Far-field induced near-field breakdown for direct nanocoating in the atmosphere

a, Schematic representation of a decaying wave (Eew) around two nanoholes with different sizes on a dielectric. For larger nanoholes with a diameter comparable to the wavelength, the evanescent fields at each edge of the nanoholes are independent and quickly decay from the boundary. For smaller nanoholes with a deep wavelength aperture, the strong interaction between the two boundaries constructively increases the optical intensity inside the nanohole and limits the light in a deep subwavelength scale. b, Modeling the distribution of the field strength E for a titanium oxide film with a nanoscale hole shown by the central region of the dimming (the light intensity inside the nanoscale hole is close to maximum, but not shown for better visualization). c, O-FIB direct nanocoating scheme (left) and free-form image obtained using a birefringent microscope (right, top) and scanning electron microscope (right, bottom). Photo: Zhen-Ze Li, Lei Wang, Hua Fang, Yang-Hao Yu, Qi-Dai Chen, Saulius Juodkazis and Hong Bo Song

Lasers are becoming one of the dominant tools in modern manufacturing. Much effort was devoted to improving the accuracy of processing, and during laser cutting, welding, marking and stereolithography in atmospheric conditions, spatial resolutions were achieved up to micrometers. A femtosecond laser (fs laser) is a particularly promising approach from this point of view, in addition to its three-dimensional (3-D) processing ability and a wide range of material use possibilities. The sizes of elements with a restriction of superdiffraction at the level of tens of nanometers, based on the effects of threshold multiphoton absorption, shrinkage, and emission depletion during stimulation, were also realized during photo-curing of polymers using laser radiation, which, unfortunately, does not apply to solid materials. Near-field optical methods provide an alternative super-resolution scheme by localizing light fields on a nanometer scale with the physical forms of sharp tips, tiny holes, nanoparticles and small protrusions. However, these approaches often rely on heavy displacement and alignment systems to maintain accurate distance between the probe and the substrate for practical manufacturing / patterning performance due to the fleeting nature of the near field.

Innovative optical patterning technology is highly desirable, which allows high-resolution non-rarefaction processing comparable to conventional FIB processing. In a new article published in Light of science and applications, scientists from the State Key Laboratory for Precision Measuring Technologies and Instruments, Department of Precision Instruments, Tsinghua University, Beijing, China, State Key Laboratory for Integrated Optoelectronics, College of Electronic Science and Technology, Jilin University, Changchun, China, and Nanotechnology Enterprise at Australian University of Technology in Swinburne reported on the near-field optical penetration approach (O-FIB), which allows nanotechnology to be applied to virtually all solid materials in the atmosphere. Recording begins with nanoholes created by multiphoton absorption induced by a femtosecond laser, and its cutting “knife tip” is sharpened by an adjustable far field of the near optical field. Spatial resolution less than 20 nm (λ / 40 for light wavelength λ) is easily achieved. O-FIB is enhanced by simple control of the polarization of the incident light to control the recording of the nano-puzzle along the designed template.

“In accordance with the continuous boundary condition of the normal component of the electric displacement, we experimentally observed the nano-localization of the light field and the polarization-vertical amplification around the nano-hole, which allows us to directly control the near-field amplification for nanoablation by the far field. Based on this idea, we implemented a free nanoscale recording with a resolution of up to 18 nm, manipulating the polarization of the laser and the beam path in real time. "

“For the self-regulation effect caused by the feedback between the light and the original seeds, our approach has the inherent resistance to the stochastic nature of the initial ablation and the ability to manipulate the line width. Our approach demonstrates the free-form writing of seamless nano-grooves with a controlled length, separation and trajectory. At the same time, the versatility of the seeding effect allows you to use the print mode over a large area, which surpasses the usual FIB. "

“Our technology has ushered in a new era of high-performance nano-processing. It is applicable for various materials and surfaces in the field of nanoelectronics, nanofluids and nanomedicine. Here we show the possibility of direct manipulation of the near field through the far field, may inspire researchers to push femtosecond laser nanotechnology or even other areas of optical processing to a higher level, "scientists predict.

There is no such thing as non-linear resolution in ultrafast laser processing

Additional Information:
Zhen-Ze Li et al., O-FIB: near-field breakdown caused by a far field for direct nanocovering in the atmosphere, Light: science and application (2020). DOI: 10.1038 / s41377-020-0275-2

O-FIB: far-field induced near-field damage for direct nanocovering in the atmosphere (2020, March 20)
retrieved March 20, 2020
from https://phys.org/news/2020-03-o-fib-far-field-induced-near-field-breakdown-nanowriting.html

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