South University of Science and Technology has made a series of progress in the field of laser super resolution nano manufacturing

Recently, Xu Shaolin, an assistant professor of the Department of Mechanical and Energy Engineering of South University of Science and Technology, published a series of papers on nature communications, advanced optical materials, laser&photonics reviews, nano letters, ACS applied materials&interfaces and other high-level journals in the field of laser micro/nano manufacturing, focusing on the theme of "laser super resolution nano manufacturing" Laser induced periodic nano grating manufacturing, linear pulse laser cross large-scale micro nano composite manufacturing, laser doping enhanced plasma etching manufacturing of durable nano cones, etc.

In terms of laser subwavelength patterned nano manufacturing, large-area splicing free ultra diffraction limit patterned nano manufacturing plays a crucial role in semiconductor, optical micro nano devices and other fields. Developing low-cost and high-efficiency preparation technologies and supporting equipment is of great significance for the high-quality development of the above fields.

The researchers used the quasi binary phase mask to filter the polarization of the beam, combined with the polarization and phase optimization, obtained ultrafast laser pulses with subwavelength patterned wavefront, used rapid scanning to form pulse separation for periodic modification/ablation, and realized the uniform and efficient manufacturing of wafer level surface patterned micro/nano structures in atmospheric environment. The prepared patterned structure is highly free and controllable in design, and has sub wavelength graphic resolution (520 nm wavelength achieves 300 nm graphic resolution), without splicing. The researchers designed and fabricated the super surface absorber device, and achieved 98% single peak and double peak absorption in the mid infrared band (3-7 μ m). The high efficiency laser subwavelength patterning processing method developed above has universality and can be applied to patterning processing of any thin film material.

Figure 1. New sub wavelength patterned shaping pulse laser lithography technology

In the controllable manufacturing of laser induced periodic nano gratings, laser induced periodic surface structure (LIPSS) can break through the diffraction limit of light and obtain subwavelength (~ λ／ 2) To ultra deep sub wavelength (～ λ／ 8) Resolution of the nano grating structure, but its structure of the space long-range disorder limits its application in industry.

Based on the study of ultrafast laser excited surface plasmon wave interference, the researchers systematically explained the cause of laser induced spatial distribution disorder of nano grating structures for the first time, and proposed the corresponding regulation strategy, namely, using the self alignment phenomenon caused by surface plasmon wave interference, to achieve efficient and large area fabrication of long range ordered subwavelength grating structures. Furthermore, the ultra fast light source is shaped to form a uniform and consistent line light source. By adjusting the laser processing strategy, thousands of two-dimensional array units are stably generated spontaneously in a single scan, achieving the goal of efficiently preparing uniform two-dimensional nanostructures on wafer size samples.

Figure 2. High efficient two-dimensional nano patterning technology developed based on laser induced periodic surface structure self alignment

In the field of online pulsed laser cross large-scale micro nano composite manufacturing, the cross large-scale hierarchical metal micro nano grid structure (sub 100nm to several micrometers) is an effective way to improve the transparency, conductivity and mechanical stability of transparent flexible electronic devices. However, the efficient and economic preparation of the above micro nano composite structures is still extremely challenging.

The researchers creatively proposed a one-step maskless linear pulse laser lithography technology. By modulating the separate ablation of linear pulse light source, metal grid lines with continuously adjustable linewidth from 50 nm to several micrometers can be efficiently prepared. The researchers used this technology to design and prepare a flexible transparent electrode. On the premise that the transmissivity is greater than 80%, a thin layer resistance of 4.6 Ω/sq is obtained. After 1000 times of bending resistance tests, it can still maintain good photoelectric performance. Further, the researchers applied this technology to prepare a flexible multidirectional strain sensor, realized the function of multidirectional strain sensing by using a single layer of film, and had significant advantages in sensitivity and responsiveness, and showed good mechanical stability and cycle stability.

Figure 3. Linear pulse laser lithography for large-scale micro nano composite manufacturing

In terms of laser doping enhanced plasma etching manufacturing of durable nano cones, surface nanostructures can effectively reduce Fresnel reflection at the interface, thereby improving the transmissivity of optical windows and realizing the application of surface antireflection. However, surface structures such as nano cones are prone to wear and fracture when subjected to friction or particle impact, which limits their applications in extreme environments.

The researchers ingeniously designed a micro frame structure to protect the surface nano cone array, so that the prepared nano cone antireflection surface also has high wear resistance. Combined with ultrafast laser processing and dry etching technology, the researchers proposed a regional laser doping composite dry etching technology, which verified the feasibility of manufacturing optical antireflection windows with high transmittance and long durability on the surface of quartz glass, intrinsic SiC and other optical windows. The design and manufacturing method proposed in this study can effectively solve the durability problem of antireflection surfaces, and is expected to promote the research and application of optical antireflection windows in extreme environments.

Figure 4. Laser Doping Enhanced Plasma Etching Manufacturing of Durable Nanocones

Source: Southern University of Science and Technology