Abstract-Tilted‐Pulse‐Front Schemes for Terahertz Generation

Lu Wang  György Tóth  János Hebling  Franz Kärtner

https://onlinelibrary.wiley.com/doi/full/10.1002/lpor.202000021

High energy single‐ to few‐cycle terahertz pulses enable the exploration of electron acceleration, strong‐field physics, and nonlinear terahertz spectroscopy. One important method of generating such terahertz pulses is using the tilted‐pulse‐front (TPF) technique. However, the needed angular dispersion leads to a spatial and temporal break‐up of the optical pump, reducing the generation efficiency and the electric field quality of the terahertz pulses. To decrease the effects caused by angular dispersion, multiple schemes with discrete pulse‐front‐tilt are suggested. Based on a 2D+1 numerical model, a systematic comparative study of the conventional TPF scheme, three discrete TPF schemes, and a scheme with spatio‐temporally chirped (STC) optical pulses is performed. Smaller optimal interaction lengths and conversion efficiencies are predicted compared to 1D models. For small pump beam sizes, it is concluded that the STC scheme delivers spatially homogeneous terahertz pulses with the highest conversion efficiency, and for short interaction lengths, the discrete TPF schemes cannot outperform the continuous ones. However, for large pump sizes, the nonlinear echelon slab delivers the spatially most homogeneous terahertz beams and has the unique potential of generating high energy terahertz pulses. In general, this work gives guidance to choose the most appropriate setup for a given terahertz experiment.