Optical properties of the polarized Dirac vacuum

An investigation is made of the propagation of laser radiation through the Dirac vacuum polarized by a strong electric field. Calculations are made of the refractive index of the vacuum and the angle of rotation of the plane of polarization of the radiation. The possibility of measuring strong electric fields is assessed. Pis’ma Zh. Tekh. Fiz. 24, 45–47 (July 26, 1998)     

A new method of dark resonance excitation on D<Subscript>2</Subscript> line in <Superscript>87</Superscript>Rb vapor

A new method based on optical pumping is proposed for increasing the parameters of dark resonance excitation on D ₂ line in ⁸⁷Rb vapor. The pumping is provided by linearly polarized two-frequency laser radiation propagating in the direction perpendicular to the probing field directed along the cell with atomic rubidium vapor. This method significantly improves the dark resonance parameters as compared to the case of pumping by a circularly polarized field. Qualitative considerations are confirmed by the results of numerical calculations.     

Magnetometry in dense coherent media

The rotation of the polarization direction of linearly polarized light produced by the nonlinear magneto-optic effect has been proposed as a sensitive measure of small magnetic fields. In this paper, the advantages of this technique in optically thick media for precision magnetometry are discussed. Results are presented for measurements of this rotation for resonant light in optically dense Rb vapour under various conditions, with and without buffer gas. The sensitivity of the measurements of small magnetic field is investigated as a function of laser frequency, laser power, beam diameter and atomic density for D ₁ line of ⁸⁷Rb.     

Polarization switching time for semiconductor laser radiation

Expressions are derived for the polarization switching time for semiconductor laser radiation. These expressions can be used to assess the influence of the laser diode parameters on the polarization switching time of the output radiation. The results of an analysis of these expressions show that the main parameters influencing the polarization switching of the output radiation from a semiconductor laser are the nonlinear gains. Pis’ma Zh. Tekh. Fiz. 23, 87–95 (May 12, 1997)     

Anisotropic polarization of radiation in quantum-confinement whispering-gallery-mode lasers

The polarization of lasing and spontaneous emission from half-disk- and disk-shaped quantum-confinement lasers operating on whispering-gallery modes with wavelengths within 2.18–2.28 μm has been studied. It is established that electric vector E of output radiation is oriented predominantly in the p-n junction plane, which is explained by the fact that radiation is generated due to electron-heavy hole transitions. Modulation of the polarized spontaneous radiation spectra has been observed.     

Laser-near-field-based Atomic Lens: Quantum Wave Optics Consideration

Abstract

This paper examines the focusing of an atomic beam by the near field of laser radiation diffracted by a small aperture. The wave properties of the atom are taken into consideration within the framework of an approximate Schrödinger equation. The possibility is demonstrated of focusing an atomic beam into a spot some 3 nm across, the atomic and laser beam characteristics being quite acceptable. The main contribution to the spot size is shown to be from spherical aberrations and diffraction effects, the chromatic aberrations of the atomic beam with a 5% velocity distribution broadening having a lesser effect.     

Modulation of the polarization of semiconductor laser radiation at constant output power

The degree of polarization of “doubly”-modulated (by the pump current and the optical confinement factor) laser radiation is analyzed by applying a method of analyzing the stability of the solutions of systems of Lyapunov differential equations to a system of rate equations. An analysis of the system of rate equations yielded its eigenvalues, also called stability coefficients, which are the characteristic time for a transition of the system from one state to another. The behavior of a doubly modulated laser was modeled mathematically and it was demonstrated that the polarization of the laser output radiation can be controlled with almost constant output power. Pis’ma Zh. Tekh. Fiz. 24, 84–90 (August 26, 1998)     

Propagation of Two Polarized Impulses through a Resonant Medium

Abstract

The propagation of strongly polarized electromagnetic waves through a resonance medium, with arbitrary angular momenta of the levels, is investigated in the adiabatic-following approximation. Exact wavefunctions of the two-level atomic system with degenerate levels in the field of a circularly (linearly) polarized wave are constructed and the picture of the shift of energy level splittings is discussed. Exact formulae for the nonlinear refractive index of the medium in the field of the circularly (linearly) polarized wave are found. The propagation of counterpropagating polarized waves—an intense pump wave and a probe light signal—through the resonance medium is studied. The studies are carried out in the scope of a two-level (one-photon resonance) and a three-level (one- and two-photon resonances) medium. Formulae are found for the induced rotation of the plane of polarization for the probing signal that are exact in terms of the intensity of the pump wave. The spectral dependence of the angle of rotation is studied, and it is shown that a series of Stark-shifted resonance poles of atomic absorption and a three-photon scattering process arise.     

Angular dependence of the signal in nonlinear polarization spectroscopy under conditions of noncollinear excitation by partially polarized radiation

The light-induced anisotropy tensor of initially isotropic media is calculated for the case of partially nominally polarized radiation. An analytic expression is obtained for the first time for the signal in a noncollinear nonlinear polarization spectroscopy system with a polarization-incoherent pump wave. Pis’ma Zh. Tekh. Fiz. 25, 79–82 (December 26, 1999)     

Generation of Optical Harmonics by Intense Pulses of Laser Radiation

Abstract

We discuss effects of optical depth, beam focusing and non-perturbative atomic response on the spectrum of optical harmonics generated by an intense beam of laser radiation (up to 10¹⁴W cm^?2) in a small volume of atomic vapour. We find remarkable enhancement of high harmonics at intensities beyond the perturbative limit.     

