S. V. Uvarova

The polarization of two-level atom in the polychromatic field

The numerical solution for polarization for two-level atom in polyharmonic field has been made. The analytical solution for partial case of symmetrical case relative to the frequency of the homogeneously broadened transition confirmed numerically. The results can be used in the nonlinear comb spectroscopy.

Nonlinear comb spectroscopy

A numerical solution for the polarization of two-level atoms that interact with a polyharmonic field was obtained. An analytical solution for the particular case of a symmetrical position of carrier frequency relative to transition frequency is possible. The results showed that nonlinear effects occur in a polarization spectrum at the small amplitudes of comb components and small frequency distances between them. Consequently, it is necessary to take into account nonlinear effects in comb spectroscopy.

Resonance in the polarization spectrum of a two-level atom in a polychromatic field

A numerical solution has been obtained for a two-level atomic system interacting with a 101-component polychromatic field. The analytical method of recurrence relations has confirmed the numerical calculations. The resonance in the polarization spectrum follows the transition frequency.

Nonlinear interaction between a two-level atom and a weak polychromatic field

The interaction between two-level media and a polychromatic field is considered in the limit of small field amplitudes. The obtained third-order corrections allow us to describe a nonlinear response to the field and intermodal interaction. The obtained polarization spectra are compared to numerical solutions to the density matrix equation in the rotating wave approximation. The results can be used in nonlinear comb spectroscopy.

Polarization spectrum of three-level atoms in weak polychromatic fields

Differential density matrix equations for a three-level atomic system driven by polychromatic fields are solved numerically. The polarization spectrum of the probe field is obtained. Ultra-narrow resonances in the polarization spectrum on the probe field frequency emerge at multiple harmonics and subharmonics.

Experimental nonlinear interference comb spectroscopy

A means of nonlinear interferential comb spectroscopy with increased sensitivity is propsed. Radiation from the comb-generator of a femtosecond laser is focused at the center of a cell with vapors of rubidium atoms, mounted in an arm of a Michelson interferometer. This technique is an improvement of Rozhdestvenski hooks method, with digital registration by the detectors on a CCD array being substituted for the photographic registration of interferograms, resulting in increased interferometric sensitivity (holographic interferometry). A primary spectrogram is processed in digital form on a dual-beam interferometer equipped with a phase modulator to improve sensitivity with the possibility of an a posteriori increase in interferometric sensitivity. Dispersive signals appear in the interferogram spectrogram on two-photon absorption lines when the pumping radiation is focused at the center of a cell with Rb vapors. Nonlinear processes of coherent radiation due to nonlinear interference effects are studied. Numerical simulations are performed that confirm the proposed theoretical model.

Nonlinear polarization in comb-spectroscopy

Two methods were applied to compute the 2-level atom driven by a polychromatic field. The first method is a direct numerical solution of the density matrix equations and the second one is a harmonic basis decomposition resulting in an infinite linear algebraic equation system. It is showed the resonance frequency mostly follows the transition frequency. But some frequency pulling or pushing is observed depending on the transition frequency inside the field component bounds or not.

Interference comb-spectroscopy with increasing sensitivity

The wide spectrum from comb - generator of femtosecond laser was applied for illuminating of Michelson interferometer with atomic vapor. The method of holographic interferometry with increasing sensitivity using phase modulator was applied for treatment of digital hologram.

Nonlinear polarization of two-level atomic medium in the weak polichromatic field

The numerical solution for population difference and polarization for two - level atoms driving by polyharmonic field was made. The analytical solution for partial symmetrical case was confirmed numerical one. The results can be used for nonlinear comb - spectroscopy.

Nonlinear Doppler - Free comb-spectroscopy in counter-propagating fields

The method of Doppler - free comb - spectroscopy for dipole transitions was proposed. The calculations for susceptibility spectrum for moving two-level atoms driving by strong counter propagating combs have been done. The used theoretical method based on the Fourier expansion of the components of density matrix on two rows on kv (v-velocity of group of atoms, k-projection of wave vector) and Ω (frequency between comb components). For testing of validity of this method the direct numerical integration was done. The narrow peaks with homogeneous width arise on the background of Doppler counter. The contrast of these peaks is large for largest amplitudes of comb-components. Power broadening is increasing with increase of field amplitudes. The spectral range of absorption spectrum is determined by the spectral range of comb generator and all homogeneous lines arise simultaneously.