Abstract-Investigating the influence of incident laser wavelength and polarization on particle acceleration and terahertz generation

A. H. Woldegeorgis, B. Beleites, F. Ronneberger, R. Grosse, and A. Gopal

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.98.061201

The interaction of a high-power laser pulse with a thin foil can generate energetic, broadband terahertz radiation. Here, we report an experimental investigation on the influence of incident laser polarization and wavelength on the terahertz emission and maximum proton energy from the target rear surface. For similar incident laser intensities, the characteristics of the particle beams and the terahertz radiation show a wavelength dependence. The results fit well with the established scaling laws for the terahertz yield and the maximum proton energy as a function of the incident laser irradiance ($I{\lambda }^2$).

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Abstract-THz Induced Nonlinear Effects in Materials at Intensities above 26 GW/cm2

A. Woldegeorgis, T. Kurihara, B. Beleites, J. Bossert, R. Grosse, G. G. Paulus, F. Ronneberger, A. Gopal

https://link.springer.com/article/10.1007%2Fs10762-018-0493-3

Nonlinear refractive index and absorption coefficient are measured for common semiconductor material such as silicon and organic molecule such as lactose in the terahertz (THz) spectral regime extending from 0.1 to 3 THz. Terahertz pulses with field strengths in excess of 4.4 MV/cm have been employed. Transmittance and the transmitted spectrum were measured with Z-scan and single shot noncollinear electro-optic pump-probe techniques. The THz-induced change in the refractive index (Δn) shows frequency-dependence and a maximum change of − 0.128$-0.128$ at 1.37 THz in lactose and up to + 0.169$+0.169$ at 0.15 THz in silicon was measured for a peak incident THz intensity of 26 GW/cm2. Furthermore, the refractive index variation shows a quadratic dependence on the incident THz field, implying the dominance of third-order nonlinearity.