Tilted-Pulse-Front Schemes for Terahertz Generation

摘要

High energy single- to few-cycle terahertz pulses enable the exploration ofelectron acceleration, strong-field physics, and nonlinear terahertzspectroscopy. One important method of generating such terahertz pulses isusing the tilted-pulse-front (TPF) technique. However, the needed angulardispersion leads to a spatial and temporal break-up of the optical pump,reducing the generation efficiency and the electric field quality of the terahertzpulses. To decrease the effects caused by angular dispersion, multipleschemes with discrete pulse-front-tilt are suggested. Based on a 2D+1numerical model, a systematic comparative study of the conventional TPFscheme, three discrete TPF schemes, and a scheme with spatio-temporallychirped (STC) optical pulses is performed. Smaller optimal interaction lengthsand conversion efficiencies are predicted compared to 1D models. For smallpump beam sizes, it is concluded that the STC scheme delivers spatiallyhomogeneous terahertz pulses with the highest conversion efficiency, and forshort interaction lengths, the discrete TPF schemes cannot outperform thecontinuous ones. However, for large pump sizes, the nonlinear echelon slabdelivers the spatially most homogeneous terahertz beams and has the uniquepotential of generating high energy terahertz pulses. In general, this workgives guidance to choose the most appropriate setup for a given terahertzexperiment.