The mechanisms and research progress of laser fabrication technologies beyond diffraction limit

Abstract

Laser is recognized as one of the top technological achievements of 20th century and plays an important role in many fields, such as medicine, industry, entertainment and so on. Laser processing technology is one of the earliest and most developed applications of laser. With the rapid development of nanoscience and nanotechnology and micro/nano electronic devices, the micro/nanofabrication technologies become increasingly demanding in manufacturing industries. In order to realize low-cost, large-area and especially high-precision micro-nanofabrication, it has great scientific significance and application value to study and develop the laser fabrication technologies that can break the diffraction limit. In this article, the super resolution laser fabrication technologies are classified into two groups, far-filed laser direct writing technologies and near-field laser fabrication technologies. Firstly, the mechanisms and progress of several far-field laser direct writing technologies beyond the diffraction limit are summarized, which are attributed to the lasermatter nonlinear interaction. The super-diffraction laser ablation was achieved for the temperature-dependent reaction of materials with the Gaussian distribution laser, and the super-diffraction laser-induced oxidation in Metal-Transparent Metallic Oxide grayscale photomasks was realized by the laser-induced Cabrera-Mott oxidation process. Besides, the multi-photon polymerization techniques including degenerate/non-degenerate two-photon polymerization are introduced and the resolution beyond the diffraction limit was achieved based on the third-order nonlinear optical process. Moreover, the latest stimulated emission depletion technique used in the laser super-resolution fabrication is also introduced. Secondly, the mechanisms and recent advances of novel super diffraction near-field laser fabrication technologies based on the evanescent waves or surface plasmon polaritons are recommended. Scanning near-field lithography used a near-field scanning optical microscope coupled with a laser to create nanoscale structures with a resolution beyond 100 nm. Besides, near-field optical lithography beyond the diffraction limit could also be achieved through super resolution near-field structures, such as a bow-tie nanostructure. The interference by the surface plasmon polariton waves could lead to the fabrication of super diffraction interference fringe structures with a period smaller than 100 nm. Moreover, a femtosecond laser beam could also excite and interfere with surface plasmon polaritons to form laser-induced periodic surface structures. Furthermore, the super-resolution superlens and hyperlens imaging lithography are introduced. Evanescent waves could be amplified by using the superlens of metal film to improve the optical lithography resolution beyond the diffraction resolution. The unique anisotropic dispersion of hyperlens could provide the high wave vector component without the resonance relationship, which could also realize the super resolution imaging. Finally, prospective research and development tend of super diffraction laser fabrication technologies are presented. It is necessary to expand the range of materials which can be fabricated by laser beyond the diffraction limit, especially 2D materials.