Multi-MV/cm longitudinally polarized terahertz pulses from laser–thin foil interaction

Abstract

Longitudinally polarized terahertz radiation offers access to the elementary excitations and particles that cannot be addressed by transverse waves. While transverse electric fields exceeding 1 MV/cm are widely utilized for nonlinear terahertz spectroscopy, longitudinally polarized terahertz waves at this field strength are yet to be realized. In this paper, we experimentally demonstrate that by focusing radially polarized terahertz fields generated from laser-thin metallic foil interaction, longitudinally polarized terahertz with record-breaking field strength above 1.5 MV/cm can be obtained. Furthermore, we also traced the evolution of the geometric phase of the longitudinal component as it propagates through focus. A novel scheme based on noncollinear electro-optic detection has been utilized to unambiguously measure the polarization states. Our result will scale up the nonlinear spectroscopy of solid materials and particle acceleration experiments where on-axis polarization plays a crucial role.

On the importance of frequency-dependent beam parameters for vacuum acceleration with few-cycle radially polarized laser beams

“…increasing steepness as g 0 becomes negative and an inflection as g 0 become positive, but with a total shift of 2π. This 2π shift conflicts with previous work on the Gouy phase in highly non-paraxial focusing [25][26][27], where they observed only a shift of π, but since we are in the paraxial regime this is to be expected.…”

Highly efficient generation of GV/m-level terahertz pulses from intense femtosecond laser-foil interactions

“…Based on the measured terahertz energy, pulse duration, and focal spot, the peak terahertz field strength is calculated to be ∼2.55 GV/m ( Zhang et al., 2021 ), which is larger than the field strength measured by the EO sampling method. This may be due to the complicated polarization of the terahertz radiation ( Woldegeorgis et al., 2018 ). Given the fact that a terahertz polarizer was not used before the EO crystal in the experiment, the measured field strength is the projection of the total field strength on the crystal axis.…”

Broadband THz Sources from Gases to Liquids

“…With tremendous advancements in laser technology, lightinduced ionization in matter including gases [1][2][3][4][5][6], clusters [7][8][9], liquids [10][11][12][13][14][15][16], and solids [17][18][19][20] has attracted considerable interest in generating coherent, intense, and broadband terahertz (THz) waves via nonlinear processes. When a laser intensity is above the ionization threshold, abundant electrons and ions are created [21][22][23].…”