Demonstration of sub-luminal propagation of single-cycle terahertz pulses for particle acceleration

Abstract

The sub-luminal phase velocity of electromagnetic waves in free space is generally unobtainable, being closely linked to forbidden faster than light group velocities. The requirement of effective sub-luminal phase-velocity in laser-driven particle acceleration schemes imposes a fundamental limit on the total acceleration achievable in free-space, and necessitates the use of dielectric structures and waveguides for extending the field-particle interaction. Here we demonstrate a new travelling-source and free space propagation approach to overcoming the sub-luminal propagation limits. The approach exploits the relative ease of generating ultrafast optical sources with slow group velocity propagation, and a group-to-phase front conversion through non-linear optical interaction near a material-vacuum boundary. The concept is demonstrated with two terahertz generation processes, non-linear optical rectification and current-surge rectification. The phase velocity is tunable, both above and below vacuum speed of light $c$, and we report measurements of longitudinally polarized electric fields propagating between $0.77c$ and $1.75c$. The ability to scale to multi-MV/m field strengths is demonstrated. Our approach paves the way towards the realization of cheap and compact particle accelerators with unprecedented femtosecond scale control of particles.

References in corpus (8)

• Single-cycle THz pulses with amplitudes exceeding 1 MV/cm generated by optical rectification in LiNbO3
• Terahertz-driven linear electron acceleration
• Laser-based acceleration of non-relativistic electrons at a dielectric structure
• Compact electron acceleration and bunch compression in THz waveguides
• Universal phase relation between longitudinal and transverse fields observed in focused terahertz beams
• Toward a terahertz-driven electron gun
• Temporal evolution of longitudinal bunch profile in a laser wakefield accelerator
• Optical Manipulation of Relativistic Electron Beams using THz Pulses

Cited by in corpus (8)

• Segmented Terahertz Electron Accelerator and Manipulator (STEAM)
• Spectral Phase Control of Interfering Chirped Pulses for High-Energy Narrowband Terahertz Generation
• Acceleration of relativistic beams using laser-generated terahertz pulses
• Spatio-temporal characterization of ultrashort laser beams: a tutorial
• Relativistic electron beam acceleration in a zero-slippage terahertz-driven Inverse Free Electron Laser scheme
• Cascaded Multi-cycle terahertz driven ultrafast electron acceleration and manipulation
• Electron-Terahertz Interaction in Dielectric-Lined Waveguide Structures for Electron Manipulation
• Visualizing femtosecond dynamics with ultrafast electron probes through terahertz compression and time-stamping