Beam Waveguide Research Articles

A thin-film polymeric waveguide beam deflector based on thermooptic effect

A thin-film polymeric waveguide beam deflector was fabricated and demonstrated. The three-layer planar waveguide was composed of UV15 as the top cladding layer, a polyimide as the core layer, and SiO/sub 2/ as the bottom cladding layer on a silicon substrate. A gold layer was deposited on the top of the waveguide by e-beam deposition and then patterned into a prism-array as the heating electrode by photolithography. Beam deflection was acquired by passing the beam through the waveguide underneath the prism array. The beam deflection angle showed the expected quadratic dependence upon the applied voltage. A maximum acquired beam deflection angle of 2.5/spl deg/ was derived at an applied voltage of 8 V. Eight resolvable spots were observed, which made possible the feasibility of a 1/spl times/8 optical switch.

Spatial solitons in discontinuous magneto-optic waveguides

The propagation of diffraction-free light beams (spatial solitons) in layered structure magneto-optic waveguides is investigated. Linear magneto-optic layers are used, but with varying degrees of complexity, coupled to optically nonlinear layers. The presence of interfaces is considered and control of spatial solitons is introduced. This control is exposed through the use of a split-field method of generating a perturbative analytical analysis. It is pointed out that these systems are very easy to create experimentally to any degree of sophistication. The approach is considered to be very promising for future all-optical processing.

Diffraction of X-ray beams in capillary waveguides

Propagation of the soft X-ray radiation generated by a small-diameter incoherent source through the capillary plane waveguide which satisfies the multimode condition is studied using the Fresnel–Kirchhoff diffraction theory. The diffraction is manifested by appearance of the diffraction fringes, dark and light bands, in the far-field zone of the capillary output. Such a behaviour of the X-ray radiation is confirmed by our experimental data. The results give explanation for the interference effect recently observed in many experiments on the grazing reflections of X-rays in single and multiple capillary optics.

On the Goubau-Schwering beam waveguide using a modified paraxial approximation

In this paper, we demonstrate that the beam waveguide can be easily postulated by using a modified version of the paraxial approximation.

Calibration of waveguide beam position monitors

To ensure overlap between the photon beam and electron beam at the SASE-FEL at the TESLA Test Facility [1], several position-sensitive diagnostics components are installed along the beamline of the FEL. For the undulator part, a new type of waveguide beam position monitors (BPMs) is designed, tested, and installed inside the beam pipe of one undulator module. This paper proposes a method to calibrate these monitors with beam-based measurements

An integrated thin-film thermo-optic waveguide beam deflector

We have demonstrated the operation of a thin-film thermo-optical beam deflector in a three-layer optical planar waveguide. The fabricated waveguide beam deflector consists of a thin-film SiO2 bottom cladding layer, a thin-film polymer top cladding layer, and alternatively positioned thin-film polymer and silica microprisms as the guiding layer. The beam deflection is achieved through the thermo-optic effect that results in opposed index changes in polymer and silica with respect to temperature changes. The measured deflection sensitivity is 0.06°/°C, for the fabricated device with a 7.0 mm interaction length at the wavelength of 632.8 nm.

LQG controller design using GUI: Application to antennas and radio-telescopes

The Linear Quadratic Gaussian (LQG) algorithm has been used to control the JPL's beam wave-guide, and 70-m antennas. This algorithm significantly improves tracking precision in a wind disturbed environment. Based on this algorithm and the implementation experience a Matlab based Graphical User Interface (GUI) was developed to design the LQG controllers applicable to antennas and radiotelescopes. The GUI is described in this paper. It consists of two parts the basic LQG design and the fine-tuning of the basic design using a constrained optimization algorithm. The presented GUI was developed to simplify the design process, to make the design process user-friendly, and to enable design of an LQG controller for one with a limited control engineering background. The user is asked to manipulate the GUI sliders and radio buttons to watch the antenna performance. Simple rules are given at the GUI display.

Analysis of longitudinal wiggler-undulator radiation in a parallel plate waveguide

In this Letter we discuss the spectral features of the radiation emitted by electrons moving in a longitudinal wiggler magnetic field in a parallel plate waveguide. The analysis of undulator radiation is aimed at to study the emission features of a longitudinal wiggler in a waveguide and compare with a standard undulator and cyclotron maser device with a reference to slippage. A small variation of beam energy or waveguide dimension drive the system away from zero-slippage condition. With finite β ⊥ of the beam electrons allows the device be appropriately tuned back to its zero-slip position. For a finite slip, the cyclotron maser provides a better slippage control in comparison to an undulator based device.

