Longitudinally polarized single-cycle terahertz pulses generated with high electric field strengths

Abstract

We demonstrate the generation of single-cycle longitudinally polarized terahertz pulses with field amplitudes in excess of 11 kV/cm using the interferometric recombination of two linearly polarized terahertz beams. High field strength transversely polarized pulses were generated by optical rectification in a matched pair of magnesium-oxide doped stoichiometric lithium niobate (MgO:SLN) crystals with a reversal in the χ333(2) orientation. The discontinuity in χ333(2) produces a polarity flip in the transverse field; the longitudinal field produced as a consequence of the transverse field discontinuity was measured in the far-field. Both the spatial and temporal profiles of the measured longitudinally polarized terahertz radiation were consistent with the propagation of the transverse discontinuity.

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

“…Many schemes have been proposed towards this end, such as photoconductive antenna [14], optical rectification with segmented electrooptic (EO) crystals [15], and plasma filaments [16]. THz pulses with transverse field amplitude over MV/cm are frequently achieved [17][18][19]; however, the maximum longitudinal field strength reported so far still stays in the range of 11 kV/cm [20]. Here we present a scheme that can be employed to generate quasi-single-cycle and longitudinally polarized THz transient with an unprecedented amplitude of 1.5 MV/cm.…”

Demonstration of sub-luminal propagation of single-cycle terahertz pulses for particle acceleration

“…To obtain acceleration over extended interaction lengths requires generation of electromagnetic modes with longitudinal electric field polarization, and real or effective phase matching of the electromagnetic carrier wave with the β < 1 velocity of the relativistic particles. Longitudinal polarized terahertz radiation can be obtained through coherent spatial addition of phase or polarity offset beams [13], through selective coupling into (or onto) geometrically defined structures [14,15], using air-plasma generation [16], using a segmented non-linear generation crystal [17], or using radially biased photoconductive antennas [18][19][20][21][22]. The phase-matching problem is however more fundamental; free space beams such as TEM 10 Gaussian modes necessarily have phase velocities greater than the vacuum speed of light, c, with the Guoy π-phase shift ultimately limiting available interaction lengths to less than a Rayleigh length [23].…”

Acceleration of relativistic beams using laser-generated terahertz pulses

“…Frequency-tunable, narrowband (100 GHz FWHM) THz pulses with approximately 2 µJ energy were generated through chirped-pulse beating 22,23 in a lithium niobate crystal (see Methods). A quasi-TEM 01 mode was generated by a phase-shifter plate providing a λ/2 shear and an effective polarity inversion 24,25 along the horizontal midline of the THz beam, which is revealed by the electro-optic sampling measurements in Fig. 1a.…”