High-accuracy finite-difference beam-propagation method for cylindrical geometry

A high-accuracy finite-difference beam-propagation method (HAFD-BPM) based on high-accuracy divided-difference formulas is presented. The truncation error in this HAFD-BPM is reduced to o(Δr)⁴in the transverse direction, whereas the error in a conventional FD-BPM is typically o(Δr)². Gaussian beam propagation in vacuum and nonlinear medium is simulated by this new method and conventional one. The comparison between them in computing time and accuracy reveals the advantage of this new method. As an example, this method is applied to the simulation of blow-up in self-focusing of a Gaussian beam. PACS 42.65.Hw; 42.25.Bs; 02.70.Bf     

Stokes-Mueller matrix polarimetry system for glucose sensing

A Stokes-Mueller matrix polarimetry system consisting of a polarization scanning generator (PSG) and a high-accuracy Stokes polarimeter is used to sense the glucose concentration in aqueous solutions with and without scattering effects, respectively. In the proposed system, an electro-optic (EO) modulator driven by a saw-tooth waveform voltage is used to perform full state of polarization (linear/circular) scanning, while a self-built Stokes polarimeter is used to obtain dynamic measurements of the output polarized light intensity. It is shown that the measured output Stokes vectors have an accuracy of 10⁻⁴, i.e., one order higher than that of existing commercial Stokes polarimeters. The experimental results show that the optical rotation angle varies linearly with the glucose concentration over the range of 0-0.5 g/dl. Moreover, glucose sensing is successfully achieved at concentrations as low as 0.02 g/dl with a resolution of 10⁻⁶ deg/mm and an average deviation of 10⁻⁴ deg. In general, the polarimetry system proposed in this study provides a fast and reliable method for measuring the Stokes vectors, and thus has significant potential for biological sensing applications.     

The analysis of π− mesons produced in nucleus-nucleus collisions at a momentum of 4.5 GeV/c nucleon in light front variables

The light front analysis of π⁻ mesons in He(Li,C), C-Ne, C-Cu and O-Pb collisions is carried out. The phase space of secondary pions is divided into two parts in one of which the thermal equilibrium assumption seems to be in a good agreement with the data. Corresponding temperatures T are extracted and their dependence on (A _P·A _T)^1/2 is studied. The results are compared with the predictions of the Quark-Gluon String Model (QGSM). The QGSM satisfactorily reproduces the experimental data for light and intermediate-mass nuclei. Received: 29 September 1999     

High-accuracy contactless method for determination of chemical composition of lithium niobate crystals by their birefringence

A high-accuracy method for determining the chemical composition of non-stoichiometric lithium niobate crystals is proposed based on precise measurements of birefringence of thin substrates using the laser ellipsometry in transmission. It is shown that, for compensators made of LiNbO₃, this method allows one to monitor the ratio Li/(Li + Nb) with an accuracy of up to ∼10⁻⁸ at λ = 0.6328 μm. The accuracy is limited by temperature fluctuations of the crystal.     

Water Vapor Measurements between 590 and 2582 cm: Line Positions and Strengths

This study involves measurements of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O vapor spectra for the region between 590 and 2582 cm⁻¹. The parameters derived from the data include line positions, energy levels, and linestrengths. The study involves high-resolution line-position measurements with samples at room temperature in the (000)–(000), (010)–(010), and (010)–(000) bands. The experimental frequencies were used along with microwave, far-infrared, and hot water emission measurements in an analysis to obtain high-accuracy rotational energy level values in the (000), and (010) vibrational states of H₂¹⁶O forJ≤ 20. The experimental linestrengths were fitted by least squares to a model in which the dipole moment was represented as a series expansion containing up to 19 dipole moment matrix elements. The measurements in this work were more extensive than reported in prior studies by this author for the (010)–(000) band.     

