Enhanced coherent terahertz Smith-Purcell superradiation excited by two electron-beams

Optics Express (Impact Factor: 3.49). 09/2012; 20(20):22627-35. DOI: 10.1364/OE.20.022627
Source: PubMed


This paper presents the studies on the enhanced coherent THz Smith-Purcell superradiation excited by two pre-bunched electron beams that pass through the 1-D sub-wavelength holes array. The Smith-Purcell superradiation has been clearly observed. The radiation emitting out from the system has the radiation angle matching the 2nd harmonic frequency component of the pre-bunched electron beams. The results show that the two electron beams can be coupled with each other through the holes array so that the intensity of the radiated field has been enhanced about twice higher than that excited by one electron beam. Consequently superradiation at the frequency of 0.62 THz can be generated with 20A/cm2 current density of electron beam based on above mechanism. The advantages of low injection current density and 2nd harmonic radiation promise the potential applications in the development of electron-beam driven THz sources.

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    ABSTRACT: Interaction between mimicking surface plasmons and electron beams provides a good opportunity to develop terahertz (THz) radiation sources. In this paper, such an interaction in a special 3-mirror quasi-optical cavity is presented and explored. The 3-mirror quasi-optical cavity acts as a resonant tunable system, the resonance frequency of which can be tuned by adjusting the distance between mirrors. The study demonstrated THz free electron superradiation from the interaction of mimicking surface plasmons and two electron beams that formed a resonance within the structure, with the 3-mirror cavity enhancing the intensity of superradiation. Moreover, this system can work in the high-harmonic superradiation region with relatively high efficiency and low current density. This concept thus shows the application potential for electron-beam-driven terahertz sources.
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    ABSTRACT: Two electron-beams' interaction in a sandwich structure composed of a bi-grating and a sub-wavelength holes array is suggested to generate THz radiation in this paper. It shows that this system takes advantage of both bi-grating and sub-wavelength holes array structures. The results demonstrate that surface waves on a bi-grating can couple with mimicking surface plasmons of a sub-wavelength holes array so that the wave-coupling is strong and the field intensity is high in this structure. Moreover, compared with the interaction in the bi-grating structure and sub-wavelength holes array structure, respectively, it shows that in this composite system the two electron-beams' interaction is more efficient and the modulation depth and radiation intensity have been enhanced significantly. The modulation depth and efficiency can reach 22% and 4%, respectively, and the starting current density is only 12 A/cm<sup>2</sup>. This radiation system may provide good opportunities for development of multi-electron beam-driven THz radiation sources.
    Preview · Article · Sep 2013 · Optics Express
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