Cavity Engineering of Dirac Semimetal Achieves 3-Order-of-Magnitude Enhancement of Terahertz Harmonics

The quest for enhanced light-matter interactions drives innovation in optoelectronics, and recent work focuses on tailoring materials to amplify nonlinear optical effects. Siyu Duan, Lili Shi, and Patrick Pilch, from TU Dortmund University, alongside colleagues including Anneke Reinold, Sergey Kovalev, and Renato M. A. Dantas, now report a dramatic increase in terahertz high-harmonic generation achieved through precise cavity engineering of a Dirac semimetal. The team fabricated a meticulously designed microstructure, integrating metallic microcavities with a thin film of the material, and demonstrates an enhancement of terahertz signals exceeding three orders of magnitude. This breakthrough significantly boosts near-field light intensity, pushing the material’s nonlinear responses into a previously inaccessible regime and paving the way for more efficient terahertz technologies.

This achievement stems from exciting the material with ultrashort laser pulses, inducing a photogalvanic effect caused by the crystal’s broken mirror symmetry. The team observed that reducing the size of the microcrystal significantly enhances the terahertz emission, revealing a strong size effect. These findings establish a promising route towards developing compact and efficient terahertz sources based on three-dimensional Dirac semimetals and open new possibilities for exploring novel optoelectronic phenomena within these materials.

Terahertz Harmonic Generation in 2D Materials

Recent research focuses on enhancing terahertz (THz) radiation generation, particularly harmonic generation, using innovative materials and structures. This field aims to create and control THz radiation for applications including imaging, spectroscopy, and communications. Scientists are investigating two-dimensional materials, such as graphene and transition metal dichalcogenides, due to their strong nonlinear optical properties. Key strategies include symmetry breaking, gating, and the creation of van der Waals heterostructures to control electronic properties and boost THz generation. The research highlights the importance of material design and advanced fabrication techniques in this rapidly evolving field, with potential applications ranging from medical diagnostics to high-bandwidth wireless communication.

Giant Terahertz Nonlinearities in Dirac Semimetal Microstructures

Scientists have achieved exceptionally strong terahertz nonlinearities by engineering a microstructure within a three-dimensional Dirac semimetal. They fabricated a structure consisting of metallic metasurface microcavities on a thin film of cadmium arsenic sulfide, dramatically increasing the intensity of terahertz excitation pulses. This resulted in a greater than three-fold enhancement in the generation of third- and fifth-order harmonic signals, pushing the material’s nonlinear response into a deeply nonperturbative regime. Theoretical models, employing semiclassical Boltzmann transport theory, explain the observed behaviour and validate the experimental results.

Giant Terahertz Nonlinearities in Dirac Semimetals

This research demonstrates a significant enhancement of terahertz nonlinearities through the innovative engineering of a microstructure within a three-dimensional Dirac semimetal. Scientists successfully fabricated a structure comprising metallic metasurface microcavities on a thin film of cadmium arsenic sulfide, dramatically increasing the intensity of terahertz excitation pulses. This resulted in a substantial enhancement in the generation of harmonic signals, pushing the material’s nonlinear response towards saturation and confirming theoretical models describing the evolution of harmonic generation. Further research will likely investigate the scalability of this technique and its integration into functional devices.