Highly-efficient spintronic terahertz emitter enabled by metal-dielectric photonic crystal

TL;DR

This paper introduces a novel metal-dielectric photonic crystal design for spintronic terahertz emitters, significantly enhancing laser absorption and THz emission efficiency through interference effects, with experimental validation showing 1.7 times improvement.

Contribution

The work proposes and demonstrates a new device structure that fully utilizes laser energy, markedly improving spintronic THz emitter efficiency via optical interference control.

Findings

Achieved 1.7 times stronger THz emission compared to existing designs.

Demonstrated theoretical and experimental agreement on laser absorption enhancement.

Showed that interference in photonic crystals can optimize THz generation.

Abstract

Spintronic terahertz (THz) emitter provides the advantages such as apparently broader spectrum, significantly lower cost, and more flexibility in compared with the commercial THz emitters, and thus attracts great interests recently. In past few years, efforts have been made in optimizing the material composition and structure geometry, and the conversion efficiency has been improved close to that of ZnTe crystal. One of the drawbacks of the current designs is the rather limited laser absorption - more than 50% energy is wasted and the conversion efficiency is thus limited. Here, we theoretically propose and experimentally demonstrate a novel device that fully utilizes the laser intensity and significantly improves the conversion efficiency. The device, which consists of a metal-dielectric photonic crystal structure, utilizes the interference between the multiple scattering waves to simultaneously suppress the reflection and transmission of the laser, and to reshape the laser field distributions. The experimentally detected laser absorption and THz generations show one-to-one correspondence with the theoretical calculations. We achieve the strongest THz pulse emission that presents a 1.7 times improvement compared to the currently designed spintronic emitter. This work opens a new pathway to improve the performance of spintronic THz emitter from the perspective of optics.