Enhanced terahertz Smith-Purcell radiation from subwavelength holes array within metamaterials

We propose to generate coherent terahertz radiation by using free-electron beams to excite arrays of rectangular sub-wavelength holes within metamaterials. The radiation is achieved due to the constructive interference of radiation from all sub-wavelength holes of the array via Smith-Purcell effect. Compared with that in conductor holes, the resonant modes in metamaterial holes have much higher intensity thanks to the excitation of terahertz surface plasmons. Thus, it can generate terahertz radiation with much higher intensity. Also, its radiating direction can be adjusted by changing the arrangement of array. It offers a promising way for developing efficient and steerable terahertz sources.