scholarly journals Formation of Subwavelength Periodic Triangular Arrays on Tungsten through Double-Pulsed Femtosecond Laser Irradiation

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2380 ◽  
Author(s):  
Hongzhen Qiao ◽  
Jianjun Yang ◽  
Jing Li ◽  
Qi Liu ◽  
Jie Liu ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Energy ◽  
Modulation Depth ◽  
Scanning Speed ◽  
Femtosecond Laser Irradiation ◽  
Laser Beams ◽  
One Dimensional ◽  
Triangular Arrays ◽  
Structure Morphology ◽  
Highly Uniform

We present a mask-free strategy for fabricating two-dimensional subwavelength periodic triangular arrays on tungsten, by focusing two orthogonally polarized and temporally delayed femtosecond laser beams using a cylindrical lens. In stark contrast to the commonly observed structures of either a single ablation spot or a one-dimensional grating, we obtained highly uniform periodic triangular arrays on the laser-exposed surface, with three equilateral sides each of 480 nm in length and about 100 nm in modulation depth. The triangular features varied with both the laser energy and the scanning speed. We found that the optical reflectivity of such a surface reduces significantly within the spectral range of 700–2500 nm. The triangular structure morphology can also be controlled by varying the time delay between the two laser beams.

scholarly journals Space-Selective Control of Functional Crystals by Femtosecond Laser: A Comparison between SrO-TiO2-SiO2 and Li2O-Nb2O5-SiO2 Glasses

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 979
Author(s):  
Xuan He ◽  
Qiming Liu ◽  
Matthieu Lancry ◽  
François Brisset ◽  
Bertrand Poumellec
Keyword(s):  
Femtosecond Laser ◽  
Second Harmonic ◽  
Scanning Speed ◽  
High Energy ◽  
Femtosecond Laser Irradiation ◽  
Laser Polarization ◽  
Electron Backscattered Diffraction ◽  
Sio2 Glass ◽  
Significant Difference ◽  
Induced Crystallization

We report on space-selective crystallization of congruent and polar Sr2TiSi2O8 crystals in a stoichiometric SrO-TiO2-SiO2 glass induced by (1030 nm, 300 fs) femtosecond laser irradiation. This allows us to compare with non-congruent laser-induced crystallization of polar LiNbO3 in non-stoichiometric Li2O-Nb2O5-SiO2 glass and gain information on the mechanism of nanocrystals orientation with the laser polarization that we pointed out previously. Using scanning electron microscopy (SEM), second harmonic generation (SHG), and electron backscattered diffraction (EBSD), we studied the laser-induced crystallization according to the laser processing parameters (pulse energy, pulse repetition rate, scanning speed). We found (1) a domain where the laser track is filled with crystals not perfectly textured (low energy), (2) a domain where an amorphous volume remains surrounded by a crystallized shell (high energy). This arises from Sr out-diffusion and may give rise to the crystallization of both SrTiO3 and Sr2TiSi2O8 phases at low speed. In the one-phase domain (at higher speed), the possibility to elaborate a tube with a perfect Fresnoite texture is found. A significant difference in size and morphology whereas the crystallization threshold remains similar is discussed based on glass thermal properties. Contrarily to Li2O-Nb2O5-SiO2 (LNS) glass, no domain of oriented nanocrystallization controlled by the laser polarization has been found in SrO-TiO2-SiO2 (STS) glass, which is attributed to the larger crystallization speed in STS glass. No nanogratings have also been found that is likely due to the congruency of the glass.

scholarly journals Single-step fabrication of microfluidic channels filled with nanofibrous membrane using femtosecond laser irradiation

2021 ◽  
Author(s):  
Amirhossein Tavangar ◽  
Bo Tan ◽  
Krishnan Venkatakrishnan
Keyword(s):  
Femtosecond Laser ◽  
Laser Irradiation ◽  
Microfluidic Channel ◽  
Scanning Speed ◽  
Single Step ◽  
Femtosecond Laser Irradiation ◽  
Microfluidic Channels ◽  
Ambient Conditions ◽  
Nanofibrous Structure ◽  
Channel Surface

In this paper, we demonstrate a new method of fabricating silicon microfluidic channels filled with a porous nanofibrous structure utilizing a femtosecond laser. The nanofibrous structure can act as a membrane used for microfiltration. This method allows us to generate both the microfluidic channel and the fibrous nanostructure in a single step under ambient conditions. Due to laser irradiation, a large number of nanoparticles ablate from the channel surface, and then aggregate and grow into porous nanofibrous structures and fill the channels. Energy dispersive x-ray spectroscopy (EDS) analysis was conducted to examine the oxygen concentration in the membrane structure. Our results demonstrated that by controlling the laser parameters including pulse repetition, pulse width and scanning speed, different microfluidic channels with a variety of porosity could be obtained.

