The non-contact microsphere ultrafast laser nanopatterning technology has emerged

In recent decades, non-contact microsphere ultrafast laser nanopatterning technology has driven significant progress and development in nanomanufacturing technology to meet the needs of improving component density and performance. However, meeting these needs requires improving the accuracy of material processing and the ability to manufacture in atmospheric environments.

Compared with other advanced processing methods, ultrafast laser processing is currently considered one of the most widely used tools in the processing of micro and nanostructures.

However, the optical diffraction limit has become a key challenge faced by ultrafast laser processing in generating extremely small features. The heat affected zone of these technologies is still much larger than that of nanostructures, which mostly have a melting zone greater than 300 nm.

In overcoming these bottlenecks, the use of dielectric microspheres as near-field lenses for super-resolution nanoimaging and nanoprocessing has sparked widespread research interest in the academic community. The Optical phenomena known as "photonic nanojet" is conducive to laser focusing to overcome the diffraction limit. In order to improve the processing capacity of ultra fast laser processing of microspheres, scientists have adopted self-assembly and microlens array lithography techniques to quickly and low-cost prepare surface patterns.

Microsphere femtosecond laser processing can not only achieve nanopore structure in contact mode, but also achieve any structure on the sample surface in non-contact mode. By lifting the microspheres to create a gap between the sample and microspheres, the working distance can be increased to a few micrometers.

This strategy results in microspheres working in the far field. In this case, by irradiating with a 405 nm lamp, 512 nm, and 800 nm femtosecond laser, the characteristic size of the surface structure can only be reduced to~300 nm, far from the optical diffraction limit. Therefore, achieving a good balance between working distance and feature size is a key issue in microsphere assisted laser manufacturing.

In order to overcome these problems, the research team of Xiamen University and the National University of Singapore jointly reported an ultrafast laser processing technology based on non-contact microspheres, which realized functional nano patterns on the surface of phase change materials less than 50 nm. This study is published in the journal Opto Electronic Advances.

The researchers also analyzed and explained the formation mechanism of these nanostructures. Through theoretical calculations, the incident laser passes through 50 μ When using m microspheres, the focusing spot size is only~678 nm. Due to the nonlinear effects of ultrafast laser, including Two-photon absorption and top threshold effect, the characteristics of nanostructures can be reduced to below 50 nm. Therefore, the surface nanostructures are attributed to the combined effect of microsphere focusing, Two-photon absorption and the top threshold effect of ultrafast laser irradiation.

This method provides a new approach for ultrafine laser surface nanomachining, and is expected to further optimize and improve its processing efficiency and degree of freedom through microsphere arrays and microsphere engineering.

Source: OFweek