Cosmic-ray antiproton constraints on light singlino-like dark matter candidates

The CoGeNT experiment, dedicated to direct detection of dark matter, has recently released excess events that could be interpreted as elastic collisions of ∼10 GeV dark matter particles, which might simultaneously explain the still mysterious DAMA/LIBRA modulation signals, while in conflict with results from other experiments such as CDMS, XENON-100 and SIMPLE. It was shown that 5-15 GeV singlino-like dark matter candidates arising in singlet extensions of minimal supersymmetric scenarios can fit these data; annihilation then mostly proceeds into light singlet-dominated Higgs (pseudo-)scalar fields. We develop an effective Lagrangian approach to confront these models with the existing data on cosmic-ray antiprotons, including the latest PAMELA data. Focusing on a parameter space consistent with the CoGeNT region, we show that the predicted antiproton flux is generically in tension with the data whenever the produced (pseudo-)scalars can decay into quarks energetic enough to produce antiprotons, provided the annihilation S-wave is significant at freeze out in the early universe. In this regime, a bound on the singlino annihilation cross section is obtained, 〈σv〉?¹⁰−26 cm³/s, assuming a dynamically constrained halo density profile with a local value of ρ_⊙=0.4 GeV/cm³. Finally, we provide indications on how PAMELA or AMS-02 could further constrain or detect those configurations producing antiprotons which are not yet excluded.     

Measurement of laser light thomson-scattered from a cooling electron beam

First results are presented from an experiment scattering laser light from a relativistic electron beam. The 5 cm diameter continuous electron beam of 28 keV kinetic energy and 2.6 A current presents an electron gas of a density of 8×10⁷ cm^–3, from which 20 ns pulses of laser light (490 nm) were scattered at a repetition rate of 15 Hz and an average power of 20 mJ per pulse. The Doppler-shifted wavelength of photons backscattered under 180° was analysed with a Fabry-Perot interferometer. This technique provides, for the first time, a non-destructive measurement of the velocity distribution in an electron beam radially resolved in space. The results presented here comprise the direct measurement of the absolute electron energy and the degree of space-charge compensation in the electron beam. The determination of an upper bound of 10^–2 for the ratio of longitudinal to transverse electron temperature implies the first direct measurement of a flattened velocity distribution.     

Modified Michelson interferometer for probing refractive index of birefringent crystal CSBN50

Based on the modified Michelson interferometer and phase analysis method, a high-accuracy method for probing the refractive index (RI) of transparent medium is proposed. The validated test was performed on a birefringent crystal CSBN50 with the estimated accuracy being up to 10⁻⁴. The ordinary and extraordinary refractive indices of CSBN50 at 632.8 nm are determined as n₀=2.32853±0.00016 and n_e=2.27664±0.00016, respectively.     

Facts and Fictions About Anti deSitter Spacetimes¶with Local Quantum Matter

We present a nonlinear realization of E ₈₍₈₎ on a space of 57 dimensions, which is quasiconformal in the sense that it leaves invariant a suitably defined “light cone” in ℝ⁵⁷. This realization, which is related to the Freudenthal triple system associated with the unique exceptional Jordan algebra over the split octonions, contains previous conformal realizations of the lower rank exceptional Lie groups on generalized space times, and in particular a conformal realization of E ₇₍₇₎ on ℝ²⁷ which we exhibit explicitly. Possible applications of our results to supergravity and M-Theory are briefly mentioned. Received: 12 August 2000 / Accepted: 2 March 2001     

