FEM investigation of leaky modes in hollow core photonic crystal fibers

Hollow-core holey fibers are promising candidates for low-loss guidance of light in various applications, e.g., for the use in laser guide star adaptive optics systems in optical astronomy. We present an accurate and fast method for the computation of light modes in arbitrarily shaped waveguides. Maxwell's equations are discretized using vectorial finite elements (FEM). We discuss how we utilize concepts like adaptive grid refinement, higher-order finite elements, and transparent boundary conditions for the computation of leaky modes in photonic crystal fibers. Further, we investigate the convergence behavior of our methods. We employ our FEM solver to design hollow-core photonic crystal fibers (HCPCF) whose cores are formed from 19 omitted cladding unit cells. We optimize the fiber geometry for minimal attenuation using multidimensional optimization taking into account radiation loss (leaky modes).Comment: 8 page

Evolution of a coherent array of Bose-Einstein Condensates in a magnetic trap

We investigate the evolution process of the interference pattern for a coherent array of Bose-Einstein condensates in a magnetic trap after the optical lattices are switched off. It is shown that there is a decay and revival of the density oscillation for the condensates confined in the magnetic trap. We find that, due to the confinement of the magnetic trap, the interference effect is much stronger than that of the experiment induced by Pedri et al. (Phys. Rev. Lett, {\bf 87}, 220401), where the magnetic trap is switched off too. The interaction correction to the interference effect is also discussed for the density distribution of the central peak.Comment: RevTex, 17 pages,9 figures. E-mail: [email protected]

JCMmode: An Adaptive Finite Element Solver for the Computation of Leaky Modes

We present our simulation tool JCMmode for calculating propagating modes of an optical waveguide. As ansatz functions we use higher order, vectorial elements (Nedelec elements, edge elements). Further we construct transparent boundary conditions to deal with leaky modes even for problems with inhomogeneous exterior domains as for integrated hollow core Arrow waveguides. We have implemented an error estimator which steers the adaptive mesh refinement. This allows the precise computation of singularities near the metal's corner of a Plasmon-Polariton waveguide even for irregular shaped metal films on a standard personal computer.Comment: 11 page

Benchmark of FEM, Waveguide and FDTD Algorithms for Rigorous Mask Simulation

An extremely fast time-harmonic finite element solver developed for the transmission analysis of photonic crystals was applied to mask simulation problems. The applicability was proven by examining a set of typical problems and by a benchmarking against two established methods (FDTD and a differential method) and an analytical example. The new finite element approach was up to 100 times faster than the competing approaches for moderate target accuracies, and it was the only method which allowed to reach high target accuracies.Comment: 12 pages, 8 figures (see original publication for images with a better resolution

Rigorous Simulation of 3D Masks

We perform 3D lithography simulations by using a finite-element solver. To proof applicability to real 3D problems we investigate DUV light propagation through a structure of size 9 microns times 4 microns times 65 nm. On this relatively large computational domain we perform rigorous computations (No Hopkins) taking into account a grid of 11 times 21 source points with two polarization directions each. We obtain well converged results with an accuracy of the diffraction orders of about one percent. The results compare well to experimental aerial imaging results. We further investigate the convergence of 3D solutions towards quasi-exact results obtained with different methods.Comment: 8 pages, 5 figures (see original publication for images with a better resolution

Assessment of the 2,4 km run as a predictor of aerobic capacity

CITATION: Burger, S.C., Bertram, S.R. & Stewart, R.I. 1990. Assessment of the 2,4 km run as a predictor of aerobic capacity. S Afr Med J, 78(9):327-329.The original publication is available at http://www.samj.org.zaENGLISH ABSTRACT: Since the 2,4 km run time test is routinely used in military training programmes as an indicator of aerobic capacity and its possible improvement, an atemtp was made to: (i) establish a regression equation of VO2(max) v. 2,4 km run time in a group of 20 young military volunteers; and (ii) determine whether this equation could be used to predict VO2(max) reliably from the 2,4 km time obtained from another group. Before and after training, VO2(max) was measured in all subjects using a treadmill test, and 2,4 km run time was determined in the field. Linear regression equations using the 2,4 km run time as the independent variable accounted for 76-92% of the variance in VO2(max), while the standard error of the estimate varied from 2,24-2,91 ml/kg/min. In the second test group, the directly measured VO2(max) was 59,89 ± 0,99 ml/kg/min, while the mean values estimated from the regression equation of the first group was 59,61 ± 1,16 ml/kg/min (P< 0.001). It was concluded that, in the population studied, the 2,4 km run time in the field reliably predicts VO2(max) measured during treadmill exercise in the laboratory.AFRIKAANSE OPSOMMING: Geen opsomming beskikbaarPublisher’s versio

Assessment of the 2,4 km run as a predictor of aerobic capacity

Since the 2,4 km run time test is routinely used in military training programmes as an indicator of aerobic capacity and its possible improvement, an attempt was made to: (i) establish a regression equation of V02max V. 2,4 km run time in a group of 20 young military volunteers; and (ii) determine whether this equation could be used to predict V02max reliably from the 2,4 km time obtained from another group. Before and after training, V02max was measured in all subjects using a treadmill test, and 2,4 km run time was determined in the field. Linear regression equations using the 2,4 km run time as the independent variable accounted for 76 - 92% of the variance in VO2max, while the standard error of the estimate varied from 2,24 - 2,91 ml/kg/min. In the second test group, the directly measured V02max was 59,89 ± 0,99 ml/kg/min, while the mean value estimated from the regression equation of the first group was 59,61 ± 1,16 ml/kg/min (P &lt; 0,001). It was concluded that, in the population studied, the 2,4 km run time in the field reliably predicts V02max measured during treadmill exercise in the laboratory

Numerical Investigation of Light Scattering off Split-Ring Resonators

Recently, split ring-resonators (SRR's) have been realized experimentally in the near infrared (NIR) and optical regime. In this contribution we numerically investigate light propagation through an array of metallic SRR's in the NIR and optical regime and compare our results to experimental results. We find numerical solutions to the time-harmonic Maxwell's equations by using advanced finite-element-methods (FEM). The geometry of the problem is discretized with unstructured tetrahedral meshes. Higher order, vectorial elements (edge elements) are used as ansatz functions. Transparent boundary conditions and periodic boundary conditions are implemented, which allow to treat light scattering problems off periodic structures. This simulation tool enables us to obtain transmission and reflection spectra of plane waves which are incident onto the SRR array under arbitrary angles of incidence, with arbitrary polarization, and with arbitrary wavelength-dependencies of the permittivity tensor. We compare the computed spectra to experimental results and investigate resonances of the system.Comment: 9 pages, 8 figures (see original publication for images with a better resolution