Article
Chemistry, Physical
Jiangyou Long, Ziyu He, Deyi Ou, Yajun Huang, Pengchao Wang, Qinglei Ren, Xiaozhu Xie
Summary: In this study, the formation of dense nanostructures on silicon carbide surfaces through femtosecond laser micromachining was investigated. The morphology and distribution of these nanostructures were found to be influenced by laser parameters, and the formation mechanism was observed through microscopic imaging.
SURFACES AND INTERFACES
(2022)
Article
Optics
Alan T. K. Godfrey, Deepak L. N. Kallepalli, Sabaa Rashid, Jesse Ratte, Chunmei Zhang, P. B. Corkum
Summary: This study presents a novel method for controlling blister formation in Laser-Induced Forward Transfer (LIFT) by using a thin metal film between two polymer films. The laser energy deposition is primarily in the metal layer, and blister expansion is driven by laser-induced spallation of the gold film.
Article
Chemistry, Physical
Kernius Vilkevicius, Algirdas Selskis, Evaldas Stankevicius
Summary: This study investigates the formation of gold nanostructures (nanobumps, nanocones, and nanojets) on the surface of metal using laser direct writing technique with different laser wavelengths. Experimental results show that shorter wavelength lasers provide a more precise and efficient fabrication process for controlling the properties of the nanostructures, making them highly suitable for practical applications.
APPLIED SURFACE SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Rahul A. Rajan, Huang Tao, Weili Yu, Jianjun Yang
Summary: Femtosecond laser processing of lead halide perovskites has been widely studied for creating micro/nanostructures and improving light emitting properties. This study investigates the photoluminescence and lasing behaviors of single crystal and polycrystalline perovskites upon femtosecond laser ablation. Different regions show different carrier recombination mechanisms due to their defect chemistries and morphologies, enabling the realization of amplified spontaneous emission. The laser modified region in polycrystalline perovskites exhibits enhanced random lasing performance due to defect passivation and grain size reduction.
MATERIALS TODAY PHYSICS
(2023)
Article
Multidisciplinary Sciences
Tomokazu Sano, Tomoki Matsuda, Akio Hirose, Mitsuru Ohata, Tomoyuki Terai, Tomoyuki Kakeshita, Yuichi Inubushi, Takahiro Sato, Kohei Miyanishi, Makina Yabashi, Tadashi Togashi, Kensuke Tono, Osami Sakata, Yoshinori Tange, Kazuto Arakawa, Yusuke Ito, Takuo Okuchi, Tomoko Sato, Toshimori Sekine, Tsutomu Mashimo, Nobuhiko Nakanii, Yusuke Seto, Masaya Shigeta, Takahisa Shobu, Yuji Sano, Tomonao Hosokai, Takeshi Matsuoka, Toshinori Yabuuchi, Kazuo A. Tanaka, Norimasa Ozaki, Ryosuke Kodama
Summary: This study reports the ultrafast lattice behaviour in iron shocked by a femtosecond laser pulse, revealing unique characteristics compared to conventional shock waves. The researchers found that the initial compression state caused by the femtosecond laser-driven shock wave is the same as that caused by conventional shock waves. They also experimentally observed the temporal deviation of peaks of stress and strain waves, as well as the existence of a plastic wave peak between them, which has not been predicted theoretically.
SCIENTIFIC REPORTS
(2023)
Article
Optics
Sikun Zhou, Shutong Wang, Baoshan Gu, Li Shen, Fei Huang, Sha Wang, Guoliang Deng, Shouhuan Zhou
Summary: In this study, self-organized micro-gratings were created inside z-cut LiNbO3 using slit-shaped femtosecond laser direct writing, and the effects of processing parameters and slit widths on grating formation were investigated. Various techniques such as Raman mapping, energy dispersive spectroscopy, and a micro polariscope were used to understand the mechanism of periodic grating generation. An optical attenuator with a spacing of 15 μm was fabricated to demonstrate the potential application of micro-gratings in optical information processing. The micro-gratings provide a pathway for expanding the applications of LiNbO3 and fabricating multifunctional photonic structures.
OPTICS AND LASER TECHNOLOGY
(2023)
Article
Optics
Marie -Pier Lord, Michel Olivier, Martin Bernier, Real Vallee
Summary: Femtosecond fiber lasers have been a game changer in laser technology industry, providing high brightness ultrashort pulses in compact, affordable, and reliable setups. This study presents the first femtosecond fiber laser operating in the visible spectrum, expanding the range of applications for such sources. The all-normal dispersion regime passively mode-locked ring cavity is based on nonlinear polarization evolution in a single-mode Pr3+-doped fluoride fiber. The compressed pulses at 635 nm have a duration of 168 fs, a peak power of 0.73 kW, and a repetition rate of 137 MHz.