Polarimetry of scattered light using heterodyne detection

Abstract

Heterodyne detection has been used to measure the polarization state of light back-scattered from various targets (including flame-sprayed aluminium, sandpaper and painted surfaces). The samples are illuminated with a linearly polarized single-frequency continuous-wave CO₂ laser operating at a wavelength of 10.6 μm. The back-scattered co-polarized and cross-polarized components are both coherently detected by beating with an optical local oscillator. This process allows the relative amplitudes and phases of the two components to be measured and hence the light's polarization state can be evaluated. When the target undergoes movement, the scattered light demonstrates the usual properties of dynamic speckle, and the technique allows observation of the time evolution of the polarization ellipse.     

Rank Prize Funds Minisymposium on Non-classical Light for Communication

Abstract

We studied both experimentally and theoretically the transmission and polarization characteristics of a Cr⁴⁺ : YAG saturable absorber crystal as a function of the intensity and polarization state of an incident laser beam. We found that a birefringent absorption behaviour is induced and we show that the experimental results are well described by a full numerical model which includes excited-state absorption as well as a ground-state cross-absorption term. By using pump-probe measurements we show that a finite cross-saturation of the absorption is achieved along the crystal axes orthogonal to the polarization of the optical radiation. No induced refractive index birefringence is observed.     

Extension of a model analysis of the degree of polarization of light

A theoretical approach is developed in which partially polarized radiation can be represented as a sum of coherent and incoherent components and also of the action of some imaginary device with time-dependent birefringence. This approach allows the Jones vector matrix method to be used for the calculations, which is important for theoretical calculations of the polarization state. Pis’ma Zh. Tekh. Fiz. 25, 74–78 (April 12, 1999)     

Motional Sidebands in the Microwave Spectra of Ions in an Rf Trap

Abstract

The atomic motion of an ion in an rf trap adds sidebands to the ion's hyperfine transitions, shifted and broadened by the space charge. Sidebands and carrier depend differently on the microwave polarization, which is determined by observing microwave spectra with the orientation of the dc magnetic field varied. This phenomenon is caused by dc amplitude and phase modulation of the microwave radiation that is partially reflected inside the trap.     

Polarization-characteristic determination for multichannel CO2 lasers

Polarization characteristics can be measured for engineering CO₂ lasers by means of an instrument consisting of two rigidly fixed insulating plates combined with radiation detectors, which are placed in such a way that the planes of incidence form an angle of 90°. The plates with detectors rotate around the propagation direction in a cyclic fashion. The main flux passes through the plates, and only the reflected paris of the beam are used in the recording. The radiation prom an LN-1,2, NM-I1 laser is partially or completely polarized for about 70–80% of the time of operation. During the rest of the time, the radiation is unpolarized or there is an ongoing change in the orientation of the polarization plane. All the channels are at least partially synchronized in polarization characteristics.Translated from Izmeritel'naya Tekhnika, No. 7, pp. 25–27, July, 1993.     

Polarization-induced curvature of a laser damage channel

Significant curvature of a laser damage channel in a metal has been observed and a correlation is reported between this effect and the polarization of the radiation. Pis’ma Zh. Tekh. Fiz. 23, 90–94 (May 26, 1997)     

High Transmission LiF Prism Monochromator for Separation of VUV Wavelengths in Frequency Mixing Experiments

Abstract

We describe a simple, high throughput, LiF prism monochromator for the vacuum ultraviolet (VUV). The instrument throughput is 30% at 145 nm and the output can be tuned within the range 120–185 nm. The very high dispersion of LiF in the VUV means that neither narrow slits nor high precision are required. The suitability of this instrument for separation of coherent VUV radiation, generated by four-wave mixing, from the intense fundamental laser radiation (at 212 nm and the visible) is demonstrated. General advantages in throughput, polarization and resistance to radiation damage of such a prism instrument compared to a diffraction grating monochromator are discussed.     

A Polarized Transfer Matrix for Electromagnetic Waves in Structured Media

Abstract

The study of electromagnetic systems with dielectric or magnetic properties that vary spatially on or below the scale set by the wavelength of the radiation considered is of interest both in the field of photonic band gap materials and in that of random multiple scattering media. A key calculation technique in both areas is the transfer matrix. We derive a new transfer matrix, written in the language of scattering between transverse polarized wave states. This could be used in either photonic band calculations or in disordered media calculations. We demonstrate the use of the new transfer matrix to describe transport through a layered random dielectric in the Rayleigh scattering regime. This problem has considerable similarities to that of non-interacting electrons in a one-dimensional random potential. A complete solution for one polarization can be given by the use of group theoretical results. The other polarization exhibits pronounced dipole effects which can easily be calculated to lowest order.     

Wavelet analysis of short harmonics generated in presence of a two colour laser field

Abstract

The Morlet wavelet spectrum of the radiation emitted by a two level atom in presence of two laser pulses with very close frequency is obtained. The wavelet spectrum gives information on the time evolution of the full spectrum and of a particular line. The beating condition stimulates the atom to emit pulses of harmonics with duration of the order of a few optical cycles of the pumping radiation. Pulse trains of 3 optical cycles (FWHM) are observed.     

Polarization separation of light beams at the interface of two mesophases

The features of reflection of the linearly polarized light beams at the interface between two regions of a nematic liquid crystal (LC) with the orthogonal director orientation have been analyzed. The relationship between light beam propagation in a LC material and polarization of laser radiation has been established. Rotation of the polarization plane of a light beam has been found for the radiation introduced through the free surface “LC—air” deformed due to the capillarity effect. The total internal reflection effect has been demonstrated experimentally together with the possibility for special separation of the orthogonally polarized light beams at the interface of two mesophases.