Enhanced Coherent Emission of Terahertz Radiation by Energy-Phase Correlation in a Bunched Electron Beam

Abstract

We report the first observation of enhanced coherent emission of terahertz radiation in a compact free electron laser. A radio-frequency (rf) modulated electron beam is passed through a magnetic undulator emitting coherent radiation at harmonics of the rf with a phase which depends on the electron drift velocity. A proper correlation between the energy and phase distributions of the electrons in the bunch has been exploited to lock in phase the radiated field, resulting in over 1 order of magnitude enhancement of the coherent emission.

High-harmonic terahertz radiation from prebunched electron beam in the tapered grating structure

“…One of the most important research areas in THz regime is the radiation sources, and in order to fill the THz gap the studies on this area are extremely intensive [1][2][3]. It seems linear electron-beam driven sources provide good ways to develop (approaches to) the compact and room temperature THz sources and there are a lot of published papers concerned the topics of backward-wave oscillators (BWO), extended interaction oscillators (EIO), orotron and free-electron lasers (FELs) and so on [4][5][6][7][8][9][10][11][12][13][14][15]. However, among these Electron-beam driven oscillator-sources, there is a key problem limited the development in THz regime: the starting current density.…”

Simulation of emission and propagation of coherent synchrotron radiation wave fronts using the methods of wave optics

“…This is not surprising, as these methods allow one to bring efficiencies of optical schemes and experimental stations to real physical limits, and to exploit all benefits provided by bright, powerful, partially-or fully-coherent SR sources of the third and fourth generation. The use of coherent spontaneous synchrotron radiation in storage rings [5][6][7][8][9] and ERLs [10,11], and the use of self-amplified emission of Free Electron Lasers [12][13][14] further increases the importance of the wave optics methods for practical calculations.…”

Using the lorentz transformation to simulate terahertz-range superradiance of picosecond electron bunches moving in an undulator field

“…In this case, coherent emission from var ious parts of the bunch is possible due to the develop ment of self bunching. In the general case, this would require an increase in the length of interaction space as compared to the case of a preset motion studied in [6][7][8][9].It should be noted that previous analyses [10][11][12][13] of the undulator SR from extended electron bunches have been performed within the framework of the method of average ponderomotor forces. The present investigation is devoted to numerical simulation of these processes using a particle in cell (PIC) code, which reduces to direct integration of a self consistent system of the Maxwell equations and the equations of motion.…”

“…In this case, coherent emission from var ious parts of the bunch is possible due to the develop ment of self bunching. In the general case, this would require an increase in the length of interaction space as compared to the case of a preset motion studied in [6][7][8][9].…”

“…At present, the required characteristics can be provided by electron beams generated by photoinjectors [4,5]. Recent investigations of free electron lasers operating in the SR regimes have been mostly concentrated on the case in which the electron bunch length is shorter than or comparable with the radiation wavelength [6][7][8][9]. Under these conditions, coherent emission from the entire bunch volume is possible without self bunching of particles and the undulator length necessary for the formation of a radiation pulse is relatively small.…”