Resonant delocalization and Bloch oscillations in modulated lattices

We study the propagation of light in Bloch waveguide arrays exhibiting periodic coupling interactions. Intriguing wave packet revival patterns as well as beating Bloch oscillations are demonstrated. A new resonant delocalization phase transition is also predicted.     

Resonant oscillations of a gas in an open tube in the shock-free wave mode

Nonlinear gas oscillations excited in an open tube by a flat piston at one of the tube ends are studied. The sinusoidal piston oscillations in the shock-free wave mode are created by a vibration exciter near the first eigenfrequency. Expressions for gas pressure oscillations are obtained for a tube with a nonrounded end without a flange and secondary flow velocity components. The influence of the piston displacement amplitude on the pressure range and secondary flow velocity of gas is studied. The theoretical calculations of the gas pressure are compared with experimental data. An estimate for the velocity of particle motion along the tube axis is presented with calculated values of the secondary flow velocity.     

Self-starting mode locking by multi-spatial-mode active waveguiding

We demonstrate a novel principle of self-starting mode locking in a compact semiconductor laser diode, where the needed saturable loss is provided by spatial effects resulting from multi-spatial-mode active waveguiding. The demonstrated device operates over a 1.54 microm wavelength range and has a repetition rate of 47 GHz. The pulse width is below 5 ps, and the average power coupled to the cleaved single-mode fiber is nearly 0 dBm.     

Nonreciprocal properties of layered gyrotropic waveguiding structures

Radiophysics and Quantum Electronics -     

Resonant oscillations of massless neutrinos in matter

Oscillations of neutrinos propagating in matter do not require that neutrinos are massive, at a fundamental level. Even if neutrinos are massless as a consequence of an exact symmetry - such as total lepton number - they can oscillate into one another if the weak interaction has a small non-universal component, whose existence would signal physics beyond the standard model. The experimental constraints and theoretical plausibility of the mechanism are discussed. Coherent neutrino and antineutrino scattering could substantially affect the late thermal phase neutrino signal from a supernova explosion.     

Resonant transmittance through periodically modulated films

We analyze the optical transmittance at normal incidence for an electron gas without losses. The electron gas is supposed to have a plane parallel slab geometry and its dielectric permittivity is assumed to be periodically modulated in one direction parallel to the interfaces. Due to surface plasmon polariton mode excitation, there exist resonance frequencies where the transmittance equals to unity. The number and positions of peaks are investigated analytically and a comparison with the analytic theory by Dykhne et al. [6] is made.     

Diffraction from modulated structures I. Periodically modulated structures

The calculation of the diffraction amplitude from the periodical distribution of a finite number of zones extending in one direction is presented. The formulae for the diffraction amplitude of a single zone in terms of its structure parameters and for the diffraction amplitude of an array of zones embedded in the matrix for various types of modulation are given.     

Resonant rayleigh scattering in semiconductor structures

Il Nuovo Cimento D - A detailed study of the relative role played by localized and/or propagating intermediate excitonic states in, resonant Rayleigh scattering (RRS) is presented for a large set...     

Resonant retuning of Rabi oscillations in a two-level system

The evolution of a two-level system in a single-mode quantum field is considered beyond the rotating wave approximation. The existence of quasi-degenerate energy levels is shown to influence the essential characteristics of temporal and amplitude Rabi oscillations of the system in a resonant manner.     

Diffraction from modulated structures II. Quasiperiodic model of the modulated structures

The present model of modulated structure assumes the variation of the number of atomic planes in the inner part of the individual zones in their array. This variation is described by the interzone correlation function. The analytical expression for the diffracted intensity from this aperiodic array of zones is also given.     

Scrape-off layer turbulence modulated by Mirnov oscillations

We investigate plasma turbulence at the scrape-off layer of TCABR tokamak. We apply a power spectral analysis to the magnetic Mirnov oscillations and electrostatic fluctuations, to quantify statistical properties and to estimate the turbulence-driven radial-particle flux. A distinctive peculiarity is the modulation of electrostatic turbulence by the Mirnov oscillations shown by the partial superposition of the frequency power spectra of these two oscillations. This characteristic allows us to investigate any possible influence of the Mirnov oscillations on particle transport. In fact, a significant part of this transport occurs at the Mirnov frequencies. The effect of this modulation is also analyzed for discharges modified by external perturbations, a DC biased electrode or an ergodic magnetic limiter.Presented at the Workshop Electric Fields Structures and Relaxation in Edge Plasmas, Nice, France, October 26–27, 2004.     

Surface plasmon-polariton waveguiding characteristics of metal/dielectric quasi-coplanar structures

A novel metal-dielectric structure for efficient confinement and guiding of surface plasmon-polaritons is proposed. The proposed quasi-coplanar geometry achieves a trenchlike mode confinement over a wide range of spectrum by substituting a trench structure with two patterned metal layers, which will simplify the fabrication steps significantly. Using the finite-element method, the modal characteristics and the impact of waveguide structural parameters on them were investigated.     

Tunable photonic Bloch oscillations in electrically modulated photonic crystals

We exploit theoretically the occurrence and tunability of photonic Bloch oscillations (PBOs) in one-dimensional photonic crystals (PCs) containing nonlinear composites. Because of the enhanced third-order nonlinearity (Kerr-type nonlinearity) of composites, photons undergo oscillations inside tilted photonic bands, which are achieved by the application of graded external-pump electric fields on such PCs, varying along the direction perpendicular to the surface of layers. The tunability of PBOs (including amplitude and period) is readily achieved by changing the field gradient. With an appropriate graded pump ac or dc electric field, terahertz PBOs can appear and cover a terahertz band in an electromagnetic spectrum.     

Diffraction from modulated structures III. Partially modulated structures and polydisperzity of zones

The present paper deals with the generalization of a model of modulated structures proposed in part II (Czech. J. Phys. B19 (1969), 1343) in that both the inner and the outer parts of the zones have variable number of atomic planes. The formula for the diffracted intensity from the assembly of such zones embedded in the matrix is also given.