Propagation characteristics of trapezoidal-cross-section ridge optical waveguides

A detailed experimental and theoretical study has been carried out on the dispersion characteristics of narrow-ridge glass-film optical waveguides formed by ion etching of photoresist. Agreement between experiment and finite-element numerical calculations varies from moderately good to excellent.     

Propagation characteristics in open-groove waveguides surrounded by rough sidewalls

The radio propagation characteristics in groove-shaped roads surrounded by rough surface sidewalls are presented. Typical sidewalls are snowpack in heavy snow regions or buildings in urban areas. In this analysis, such roads are modeled by a straight groove waveguide with statistically rough sidewalls. A simple geometrical optical approach is applied to calculate the field strength along the longitudinal direction of the road as well as transversely across the road. The theoretical results are compared with previously presented experimental results. The theoretical results show that the surface roughness causes an additional propagation loss in regions far from the transmitting point and that the field strength in the cross section exhibits a cosine distribution with a slightly changing magnitude. These theoretical characteristics agree with the experimental results.<>     

Propagation in two circular coaxial waveguides

Two variants of the circular waveguide loaded with a coaxial dielectric rod are discussed. The first has conducting hoops around the rod, the second has conducting discs across the rod, the planes of the closely spaced hoops or discs being normal to the waveguide axis. The characteristic equations for the two systems are given, and a consistent mode notation is suggested.     

Propagation losses in metal-film-substrate optical waveguides

The propagation losses in metal-film-substrate two-dimensional optical waveguides are calculated. Losses for confined modes may become large and are at least an order of magnitude larger for TM than for TE modes. Higher order modes suffer more loss than the fundamental mode. Such mode-dependent loss can make efficient mode analyzers, useful for integrated optics modulation schemes.     

Propagation of Gaussian beams in dielectric waveguides

The propagation of Gaussian beams in both a homogeneous medium and a lenslike medium is treated. The correct Helmholz equation derived by the author is used to obtain the analytic solutions, taking into account the diffraction effect. Based on this, the beamwidth and the form of the wavefront are considered. The beamwidth will increase monotonically in the homogeneous medium and will be sinusoidal in the lenslike medium; that is, in the lenslike medium, the width will alternately increase and decrease     

Propagation of electromagnetic pulses in terrestrial waveguides

The propagation of electromagnetic waves over the earth's surface is considered under transient conditions. The source is taken to be a vertical electric dipole whose current moment is suddenly established. The build-up of the radiated field is calculated under various assumed corditions. It is shown, even in the absence of an ionospherically reflected wave, that the influence of earth curvature has a pronounced effect on the distortion of the original pulse shape. For great distances (i.e., d>2000 km), it is found to be more convenient to regard the field as a sum of modes. Particular attention is given to the transient characteristics of the dominant mode as a function of the source waveform.     

Propagation of infrared radiation in hollow microstructuralcylindrical waveguides

Theoretical and numerical results are presented on the propagation of infrared radiation in TE₀₁-, TM₀₁-, and TE₁₁-like modes in an empty cylindrical, gold-coated waveguide of micron dimensions. Low-loss propagation is possible for the TE₀₁-like mode, whose configuration is similar to that of the TE₀₁ mode in a guide with perfectly conducting walls. Propagation is more lossy for the TM₀₁- and TE₁₁-like modes. While for small guide radii these modes resemble the TM₀₁ and TE₁₁ modes in a guide with perfectly conducting walls, they transform into surface waves as the guide radius is increased, with losses that are independent of guide radius     

Propagation in periodically loaded waveguides with higher symmetries

A generalization of Floquet's theorem is presented for periodically loaded closed waveguides possessing a certain class of higher symmetries which includes the screw and glide symmetries. These symmetries frequently appear in microwave structures such as filters, traveling-wave tubes, and traveling-wave antennas. The theorem states that the natural modes are eigenvectors of the symmetry operator characterizing the structure. An alternative derivation of the theorem using an equivalent network representation leads naturally to a simple method for constructing the qualitative dispersion (Brillouin) diagrams for structures with screw or glide symmetry.     

Propagation of electromagnetic waves in two-dimensionally periodic thin-film waveguides

A simplified mathematical model of two-dimensionally(2D) periodic thin-film wavegmide is proposed and the characteristics of wave propagation are shown to be governed by a five-term recurrence relation with dyadic admittance coefficients. The generalized transverse resonance method can be used to analyze any complicated 2D periodic thin-film waveguide. The dispersion characteristics are described by both approximation analysis and numerical calculation. The theoretical explanation and physical understanding of the effecis of 2D periodic modulation provided by our analysis and resulis can give sound support to the engineering applications.     

