Aligned copper nanorod arrays for highly efficient generation of intense ultra-broadband THz pulses

TL;DR

This paper presents a novel method using aligned copper nanorod arrays to generate intense, ultra-broadband THz pulses with significantly enhanced energy, leveraging laser interactions and coherent transition radiation.

Contribution

The study introduces aligned copper nanorod arrays as targets for efficient broadband THz pulse generation, demonstrating substantial energy enhancements over traditional copper targets.

Findings

13.8 times THz energy enhancement with 5 μm nanorods

Maximum 28 times energy increase at 60 μm nanorods for high frequencies

Good agreement between particle-in-cell simulations and experimental results

Abstract

We demonstrate an intense broadband terahertz (THz) source based on the interaction of relativistic-intensity femtosecond lasers with aligned copper nanorod array targets. For copper nanorod targets with length 5 \mu m, a maximum 13.8 times enhancement in the THz pulse energy (in $\leq$ 20 THz spectral range) is measured as compared to that with a thick plane copper target under the same laser conditions. A further increase in the nanorod length leads to a decrease in the THz pulse energy at medium frequencies ($\leq$ 20THz) and increase of the electromagnetic pulse energy in the high-frequency range (from 20 - 200 THz). For the latter, we measure a maximum energy enhancement of 28 times for the nanorod targets of length 60 \mu m . Particle-in-cell simulations reveal that THz pulses are mostly generated by coherent transition radiation of laser produced hot electrons, which are efficiently enhanced with the use of nanorod targets. Good agreement is found between the simulation and experimental results.