THz radiation from plasma oscillators

Laser-driven plasma can serve as a powerful source of terahertz (THz) radiation. In the plasma-based schemes, such as laser pulses induce a single-pass drift motion of electrons, leading to the emission of low-frequency, broadband radiation. Approaches such as two-color or CTR roughly falls into this category. Alternatively, plasma waves can act as radiation sources. However, since plasma waves typically propagate more slowly than electromagnetic waves in vacuum, their coupling efficiency is limited. To enhance coupling, methods such as mode conversion, magnetization, and density gradients have been proposed, yielding promising results. In this presentation, I introduce a different approach of localizing plasma oscillations into harmonic-like oscillators. Electrons oscillating in-phase within a finite-sized plasma oscillator can emit radiation via a multipole antenna mechanism. I present two specific schemes: 1. dipole-like plasma oscillators and 2. radial plasma oscillators, which are generated either by colliding or co-propagating detuned laser pulses. I report a conversion efficiency up to 1%, a spectral width less than 5%, and a high output field strength up to GV/m.