Communications in Physics

We present a comparative study of optical bistability (OB) in three-level atomic configurations, including $\Lambda $-, cascade-, and V- types under the conditions of electromagnetically induced transparency (EIT). In the steady regime, the input-output intensity relations for the OB in each configuration have been derived in analytical form. The model allows one to construct a clear picture on how the threshold intensity, and other characteristics of the OB are continuously modified with respects to controllable parameters of the laser fields, cooperation parameter, and other physical parameters of atomic system. The results showed that the threshold intensity of OB in \(\Lambda \)-type system is much less than the other ones and the threshold intensity of OB in V-type system is the largest one. The analytical result is convenient to choose excitation configuration for experimental observations and related applications in photonic devices.

In this paper, we will consider a model of nonlinear system with random telegraph noises and a Raman ring laser by modeling the laser pump light by a pregaussian process and find an exactly soluble equations for the stationary probability distribution of fluctuations in this nonlinear system under the influence of two-telegraph noise. In consequence, we will obtain the so-called noise reduction in this system: the Stokes output of this laser tends to the stabilize under the influence of the broad-band two-telegraph pregaussian pump and compare this results with that obtained in our previous paper (Cao Long Van, Doan Quoc Khoa, Opt. Quant. Electron. 43, 137 (2012)) for the case of one telegraph noise.

We report the successful development of an all-solid state laser based on a Czochralski method-grown cerium-doped lithium calcium aluminum fluoride (Ce3+:LiCaAlF6 or Ce:LiCAF) crystal as the gain medium. Results for the broadband, narrow linewidth and short pulse laser emission are obtained by pumping the crystal with 7 ns pulses from the fourth harmonics (266 nm) of a Nd:YAG laser operating at 10 Hz. The effects of output coupler reflectivity, resonator length and pump energy on the laser pulse duration were explored. With broadband configuration, a maximum output pulse energy of 3.4 mJ and a slope efficiency of about 33% were achieved. By optimizing the parameters of the resonator and pump laser energy, 450 ps UV laser pulses were generated from resonator transient conditions of low-Q and short resonator under a near threshold pump energy. With narrow linewidth configuration, where the end mirror is replaced by a grating, tunability from 281 nm to 299 nm is also achieved with a linewidth of about 0.2 nm.

Abstract. The flux-weighted average cross section for the 186W(γ,p)185Ta reaction induced with 70 MeV bremsstrahlung end-point energy was measured using the activation method in combination with off-line gamma activity measurement. The 27Al(γ,2pn)24Na monitor reaction was used for the determination of the bremsstrahlung flux. The bremsstrahlung photons used to produce the photonuclear reactions were generated from a thin tungsten (W) converter by bombardment with a 70 MeV electron beam. The experimental flux-weighted average cross section is compared with the theoretical prediction, for which the absolute cross section was calculated using the TALYS 1.95 code and the bremsstrahlung spectrum was simulated using the computer program MCNPX. The present experiment was carried out at the 100 MeV electron linac of the Pohang Accelerator Laboratory, POSTECH, Pohang, Korea.

Based on guides RG 1.109, RG 1.111 published by United States Nuclear Regulatory Commission (USNRC)~our~research~concentrates on assessing radiation doses caused by radioactive substances released from the nuclear power plant (NPP) Ninh Thuan 1 to the environment under scenario of an INES-level 5 nuclear accident caused by two incidents of the station black out (SBO) and loss of coolant accident (LOCA) using software~RASCAL4.3~provided by the Emergency Operations Center of USNRC. The plant Ninh Thuan 1 is assumed to use the VVER-1200 technology with a total power of 2400 MW\(_{e}\). The input data for the model calculations is based on building the accident scenario, the technical parameters of VVER-1200 technology and the meteorology. The meteorological data on dry and rainy seasons, which are typical for the Ninh Thuan region was also considered. The \(X/Q\) (s/m\(^{3}\)) quality and the maximum dose values were calculated within an area of 40 km radius from the NPP site, where \(X/Q\) (s/m\(^{3}\)) is the ratio of activity concentration to release rate. Based on the obtained results on dose distribution the necessary measures for nuclear emergency preparedness have been proposed according to the IAEA recommendations.

