A tunable source of coherent terahertz radiation driven by the microbunched electron beam

Abstract

The studies of coherent terahertz (THz) tunable Smith-Purcell radiation source driven by the microbunched electron beam are presented. We discuss the conceptual design of a high power and broadly tunable THz radiation source capable of bridging the THztechnological gap. The results of the numerical and analytical studies using different software packages, models and approaches are shown and good agreement between the results is demonstrated. The spectra of the coherent Smith-Purcell radiation (cSPr) excited by a single bunch and train of the microbunches are compared and the excitation of the harmonics of cSPr is discussed. It is shown that varying the distance between microbunches the power and the frequency of the output cSPr can be controlled.

BBU instability in rectangular dielectric resonator

“…Such a narrowing of the excited field spectrum, as presented above, is characteristic not only for resonators and Cherenkov radiation excitation. For example, in papers [22,23], which are devoted to the generation of Smith-Purcell radiation in grating structures, regularization of the spectrum was also observed. The main reason of this effect is the use of a regular bunch sequence for an electromagnetic excitation.…”

Smith–Purcell Radiation from Highly Mobile Carriers in 2D Quantum Materials

“…There has been a recent theoretical proposal to use a train of microbunched free electrons to generate coherent THz SP radiation. [ 89 ] However, such a system would necessitate an energy‐recovery linear accelerator with physical space of $$\approx 10\ \textrm {m}^3$$, and the challenge of maintaining beam collimation would still exist. With high‐carrier density 2D materials, it may be possible to achieve coherent SP radiation by exciting sequential pulses of hot electrons separated by a distance of d bunch , as illustrated in Figure 4c.…”

High-power, tunable source of coherent THz radiation driven by a microbunched electron beam

“…Coherent Smith-Purcell radiation (cSPr) is emitted when a short (in comparison with the generated wavelength) charged particle beam propagates in the vicinity of the surface of a periodic structure (grating) [1][2][3][4][5][6][7]. The energy generated by the bunch of the relativistic electrons is proportional to the square of the number of the electrons in the bunch.…”

“…The energy generated by the bunch of the relativistic electrons is proportional to the square of the number of the electrons in the bunch. It was demonstrated [3][4][5][6] that if the beam is microbunched the radiation generated by the microbunches which are located simultaneously above the same grating is coherent and its frequency is determined by the micro-bunch spacing [4]. The concept can be used to design source of the high intensity, THz coherent radiation [5][6].…”

“…The use of the cSPr is attractive due to: simple tuneability of the cSPr; possibility to observe narrow spectrum line (below 0.1% of the operating frequency); high stability, purity and intensity (above kW power level) of the radiation, and the source of the radiation can be compact and relatively efficient. There are three scale parameters associated with such radiators and which define the properties of the radiation: the number of the grating periods Ngr, the number of microbunches in the train Nb above the grating at any instance and the periodicity of the microbunches Tb [3][4][5][6]. These parameters give: the minimal width of the radiation single line in the far field zone ~/ Ngr (spectral resolution); the width of the main spectral lobe generated ~/Nb, and the main lobe's central frequency 0 ~ 1/Tb.…”