Temperature effects on surface plasmon enhanced Smith-Purcell terahertz radiation for InSb-based grating

Abstract

An electron beam passing over metallic gratings can generate Smith-Purcell radiation in THz region. The emission frequency and angle strongly depend on the period of gratings which is previously designed. Very recently, the enhanced Smith-Purcell radiation by surface plasmon (SP) excitation has been demonstrated. The high-energy electrons deposited on the substrate will cause the temperature of substrate to increase. However, the temperature effect of the substrate on the properties of Smith-Purcell radiation is seldom discussed. In this work, the temperature effects on Smith-Purcell THz radiation for electron beam passing over the InSb-based gratings are examined. The FDTD method is used to simulate the process of electron moving and radiation emission. The mechanisms of temperature modulated Smith-Purcell radiation are elucidated by considering the dispersion curves of investigated grating and electron beam. The simulation results show that the intensity of radiation is increased by four times as comparing to that of the metal-based grating, which is ascribed to excitation of SP and mimic SP in InSb-based gratings. The operation frequency and radiation angle of enhanced radiation is modulated by the change of substrate's temperature (at fixed electron beam energy). The proposed device can be applied to realizing the compact and tunable THz radiation source.