Terahertz emission during laser-plasma interaction: effect of electron temperature and collisions
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RESEARCH
Terahertz emission during laser‑plasma interaction: effect of electron temperature and collisions Hitendra K. Malik1 · Divya Singh2 Received: 21 July 2020 / Accepted: 23 August 2020 © Islamic Azad University 2020
Abstract The electron-neutral collisions in the plasma become crucial with regard to the generation of THz radiation when thermal motion of the electrons is considerable. If we look at the mechanism of THz emission, this is only the movement/oscillations of the electrons which is responsible for the excitation of nonlinear current that generated the THz radiation. The present work aims to disclose the role of thermal motion of the plasma electrons to the resonance condition and the THz emission when two co-propagating super-Gaussian laser beams beat in the plasma. The dynamics of the plasma electrons and subsequent generation of nonlinear current are discussed in greater detail for the emission of THz radiation. Keywords Laser-plasma interaction · Ponderomotive force · Terahertz radiation · Electron temperature · Super-Gaussian laser · Efficiency
Introduction Several applications such as characterization of materials, imaging, communication, medical diagnostics make use of THz radiations for their better efficiency. The frequency of these radiations lies between 100 GHz and 10 THz. These radiations can be achieved by various mechanisms which include Cherenkov wakes [1–3] and inverse Compton scattering based on X-ray radiation [4]; even soft X-rays have been found to emit from TIN plasmas [5]. The interaction of laser pulses with magnetized plasma has led to the emission of THz radiation [6–8]. Some instabilities can be responsible for the emission of such radiation [9]. Laser beating is one of the mechanisms of producing the THz radiation [10]. Some researchers have also established a relationship between the signals corresponding to the THz radiation and X-rays [11]. Magnetic field has been found to enhance the intensity of the emitted THz radiation in laser-plasma interaction [12]. The tunnel ionized plasma can also radiate when a femtosecond laser pulse is launched to this and where dipole oscillations * Hitendra K. Malik [email protected] 1
Plasma Waves and Particle Acceleration (PWAPA) Laboratory, Department of Physics, Indian Institute of Technology, Delhi, New Delhi 110 016, India
Rajdhani College, Delhi University, Delhi, New Delhi, India
2
take place due to the residual momentum imparted by the lasers to the plasma electrons [13]. Extremely powerful THz radiations have also been achieved by interaction of chirped [14] and few cycle laser pulses [15] with plasmas. The above literature proves that the spatial profile of the laser pulses is very important for achieving the THz radiation of specific characteristics during the interaction of laser beams with plasmas. The temporal profile of the lasers has also played an important role in other mechanisms [16, 17]. For laser-plasma interaction, Ostermayr et al. [18] and Devi and Malik [19] have employed super-Gaussian pulses o
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