scholarly journals Влияние легирования на свойства аморфного гидрогенизированного кремния, облученного фемтосекундными лазерными импульсами

2018 ◽  
Vol 60 (4) ◽  
pp. 637
Author(s):  
К.Н. Денисова ◽  
А.С. Ильин ◽  
М.Н. Мартышов ◽  
А.С. Воронцов
Keyword(s):  
Comparative Analysis ◽  
Femtosecond Laser ◽  
Laser Irradiation ◽  
Amorphous Matrix ◽  
Laser Energy ◽  
Hydrogenated Amorphous Silicon ◽  
Femtosecond Laser Irradiation ◽  
Boron Doped ◽  
Nanocrystal Formation ◽  
Hydrogenated Amorphous

AbstractA comparative analysis of the effect of femtosecond laser irradiation on the structure and conductivity of undoped and boron-doped hydrogenated amorphous silicon ( a -Si: H) is performed. It is demonstrated that the process of nanocrystal formation in the amorphous matrix under femtosecond laser irradiation is initiated at lower laser energy densities in undoped a -Si: H samples. The differences in conductivity between undoped and doped a -Si: H samples vanish almost completely after irradiation with an energy density of 150–160 mJ/cm^2.

Investigation of Femtosecond Laser Irradiation on Fused Silica Etching Selectivity

2004 ◽  
Vol 850 ◽  
Author(s):  
Yves Bellouard ◽  
Ali A. Said ◽  
Mark Dugan ◽  
Philippe Bado
Keyword(s):  
Femtosecond Laser ◽  
Laser Irradiation ◽  
Structural Changes ◽  
Scanning Speed ◽  
Fused Silica ◽  
Index Of Refraction ◽  
Femtosecond Laser Irradiation ◽  
Etching Selectivity ◽  
Line Patterns ◽  
Chemical Selectivity

ABSTRACTFemtosecond laser irradiation has various noticeable effects on fused silica. It can locally increase the index of refraction or modify the material chemical selectivity. Regions that have been exposed to the laser are etched several times faster than unexposed regions. Various observations reported in the literature seem to show that these effects are possibly related to a combination of structural changes and the presence of internal stress. However, a detailed analysis of the contribution of both effects is still lacking.In this paper, we present systematic SEM-based investigations performed on fused silica (a-SiO2). Line-patterns were first scanned on the substrate using a femtosecond laser and then etched in a low-concentration HF solution. The effects of various laser parameters like power and scanning speed are analyzed and we show further evidence of an interface between two different etching regimes.

Photo-conversion and evolution of one-dimensional Cu nanoparticles under femtosecond laser irradiation

2008 ◽  
Vol 254 (16) ◽  
pp. 4992-4998 ◽  
Author(s):  
Gang Chang ◽  
Yasuhiko Shimotsuma ◽  
Masaaki Sakakura ◽  
Toshirou Yuasa ◽  
Hidekazu Homma ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Irradiation ◽  
Femtosecond Laser Irradiation ◽  
Cu Nanoparticles ◽  
One Dimensional

scholarly journals Space-Selective Control of Functional Crystals by Femtosecond Laser: a Comparison Between SrO-TiO2-SiO2 and Li2O-Nb2O5-SiO2 Glasses

2020 ◽  
Author(s):  
He Xuan ◽  
Liu Qiming ◽  
Lancry Matthieu ◽  
Brisset François ◽  
Poumellec Bertrand
Keyword(s):  
Femtosecond Laser ◽  
Second Harmonic ◽  
Scanning Speed ◽  
High Energy ◽  
Femtosecond Laser Irradiation ◽  
Laser Polarization ◽  
Electron Backscattered Diffraction ◽  
Sio2 Glass ◽  
Significant Difference ◽  
Induced Crystallization