Present status of the theory of relativistic plasma microwave electronics

Theoretical research on high-power microwave sources based on stimulated emission from relativistic election beams in plasma waveguides and resonators is reviewed. Both microwave amplifiers and oscillators are investigated. Two mechanisms for stimulated emission—resonant Cherenkov emission from a relativistic electron beam in a plasma and nonresonant Pierce emission arising from the onset of a high-frequency Pierce instability—are studied theoretically. The theory developed here is motivated by recent experiments carried out at the Institute of General Physics of the Russian Academy of Sciences and is aimed at creating high-power pulsed plasma microwave sources [both narrowband (Δω/ω<0.1) and broadband (or noisy, Δω/ω≈1)] based on high-current relativistic electron beams. Although the paper is devoted to theoretical problems, all analytic estimates and numerical calculations are made with real experiments in mind and theoretical results are compared with reliable experimental data. Special attention is paid to the opportunity to progress to short (millimeter) and long (decimeter) wavelength ranges. Some factors that influence the formation of the wave spectra excited by relativistic electron beams in plasma sources are discussed.

A time-domain beam-propagation method for analyzing pulsed optical beams in second-order nonlinear waveguides

The linear time-domain beam propagation method (TD–BPM) has been extended to model the propagation of pulsed optical beams in second-order nonlinear optical material of integrated waveguides. The coupled nonlinear wave equations have been derived and discretized using the explicit finite-difference method. The nonlinear TD–BPM method developed in the present work is very efficient, and is simple to implement. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 28: 253–257, 2001.

The effect of ground vias on changing signal layers in a multilayered PCB

generation TDBPMSHG , which is an extension of the linear TDBPM. It involves solving the coupled parabolic nonlinear equations using the explicit finite-difference technique, where all spatial and time variations were retained in the analysis. The technique was also applied to model pulsed optical beams in a dielectric waveguide containing secondorder nonlinear effects. It is concluded that the method is very efficient and simple to implement. The TDBPMSHG is well suited for the study of the unidirectional propagation of compact temporal pulses over long distances in a guidedwave environment. In addition, the method should find application in the study of spatiotemporal optical solitons in media with quadratic nonlinearity 17 .

A millimeter-wave cassegrain antenna using shaped beam waveguide feed

As a way to increase the efficiency of the focused beam-fed Cassegrain antenna with a large aperture for use at millimeter-wave frequencies, a method is proposed for shaping the surface of two focusing reflectors in the focused beam waveguide feed. The reflector surface shaping method is presented. Since the reflector is used at millimeter-wave frequencies, it is necessary to take into account the effect of the aberration caused by the deformation of the reflector surface on the radiation characteristics. Both the sub- and main reflectors have quadratic surfaces. The aberration in the main reflector due to self weight deformation can be corrected with the deformation of the subreflector in the homologic design. Hence, in order to validate the present beam shaping method, it is necessary to evaluate the effects of the aberration caused by the alignment error of each focusing reflector on the radiation characteristics. In this paper, a method of shaping the two focusing reflectors is applied to the new 10-m antennas for the millimeter-wave interferometer of Nobeyama National Observatory (model No. 6). The alignment errors in the parallel shift in three axis directions and the rotating motion about the axes are assumed, and the aberration and the gain degradation are quantitatively investigated when each focusing reflector is deformed. It is shown that the grain degradation is small in the range of realizable alignment errors and that the method of shaping the surfaces of two focusing reflectors is effective as a reflector shaping method for a millimeter-wave large-aperture antenna. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 84(4): 39–47, 2001

Characterization of folded beam waveguide absorbers for damping of flexural vibrations in a thick plate

Characterization of folded beam waveguide absorbers for damping of flexural vibrations in a thick plate

Comment on the paper “subwavelength diameter of light beams in active waveguides”

In a recent paper Kuznetsova considered the case of a cylindrical waveguide containing an amplifying medium and concluded that there is no frequency cutoff for such a case: for an arbitrary small radius a of the waveguide ~but smaller than the cutoff radius acut) and an arbitrary small amplification d ~thus the complex permittivity of a medium is x5e2id), light can propagate through such a waveguide with an amplification. This possibility, if it exists, of course, would be of extreme importance for near-field optics and fiber communications.

