Pulse delay at diffractive structures under resonance conditions

An optical pulse incident upon a diffractive structure under resonance conditions may undergo a temporal delay. The effect is demonstrated with a pulse of Gaussian profile at two geometries: a waveguide grating and a single-mode waveguide. It is shown that the order of magnitude of the delay can be controlled by the parameters of the structures.     

Beam switching with binary single-order diffractive gratings

A new type of a micro-optomechanical dielectric switch in free-space configuration for visible light is proposed and experimentally demonstrated. The combination of scalar and rigorous diffraction analysis of Gaussian beams predicts high high switching efficiency with a single/noise ratio of better than 40 dB.     

Ultrashort pulse propagation under manipulated resonance conditions

The propagation of a polarized ultrashort laser pulse is analyzed by the inverse scattering method under initial conditions including a spatial pulse profile, a state of the medium, and a “switched-on” resonant atom-field interaction. Magnetic degeneracy of atomic levels is taken into account. The Maxwell-Bloch equations are rewritten in Hamiltonian form without redefining the spatial and temporal variables. The inverse scattering method is based on an analysis of a new spectral problem. Gelfand-Levitan-Marchenko-type equations are derived, a soliton solution is obtained, and the changes in parameters of two solitons after their collision are calculated. A possible experimental setup for implementing the system under analysis is discussed.     

Impedance conditions for resonance propagation and resonance localization of waves in barrier structures

Impedance conditions for the resonance propagation and resonance localization of waves in barrier structures are formulated. Analytical expressions for the eigenvalues of various barrier structures are derived.     

Beam delivery of femtosecond laser radiation by diffractive optical elements

Received: 4 February 1998/Accepted: 22 April 1998     

Level splitting in semimagnetic semiconductors under spin-magnetophonon resonance conditions

The splitting of electronic levels in quantum wells of semimagnetic semiconductors typically characterized by large effective g factors is analyzed theoretically. They are found to be capable of supporting resonance, provided the Zeeman spin-level splitting is equal to the energy of the longitudinal optical phonon ?ω_‖. The resonance condition can be written as ?ω_‖ = gμ_B B. This condition can be satisfied by choosing the magnetic field Bsuch that the sum of the energies of the lowest spin level and the optical phonon coincides with the energy of the highest level. It is shown that these two degenerate energy levels should experience mutual repulsion. The magnitude of the corresponding splitting depends on both the electron-phonon and spin-orbit interactions in semiconductors; moreover, it turns out substantially lower than the Zeeman energy gμ_B B. Resonant passage of light through and its reflection from a quantum well are considered as one of possible ways to observe this energy level splitting.     

Saturation of two-level systems under pulsed stochastic resonance conditions

Pulsed stochastic excitation of a two-level system described by Bloch equations is studied. An equation for the average powers of the components of the state vector of the system is obtained on the basis of the theory of stochastic differential equations, and solved. The dynamical and nonlinear properties of the response of a system under pulsed stochastic resonance conditions are analyzed and the results are compared with the corresponding stationary state. The results obtained can be used in spectroscopy and for analysis of nonlinear filters based on the saturation effect and intended for processing rf and light range signals. Zh. Tekh. Fiz. 69, 65–69 (December 1999)     

Time evolution of incoherent scattering under double gamma-NMR resonance conditions

Incoherent Mössbauer scattering under the condition of double gamma-NMR resonance is considered. A radio frequency field mixes the hyperfine sublevels of a nucleus. Thus, quasi energy splitting in the rotating frame takes place. Time dependencies of the intensity of scattered radiation have been analysed both under the CEMS condition and in the regime of Mössbauer spectroscopy with synchrotron radiation.     

Depolarization of light in magnetooptical crystals under magnetomechanical resonance conditions

Taking into account multiple reflections inside a magnetooptical crystal under conditions of magnetomechanical resonance, we determine the change of polarization degree of light passing through the sample using methods of Muller matrices and of the Stokes vector.     

