Cover story: Chen LW, Hong MH. Functional nonlinear optical nanoparticles synthesized by laser ablation. Opto-Electron Sci 1, 210007 (2022)

Nonlinear optical materials are the fundamental building blocks critical for many fields ranging from scientific research, industrial production, to military. It is an important research direction with various applications in laser manufacturing, nanostructures’ fabrication, sensor design, optoelectronics, biophotonics, and quantum optics, etc. After many years of development, nonlinear optics has become the pillars for various frontier research and widely used optical systems, including laser fabrication, optical imaging, information processing and communications, as well as nanoscale lithography. Advances in the nonlinear optics can potentially boost many disciplines.

Nanoparticles are one of the most important members of functional materials that are widely studied, which has a long history of thousands years. Nanoparticles demonstrate great potentials due to their flexibility to engineer and enhance their nonlinear optical properties superior to their bulk counterparts. How to produce nonlinear optical nanoparticles in large scale, high repeatability, and low cost remains to be a challenge. In this review article, laser ablation is highlighted as a dynamic process to remove target materials from a solid substrate under high power short pulse laser irradiation. It can be conducted in air, liquid, and vacuum. Combined with external electrical or magnetic fields, chemical reactions, and pre/post-treatment. This method can achieve various purposes, including surface engineering, defect modification, and fragmentation. Great flexibility and possibilities are offered based on nonlinear optical nanoparticles.