Researchers from the University of California, Berkeley, led by Professor Zhenjiang Zhao, have made significant strides in the field of high-harmonic generation (HHG) in two-dimensional materials. Their work, published in the journal Nature Photonics, offers a novel approach to controlling and optimizing HHG in monolayer tungsten disulfide (WS2), which could have practical applications in the energy sector, particularly in the development of compact extreme ultraviolet (EUV) sources for advanced manufacturing and imaging technologies.
High-harmonic generation is a process where intense laser light is used to generate high-energy photons, or harmonics, from a material. This process can be used to create coherent EUV light sources, which are essential for various applications, including semiconductor manufacturing and high-resolution imaging. However, achieving precise control over the emission and understanding the complex quantum pathways involved has been a significant challenge.
The researchers demonstrated through first-principles simulations that HHG in monolayer WS2 can be precisely controlled by combining two-color laser fields with mechanical strain engineering. This dual-mode strategy provides unprecedented control over harmonic yield, polarization, and spectral features. By adjusting the relative phase of the two-color laser field, the researchers could switch the quantum coherence of electron-hole pairs on a sub-femtosecond timescale, thereby maximizing harmonic emission.
Moreover, the researchers found that applying tensile strain to the material acts as a powerful amplifier for the harmonic yield. This is due to a dual mechanism: strain-modified band dispersion enhances the intraband current, while a reshaping of the Berry curvature dramatically boosts the anomalous velocity contribution to the interband response. This quantum geometric effect results in a robust, linear dependence of the harmonic yield on strain and a significant amplification of the perpendicularly polarized harmonics.
The practical implications of this research for the energy sector are significant. Compact EUV sources derived from HHG in two-dimensional materials could revolutionize semiconductor manufacturing, enabling the production of smaller, more efficient chips for various applications, including renewable energy technologies and electric vehicles. Additionally, the ability to map strain and quantum geometric properties of materials using all-optical methods could lead to the development of new materials with enhanced properties for energy storage and conversion.
In summary, the researchers have established a versatile framework for optimizing solid-state HHG and introduced a powerful all-optical method to probe quantum geometric effects in materials. Their findings position monolayer WS2 as a model system for exploring attosecond physics at the nexus of bulk and atomic scales, paving the way for advancements in the energy sector and beyond.
This article is based on research available at arXiv.