共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
X.J. Wu T.Q. Jia F.L. Zhao M. Huang N.S. Xu H. Kuroda Z.Z. Xu 《Applied Physics A: Materials Science & Processing》2007,86(4):491-495
Uniform arrays of periodic nanoparticles with 80-nm period are formed on 6H-SiC crystal irradiated by circularly polarized
400-nm femtosecond laser pulses. In order to understand the formation mechanism, the morphology evolvement as a function of
laser pulse energy and number is studied. Periodic nanoripples are also formed on the sample surface irradiated by linearly
polarized 400-, 510- and 800-nm femtosecond laser pulses. All these results support well the mechanism that second-harmonic
generation plays an important role in the formation of periodic nanostructures.
PACS 79.20.Ds; 42.62.Cf; 61.80.Ba; 81.05.Cy; 78.30.Am 相似文献
3.
Mengdi Qian Ye Dai Xiaona Yan Guohong Ma 《Applied Physics A: Materials Science & Processing》2014,114(4):1031-1037
We investigate the morphology change of Au film on sapphire substrate by irradiating with a 1 kHz femtosecond pulse laser. Under observation of a scanning electron microscope, a textured nanostructure was formed in the exposed area on Au film due to laser ablation and subsequent stress relaxation. This process was strongly determined by the laser intensity profile and the dynamics of molten liquid. With the increasing of laser pulses number, the Au film was broken down and then a few polarization-dependent nanoripples arranged in the same direction appeared on the sapphire surface, which may result from a spatial modulation of energy due to the interference between the incident light and the excited surface plasmon polaritons. In addition, we used an energy dispersive spectrometer to analyze the chemical composition of nanoripples on the surface and in the ablated crater, respectively. The changes of O and Al elements implied that a complicated chemical transformation participated in the nanoripples formation process. We believe that present results are very useful for the analysis of the interaction between femtosecond laser and solids, especially the film material. 相似文献
4.
Yuto?Tanaka Nikolay?N.?Nedyalkov Minoru?Obara 《Applied Physics A: Materials Science & Processing》2009,96(1):91-98
We present new results for laser excited semiconductor crystals probed by ultrashort x-ray pulses diffracted by the crystal
lattice. First we discuss acoustical phonons of semiconductors, i.e. indium antimonite and germanium, and then we describe
the temporal evolution of the laser-induced metal–semiconductor phase transition of samarium sulfide. 相似文献
5.
6.
Lingling Ran 《Applied Surface Science》2010,256(8):2315-5218
Laser-induced periodic surface structures with different spatial characteristics have been observed after multiple linearly polarized femtosecond laser pulse (120 fs, 800 nm, 1 Hz to 1 kHz pulse repetition frequency) irradiation on alloys. With the increasing number of pulses, nanoripples, classical ripples and modulation ripples with a period close to half of classical ripples have all been induced. The generation of second-harmonic has been supposed to be the main mechanism in the formation of modulation ripples. 相似文献
7.
Shazia Bashir M. Shahid Rafique Ali Ajami Wolfgang Husinsky Umm-i-Kalsoom 《Applied Physics A: Materials Science & Processing》2013,113(3):673-681
The present work deals with growth of nanoscale periodic and dot-like structures on the surface of stainless steel (SS) by the irradiation of femtosecond laser pulses. For this purpose Ti: Sapphire femtosecond laser pulses (wavelength of 800 nm, pulse length of 25 fs and pulse repetition rate of 1 kHz) were employed in a dry (air) and liquid confined (deionized water and ethanol) environments. The targets were exposed to 1000 succeeding pulses for various fluences ranging from 50 to 150 mJ?cm?2. Nanoscale structures including ripples, and dots were observed by SEM analysis. The growth and dependence of structure-formation on the ambient environment and laser fluence in both central as well as peripheral ablated areas is systematically investigated. The development of nanostructures and nanoripples is correlated with structural analysis carried out by micro Raman spectroscopy. 相似文献
8.
R. A. Ganeev D. Y. Lei C. Hutchison T. Witting F. Frank W. A. Okell T. R. Roschuk S. A. Maier J. W. G. Tisch J. P. Marangos 《Applied Physics A: Materials Science & Processing》2013,112(2):457-462
We report the study of extended nanoripple structures formed during the interaction of high-intensity 3.5 fs pulses with a moving silicon wafer. The optimization of laser intensity (8×1013 W?cm?2) and sample moving velocity (1 mm?s?1) allowed the formation of long strips (~5 mm) of homogeneous nanoripples along the whole area of laser ablation. The comparison of nanoripples produced on the silicon surfaces by few- and multi-cycle pulses is presented. We find that few-cycle pulses produce sharp and more homogenous structures than multi-cycle pulses. 相似文献
9.
