Luis Nasi | Searcharxiv

arXiv2026

A novel accelerating structure based on a tapered parallel-plate waveguide with an integrated dielectric terahertz-driven accelerator

We present a novel dielectric terahertz-driven accelerator (DTA) that integrates a dual-pillar grating structure within a tapered parallel-plate waveguide (TPPWG). This compact setup enables efficient particle acceleration using multi-cycle, narrowband terahertz (THz) pulses. The TPPWG serves a dual role: it enhances the THz field via geometric tapering and delivers it to the dielectric structure by efficient coupling. Experimental validation of the THz field inside the waveguide is conducted using electro-optic sampling. Optimization of waveguide parameters through time-domain simulations reveals a sixfold peak electric field amplification at the end of the waveguide. The dielectric accelerator is tailored for maximum acceleration by adjusting the DTA pillar radius and vacuum channel gap for relativistic electron beams. Particle-in-cell (PIC) simulations demonstrate that the structure supports net acceleration with gradients up to 120 MeV per m for 0.1 GV per m field strengths, and can accommodate bunch charges up to 10 pC with minimal degradation. Energy spread evolution and beam dynamics are discussed in detail, including the role of phase slippage and bunch length. This work establishes the DTA-integrated TPPWG as a compact and scalable platform for high-gradient THz-driven acceleration, combining simple fabrication and design, strong field enhancement, and compatibility with existing electron sources. It opens new pathways toward practical, tabletop accelerators for scientific and industrial applications.

physics.acc-ph↗

arXiv2025

Comparative analysis of optical rectification-based multicycle terahertz pulse generation techniques

Numerical investigations of multicycle terahertz pulse generation based on wafer stack and tilted pulse front pumped lithium niobate setups concerning the conversion efficiency and the resulting temporal shape and spectrum were performed. Pumping by Fourier-limited-, chirped-, and intensity-modulated pulses, as well as pulse sequences was considered. Wafer stacks give a maximum efficiency when the pump pulse duration is 0.243 times the temporal period of the generated THz pulse. In wafer stacks, increasing the number of pulses in a sequence drastically increases the efficiency. A five-period wafer stack tailored for a 0.15 THz frequency achieves a maximum efficiency of almost 0.1% when pumped by a single, 1.5 ps pulse with an intensity of 100 GW$^2$/cm$^2$, and 0.3% when pumped by a sequence of five pulses. In a similar wafer stack of 10 periods, the efficiency with the same pulse sequence reaches 0.7%. For a large pump pulse number, the efficiency increase approaches a factor equal to the number of wafer pairs. For a given number of THz cycles, the highest efficiency is obtained when the number of wafer stack periods and pump pulses are equal to half the number of cycles. For relatively small cycle numbers, tilted-pump-front setups were found to yield the highest conversion efficiencies.

physics.optics↗