A relativistic quark model for mesons with an instanton-induced interaction

We present new results of a relativistic quark model based on the Bethe-Salpeter equation in its instantaneous approximation. Assuming a linearly rising confinement potential with an appropriate spinorial structure in Dirac space and adopting a residual interaction based on instanton effects, we can compute masses of the light mesons up to highest observed angular momenta with a natural solution of the U _A(1) problem. The calculated ground states masses and the radial excitations describe the experimental results well. In this paper, we will also discuss our results concerning numerous meson decay properties. For processes like π⁺/K ⁺↦e ⁺υ_eγ and 0^-↦γγ at various photon virtualities, we find a good agreement with experimental data. We will also comment on the form factors of the K _?3 decay and on the decay constants of the π, K and η mesons. For the sake of completeness, we will furthermore present the electromagnetic form factors of the charged π and K mesons as well as a comparison of the radiative meson decay widths with the most recent experimental data. Received: 28 August 2000 / Accepted: 12 September 2000     

A New Method for Accurately Measuring Temperature Dependence of Refractive Index

A new high-accuracy method for measuring temperature dependence of refractive index is proposed and applied to some polymer waveguides. The method uses 3 m-lines from a grating coupler on the waveguide surface, and has an accuracy of better than 1 × 10^–5 (1/°C). The grating period dependent on the temperature does not affect the accuracy. The measurement thermo-optic (TO) coefficients of polycarbonate (PC) and polymethyl methacrylate (PMMA) are strongly dependent on the waveguide structure in contrast with the previously reported value. It is found that the TM-mode refractive index of UV-curing polymer (J-91) increases with the increase in temperature, contrary to common expectations for polymers. A highly efficient TO switch is expected using the J-91 polymer waveguide.     

Pressure dependence of the electron density in solid iodine by the maximum-entropy method

Abstract

A direct observation of the electron density of solid iodine has been attempted in order to study the electron-density delocalization process due to pressure-induced metallization. A high-accuracy x-ray powder diffraction measurement was carried out with a diamond anvil cell and an imaging plate on a synchrotron-radiation source. The maximum entropy method was employed to analyze the data and to obtain electron-density maps under pressures up to 20 GPa. The electron density between adjacent iodine molecules has been shown to gradually increase with increasing pressure; also, a two-dimensional network is formed at a density level of 0.2 e/ų at around 16 GPa.     

Formulation and picture of quantum phase

Based on the concept of classical phase, we formulate a new explanation for the quantum phase from the quantum mechanical point of view. The quantum phase is the canonically conjugate variable of an angular momentum operator, which corresponds to the angular position φ in an actual physical space with a classical reference frame, but it takes a complex exponential form e ^iφ≡cosφ+i sinφ in the abstract Hilbert space of a quantum reference frame. This formulation is simply the famous Euler formula in a complex number field. In particular, when φ = π/2, the correlative quantum phase is a unitary pure imaginary number e ^iπ/2≡cos(π/2)+i sin(π/2) ≡ i. By using a photon state-vector function that is the general solution of photon Schr?dinger equation and can completely describe a photon’s behavior, we discuss the relationship between the angular momentum of a photon and the phase of the photon; we also analyze the intrinsic relationship between the macroscopic light wave phase and the microscopic photon phase.     

Optoelectronic array interconnections

Two-dimensional parallel optoelectronic links are proposed for interconnections between electronic boards. Experiments were performed with LED-arrays and laserdiodes as the light transmitter, multimode fibre-arrays and imaging systems for light guiding and a CMOS opto-ASIC as highly sensitive light-receiver (detection limit is 1 fJ bit^–1 at a bit error rate of less than 10^–9). In the experiment each channel has a data rate of 10 Mbits^–1, the system is designed for 128 parallel channels occupying an area of less than 1 cm² and thus providing an overall throughput of more than 1 Gbits^–1. The applications are connections between CPUs and shared memories within a multiprocessor system.     

