Analysis of Smith-Purcell radiation in optical region.

Smith-Purcell radiation (SPR), emitted when an electron beam is traveling above a metallic grating, has attracted a lot of attention as a source of electromagnetic (EM) radiation in the millimeter to visible spectrum. We conducted a theoretical investigation of SPR in the optical region using a two-dimensional finite-difference time-domain (FDTD) method. The permittivity of metal was represented using the Drude model.

A grating-bicoupled plasma-wave photomixer with resonant-cavity enhanced structure.

A novel terahertz plasma-wave photomixer that can improve the conversion gain and terahertz radiation power is proposed and evaluated. The photomixer is based on a high-electron mobility transistor and incorporates doubly interdigitated grating strips for the gate electrodes that periodically localize the 2D plasmons in 100-nm regions with a micron-order interval. A vertical cavity structure is formed in between the top metal grating and a terahertz mirror placed at the backside.

Effect of a thin dielectric layer on terahertz transmission characteristics for metal hole arrays.

We studied the role of surface-plasmon polaritons (SPPs) in a bandpass transmission property of two-dimensional metal hole arrays (2D-MHAs) by investigating the effect of thin dielectric layers on the 2D-MHA surfaces. We measured zero-order transmission spectra of the 2D-MHAs by changing the thickness of the dielectric layer and found that the bandpass transmission peak shifted to the lower-frequency side with increasing layer thickness, owing to the change of the resonant frequency of the SPP. This result shows that SPPs play a crucial role in the transmission property of 2D-MHAs in the terahertz region.