The Smith-Purcell radiation occurs when electrons move above a metallic diffraction grating. Its mechanism can be explained by the radiation of a moving oscillating dipole. Based on this, increasing the number of the dipole oscillations will be an effective way to enhance Smith-Purcell radiation. Here, we use a rectangular metal above the grating ridge. When electrons pass through the gap between the ridge and rectangular metal, there are two image charges arising. The theory analysis and the numerical calculation results well agree with the computer simulation results. The enhancement has promising prospect in developing high-power and efficient THz sources.

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Ping Zhang and Xiaosong Wang, "The enhanced terahertz Smith Purcell radiation from two moving dipole oscillations," Proc. SPIE 10756, Terahertz Emitters, Receivers, and Applications IX, 1075607 (Presented at SPIE Optical Engineering + Applications: August 19, 2018; Published: 14 September 2018); https://doi.org/10.1117/12.2320086.