Propagation and radiation properties of corrugated cylindrical coaxial waveguides

A theoretical study is given for the behavior of cylindrical coaxial waveguides having reactive (corrugated) surfaces. After a general analysis assuming independent values for the surface reactances, the propagation and radiation properties for specific surfaces are considered. These include the case where 1) both surfaces are smooth-walled; 2) one surface is smooth-walled with the other corrugated; and 3) both surfaces are corrugated such that they have equal values for the surface reactance.     

Attenuation characteristics of coplanar waveguides

Some preliminary Q measurement results obtained on coplanar waveguides are reported. The novel surface strip transmission lines have loss characteristics similar to those of microstrip lines of the same width and characteristic impedance.     

Propagation of electromagnetic waves in planar metamaterial waveguides and radiation of antennas based on such waveguides

Propagation of electromagnetic waves in planar waveguides made of metamaterials with negative values of the relative permittivity and relative permeability is analyzed. The specific features of radiation from antennas manufactured on the basis of planar metamaterial waveguides are studied. It is shown that radiation of such antennas is characterized by the backfire radiation effect, i.e., the maximum of the radiation pattern is formed at 180°. The causes of this effect and the conditions for its appearance are revealed. It is proved that this effect appears only in the antennas manufactured on the basis of metamaterial waveguides with negative values of the relative permittivity and relative permeability. A design version of a scanning two-mode antenna operating on the basis of this effect is proposed.     

Propagation in rectangular waveguides periodically loaded with cylindrical posts

The analysis of propagation in periodically loaded waveguide structures is conducted. The eigenvalue equation is derived to determine the propagation constants of the Floquet modes. Theoretical and experimental investigations of semi-periodic structures and their scattering matrices are performed. The existence of passbands and stopbands, which are characteristic for periodic structures, is shown.     

Dispersion characteristics of diffused channel waveguides

A variational method is used to calculate dispersion curves for channel waveguides fabricated by masked diffusion. Composition profiles for the waveguides are obtained by numerical solution of the diffusion equation, assuming that the diffusant concentration in the unmasked region of the substrate surface is constant during the diffusion process. A linear dependence of refractive index change on diffusant concentration is assumed. The dependence of the number of guided modes on mask gap width and diffusion depth is determined as an aid to the design of modulators and switches for integrated optics.     

Dispersion characteristics of strip dielectric waveguides

A simple and accurate dispersion relation is derived for the guided mode of a strip dielectric waveguide. This relation shows explicitly the effect of the width of the waveguide and involves only the solution for a single three-layer slab waveguide. It is found that there always exist a strip waveguide with a specific aspect ratio in which the E_mn^x and E_mn^y modes propagate at the same phase velocity     

Surface emitting characteristics of silicon waveguides

This paper concerns the surface emitting characteristics of silicon waveguides in the millimeter-wave frequency band. The waveguides used in the experiment are rectangular slabs of high resistivity silicon (30,000 ohm-cm). A series of periodic perturbations on the waveguide surface provide a radiating antenna. A rectangular grating with a period of Λ=1.8 mm, a height of 0.35 mm, and a duty cycle of 0.46 was sawn into the top surface of a silicon waveguide with a width of 3 mm and a height of 1.41 mm. Experiments were performed to measure the attenuation, dispersion and the radiation characteristics of the waveguides. The test setup was used to monitor the frequency, radiation angle, and the radiated power. Measurements are made over a band of frequencies around the second Bragg frequency. The detector was scanned from 88–95 GHz and changes were observed in the attenuation constant, dispersion relation and the far field radiation pattern. From these results we were able to verify the grating theory.     

Dispersion characteristics of cylindrical coplanar waveguides

A full-wave analysis of the coplanar waveguide (CPW) printed on a cylindrical substrate is presented, and the dispersion characteristics of the cylindrical CPW are studied. Numerical results of the effective relative permittivity are calculated using a Galerkin's moment-method calculation. Experiment is also conducted, and the measured data are in good agreement with the theory     

Propagation properties for five-layer symmetric slab waveguides including left-handed materials

In this paper, we discussed a slab wave-guide of five layers, The core is a left-handed material, but the claddings are right-handed materials. A dispersion equation of TE modes is obtained by using Maxwell＇s equations, and some new dispersion characteristics are obtained based on the equation.     

Propagation properties for five-layer symmetric slab waveguides including left-handed materials

In this paper,we discussed a slab wave-guide of five layers,The core is a left-handed material,but the claddings are right-handed materials. A dispersion equation of TE modes is obtained by using Maxwell's equations,and some new dispersion characteristics are obtained based on the equation.