The slow-wave dispersive properties of a traveling-wave tube (TWT) changes considerably when either the helix is supported by a dielectric or the waveguide is filled with plasma. The dispersive properties of the dielectric-supported helix waveguide have been examined for different geometric parameters of the helix waveguide. The dispersion relation of the helix mode is found to be upshifted by ...

A porous silicon waveguide with integrated grating coupler is demonstrated as a new platform for portable detection of chemical and biological molecules. The two-layer porous silicon waveguide is formed by electrochemical etching and a photoresist grating is fabricated directly on the waveguide core by means of electron beam lithography. Angle-resolved reflectance measurements reveal distinct p...

Travelling wave in a helical wave guide is considered for electron acceleration. A first determination of the travelling wave modes using a partial wave expansion (PWE) and a point matching method is presented. It gives a rapid solution for moderate deformation of the guide relative to a straight cylinder. Strong deformations will give higher accelerating gradient but the PWE diverges. Two meth...

We report on optical channel waveguiding in an organic crystalline waveguide produced by direct electron beam patterning. The refractive index profile as a function of the applied electron fluence has been determined by a reflection scan method in the nonlinear optical organic crystal 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST). A maximal refractive index reduction of Deltan1...

Except for heating losses in metal, propagating plasmons also suffer a lot from radiation losses. In this paper, electron beams are proposed as a way to excite higher-order, multipolar plasmons, which would otherwise not be excited by light, as a way to reduce radiation losses. Specifically, electron excited guided plasmons in a coupled nanoparticle chain and a symmetrical four-wire waveguide a...

Free Electron Lasers up to the visible regime are dominated by diffraction effects, resulting in a radiation size much larger than the electron beam. Thus the effective field amplitude at the location of the electron beam, driving the FEL process, is reduced. By using a waveguide, the radiation field is confined within a smaller aperture and an enhancement of the FEL performance can be expected...

Phase shifts in the propagating electromagnetic field of a Cherenkov free-electron laser (CFEL) can affect its gain. The phase velocity of an electromagnetic wave varies, for example, when the lined waveguide is inhomogeneous along its length. In this paper, we study quantitatively the saturated power of a particular CFEL at both weak and strong electron-beam pumping when the inner radius of th...