Generation and characterization of coherent terahertz radiation from 100-TW laser-wakefield acceleration

TL;DR

This study experimentally investigates terahertz radiation produced by 100-TW laser-wakefield acceleration, revealing a quadratic dependence on charge and laser energy, and characterizing the THz pulse's broadband, sub-picosecond nature.

Contribution

The paper provides the first detailed characterization of THz emission from 100-TW LWFA, establishing a scaling law and identifying coherent acceleration radiation as the dominant mechanism.

Findings

THz energy scales quadratically with charge and laser energy

THz pulse duration is sub-picosecond and broadband

THz spectrum spans approximately 1-20 THz

Abstract

We experimentally characterized terahertz (THz) radiation emitted from laser-wakefield acceleration (LWFA) driven at 100-TW laser power. Simultaneous measurements of the laser energy, electron-bunch charge, and THz energy reveal a quadratic dependence of the THz energy on both charge and laser energy. This behavior indicates coherent collective emission in the generation process and provides a useful scaling law for THz output. Microbolometer-based beam profiling shows a relatively large THz beam divergence (~0.2 rad). Single-shot THz interferometry further shows that the emitted THz pulse is sub-picosecond in duration and broadband. Combining the beam-profile and interferometric measurements, the THz spectrum is expected to span approximately 1-20 THz. Together, these results support coherent acceleration radiation as the dominant mechanism for THz generation in 100-TW LWFA.