S. A. Pulkin

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.

Digital holographic Michelson interferometer for nanometrology

The paper considers the dynamic holographic interferometry schemes with amplification (multiplication) of holographic fringes and with correction for distortions, imposed by the interferometer scheme elements. The use of digital microscope and of the matrix light modulator with direct addressing provides the completely digital closed-loop performance of the overall system for real-time evaluation of nano-scale objects size. Considered schemes were verified in the laboratory experiment, using the Michelson micro-interferometer, equipped by the USB-microscope and digital holography stage, equipped by the Holoeye spatial light modulator.

Digital holographic interferometer with correction of distortions

The article considers the use of holographic interferometer to overwrite the holograms for distortion correction. Each optical system contains some deviations of the beam path, called aberrations of the optical system. They are considered in the resulting interference figure as a distortion of the bands. While increasing the sensitivity of the interference pattern, new aberrations caused by re-registration of the installation in addition to the aberrations already presented on the interferogram caused by the initial record, also multiplied by N times, are introduced N times. In this experiment we decided to use a modified setup with spatially combined interferograms with use of reflective SLM (spatial light modulator) LETO and digital image handling of the interferograms recorded by CCD or CMOS camera.

Transformation of Rozhdestvensky Hooks in digital holographic interferometer

The method of amplification of hologram was applied to the so-called Rozhdestvenskiy hooks, that were obtained in the Rozhdestvenskiy interferometer (Michelson interferometer, combined with a grating spectrograph). In such a device the absorption lines reveal themselves as specific “hooks”, whose curvature provides the information about the atomic oscillator force. The holographic amplification “smoothes” the hooks and thus makes their analysis much simpler.

High-Resolution Femtosecond Comb Spectroscopy

Today, I will talk about non-linear comb spectroscopy . What are the advantages of comb spectroscopy? They span a very wide spectrum, making simultaneously possible detection of a large number of spectral lines, with high-field intensity, high resolution, and high spectral brightness.

Digital holographic amplification of interferograms in the Michelson interferometer using the phase-only LCOS modulator

The method of amplification of hologram was applied to the so-called Rozhdestvenskiy hooks, that were obtained in the Rozhdestvenskiy interferometer (Michelson interferometer, combined with a grating spectrograph). In such a device the absorption lines reveal themselves as specific “hooks”, whose curvature provides the information about the atomic oscillator force. The holographic amplification “smoothes” the hooks and thus makes their analysis much simpler.

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.