Dielectric properties of EVA rubber composites at microwave frequencies theory, instrumentation and measurements.

This work describes and evaluates a technique for determining the dielectric properties of carbon-black filled Ethylene Vinyl Acetate (EVA) rubber and presents results on the studies of the effect of frequency on the permittivity and microwave conductivity using resonant cavity perturbation method. The measurements are performed with the aid of a Network Analyzer in X-band. The simplicity of this method lies in the fact that the dielectric properties can be obtained directly from the analytical formula without taking recourse to calibration.

Optical fields of the lowest modes in a uniformly active thin subwavelength spiral microcavity.

A numerical study is presented of several lowest in frequency modes in a spiral microlaser. The modes in an arbitrarily shaped active cavity are considered as solutions to the two-dimensional eigenproblem for the Muller boundary-integral equations. After discretization using the Nyström-type algorithm, the eigenvalues are found in terms of frequency and material-gain threshold.

Lasing frequencies and thresholds of the dipole supermodes in an active microdisk concentrically coupled with a passive microring.

The lasing spectra and threshold values of material gain for the dipole-type supermodes of an active microdisk concentrically coupled with an external passive microring are investigated. TE polarized modes are treated accurately using the linear electromagnetic formalism of the 2-D lasing eigenvalue problem (LEP) with exact boundary and radiation conditions. The influence of the microring on the lasing frequencies and thresholds is studied numerically, demonstrating threshold reduction opportunities.

Threshold reduction in a cyclic photonic molecule laser composed of identical microdisks with whispering-gallery modes.

Lasing modes in cyclic photonic molecules (CPMs) composed of several identical thin semiconductor microdisks in free space are studied in a linear approximation. Maxwell's equations with exact boundary conditions and the radiation condition at infinity are considered as a specific eigenvalue problem that enables one to find natural frequencies and threshold gains. It is demonstrated that careful tuning of the distance between the disks in CPMs is able to drastically reduce the lasing thresholds of the whispering-gallery modes having small azimuth indices.

New cavity perturbation technique for microwave measurement of dielectric constant.

A new cavity perturbation technique is presented for microwave measurement of dielectric constant, which uses a modified cylindrical reentrant cavity. Though suitable for only low dielectric constants, the method has the advantages, (a) sample area does not appear in the calculations, (b) only the ratio of frequency shifts due to two samples of same area and different thickness is involved, and (c) calibration of the measuring system with known dielectric is not necessary.

Method of measuring loaded Q-factor of single-ended cavity resonators using reflection bridge.

A bridge method of determining the loaded Q-factor and coupling coefficient of single-ended cavity resonators is described. The measuring system consists of a hybrid-T or ''magic T'' bridge with one of the collinear arms terminated by the cavity and the other by a precision attenuator followed by a variable precision short. The experimental procedure essentially measures the reflection coefficient of a cavity resonator as a function of frequency by balancing the bridge, using an oscillator with variable frequency amplitude modulation as the source.