Skin effect under the conditions of ferromagnetic and spin-wave resonance

An expression for the electromagnetic field penetration depth in a metallic magnetic layer is derived taking into account the complexity of the high-frequency permeability under the conditions of ferromagnetic and spin-wave resonance. The frequency dependences of the skin depth and its dependences on the magnitude and type of spin pinning are determined from a numerical analysis of the solutions of the motion equation for magnetization. Some features of the dependences associated with the nature of the spin-wave spectrum are revealed.     

Diffraction dissociation,the deck mechanism and diffractive resonance production

We have constructed a model amplitude for the diffractive production of resonant states in the presence of Deck amplitudes: rescattering corrections to the Deck amplitudes are included. We have found that gross distortion of the resonance may occur and also that the phase of the diffractively produced system may vary very slowly, despite the existence of resonances: the only requirement is that the phase of the Deck amplitude leads the production phase of the resonance by ≈40°. Our model simultaneously accommodates the well established lack of phase variation in the diffractively produced 1⁺ s-wave (A1) ?π system and the details of the variation of intensity with mass, with resonance parameters M_A1 ≈ 1.3 GeV/c² and Γ_A1 ≈ 240 MeV/c². The analogous Kππ (Q) diffractive enhancement fits satisfactorily into the same framework. Our model also accounts for a number of features of diffractive N¹ production.     

Hard diffractive quarkonium hadroproduction at high energies

We present a study of heavy quarkonium production in hard diffractive processes by pomeron exchange for Tevatron and LHC energies. The numerical results are computed using a recent experimental determination of the diffractive parton density functions in the pomeron and these are corrected by unitarity corrections through the gap survival probability factor. We give predictions for single as well as central diffractive ratios. These processes are sensitive to the gluon content of the pomeron at small Bjorken variable x and may be particularly useful in studying small-xphysics. They may also be a good place to test the different available mechanisms for quarkonium production at hadron colliders. PACS 13.60.Hb; 12.38.Bx; 12.40.Nn; 13.85.Ni; 14.40.Gx     

Four-wave mixing under conditions of Doppler-free resonance induced by strong radiation

The possibilities of enhancing the nonlinear optical response of a gaseous medium and the radiation conversion efficiency in four-wave mixing processes through the use of atomic coherence effects and the induced elimination of the Doppler broadening of resonances are investigated. Numerical illustrations of the effects are given for experiments in progress. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 2, 98–103 (25 January 1999)     

Spin-wave resonance in magnetic films under conditions of the skin effect

The spin-wave resonance spectrum of a ferromagnetic film magnetized normally to its surface is investigated as a function of the finite depth of penetration of the high-frequency field into the film with due regard for damping in the spin system and different types of surface-spin pinning. The exact numerical solution of the equation of motion for magnetization is obtained by considering the finite thickness of the skin layer. For a substantially inhomogeneous distribution of the high-frequency field over the layer thickness, the change in the resonance shape at frequencies close to the ferromagnetic resonance frequency is observed in addition to the broadening of all the resonance peaks and the decrease in their amplitudes.     

Beam delivery system with a non-digitized diffractive beam splitter for laser-drilling of silicon

We report a beam-delivery system consisting of a non-digitized diffractive beam splitter and a Fourier transform lens. The system is applied to the deep-drilling of silicon using a nanosecond pulse laser in the manufacture of inkjet printer heads. In this process, a circularly polarized pulse beam is divided into an array of uniform beams, which are then delivered precisely to the process points. To meet these requirements, the splitter was designed to be polarization-independent with an efficiency>95%. The optical elements were assembled so as to allow the fine tuning of the effective overall focal length by adjusting the wavefront curvature of the beam. Using the system, a beam alignment accuracy of<5 μm was achieved for a 12-mm-wide beam array and the throughput was substantially improved (10,000 points on a silicon wafer drilled in ~1 min). This beam-delivery scheme works for a variety of laser applications that require parallel processing.