Generation of two-color terahertz radiation using Smith-Purcell emitter and periodic dielectric layers

This paper proposes and simulates three vacuum state devices each of which generates two-color terahertz radiation by Smith-Purcell emitter and dielectric layers. Each of the devices is a SiO2-made vacuum tube consisting of a Smith-Purcell emitter located at the bottom of the tube and also periodic dielectric layers located at the top. Smith-Purcell structure is a metal grating above which electron beam is generated closely by the cathode and are collected by a collector in another side of the grating. The emitter generates two terahertz radiations including evanescent and coherent Smith-Purcell radiations. While the evanescent radiation is the first harmonic of the emitted radiation, coherent Smith-Purcell radiation is the second and dominant one. The coherent Smith-Purcell radiation is emitted in a specific angle calculated by Smith-Purcell relation. The emitted coherent Smith-Purcell radiation coincides with periodic grating dielectric layers made of Si and SiO2 on top of the vacuum tube, and the transmitted pulse is transformed to two-terahertz pulses. The output of each device is a two-color terahertz pulse. Two generated terahertz wavelengths are very applicable in pump-probe experiments.