Dispersion characteristics and spatial field distributions in the photonic crystal waveguides and Bragg ones are considered. It is shown that these waveguides can be used as slow-wave systems in the THz vacuum electron devices.
The new detector of acoustic oscillations of the medium suggested. The basic laws of detecting acoustic oscillations were investigated by means of computer and physical modeling.
The maxima of the acousto-optic interaction are determined for biaxial SrB 4 O 7 crystals. As it is shown, the highest value of the acousto-optic figure of merit M 2 is equal to 0.63-10 -15 s 3 /kg and achieved in the case of the isotropic diffraction of the electromagnetic wave propagating in [010] direction on the fast qausi-transversal acoustic wave propagating in direction with angular parameters θ p = 47°, φ p = 180°.
In optical experiments electromagnetic field manifests itself as a quantum-statistical object. Its state should be described with a statistical operator or with correlation functions calculated with it. A rather full description of field is provided with field amplitudes and simultaneous binary functions. Incidentally Glauber functions serve as a tool for diagnostics of field properties. The correlation functions are regarded as averaged macroscopic values and can be calculated as electrodynamic parameters of medium. The paper presents a scheme of such calculations for a system of two-level emitters interacting via field (Dicke model). Evolution equations are built on the basis of Bogolyubov reduced description method. Solving them can be put in life with modern computational technologies such as GPU.
We analyze the scattering of a plane TE electromagnetic wave of the visible range of wavelengths by a silver nano-cylinder with a concentric dielectric coating. The emerging plasmon resonances are treated using both the conventional presentation of the spatial distribution of the field amplitude nearby the object and by the spatial distribution of the Umov-Poynting vector. We demonstrate that application of the Umov-Poynting vector has obvious advantages: the standing and traveling waves are well resolved, simultaneously; the object interfaces become clearly visible in the spatial distribution. Unexpected impact is observed of the dielectric constant of the coating on the type of the plasmon resonance and the spatial field distribution.
Resonant two-photon annihilation of an electron-positron pair in the field of a moderately strong circularly polarized wave is investigated theoretically. The partial cross-section is derived. It is shown that the resonant differential cross-section can be different from that in the absence of the external field.
Modelling of degradation process in functional high-reliable temperature-sensitive Cu0.1Ni0.8Co0.2Mn1.9O4 ceramics is performed. It is shown that additives of NiO phases formed during sintering and localized near grain boundaries of ceramics suppress ageing process in these materials. This effect is character for monolithized fine-grain ceramics obtained due to thermal energy transformed during sintering. It is established that ageing kinetics in Cu0.1Ni0.8Co0.2Mn1.9O4 ceramics are described by relaxation function of DeBast-Gillard or Williams-Watts independent on composition of ceramics.
We apply Monte Carlo wave function method and classical mechanics to description of the atomic motion in the field of laser radiation. Simultaneous use of quantum and classical mechanics for description of inner and translational motion avoids quantization of the translational degrees of freedom. The calculation are carried out for the example of atomic motion in the field of counter-propagating laser waves, one of which repeats the other. It is shown that such scheme of the atom-field interaction leads to confinement of atoms and their cooling by the same laser beams for proper the atom-field interaction parameters. The cases of laser pulses, bichromatic waves and stochastic field (the model of coloured noise) are analyzed.
In this work, the design of a Chirped Mirror (CM) is presented. The response of the mirror and its performance for pulse compression is analyzed using a FDTD (Finite-Difference Time-Domain) based method. The Chirped Mirror is designed to compensate a 2.3 mm thick Sapphire crystal at a wavelength around 800 nm. This design is suitable for dispersion compensation in a Ti:sapphire laser. It shows smooth dispersion characteristics and a high reflectivity band in wavelength range 500-1200 nm.