The elastic scattering cross section measured at energies \(E\lesssim 10\) MeV/nucleon for some light heavy-ion systems having two identical cores like \(^{16}\)O+\(^{12}\)C exhibits an enhanced oscillatory pattern at the backward angles. Such a pattern is known to be due to the transfer of the valence nucleon or cluster between the two identical cores. In particular, the elastic \(\alpha\) transfer has been shown to originate directly from the core-exchange symmetry in the elastic \(^{16}\)O+\(^{12}\)C scattering. Given the strong transition strength of the $2^+_1$ state of $^{12}$C and its large overlap with the $^{16}$O ground state, it is natural to expect a similar \(\alpha\) transfer process (or inelastic \(\alpha\) transfer) to take place in the inelastic \(^{16}\)O+\(^{12}\)C scattering. The present work provides a realistic coupled channel description of the \(\alpha\) transfer in the inelastic \(^{16}\)O+\(^{12}\)C scattering at low energies. Based on the results of the 4 coupled reaction-channels calculation, we show a significant contribution of the \(\alpha\) transfer to the inelastic \(^{16}\)O+\(^{12}\)C scattering cross section at the backward angles. These results suggest that the explicit coupling to the \(\alpha\) transfer channels is crucial in the studies of the elastic and inelastic scattering of a nucleus-nucleus system with the core-exchange symmetry.

We calculate excitation spectra of cubic perovskites ATiO3 (A = Ca, Sr, Ba, Pb). The calculations are performed within the time-dependent density functional theory, including local field effects. The theoretical calculations show that the perovskites have a plasmon mode at around 12 eV, which is not observed in experiments.

Modification of the chemical and physical properties with respect to element component in atomic clusters has paved the way for great potential in both fundamental study and applications. An investigation on the structure, stability and magnetic properties of gold clusters doped by Cr and Mo (Au12Cr and Au12Mo) is discussed in this work, using the density functional theory calculation. The bond strength of AuM dimers governs the globally minimum structural evolution in the Au12M clusters, which can be classified into two principal forms: the icosahedral (Mo dopant) and the cone-like structures (Cr dopant). The average binding and dissociation energies indicate that the enhanced stability of cluster stem from the contribution of Cr/Mo atom. The molecular orbital (MO) diagram and the spin distribution are computed to better understand the electronic configuration and magnetic behavior of the studies clusters. The Au12Cr has a significant magnetic moment of 4 µB. Conversely, the magnetic moment is completely quenched in Au12Mo cluster. Furthermore, the IR spectra of Au12M are also predicted.

We investigate the zero and finite temperature transport properties of a quasi-two-dimensional electron gas in a GaAs/InGaAs/GaAs quantum well under a magnetic field, taking into account many-body effects via a local-field correction. We consider the surface roughness, roughness-induced piezoelectric, remote charged impurity and homogenous background charged impurity scattering. The effects of the quantum well width, carrier density, temperature and local-field correction on resistance ratio are investigated. We also consider the dependence of the total mobility on the multiple scattering effect.

This paper presents a new design of Ge20Sb5Se75 large-solid-core photonic crystal fiber (PCF) with a 1st-ring-removed square lattice. Using the full vector finite element method for anisotropic perfectly matched layers, we numerically examine the dispersion characteristics of the PCF in the wavelength range spanning from 1.5 µm to 6.0 µm. The results reveal that photonic crystal fibers exhibit a variety of dispersion properties, including all-normal and anomalous dispersion, featuring one or two zero dispersion wavelengths (ZDWs). We propose two designs with optimal dispersion characteristics based on our numerical simulations. These designs have small lattice constants (Ʌ = 1.0 µm; Ʌ = 1.5 µm) and low fill factors (d/Ʌ = 0.3; d/Ʌ = 0.35). Furthermore, these selected fibers offer high nonlinearity and low confinement loss, making them excellent candidates for a wide range of optical applications.