, which are imposed on the classical waves, on the generated fields. The degrees of squeezing in both optical waveguides in the nonlinear coupler are calculated numerically and their relations to the solutions of the classical equations of motion are discussed. The effect of the input relative phase between the classical optical fields on the output squeezing is also discussed.

Effect of superposition of light through a beam splitter on nonclassicality

We analyzed the properties of superposition of light through a beam splitter and investigated the variations of the nonclassical measure and Mandels Q-parameter. We found in the case of single input the output field possesses a reduced nonclassical measure due to the amplitude reduction through the beam splitter. In the case when two input fields are nonclassical, the output field becomes less nonclassical in a sense that the nonclassical measure (Q-parameter) of the output field is bounded below (above) a certain value subjected to the given transmittance or reflectance of the beam splitter. We also show that the nonclassical input field can be changed into a classical field as the result of superposition with thermal light.

Nonclassical measure of cavity field interacting with thermal reservoir

Abstract The time variation of the nonclassical measure of the cavity field interacting with a thermal reservoir is examined. From the knowledge of the quasi-probability distribution function of the cavity field as a function of time, the nonclassical measure of the state is explicitly calculated in terms of the initial nonclassical measure, the decay constant, and the average number of photons in the reservoir. The nonclassical measure of the sub-Poissonian character is also considered and it is confirmed that the sub-Poissonian character, for an initial Fock state, disappears in half the time required for the cavity field to become classical.

The quasi-homogeneous approximation for a class of three-dimensional primary sources

We investigate the validity of the quasi-homogeneous approximation for three-dimensional primary Gaussian Schell-model sources. It is shown that the quasi-homogeneous approximation is not valid for such a source unless two conditions are satisfied, one of which depends only upon the spatial characteristics of the source, and the other depends upon the wavelength of the radiation. The second of these conditions appears not to have been appreciated in previous work relating to the quasi-homogeneous approximation, and its significance to the foundations of radiometry is discussed.

Phase modulation of electromagnetically induced grating in a four-level system

Electromagnetically induced phase grating (EIPG) is investigated in a microwave-coupled four-level atomic system, where the two closely spaced lower levels are driven by a microwave field. In the presence of a microwave field, the diffraction efficiency of grating is improved greatly by phase modulation. For this case, one can properly tune the interaction length of the atomic sample, modulate detuning of the microwave and the probe fields, and obtain the high diffraction efficiency of 32% approximately.