Журнал лазеров, оптики и фотоники

In the framework of adiabatic approximation the electronic states and direct interband absorption of light in the asymmetric double quantum dot molecule (QDM) having a shape of Cassini lemniscate revolution are discussed. Analytical expressions for the wave functions and energy spectrum of the electron in the QDM are derived. Nonmonotonic split and step-like behavior of the energy spectrum is revealed due to the possibility of the electron tunneling between quantum dots (QDs) in the molecule. The corresponding selection rules of quantum transitions for the direct interband absorption of light are obtained. The absorption edge characteristics depending on the QDM geometrical sizes are also revealed.

Surface plasmonic nanostructures with cross-shaped-hole array in metal thin films are studied for multispectral filters, which cover visible to near-infrared wavelengths. Surface plasmons are induced from incident wave by the periodic arrays of nanostructures of the metal thin film, and then localized surface plasmon polaritons oscillate in the cavity, which is formed by two surfaces of metals through near-field excitation. The transmission spectra of light through these nanostructures are investigated with the finite-difference time-domain method; our simulations show that the features of the hole, and the periods of the array along with other parameters are critical to the optical spectral performance. The optical characterizations of our fabrications of these nanostructures milled by focused ion beam demonstrated very similar results of transmission spectra of simulation results. The simulations demonstrate he optical performance of the metal nanostructures, it is possible to obtain desired multispectral filters by programming parameters of those plasmonic nanostructures.

In this research Ag thin layers on silicon p-type substrate with crystal orientation (100) and 300, 360 and 400 nm thicknesses by thermal evaporation was deposited. Four-point probe and XRD analysis of surface layers consequently for study electrical properties included of sheet resistance, conductivity, resistivity and investigation of Ag phase formed, was done. As result XRD was shown that at 400 nm the best state of silver face-central cubic (FCC) structure with crystal orientation (200) was formed and by Deby-Scherrer formula distance between successive plates was calculated 8.94 nm. Four-point illustrated that sheet resistance and electrical resistivity with increase thickness, decreases while conductance increases. At 400 nm thickness Ag layer has the most conductivity and the lowest resistance.

Elastic optical networks (EONs) based on orthogonal frequency-division multiplexing (OFDM) are considered a promising solution for the next optical network’s generation. It basically makes it possible to choose an adequate portion of the available spectrum to satisfy the requested capacity. In this paper, we consider the impact of spectrum fragmentation along the optical single/multipath routing transmission on the efficiency of the EONs. This involves reducing the fragmentation effects by dynamically updating and controlling the minimum bandwidth allocation granularity (g).We adopt linear and nonlinear dynamic mechanisms, which are denoted as LDAÉ¡ and NLDAÉ¡, respectively, to choose proper band width granularities that are proportional to the optical link/path bandwidth fragmentation status. In order to avoid neither splitting the capacity request over many routing paths, which would increase the management complexity, nor encouraging single path transmission, the proposed schemes aim to choose a proper bandwidth allocation granularity (g) of a predefined set of suggested values. Simulation results show that varying the bandwidth granularity based on the optical path fragmentation status can offer improved performance over fixed granularity with respect to the bandwidth blocking probability, the number of path splitting, the throughput, and differential delay constraint issue in terms of: the network bandwidth utilization and multipath distribution.

The scintillation detector (SD) based on organic plastic scintillator (OPS) is one of the basic detectors in HEP experiments. Technologies for production of OPSs as strips and tiles, their optical and physical properties, light collection based on wavelength shifting (WLS) fibers coupled to multipixel vacuum and silicon PMs are presented. SDs are multifunctional: calorimeters, triggers, tracking, time-of-flight and veto systems are the examples of their applications. The use of SDs in many HEP experiments on the search for quarks, new particles and H bosons (D0, ATLAS, CMS), quark-gluon plasma (ALICE), CP violation (LHCb, KLOE), ν-oscillation (MINOS, OPERA), cosmic particles (AMS-02) are discussed. SDs hold great promise for future HEP experiments due to their ability of high segmentation, WLS fiber light collection and multipixel silicon PM readout.

The effect of ellipticity ratio on low bend loss, high nonlinearity, wideband high birefringence and low confinement loss in a hexagonal spiral thermoplastic polymer based PCF having air holes with Kerr nonlinearity is investigated. Moreover, the above all property are simulated initially with wide range of wavelength (for different value ellipticity ratio) and secondly with ellipticity ratio at an operating wavelength of 1.55 μm. Through the optimization of arrangement and diameter of elliptical air holes, the designed spiral PCF offers low bend loss, high nonlinearity depends on mode field area (As small as mode field area, increase the nonlinearity), high birefringence and nonzero dispersion for X/Y polarization within the wavelength range of 0.5 to 1.75 μm. These results seem to be most useful in optical communication.

Femtosecond oscillator is first step to generate femtosecond laser pulse. Simulation of the laser beam behavior in the oscillator cavity, especially in the gain medium is essential to realize and optimize the oscillator output pulse characteristics. In this work, at first we simulate the laser beam propagation in a folded cavity with curved mirrors in symmetric and asymmetric designs using the ABCD ray tracing technique for a Gaussian beam shape to achieve influence of Kerr lens modelocking in sagittal plane. We use split-step method to obtain the beam intensity changes in the ti:sa rod and shooting method to calculate the beam spot size on the first cavity mirror. In following the influence of the gain medium position changes on the size and position of the beam waist and also on the misalignment sensitivity parameter for the sagittal plane is simulated. Furthermore the misalignment sensitivity parameter and the size and position of the beam waist are not identical for the beams in the sagittal plane, therefore to actualize an optimum design it is necessary to simulate the beam propagation in plane which is not usually considered in early design because of complication of the simulation.