Wave interactions in periodic structures and periodic dielectric waveguides

Free Electron Laser

Gover, Avraham ; Yariv, Amnon

University:California Institute of Technology

Department:Engineering and Applied Science

关键词: Free Electron Laser;   

Others  :  https://thesis.library.caltech.edu/8556/1/Gover_a_1976.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

This work is concerned with a general analysis of wave interactionsin periodic structures and particularly periodic thin filmdielectric waveguides.

The electromagnetic wave propagation in an asymmetric dielectricwaveguide with a periodically perturbed surface is analyzed interms of a Floquet mode solution. First order approximate analyticalexpressions for the space harmonics are obtained. The solution isused to analyze various applications: (1) phase matched second harmonicgeneration in periodically perturbed optical waveguides;(2) grating couplers and thin film filters; (3) Bragg reflection devices;(4) the calculation of the traveling wave interaction impedancefor solid state and vacuum tube optical traveling wave amplifierswhich utilize periodic dielectric waveguides. Some of these applicationsare of interest in the field of integrated optics.

A special emphasis is put on the analysis of traveling waveinteraction between electrons and electromagnetic waves in variousoperation regimes. Interactions with a finite temperature electronbeam at the collision-dominated, collisionless, and quantum regimesare analyzed in detail assuming a one-dimensional model and longitudinalcoupling.

The analysis is used to examine the possibility of solid statetraveling wave devices (amplifiers, modulators), and some monolithicstructures of these devices are suggested, designed to operate at thesubmillimeter-far infrared frequency regime. The estimates ofattainable traveling wave interaction gain are quite low (on the orderof a few inverse centimeters). However, the possibility of attainingnet gain with different materials, structures and operation conditionis not ruled out.

The developed model is used to discuss the possibility andthe theoretical limitations of high frequency (optical) operation ofvacuum electron beam tube; and the relation to other electron-electromagneticwave interaction effects (Smith-Purcell and Cerenkovradiation and the free electron laser) are pointed out. Finally, thecase where the periodic structure is the natural crystal lattice isbriefly discussed. The longitudinal component of optical space harmonicsin the crystal is calculated and found to be of the order ofmagnitude of the macroscopic wave, and some comments are made on thepossibility of coherent bremsstrahlung and distributed feedbacklasers in single crystals.