S. Kielich

Self-squeezing of light propagating through nonlinear optically isotropic media

Abstract In an isotropic medium in which light self-induces a cubic optical nonlinearity, the light field is shown to be in squeezed states on traversal of the medium. The dependence of the squeezing effect on the polarization state of the field and the nonlinear molecular parameters is derived explicitly. A comparison is made to the photon antibunching effect in the same phenomenon.

Squeezing in the third-harmonic field generated by self-squeezed light

A new mechanism for producing squeezed states in the third-harmonic field generated in isotropic media is discussed. It is shown that considerable squeezing is obtained if the third-harmonic field is generated by self-squeezed light resulting from a nonlinear propagation process. Analytical formulas describing this novel way of producing squeezed states are derived and illustrated graphically, showing strong correlations of squeezing in the fundamental and the third-harmonic beams.

Quantum fluctuations in the Stokes parameters of light propagating in a Kerr medium

Abstract The quantum theory of light propagation in a nonlinear Kerr medium is applied to calculate the Stokes parameters and their variances in the process of light propagation. Exact quantum formulae are derived for the expectation values of the Stokes operators and thus for the azimuth θ and ellipticity η of the beam. The role of quantum fluctuations in light polarization characteristics is discussed. The periodic behaviour of quantum evolution of the light polarization is revealed explicitly. It is shown that the degree of polarization is diminished at early stages of each period of the evolution but then reverts to its initial state of complete polarization at the end of the period. The variances of the Stokes parameters are also periodic and intensity-dependent; however, they never fall below their coherent state values.

Photon Antibunching and Squeezing

The occurrence of photon antibunching and squeezing is strongly connected with nonlinear optical phenomena in general. Recent results are presented for two-atom resonance fluorescence, the anharmonic oscillator, nonlinear propagation of light and higher-harmonic generation.

On the Possibility of Almost Complete Self-squeezing of Strong Electromagnetic Fields

The propagation of quantized electromagnetic fields through optically isotropic media with cubic optical nonlinearity is considered. Analytical solutions are presented in closed form showing that the light field can emerge from the medium in a squeezed quantum state. A detailed numerical analysis of the results is performed and presented graphically. Over 90 per cent of the squeezing permitted by quantum-mechanical theory is achieved in this way. The dependence of the squeezing effect on the polarization state of the field and the nonlinear molecular parameters is also discussed.

Laser-induced autoionization from a double Fano system

We discuss a system with two discrete levels embedded in one continuum, which, after Fano diagonalization, gives a double Fano profile with two zeros. The second zero, which is located between the two levels, does not disappear even when the asymmetry parameter q goes to infinity. The spectrum of photoelectrons from such a system is calculated for any strength of the exciting field.

Quantum beats and superradiant effects in the spontaneous emission from two nonidentical atoms

The problem considered is that of the spontaneous emission from two nonidentical two-level atoms coupled to a continuum of quantized electromagnetic modes. The atoms are separated by distances comparable to the resonant wavelength and have different transition frequencies and natural linewidths. Correlation functions and radiation rates are expressed in terms of expectation values of time-dependent atomic operators. The radiation pattern, total radiation rate and spectral distribution of radiation are obtained with the initial conditions that only one atom is excited and that the system is fully inverted. We find that the radiation pattern and total radiation rate show quantum beats when initially only one atom is excited. Moreover, the total radiation rate for strong interatomic interaction becomes greater than its initial value at the beginning of the emission process. This “superradiant” property is absent for two identical atoms. For initially fully inverted system, the radiation pattern and total radiation rate decay monotonically in time. Some weak beats can appear for drastically different atoms. The spectrum of radiation calculated for the case of strong interatomic interaction, i.e., for separations much smaller than the resonant wavelength shows two peaks, located at frequency ±Ω12, contrary to the case of identical atoms, when the spectrum consists of only one peak located at the frequency +Ω12.

Squeezed states in the transient regime of resonance fluorescence

The nonclassical nature of the so-called squeezed states of electromagnetic fields has recently been discussed in connection with the phenomenon of resonance fluorescence from a coherently driven two-level atom.1 It has been shown that either the in-phase component E1 or the out-of-phase component E2 of the fluorescent field can become squeezed if the Rabi frequency Ω of the ex- citing field is sufficiently low. Squeezing is defined as a negative value of the normally ordered variance 〈: (ΔE1)2:〉 (or 〈:(ΔE2)2:〈). To satisfy this condition in the steady state, if the exciting field is tuned perfectly to the atomic transition, the Rabi frequency Ω has to be less than √2y, with 2y = A—the Einstein coefficient for spontaneous emission. Off-resonance excitation further lowers this critical value of 0. Walls and Zoller1 have indicated, without giving the details, that, in a transient regime, the squeezing effect can become twice as large as in the steady state.

Resonance fluorescence spectrum of two atoms, coherently driven by a strong resonant laser field

Abstract In Lehmbergs approach, we consider the resonance fluorescence spectrum of two radiatively interacting atoms. In the strong field limit we have obtained analytical solutions for the spectrum of the symmetric and antisymmetric modes without decoupling approximation. Our solutions are valid for all values of the distance r12 separating the atoms. The spectrum of the symmetric modes contains additional sidebands in 2Ω (Ω is the Rabi frequency) with amplitude dependent on (a/Ω)2, where a is a parameter dependent on r12. The antisymmetric part of the spectrum has no additional sidebands in 2Ω. For small distances r12 (a=1) our results for the symmetric modes are identical with those of Agarwal et al. apart from the so-called scaling factor. For large distances r12 (a=0) the spectra of the symmetric and antisymmetric modes are identical with the well-known one-atom spectrum.

Squeezed states in resonance fluorescence of two interacting atoms

Abstract The possible existence of so-called “squeezed” states in two-atom resonance fluorescence is discussed in Lehmbergs master equation approach. It is shown that squeezing strongly depends on interatomic separations r 12 . For large r 12 one of the quadrature components is squeezed, and as r 12 decreases its squeezing decreases in order to appear in the other quadrature component for certain value of r 12 . For very small r 12 fluctuations in both components tend to zero.