Article
Optics
Sungkwon Shin, Woojin Lee, Jong Kab Park, Doh-Hoon Kim
Summary: This paper presents a femtosecond laser processing method to precisely control taper angles of micro-holes. The ablation depth depends on the ablation rate, number of repetitions for scanning, beam size, and spot overlap ratio, which in turn influence the taper angles. We developed a multilevel material processing method involving analytical models to achieve desired taper angles on 64FeNi alloy sheets.
OPTICS AND LASER TECHNOLOGY
(2023)
Article
Chemistry, Physical
Tauras Bukelis, Eugenijus Gaizauskas, Ona Balachninaite, Domas Paipulas
Summary: Laser induced periodic surface structures (LIPSS) were analyzed on steel and copper surfaces in detail. The thermal conductivity differences between the two metals determine the rate of extinguishing of laser-induced temperature modulation. Femtosecond laser radiation sources with different wavelengths were used to inscribe low spatial frequency LIPSS. For steel samples, regular LIPSS were formed for both wavelengths but their regularity decreased with shorter wavelength. For copper samples, LIPSS with lower regularity were formed and even absent in one of the scanning methods at UV wavelength. Numerical analysis based on the 2D heat diffusion equation revealed that temperature modulation decreased considerably faster in copper and at higher modulation frequency.
SURFACES AND INTERFACES
(2023)
Article
Optics
Keiichi Bamoto, Haruyuki Sakurai, Shuntaro Tani, Yohei Kobayashi
Summary: This study demonstrated the use of Bayesian optimization as an efficient method to find the optimal conditions for laser processing. It showed that the optimum set of parameters to achieve a desired shape can be obtained autonomously and more than an order of magnitude faster than with a simple grid-search.
Article
Materials Science, Coatings & Films
Chen Wu, Xudong Fang, Qiang Kang, Hao Sun, Libo Zhao, Bian Tian, Ziyan Fang, Maolin Pan, Ryutaro Maeda, Zhuangde Jiang
Summary: This study utilized femtosecond laser to etch SiC and investigated the microscopic mechanism of carrier concentration and temperature change. Results showed that the ablation threshold was related to laser pulse number and processing medium, and a mechanism model based on cleavage phenomenon was established. The processing media significantly affected the surface roughness and chemical bond characteristics of SiC.
SURFACE & COATINGS TECHNOLOGY
(2021)
Article
Chemistry, Multidisciplinary
Wanlin He, Bo Zhao, Jianjun Yang, Junqing Wen, Hua Wu, Shaoli Guo, Lihua Bai
Summary: In this study, we demonstrate a new approach to control the formation of low spatial frequency surface structures on 4H-SiC crystal surface by using three temporally delayed femtosecond laser beams. By manipulating the time delay among the laser beams, we can flexibly switch between two types of surface structures. The experimental results are well explained by a physical model and provide a simple and controllable method for the large-scale assembly of complex functional nanostructures on semiconductor materials.
Article
Optics
Junqiang Guo, Mengmeng Wang, Qitong Guo, Tong Zhu, Mingchen DU, Pu Zhao, Lihui Feng
Summary: In this study, the researchers found that the plasma ejected during GaP crystal ablation changed from cylindrical to planar propagation with increasing laser fluence. The energy of propelling shockwaves accounted for 12% to 18% of the laser pulse energy at all fluences above the ablation threshold. A prominent plasma splitting was observed at a slightly higher fluence than the threshold, and the plasma protruded out of the shockwaves. The temperature difference between the plasma and the shockwave confirmed the heating effect of the plasma during ablation.
Article
Physics, Multidisciplinary
X. F. Shen, A. Pukhov, B. Qiao
Summary: This study proposes and demonstrates an all-optical single laser scheme to generate proton beams with low energy spread and high energy by irradiating the edge of a microtape with a femtosecond petawatt laser. This new approach opens up a promising route for the development of future compact ion sources.
Article
Materials Science, Multidisciplinary
Phuong Thi Nguyen, Jina Jang, Seok-Min Kim, Taeseung Hwang, Junyeob Yeo, Costas P. Grigoropoulos, Jung Bin In
Summary: In this study, laser-induced reshaping was utilized to create periodic silicon nanostructures with different geometries, and the effects of irradiation parameters on their reshaped morphology were systematically investigated. The reshaped PSNs exhibited tunable reflection spectra by varying the characteristics of the reshaping-laser input, offering a promising approach for site-selective fabrication of optically tunable 3D nanostructures.
