Georg Goubau

Bio: Georg Goubau is an academic researcher from United States Department of the Army. The author has contributed to research in topics: Wave propagation & Longitudinal wave. The author has an hindex of 7, co-authored 9 publications receiving 1673 citations.

Surface Waves and Their Application to Transmission Lines

Abstract: In this paper the applicability of non‐radiating surface waves for transmission lines is investigated. Two types of waves are considered. The first one, originally studied by A. Sommerfeld, is guided by a cylindrical conductor of finite conductivity. Although this wave type has (under comparable conditions) much lower attenuation than the waves in coaxial cables or rigid wave guides, its practical application is restricted by the fact that the extension of the field is very large. Efficient excitation and undisturbed propagation of this wave mode are feasible only for very high frequencies. The other wave type considered in this paper has not been treated in the literature. It is guided by a conductor which is coated with a dielectric layer or the surface of which is otherwise modified; for example, by being threaded. The field of this wave type has a structure similar to that of Sommerfeld's wave, but the extension of the field can be controlled by the surface modification. Thus low loss transmission lines on the basis of this wave type become feasible for frequencies above 100 megacycles. The information necessary for the design of such lines is given and the agreement between the theoretically expected transmission losses and the measured transmission losses is checked.

On the guided propagation of electromagnetic wave beams

Abstract: Any field in a half-space can be described by a continuous spectrum of cylindrical waves. If this spectrum comprises substantially only waves whose propagation constant is very close to the plane wave propagation constant, the field can be resolved into a set of elementary wave beams which are characterized by Laguerre polynomials. They satisfy orthogonality relations like the wave modes in a waveguide. The elementary beams or "beam modes" can be reiterated and guided by reconstituting the cross-sectional phase distribution at certain intervals. Reiterative beams are utilized in the beam waveguide. The finite size of the phase resetting devices effects a modification of the reiterative beam modes and causes diffraction losses. These losses decrease very rapidly with increasing diameter of the phasing devices.

Waves on interfaces

Abstract: In wave propagation along plane or cylindrical interfaces a distinction is made between truly guided waves (surface waves) and partially guided waves (radiating waves). When dissipation losses are involved, surface waves no longer represent the asymptotic field near the interfaces at large distances from the source. In order to separate them from the total field it is necessary to have a criterion for radiating waves which are free of any surface wave components. Such a criterion exists in the form of orthogonality relations which are the mathematical formulation of the concept that an ideal antenna which excites only a surface wave should not receive a radiating wave.

Experimental studies on a beam waveguide for millimeter waves

Abstract: The beam waveguide utilizes reiterative wave beams which are guided by resetting the cross-sectional phase distributions at periodic intervals. The major purpose of the measurements was to obtain data concerning the inherent losses of the guide, including the diffraction loss, caused by energy by-passing the phase transformers, and the dielectric and reflection losses of the transformers. Resonance measurements with an "open cavity," consisting of a section of a beam waveguide terminated by plane reflector walls, yielded the over-all losses of the phase transformers. In order to isolate the diffraction loss, pulse measurements were made between two reflectors, slightly curved to reset the phase distribution in the reflected beam. These measurements also gave information on the build-up of the reiterative wave beam. The experimental data support the theory which predicts that the diffraction losses of reiterative beams can be made extremely small.

Plasmonics: Fundamentals and Applications

Abstract: Fundamentals of Plasmonics.- Electromagnetics of Metals.- Surface Plasmon Polaritons at Metal / Insulator Interfaces.- Excitation of Surface Plasmon Polaritons at Planar Interfaces.- Imaging Surface Plasmon Polariton Propagation.- Localized Surface Plasmons.- Electromagnetic Surface Modes at Low Frequencies.- Applications.- Plasmon Waveguides.- Transmission of Radiation Through Apertures and Films.- Enhancement of Emissive Processes and Nonlinearities.- Spectroscopy and Sensing.- Metamaterials and Imaging with Surface Plasmon Polaritons.- Concluding Remarks.

