Rotationally symmetric colorization of metal surfaces through omnidirectional femtosecond laser-induced periodic surface structures

Abstract

Following femtosecond (fs) laser pulse irradiation, the formation of a new type of low-spatial-frequency laser-induced periodic surface structure (LSFL) patterns, namely, omnidirectional LSFLs (OD-LSFLs) with the periodic ordering of their orientations, are investigated on Ni in this Letter. Using a liquid crystal polymer patterned depolarizer, we periodically rotate the polarization of fs laser pulses across the laser spot and create OD-LSFLs by raster scanning fs laser pulses. We also show that the period of the OD-LSFL orientation rotation can be controlled with the defocused distance, and OD-LSFLs can significantly expand the viewing angle of the structural colors in the azimuthal direction without noticeable color degradations.

Multi-Angular Colorimetric Responses of Uni- and Omni-Directional Femtosecond Laser-Induced Periodic Surface Structures on Metals

“…This gap is deliberately inserted to eliminate any unwanted effects on structural coloration, resulting from the decreases in the reflectance [ 2 ] and period [ 24 ] of LSFLs by means of extra pulses of irradiation due to the overlapping of scanlines. Within a single scanline of OD-LSFLs, the number and period of LSFL orientation rotations by 180° are about 4 and 18 μm, respectively, and this is consistent with our previous work where the same defocused distance was used [ 19 ].…”

“…In this paper, we measure the modified colorimetric behavior of metal surfaces at multiple detection angles due to two types of LSFL patterns, UD-LSFLs and OD-LSFLs, produced by fs laser pulse irradiation with linear and periodically rotating polarizations. This work builds on our earlier study [ 19 ] and reports on angle-resolved distinctive characteristics of colors arising from quasi-periodic structural details at the nanometer scale. With the CIE standard illuminant D65, we show that both UD- and OD-LSFLs on metals can transform polished metals to gonio-apparent materials, and each has its unique behavior of colorimetric responses, depending on both the detection and rotation angles.…”

“…Recently, we fabricated a new type of LSFL pattern, namely omnidirectional LSFLs (OD-LSFLs), expanding the viewing angle of structural colors by periodically ordering the orientation of LSFLs within the scanline [ 19 ]. Furthermore, compared to traditional LSFLs with a single orientation, unidirectional LSFLs (UD-LSFLs), OD-LSFLs uniformly distribute structural colors to all the azimuthal angles and show rotationally symmetric colorization under the normal illumination incidence [ 19 ].…”

Femtosecond laser‐produced optical absorbers for solar‐thermal energy harvesting

“…38,39 Larger laser irradiance and/or slow scan speed can produce deeper microgrooves and larger sizes of nanoparticles, while lower laser irradiance and/or faster scan speed can produce shallow microgrooves and smaller sizes of nanoparticles. The number of scans on the same line, 60 electric field orientation, 62,63 and ambient environment 64 are other control parameters to control the size and density of nanoparticles, the orientation of nanostructures, 65 and chemical composition. For example, different gas ambient or liquid media can be chosen to change the chemical composition of the laserprocessed surfaces.…”

Stacked Polarizing Elements for Controlling Parameters of Surface Relief Gratings Written in Photosensitive Materials

“…The interference of two laser beams generates a periodically modulated intensity distribution for the processing of materials [ 15 , 16 , 17 ]. Laser-induced periodic surface structures (LIPSSs) formed using pulsed laser radiation [ 18 , 19 ] are used for the fabrication of subwavelength SRGs. To change the period of the formed periodic relief in these cases, it is necessary to change the wavelength of the illuminating laser radiation or change the parameters of the elements in the optical laser-writing setup.…”