Femtosecond Laser Precision Engineering: From Micron, Submicron, to Nanoscale

Abstract

As a noncontact strategy with flexible tools and high efficiency, laser precision engineering is a significant advanced processing way for high-quality micro-/nanostructure fabrication, especially to achieve novel functional photoelectric structures and devices. For the microscale creation, several femtosecond laser fabrication methods, including multiphoton absorption, laser-induced plasma-assisted ablation, and incubation effect have been developed. Meanwhile, the femtosecond laser can be combined with microlens arrays and interference lithography techniques to achieve the structures in submicron scales. Down to nanoscale feature sizes, advanced processing strategies, such as near-field scanning optical microscope, atomic force microscope, and microsphere, are applied in femtosecond laser processing and the minimum nanostructure creation has been pushed down to ~25 nm due to near-field effect. The most fascinating femtosecond laser precision engineering is the possibility of large-area, high-throughput, and far-field nanofabrication. In combination with special strategies, including dual femtosecond laser beam irradiation, ~15 nm nanostructuring can be achieved directly on silicon surfaces in far field and in ambient air. The challenges and perspectives in the femtosecond laser precision engineering are also discussed.

Integration of Multifocal Microlens Array on Silicon Microcantilever via Femtosecond-Laser-Assisted Etching Technology

“…First, undoped silicon wafers were cleaned with acetone, ethanol, and deionized water for 30 min to obtain a clean surface. The femtosecond laser (343 nm, 200 kHz, 280 fs (Light Conversion Pharos, Vilnius, Lithuania)) is tightly focused through a high numerical aperture objective lens (NA = 0.95, 40×) and matched with a three-dimensional piezoelectric platform (the strokes of the xand y-axes are 1.5 mm, that of the z-axis is 100 µm, and accuracy is 1 nm) to realize the preparation of micro/nanostructures on the silicon surface [24][25][26][27][28][29]. In addition, the femtosecond laser can also be used to process other materials via multi-photon absorption, for example, lift off GaN [30,31].…”

Far‐Field Parallel Direct Writing of Sub‐Diffraction‐Limit Metallic Nanowires by Spatially Modulated Femtosecond Vector Beam

“…Ultrafast laser direct writing techniques exhibit the ability to achieve precision and repeatable micro-/nanostructures on a large variety of materials with little sensitivity to processing conditions. [14][15][16][17] Highnumerical aperture (NA) objective lens is commonly used for increasing resolution in nanostructure fabrication, but how to surpass the diffraction limit remains a critical issue. [18] To overcome this limitation, manufacturing methods based on some unique optical effects which support effective fabrication of high-resolution nanowires are exploited, including photopolymerization from nonlinear absorption, [19][20][21][22] laser-excited plasmonic lithography, [23][24][25][26][27] and locally near-field ablation.…”

Picosecond Bessel Beam Fabricated Pure, Gold-Coated Silver Nanostructures for Trace-Level Sensing of Multiple Explosives and Hazardous Molecules

“…Across the scientific community, numerous innovative approaches have been pursued in order to reach a high-flourishing upswing in optical responses of the nano-photonic systems in diverse terms. Aiming for such advancements in miscellaneous nano-scale optical features, such as fabrication of diverse nanoparticles (NPs) in liquids [1][2][3][4][5], exotic nanostructures (NSs) (in air/liquid) with desired plasmonic response, and attaining enhanced optical features, such as surface-enhanced Raman spectroscopy (SERS), significant improvisations have been undertaken in laser-matter interaction research. Implementation of non-Gaussian beam profile in laser ablation, and engagement of different off-axis geometrical optics has been quite significant.…”