Time-domain finite-difference beam propagation method

A new technique to model the behavior of pulsed optical beams in waveguides is proposed and analyzed. The technique is an extension of the traditional continuous-wave beam propagation method (BPNI) to include time dependence, therefore called the time-domain BPM (TD-BPM). The method was tested using different waveguide examples and it is concluded that the technique is simple and accurate. Compared with the finite-difference TD method, the new TD-BPM is more efficient in terms of computer memory and execution time especially for large optical devices.

Subwavelength diameter of light beams in active waveguides

It is shown that there is no frequency cutoff in a uniform cylindrical waveguide containing an amplifying medium. Waves of any frequency grow in the direction of propagation, and for small transverse sections the growth rate is inversely proportional to the waveguide diameter.

A phase-control approach for a large-element coherent microwave power uplink system

Signal combining efficiencies of 98% have been achieved on low-Earth orbiting (LEO) debris with phase-locking of time-overlapped radar pulses from a two-element phased-array consisting of two 34-m beam waveguide steerable paraboloid antennas separated by 204 m. The uplink arraying at 7.19 GHz has been achieved for tracks from about 10/spl deg/ elevation at signal rise to 4/spl deg/ elevation at signal set under varying weather conditions (e.g., hail failing on one antenna). The typical root mean square (RMS) phase error for two coherent 100-/spl mu/s 50-Hz 5-kW peak pulses reflected from LEO debris with signal-to-noise ratio (SNR) >23 dB is less than 4/spl deg/. The phase-control system design, methods of calibration, and details of the design control table of phasing error contributors are presented and discussed. Based upon the measured performance, we predict that transmitting antennas for the Deep Space Network (DSN) could be coherently arrayed for up to hours at a time given static phase error calibrations on exo-atmospheric debris. Applications for this technique include low-cost implementation of high-power microwave transmitters for deep-space communication and radars for exploration of other planets and as part of a defense against comets and asteroids.

The characterization of a 34-meter beam-waveguide antenna at Ka band (32.0 GHz) and X band (8.4 GHz)

New antennas for the NASA Deep Space Network (DSN) have been built to replace the aging antennas of older designs for deep-space communications. These new antennas incorporate a new dual-shape design as well as a beam waveguide (BWG), which utilize a series of additional secondary mirrors to relocate the focal point into a stationary room below the main reflector. The advantages of using such a design include increased isolation of the feed package from outside environmental factors, such as moisture, wind, and temperature changes; and ease of access to the equipment for maintenance, troubleshooting and repair purposes. This article reports on the performance of a beam waveguide antenna at X-band and Ka-band microwave frequencies. The Ka-band antenna performance experiment (KaAP) antenna-efficiency measurements presented in this article were acquired at the Goldstone DSS-13 research and development (R&D) beam-waveguide antenna between December, 1993, and November, 1995. The measured antenna efficiency and ground-station figure-of-merit (gain divided by operating system noise temperature) as a function of elevation angle and their uncertainties are presented. Also described are the station configuration, the measurement technique, the modeling used in the analysis processing, and the historical evolution of the DSS-13 Ka-band antenna-efficiency measurements as progressive improvements and configuration changes were implemented.

Analysis of an Optically Controlled Nonlinear Directional Coupler

An optically controlled nonlinear directional coupler (NLDC) to be useful in optical integrated circuits has been analyzed. The optical control is achieved through the interactions between a laser beam and surrounding semiconductor medium. The effect of plasma density, laser beam wavelength and waveguide with on the performance of the coupler including critical power has been thoroughly investigated. A far better performance compared to a simple NLDC has been achieved.

Power loss for multimode waveguides and its application to beam-waveguide system

The conventional way of expressing power loss in decibels/meter for a multimode waveguiding system with finite wall conductivity (such as a beam-waveguide (BWG) system with protective shroud) can be incorrect and misleading. The power loss (in decibels) for a multimode waveguiding system is, in general, not linearly proportional to the length of the waveguide. New power-loss formulas for multimode system are derived in this paper for arbitrarily shaped conducting waveguide tubes. In these formulas, there are factors such as [exp(jx)-1]/(jx), where x=(/spl beta//sub a/-/spl beta//sub b/)l, with /spl beta//sub a/ and /spl beta//sub b/ being the propagation constants of the different propagating modes and l being the distance from the source plane to the plane of interest along the guide. For a large BWG supporting many propagating modes, /spl beta//sub a/'s are quite close to /spl beta//sub b/'s, thus the mode coupling terms remain important for a very long distance from the source plane. The multimode power loss formula for a large circular conducting tube has been verified by experiments. This formula was also used to calculate the additional noise temperature contribution due to the presence of a protective shroud surrounding a millimeter-wave BWG system.