CURRENT APPLIED PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Rodica Borcia, Ion Dan Borcia, Michael Bestehorn, Olga Varlarnova, Kevin Hoefner, Juergen Reif
Article
Physics, Condensed Matter
Olga Varlamova, Juergen Reif, Michael Stolz, Rodica Borcia, Ion Dan Borcia, Michael Bestehorn
EUROPEAN PHYSICAL JOURNAL B
(2019)
Article
Physics, Fluids & Plasmas
Sebastian Richter, Michael Bestehorn
PHYSICAL REVIEW FLUIDS
(2019)
Article
Mechanics
Peder A. Tyvand, Michael Bestehorn
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2020)
Article
Mechanics
Ion Dan Borcia, Rodica Borcia, Wenchao Xu, Michael Bestehorn, Sebastian Richter, Uwe Harlander
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2020)
Article
Multidisciplinary Sciences
Michael Bestehorn
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2020)
Article
Thermodynamics
Michael Bestehorn, Alejandro P. Riascos, Thomas M. Michelitsch, Bernard A. Collet
Summary: The study analyzed the dynamics of independent random walkers on a graph and developed a model of epidemic spreading. By implementing this model in computer simulations, researchers studied the space-time evolution of emerging infection patterns.
CONTINUUM MECHANICS AND THERMODYNAMICS
(2021)
Article
Mechanics
Peder A. Tyvand, Camilla Mulstad, Michael Bestehorn
Summary: The study investigates a nonlinear Cauchy-Poisson problem with impulsive surface forcing both theoretically and numerically. It explores the effects of different pressure impulses on the subsequent inviscid free-surface flow, finding that only relatively weak pressure impulses result in oscillatory waves while pressure impulses exceeding one gravitational unit lead to surface breaking before a full gravitational oscillation is completed.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Peder A. Tyvand, Camilla Mulstad, Michael Bestehorn
Summary: A fully nonlinear Cauchy-Poisson problem is investigated analytically by a small-time expansion technique. The problem involves an inviscid incompressible fluid layer with an initially horizontal surface, forced into motion by an impulsive surface pressure. A comparison is made between the Lagrangian solution to second order and other solution procedures for the same nonlinear problem. Good agreement is found between the Lagrangian and Eulerian solutions, which diverge abruptly at a certain point.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Andrey Pototsky, Alexander Oron, Michael Bestehorn
Summary: We find that a small floating liquid drop has two stable shapes under terrestrial gravity, both with different radii of the triple-phase contact line. Static stability analysis shows that both shapes could be stable if the drop volume is below a certain critical value. Experiments demonstrate the existence of multiple contact line radii for floating water drops on commercial oil.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Physics, Fluids & Plasmas
M. Bestehorn, D. Sharma, R. Borcia, S. Amiroudine
Summary: This paper investigates binary fluids using phase field modeling coupled with Navier-Stokes equations. The study shows the behavior of fluid pairs with different properties at different temperatures, and analyzes the changes in interface tension and width. The experiment results reveal that different stability modes and nonlinear flow patterns occur based on the consolute temperature and depth layer.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Physics, Fluids & Plasmas
Rodica Borcia, Ion Dan Borcia, Michael Bestehorn, Deewakar Sharma, Sakir Amiroudine
Summary: This study proposes an extended scheme based on the phase field model to investigate immiscible/miscible liquids. The research finds that the liquids are immiscible below the critical temperature and perfectly miscible above it. Numerical simulations reveal the behavior of liquid mixtures and droplets in temperature gradients.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Michael Bestehorn, Thomas M. Michelitsch, Bernard A. Collet, Alejandro P. Riascos, Andrzej F. Nowakowski
Summary: This study introduces a compartment model with memory to analyze the dynamics of epidemic spreading in a constant population. The model incorporates a random duration of immunity, which introduces a memory effect that significantly impacts the epidemic dynamics. Computer simulations are used to investigate the influence of this memory effect on the space-time dynamics of the spreading, identifying relevant parameters for the spread or extinction of an epidemic.
Article
Physics, Fluids & Plasmas
S. A. Piriz, A. R. Piriz, N. A. Tahir, S. Richter, M. Bestehorn
Summary: The linear evolution of the incompressible Rayleigh-Taylor instability for the interface between an elastic-plastic slab medium and a lighter semi-infinite ideal fluid beneath the slab is developed, providing stability maps in the space determined by initial perturbation amplitude and wavelength. A scaling law for minimum initial perturbation amplitude required for instability and corresponding perturbation wavelength is found, allowing for interpretation of recent experiments.