Laser Beams and Resonators

Abstract: This paper is a review of the theory-of laser beams and resonators. It is meant to be tutorial in nature and useful in scope. No attempt is made to be exhaustive in the treatment. Rather, emphasis is placed on formulations and derivations which lead to basic understanding and on results which bear practical significance.

The History of Power Transmission by Radio Waves

Abstract: The history of power transmission by radiowaves is reviewed from Heinrich Hertz to the present time with emphasis upon the free-space microwave power transmission era beginning in 1958. The history of the technology is developed in terms of its relationship to the intended applications. These include microwave powered aircraft and the Solar Power Satellite concept.

Hollow metallic and dielectric waveguides for long distance optical transmission and lasers

Abstract: The field configurations and propagation constants of the normal modes are determined for a hollow circular waveguide made of dielectric material or metal for application as an optical waveguide. The increase of attenuation due to curvature of the axis is also determined. The attenuation of each mode is found to be proportional to the square of the free-space wavelength λ and inversely proportional to the cube of the cylinder radius a. For a hollow dielectric waveguide made of glass with v = 1.50, λ = 1μ, and a = 1 mm, an attenuation of 1.85 db/km is predicted for the minimum-loss mode, EH 11 . This loss is doubled for a radius of curvature of the guide axis R ≈, 10 km. Hence, dielectric materials do not seem suitable for use in hollow circular waveguides for long distance optical transmission because of the high loss introduced by even mild curvature of the guide axis. Nevertheless, dielectric materials are shown to be very attractive as guiding media for gaseous amplifiers and oscillators, not only because of the low attenuation but also because the gain per unit length of a dielectric tube containing He-Ne “masing” mixture at the right pressure can be considerably enhanced by reducing the tube diameter. In this application, a small guide radius is desirable, thereby making the curvature of the guide axis not critical. For λ = 0.6328μ and optimum radius a = 0.058 mm, a maximum theoretical gain of 7.6 db/m is predicted. It is shown that the hollow metallic circular waveguide is far less sensitive to curvature of the guide axis. This is due to the comparatively large complex dielectric constant exhibited by metals at optical frequencies. For a wavelength λ = 1μ and a radius a = 0.25 mm, the attenuation for the minimum loss TE 01 mode in an aluminum waveguide is only 1.8 db/km. This loss is doubled for a radius of curvature as short as R ≈ 48 meters. For λ = 3μ and a = 0.6 mm, the attenuation of the TE 01 mode is also 1.8 db/km. The radius of curvature which doubles this loss is approximately 75 meters. The

Resonant modes in a maser interferometer

Abstract: A theoretical investigation has been undertaken to study diffraction of electromagnetic waves in Fabry-Perot interferometers when they are used as resonators in optical masers. An electronic digital computer was programmed to compute the electromagnetic field across the mirrors of the interferometer where an initially launched wave is reflected back and forth between the mirrors. It was found that after many reflections a state is reached in which the relative field distribution does not vary from transit to transit and the amplitude of the field decays at an exponential rate. This steady-state field distribution is regarded as a normal mode of the interferometer. Many such normal modes are possible depending upon the initial wave distribution. The lowest-order mode, which has the lowest diffraction loss, has a high intensity at the middle of the mirror and rather low intensities at the edges. Therefore, the diffraction loss is much lower than would be predicted for a uniform plane wave. Curves for field distribution and diffraction loss are given for different mirror geometries and different modes. Since each mode has a characteristic loss and phase shift per transit, a uniform plane wave which can be resolved into many modes cannot, properly speaking, be resonated in an interferometer. In the usual optical interferometers, the resolution is too poor to resolve the individual mode resonances and the uniform plane wave distribution may be maintained approximately. However, in an oscillating maser, the lowest-order mode should dominate if the mirror spacing is correct for resonance. A confocal spherical system has also been investigated and the losses are shown to be orders of magnitude less than for plane mirrors.