Demonstration of a low-frequency three-dimensional terahertz bullet with extreme brightness

Abstract

The brightness of a light source defines its applicability to nonlinear phenomena in science. Bright low-frequency terahertz (o5 THz) radiation confined to a diffraction-limited spot size is a present hurdle because of the broad bandwidth and long wavelengths associated with terahertz (THz) pulses and because of the lack of THz wavefront correctors. Here using a present-technology system, we employ a wavefront manipulation concept with focusing optimization leading to spatio-temporal confinement of THz energy at its physical limits to the least possible three-dimensional light bullet volume of wavelength-cubic. Our scheme relies on finding the optimum settings of pump wavefront curvature and post generation beam divergence. This leads to a regime of extremely bright PW m À 2 level THz radiation with peak fields up to 8.3 GVm À 1 and 27.7 T surpassing by far any other system. The presented results are foreseen to have a great impact on nonlinear THz applications in different science disciplines.

Extreme nonlinear terahertz electro-optics in diamond for ultrafast pulse switching

“…The THz source used here is an example for an advanced, multi-octave-spanning THz source where the beam quality is generally challenged by spatial inhomogeneities. 10,22,23 Assuming a maximum frequency of 10 THz, the scale of inhomogeneity is expected to be more than 30 µm (due to diffraction limits) which is not smaller than the probe spot size. However, in terms of resolution, the THz imaging technology presently available hardly satisfies the experimental needs for characterizing a tightly focused THz beam 10 and does not give any information about the spatio-temporal evolution of the THz intensity profile.…”

“…10,22,23 Assuming a maximum frequency of 10 THz, the scale of inhomogeneity is expected to be more than 30 µm (due to diffraction limits) which is not smaller than the probe spot size. However, in terms of resolution, the THz imaging technology presently available hardly satisfies the experimental needs for characterizing a tightly focused THz beam 10 and does not give any information about the spatio-temporal evolution of the THz intensity profile. In the following, we show that THz Kerr gating is a powerful tool for space-time resolved mapping of the THz intensity profile along the THz bullet.…”

“…We used a special scheme of wavefront control and improved THz focusing to reach extremely intense THz electric field of 83 MV/cm with spectral peak ∼ 3.5 THz. 10 The source employs optical rectification of a mid-infrared pulse from an optical parametric amplifier pumped by a TW-scale Ti:sapphire laser system. 11 The temporal THz field shape of the resulting 50 µJ THz pulse is measured by electrooptical means in a 50 µm thin GaP <110> crystal with a balanced photodiode detection scheme.…”

“…11 The temporal THz field shape of the resulting 50 µJ THz pulse is measured by electrooptical means in a 50 µm thin GaP <110> crystal with a balanced photodiode detection scheme. 10,12,13 The maximum field strength was calculated from the THz focus size, temporal trace, and pulse energy from a calibrated THz energy meter (Gentec THz12D-3S). 10 To induce the Kerr modulation, the intense terahertz pulse co-propagates through a diamond window collinearly with the 50 fs pulse centered at 800 nm to be switched.…”

“…10,12,13 The maximum field strength was calculated from the THz focus size, temporal trace, and pulse energy from a calibrated THz energy meter (Gentec THz12D-3S). 10 To induce the Kerr modulation, the intense terahertz pulse co-propagates through a diamond window collinearly with the 50 fs pulse centered at 800 nm to be switched. The diamond window serving as an EO modulator has a diameter of 4.5 mm and a thickness of 0.5 mm.…”