We report on space-selective crystallization of congruent and polar Sr2TiSi2O8 crystals in a stoichiometric SrO-TiO2-SiO2 glass induced by (1030 nm, 300 fs) femtosecond laser irradiation. This allows us to compare with non-congruent laser induced crystallization of polar LiNbO3, in non stoichiometric Li2O-Nb2O5-SiO2 glass and gain information on the mechanism of nanocrystals orientation with the laser polarization that we pointed out previously. Using scanning electron microscopy (SEM), Second-harmonic generation (SHG) and electron backscattered diffraction (EBSD), we studied the laser induced crystallization according to the laser processing parameters (pulse energy, pulse repetition rate, scanning speed). We found 1) a domain where the laser track is filled with crystals not perfectly textured (low energy), 2) a domain where an amorphous volume remain surrounded by a crystallized shell (high energy). This arises from Sr out-diffusion and may gives rise to crystallization of both SrTiO3 and Sr2TiSi2O8 phases at low speed. In the one-phase domain (at higher speed), it is found the possibility to elaborate a tube with a perfect fresnoite texture. Significant difference in size and morphology whereas crystallization threshold remains similar are discussed based on glases thermal propeties. Contrarily to Li2O-Nb2O5-SiO2 (LNS) glass, no domain of oriented nanocrystallization controlled by the laser polarization has been found in SrO-TiO2-SiO2 (STS) glass, which is attributed to the larger crystallization speed in STS glass. No nanogratings have also been found that is likely due to the congruency of the glass.

scholarly journals Photothermal Response of Hollow Gold Nanorods under Femtosecond Laser Irradiation

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 711 ◽  
Author(s):  
Rongping Gan ◽  
Haihua Fan ◽  
Zhongchao Wei ◽  
Haiying Liu ◽  
Sheng Lan ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Irradiation ◽  
Cross Section ◽  
Temperature Rise ◽  
Absorption Cross Section ◽  
External Medium ◽  
Laser Energy ◽  
Gold Nanorod ◽  
Femtosecond Laser Irradiation ◽  
Absorption Cross

The photothermal kinetics of hollow gold nanorod (HGNR) under femtosecond laser irradiation are studied numerically with finite-element methods and a two-temperature model. Compared with solid gold nanorod (SGNR) with the same aspect ratio (AR), the localized surface plasmon resonance (LSPR) peak of HGNR can be red-shifted to the second near-infrared window, and the absorption cross-section of HGNR can be larger than that of SGNR. In addition, under the influence of an applied numerically electromagnetic field (simulated femtosecond laser irradiation), the heat generated by HGNR makes the temperature rise of the surrounding medium faster and higher. Compared with SGNR with the same resonance wavelength, HGNR has a slightly smaller absorption cross-section but can achieve a higher temperature rise of the external medium. In addition, the laser energy, required to achieve the critical temperature for selective photothermal damage of tumor cells, is also significantly reduced. Moreover, with the same incident laser energy, the decreasing of HGNR shell thickness leads to an increase of the temperature rise of the external medium, while the change of femtosecond laser pulse width will not significantly change the temperature rise of its lattice and the external medium. In short, this study aims to provide some useful insights for the applications of HGNR in photothermal tumor therapy.

scholarly journals Single-step fabrication of microfluidic channels filled with nanofibrous membrane using femtosecond laser irradiation

2021 ◽  
Author(s):  
Amirhossein Tavangar ◽  
Bo Tan ◽  
Krishnan Venkatakrishnan
Keyword(s):  
Femtosecond Laser ◽  
Laser Irradiation ◽  
Microfluidic Channel ◽  
Scanning Speed ◽  
Single Step ◽  
Femtosecond Laser Irradiation ◽  
Microfluidic Channels ◽  
Ambient Conditions ◽  
Nanofibrous Structure ◽  
Channel Surface

In this paper, we demonstrate a new method of fabricating silicon microfluidic channels filled with a porous nanofibrous structure utilizing a femtosecond laser. The nanofibrous structure can act as a membrane used for microfiltration. This method allows us to generate both the microfluidic channel and the fibrous nanostructure in a single step under ambient conditions. Due to laser irradiation, a large number of nanoparticles ablate from the channel surface, and then aggregate and grow into porous nanofibrous structures and fill the channels. Energy dispersive x-ray spectroscopy (EDS) analysis was conducted to examine the oxygen concentration in the membrane structure. Our results demonstrated that by controlling the laser parameters including pulse repetition, pulse width and scanning speed, different microfluidic channels with a variety of porosity could be obtained.

Generation of nano-bumps on transparent quartz glass surface under femtosecond laser irradiation

2008 ◽  
Author(s):  
Wei Guo ◽  
Zeng Bo Wang ◽  
Lin Li ◽  
Zhu Liu ◽  
Boris Luk’yanchuk ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Irradiation ◽  
Quartz Glass ◽  
Glass Surface ◽  
Femtosecond Laser Irradiation
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