A Variational Theory for Light Rays in Stably Causal Lorentzian Manifolds: Regularity and Multiplicity Results

This paper is dedicated to the study of light rays joining an event p with a timelike curve γ in a light–convex subset &\Lambda; of a stably causal Lorentzian manifold . We set up a functional framework, defined intrinsically, consisting of a family of manifolds and a positive functional Q defined on them. The critical points of Q on approach, as , the lightlike, future pointing geodesics joining p and γ. We prove some regularity results, including the C ¹–regularity of , the C ²–regularity of Q on and the C ²–regularity of its critical points. Using them, we develop a Ljusternik–Schnirelman theory for light rays, obtaining some multiplicity results, depending on the topology of the space of all lightlike curves joining p and γ. Received: 9 April 1996 / Accepted: 27 December 1996     

Searches for gamma-quanta from local sources by a wide-angle imaging telescope

Summary A new Cherenkov imaging telescope SHALON equipped with a very high-definition camera (144 pixels, imaging 7.2⁰×7.2⁰) takes data since 1993 at a mountain altitude of 3338 m. We discuss some results of the observations of the indicated gamma-ray sources and the discrimination methods between gamma-rays and protons. Selection of showers produced by gamma-quanta from a background of showers produced by protons has been made according to the following criteria: 1) alpha<20⁰; 2) length/width>1.6 for γ; 3) Cherenkov light intensity in pixels with max light to the light in the light pixels near around is >0.2 for γ and <0.6 for p; 4) Cherenkov light intensity in pixels with max light to all light in imaging excluding in centre is >0.8 for γ and <0.8 for p; 5) distance for γ is <3.5 pixels.I _Crab=(0.95±0.18)·10⁻¹² cm⁻²c⁻¹.I _Mark421=(0.98±0.36)·10⁻¹² cm⁻²c⁻¹. Paper presented at the Special Session on ground-based gamma-ray astronomy of the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Doppler spectroscopy of a beam in the channel of a H− ion source

It is shown that high-accuracy contact-free measurements of the divergence and emittance of an accelerated H⁻ ion beam at the exit from the source can in principle be performed by passive Doppler spectroscopy of a beam of excited hydrogen atoms produced by neutralization of the ions with excitation on the residual gas in the source channel. The intensity of the H_α-line radiation detected by the Doppler system is calculated, taking into account the principal processes leading to the excitation and deexcitation of the 3s, 3p, and 3d levels of the hydrogen atoms in the beam, for residual gas densities of the order of 10⁻⁴–10⁻⁵ Torr in the source channel. The computed H_α-line intensity was confirmed experimentally, making it possible to perform photoelectronic detection of the spectral contour of the line in the current mode rather than the photon-counting mode. Zh. Tekh. Fiz. 68, 15–18 (June 1998)     

Global Regularity of Wave Maps¶II. Small Energy in Two Dimensions

We show that wave maps from Minkowski space ℝ^{1+ n} to a sphere S ^{m −1} are globally smooth if the initial data is smooth and has small norm in the critical Sobolev space , in all dimensions n≥ 5. This generalizes the results in the prequel [40] of this paper, which addressed the high-dimensional case n≥ 5. In particular, in two dimensions we have global regularity whenever the energy is small, and global regularity for large data is thus reduced to demonstrating non-concentration of energy. Received: 14 December 2000 / Accepted: 18 June 2001     

Novel method to determine the actual surface area of a laser-nanotextured sensor

The actual surface area of a gold-coated conductive layer over the laser nano-textured surface of sapphire is determined using an electrochemical cyclic voltammetry. The method is down scaled to measure the sensing surface area of 200 × 200 μm² on a laser-ablated ripple sensor used for surface-enhanced Raman spectroscopy/scattering (SERS). Ripple SERS sensors made on different substrates of high refractive index materials such as GaP, diamond, SiC, and Al₂O₃ make a versatile sensing platform with the detection of analyte (here a thiophenol) down to 10 nM concentrations. Direct measurement of the surface area provides a powerful tool to investigate roughness, porosity, and morphology of coatings used for SERS or other light harvesting surfaces such as solar cells. Novelty of the proposed method is in the use of cathodic peak of surface passivation–activation cycle for calculation of surface charge. The method enables high-accuracy surface area measurements from as small as 0.01 mm² pads up to functional solar cells.