Abstract-Two-Color TeraHertz Radiation by a Multi-Pass FEL Oscillator

 

Michele Opromolla,  Vittoria Petrillo,

https://www.mdpi.com/2076-3417/11/14/6495

In this paper, we show that an electron beam produced by a super-conducting linac, driven in a sequence of two undulator modules of different periods, can generate two-color Terahertz radiation with wavelengths ranging from 100 μ$$m to 2 μ$$m. The generated pulses are synchronized, both MW-class, and highly coherent. Their specific properties and generation will be discussed in detail. Besides the single-spike pulse structure, usually observed in oscillators, we show that both the THz pump and probe can be modulated in a coherent comb of pulses, enabling periodic excitation and stroboscopic measurements.

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

Kiyanoush Goudarzi, Samiye Matloub, Ali Rostami

https://link.springer.com/article/10.1007/s11082-019-1749-4

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.