In this paper, the stress effects on solidification microstructures during laser sintering of alloy powders are investigated, using a phase field approach. Coupling equations among phase, temperature, concentration and strain/stress are derived based on thermodynamic considerations. Thermal and concentration expansions, transformation dilatation, and strain deformation dependency on phase transformation are included in the formulation. A linear stability analysis of solidification front is carried out, to find dispersion relations and a spectrum of wave numbers of unstable perturbations. It is shown, that, in addition to the thermal and mass transfer processes, the strain field generated during microstructure evolution is another important factor that affects the instability mode. An increase in stress increases the maximally wavelength and amplification rate of the unstable fluctuations.
This paper presents results theoretical modeling of angular characteristics dual-layer gratings (gold-coated polycarbonate gratings) and optimization geometrical parameters such structures have been carried out for sensing applications in visible spectrum region.
Resonant scattering of ultrarelativistic electrons in the field of two strong pulsed laser waves is studied theoretically. Under the resonance, scattering of electron by an electron in the field of two laser pulsed waves is effectively divided into two consecutive processes of the first order similar to the laser-induced Compton process. Resonant scattering kinematics is qualitatively different in the case of a strong field. The shape of resonant peak is affected by ponderomotive forces. Comparative analysis was performed for resonant cross section of laser-modified electron-electron scattering and cross section of field-free process. The obtained results may be experimentally verified, for example, by scientific facilities at sources of pulsed laser radiation (SLAC, ELI, XCELS).
The laser resonator with the infinitely adjustable of output light is represented. Adjustment is performed in a wide range. The diameter of the laser output beam is changed at the adjustment. This resonator suitable for lasers of a wide range of frequencies, including for terahertz lasers.
By mathematical modeling methods the dependence of running-wave interferometer (RWI) output spectrum from the excitation conditions and the interferometer parameters were studied in detail. Also a comparison of half-wave length RWI simulation results with the theoretical calculations was performed.
This work describes the research and calculation of absorption and scattering cross sections of the three-layer nanoshell Au-SiO 2 -Au elliptical shape using the method of dipole equivalence in the near infrared region of the spectrum.
Although still underestimated in computational optics and photonics, the conversion of electromagnetic field problems to the Fredholm second kind integral equations (IEs), also called analytical regularization, and finally Fredholm second-kind infinite-matrix equations has many remarkable merits. We discuss them at the background of specific features of material properties of metals and dielectrics in the optical range.
The review on the quantum electrodynamics (QED) processes proceeding in strong pulsed light fields, realized in modern powerful pulsed lasers is presented. Resonant and coherent processes of quantum electrodynamics in strong laser fields are considered. Following QED processes in the pulsed laser field are considered: resonant scattering of ultrarelativistic electrons, resonance of exchange amplitude of a photon by an electron, parametric interference effect in electron-nucleus scattering in the field of two pulsed laser waves. It is demonstrated that the resonant cross sections may be several orders of magnitude greater than the corresponding cross sections in the absence of an external field. Results obtained may be experimentally verified, for example, by the scientific facilities at sources of pulsed laser radiation (SLAC, FAIR, XFEL, ELI, XCELS).
A systematic approach for designing photonic crystal based band-pass filters with different filter characteristics has been presented in this paper. The filter characteristics are manipulated by varying the location of the defects in a photonic crystal waveguide. The photonic crystal waveguide is modeled as a dispersive transmission line and the defects are modeled by equivalent electrical T-networks. A filter then is visualized as a cascade of the T-networks with suitable interconnecting sections of transmission line. S-parameters are used to find the transmission and reflection frequency response of the filter. An optimization approach is used to obtain the most optimal locations of the defects which give the desired frequency response. It is shown that more than one defect combinations are possible for getting the desired filter characteristics.
Resonance scattering of a lepton by a lepton in the field of two codirectional pulsed laser waves within the interference kinematical region is theoretically studied. Stimulated emission and absorption of waves' photons by lepton is correlated in the interference region. Resonance conditions in the interference region are specified. Analytical expressions for amplitude and differential cross section for circular polarization are obtained. The cross section contains a resonant peak, its altitude and width are determined by external waves parameters. Considerable effect of wave polarization on scattering of a lepton by a lepton is specified. The obtained results can be verified at the facility FAIR (Darmstadt, Germany).
