Abstract-Full 3D+1 modelling of the tilted-pulse-front setups for single-cycle terahertz generation

Lu Wang, Tobias Kroh, Nicholas H. Matlis, Franz Kaertner

https://arxiv.org/abs/1908.09581

The tilted-pulse-front setup utilizing a diffraction grating is one of the most successful methods to generate single- to few-cycle terahertz pulses. However, the generated terahertz pulses have a large spatial inhomogeneity, due to the noncollinear phase matching condition and the asymmetry of the prism-shaped nonlinear crystal geometry, especially when pushing for high optical-to-terahertz conversion efficiency. A 3D+1 (x,y,z,t) numerical model is necessary in order to fully investigate the terahertz generation problem in the tilted-pulse-front scheme. We compare in detail the differences between 1D+1, 2D+1 and 3D+1 models. The simulations show that the size of the optical beam in the pulse-front-tilt plane sensitively affects the spatio-temporal properties of the terahertz electric field. The terahertz electric field is found to have a strong spatial dependence such that a few-cycle pulse is only generated near the apex of the prism. The part of the beam farther from the apex contains a large fraction of the energy but has a waveform that deviates from a few-cycle. This strong spatial dependence must be accounted for when using the terahertz pulses for strong-field physics and carrier-envelope-phase sensitive experiments such as terahertz acceleration, coherent control of antiferromagnetic spin waves and terahertz high-harmonic generation.

Abstract-Broadband terahertz generation with a stair-step echelon

Koustuban Ravi, Benjamin Ofori-Okai, Prasahnth Sivarajah, Wenqian Huang, Franz Kaertner, and Keith Nelson

https://www.osapublishing.org/abstract.cfm?uri=cleo_si-2017-STu3J.1&origin=search

A method to overcome limitations of conventional broadband terahertz generation techniques is presented. A stair-step echelon allows for the creation of superior tilted-pulse-fronts to yield larger frequencies and bandwidths, energy conversion efficiencies exceeding 5%.

© 2017 OSA

Abstract-Terahertz-driven linear electron acceleration

Kyung-Han Hong, Ravi Koustuban, Arya Fallahi, Gustavo Moriena, R. J. Miller, Ronny Huang, Franz Kaertner,

http://dspace.mit.edu/handle/1721.1/100509?show=full

The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30–50 MeV m[superscript −1] gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. These ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams.