Field representation for optical defect resonances in multilayer microcavities using quasi-normal modes

Quasi-normal modes are used to characterize transmission resonances in 1D optical defect cavities and the related field approximations. We specialize to resonances inside the bandgap of the periodic multilayer mirrors that enclose the defect cavities. Using a template with the most relevant QNMs a variational principle permits to represent the field and the spectral transmission close to resonances

Transparent-Influx Boundary Conditions for FEM Based Modelling of 2D Helmholtz Problems in Optics

A numerical method for the analysis of the 2D Helmholtz equation is presented, which incorporates Transparent-Influx Boundary Conditions into a variational formulation of the Helmholtz problem. For rectangular geometries, the non-locality of those boundaries can be efficiently handled by using Fourier decomposition. The Finite Element Method is used to discretise the interior and the nonlocal Dirichlet-to-Neumann operators arising from the formulation of Transparent-Influx Boundary Conditions

Variational coupled mode theory and perturbation analysis for 1D photonic crystal structures using quasi-normal modes

Quasi-normal modes are used to directly characterize defect resonances in composite 1D Photonic Crystal structures. Variational coupled mode theory using QNMs enables quantification of the eigenfrequency splitting in composite structures. Also, variational perturbation analysis of complex eigenfrequencies is addressed

Weakly nonparaxial effects on the propagation of (1+1)D spatial solitons in inhomogeneous Kerr media

The widely-used approach to study the beam propagation in Kerr media is based on the slowly varying envelope approximation (SVEA) which is also known as the paraxial approximation. Within this approximation, the beam evolution is described by the nonlinear Schrödinger (NLS) equation. In this paper, we extend the NLS equation by including higher-order terms to study the effects of nonparaxiality on the soliton propagation in inhomogeneous Kerr media. The result is still a one-way wave equation which means that all back-reflections are neglected. The accuracy of this approximation exceeds the standard SVEA. By performing several numerical simulations, we show that the NLS equation produces reasonably good predictions for relatively small degrees of nonparaxiality, as expected. However, in the regions where the envelope beam is changing rapidly as in the breakup of a multisoliton bound state, the nonparaxiality plays an important role

Field representations for optical defect microcavities in 1D grating structures using quasi-normal modes

Quasi-Normal Modes are used to characterize transmission resonances in 1D optical defect cavities and the related field approximations. Using a mirror field and the relevant QNM, a variational principle permits to represent the field and the spectral transmission close to resonances

Global and local cutoff frequencies for transverse waves propagating along solar magnetic flux tubes

The propagation of linear transverse waves along a thin isothermal magnetic flux tube is affected by a global cutoff frequency that separates propagating and non-propagating waves. In this paper, wave propagation along a thin but non-isothermal flux tube is considered and a local cutoff frequency is derived. The effects of different temperature profiles on this local cutoff frequency are studied by considering different power-law temperature distributions as well as the semi-empirical VAL C model of the solar atmosphere. The results show that the conditions for wave propagation strongly depend on the temperature gradients. Moreover, the local cutoff frequency calculated for the VAL C model gives constraints on the range of wave frequencies that are propagating in different parts of the solar atmosphere. These theoretically predicted constraints are compared to observational data and are used to discuss the role played by transverse tube waves in the atmospheric heating and dynamics, and in the excitation of solar atmospheric oscillations.Comment: To be publishd in ApJ Vol. 763. 10 pages, 3 Postscript figure

Effect of Bilayer Thickness on Membrane Bending Rigidity

The bending rigidity $k_c$ of bilayer vesicles self-assembled from amphiphilic diblock copolymers has been measured using single and dual-micropipet techniques. These copolymers are nearly a factor of 5 greater in hydrophobic membrane thickness $d$ than their lipid counterparts, and an order of magnitude larger in molecular weight $\bar{M}_n$. The macromolecular structure of these amphiphiles lends insight into and extends relationships for traditional surfactant behavior. We find the scaling of $k_c$ with thickness to be nearly quadratic, in agreement with existing theories for bilayer membranes. The results here are key to understanding and designing soft interfaces such as biomembrane mimetics

Electromagnetic Structure of the Z_c(3900)

The observation of the exotic quarkonium state Z_c(3900) by the BESIII and Belle collaborations supports the concept of hadronic molecules. Charmonium states interpreted as such molecules would be bound states of heavy particles with small binding energies. This motivates their description using an effective theory with contact interactions. In particular, we focus on the electromagnetic structure of the charged state Z_c(3900). Using first experimental results concerning spin and parity, we interpret it as an S-wave molecule and calculate the form factors as well as charge and magnetic radii up to next-to-leading order. We also present first numerical estimations of some of these observables at leading order.Comment: 5 pages, 4 figures, final version to appear in Phys. Lett.