As a cost-effective lithography technology, laser direct writing (LDW) can be used to achieve maskless rapid writing under non-vacuum conditions using a continuous or pulsed laser, which greatly reduces the device manufacturing cost and is a competitive processing technology. Compared with common photolithography, focused ion beams, and electron beam lithography, LDW technology has the advantages of using large-area, cost-effective, simple, and efficient processes as well as environmentally friendly fabrication. Since Gale et al. successfully fabricated microlens arrays using LDW in 1983, LDW has attracted increasing attention. LDW systems are widely used to fabricate various microstructures and devices. However, with technological developments, the degree of miniaturized integration of devices is increasing, and the demand for nanofabrication is becoming more diversified and refined. However, due to the diffraction limit, achieving ultrahigh-precision machining at the nanoscale has proven difficult with LDW. Traditional LDW cannot simultaneously obtain a large focal depth and high resolution because of the contradiction between the focal depth and resolution. This causes the fabrication resolution to hover around the microscale for a long time, and the acceptor material should be thick, which restricts its application in nanoscale processing. However, the acceptor materials used in traditional LDW for fabrication are limited to organic photoresists, which employ complex processing and have high material processing costs. In addition, an organic photoresist under laser writing can induce only a photochemical reaction during the writing process, which significantly limits its application. Due to the diffraction limit in an optical system, the traditional LDW developed along the existing technological trajectory means that overcoming the aforementioned difficulties is not easy. Accordingly, to expand the applications of laser fabrication, developing new-type nanosecond LDW with more powerful functions has become necessary and urgent.

Progress Based on the difficulties encountered in LDW technology, a new-type nanosecond LDW system based on the principle of laser-matter nonlinear interaction was developed in this study, and the related research progress and new discoveries were summarized. The principle of laser-matter nonlinear interaction in a new-type nanosecond LDW system was introduced (Fig. 1). To test the working principle, the new-type nanosecond LDW system with proprietary intellectual property rights was developed in a laboratory (Fig. 2). Super-resolution structures were fabricated (Figs. 3‒4). The new-type nanosecond LDW system has natural advantages when applied to various materials (Fig. 5). The laser irradiates a metallic film on a glass substrate and forms a metal-transparent (MTMO) gray mask. A lens array and various solid structures also be fabricated using this type of grayscale mask (Figs. 6‒7). The interaction between the laser and metal film leads to grain refinement as a surface enhanced Raman spectroscopy (SERS) chip (Fig. 8). Using only one step, an arbitrary micro/nanotube can be fabricated in the metal interlayers (Fig. ‍9). The new-type nanosecond LDW system can also be used in 2D materials such as patterning ordered strain structures in 2D materials (Fig. 10) and laser doping to modulate the properties of MoTe₂ (Fig. 11). Super-resolution fabrication has also been realized for various acceptor materials. Examples include super-resolution GaAs nanograting, path-directed and maskless fabrication of ordered TiO₂ nanoribbons, and sub-5-nm gap electrodes and arrays (Figs. 12‒14). In terms of surface structure fabrication, researchers previously developed a strategy for controlling wrinkle patterns using a new-type nanosecond LDW system. In addition, basic units of wrinkles as well as interaction rules between these basic units have been introduced, and this technology has been used to prepare kaleidoscopic masks (Fig. 15‒17). In addition, LDW can be used for the patterning synthesis of perovskite quantum dot materials (Fig. 18). Fig. 19 shows some novel super-resolution nanostructures fabricated using the new-type nanosecond LDW system.

Conclusions and Prospects The laser-matter nonlinear interaction principle applied to new-type nanosecond LDW systems is a unique strategy for using multi-acceptor materials and super-resolution fabrication. New-type nanosecond LDW systems have been successfully commercialized and used in large-area, super-resolution, and many non-traditional processing fields. Although the new-type nanosecond LDW technology has made great progress, it must be further improved in terms of equipment and application. We believe that this new-type nanosecond LDW will advance frontier technologies and play a major role in academia and engineering.

The realization of nanotechnology depends on nanoscale structures and devices that are based on micro-nano processing technology. Many types of micro-nano fabrication technologies exist, including photolithography, electron beam lithography, and focused ion beams. Since their advent, lasers have been used in various fields such as laser drilling, welding, cutting, engraving, and heat treatment. In recent years, the development of laser fabrication has become an important part of the field of micro-nano fabrication.