Superhydrophobic surfaces fabricated by microstructuring of stainless steel using a femtosecond laser 总被引:1,自引:0,他引:1
Fabrication of superhydrophobic surfaces induced by femtosecond laser is a research hotspot of superhydrophobic surface studies nowadays. We present a simple and easily-controlled method for fabricating stainless steel-based superhydrophobic surfaces. The method consists of microstructuring stainless steel surfaces by irradiating samples with femtosecond laser pulses and silanizing the surfaces. By low laser fluence, we fabricated typical laser-induced periodic surface structures (LIPSS) on the submicron level. The apparent contact angle (CA) on the surface is 150.3°. With laser fluence increasing, we fabricated periodic ripples and periodic cone-shaped spikes on the micron scale, both covered with LIPSS. The stainless steel-based surfaces with micro- and submicron double-scale structure have higher apparent CAs. On the surface of double-scale structure, the maximal apparent CA is 166.3° and at the same time, the sliding angle (SA) is 4.2°. 相似文献
10.
从理论和实验上研究了利用光注入半导体激光器对高重复速率光脉冲产生的周期振荡和时钟分频现象.结果表明,光注入半导体激光器引起的二倍周期振荡是使注入脉冲重复频率分频的直接原因.通过耦合速率方程,数值模拟了半导体激光器在外光注入时输出光的时间序列和功率谱,并且分析了激光腔内各种周期振荡的特征.研究表明,当注入光使半导体激光器出现稳定的二倍周期振荡,且注入光的重复频率为此振荡频率的二倍时,时钟分频即可产生实验中,采用重复频率为6.32GHz的光脉冲注入Fabry-Perot激光器,实现了3.16GHz时钟分频信号
关键词:
周期振荡
时钟分频
光谱侧带
光注入 相似文献
11.
Stoian R Rosenfeld A Ashkenasi D Hertel IV Bulgakova NM Campbell EE 《Physical review letters》2002,88(9):097603
We report time-resolved studies using femtosecond laser pulses, accompanied by model calculations, that illuminate the difference in the dynamics of ultrashort pulsed laser ablation of different materials. Dielectrics are strongly charged at the surface on the femtosecond time scale and undergo an impulsive Coulomb explosion. This is not seen from metals and semiconductors where the surface charge is effectively quenched. 相似文献
12.
We present periodic ripples and arrays of protrusions formed on the surface of silicon after irradiation by low-fluence linearly polarized femtosecond laser pulses. Laser-induced periodic surface structures (LIPSS) are observed for irradiation at center wavelengths of 800, ∼ 1300, and ∼ 2100 nm, with the structure periods somewhat less than the incident wavelengths in air. Additionally, we observe structures with spatial periods substantially less than the incident laser wavelengths. These sub-wavelength periodic structures form only when the photon energy is less than the silicon bandgap energy. We discuss a number of factors which may contribute to the generation of this surface morphology. 相似文献
13.
14.
In this work, we studied a method of laser-induced coloration of metals, where small-scale spatially periodic structures play a key role in the process of color formation. The formation of such structures on a surface of AISI 304 stainless steel was demonstrated for the 1.06 µm fiber laser with nanosecond duration of pulses and random (elliptical) polarization. The color of the surface depends on the period, height and orientation of periodic surface structures. Adjustment of the polarization of the laser radiation or change of laser incidence angle can be used to control the orientation of the structures. The formation of markings that change their color under the different viewing angles becomes possible. The potential application of the method is metal product protection against falsification. 相似文献
15.
利用波长为800 nm的飞秒激光,在空气和去离子水中诱导钛表面形成不同的周期条纹结构。在空气中,激光能量密度为0.265 J/cm2时,钛表面主要形成周期为500~560 nm低空间频率条纹结构;激光能量密度为0.102 J/cm2时,主要形成的是周期为220~340 nm高空间频率条纹结构。两种条纹均垂直于入射激光偏振方向,且条纹周期随着脉冲重叠数的增大而增大。在水中,除形成垂直激光偏振方向、周期为215~250 nm的高空间频率条纹结构,还形成了平行于激光偏振方向且周期约为入射激光波长八分之一的高空间频率条纹结构。利用表面等离子体理论、二次谐波及Sipe理论对各种周期条纹结构的形成机理进行分析,发现周期条纹结构的形成与钛表面氧化层有密切的关系。 相似文献
16.
A theory of defect-strain instability with formation of periodic surface relief in semiconductors irradiated by ultra-short
(τp=10-13 s) powerful laser pulses is developed. The period and time of formation of surface relief are calculated. Regimes of multi-pulse
laser ablation leading to formation of either a smooth surface or arrays of surface-relief spikes are pointed out and corresponding
experimental results are interpreted from the viewpoint of the developed theory.
Received: 4 December 2000 / Accepted: 23 July 2001 / Published online: 11 February 2002 相似文献
17.
We experimentally study the influence of the laser-induced drift (LID) of dopant electrons and atoms on the optical properties
of semiconductors. It is shown that the LID of electrons results in a dramatic change in the refractive index in the region
of laser-radiation output from semiconductor crystals, impairement of the total internal reflection in semiconductors, and
the occurrence of astigmatism during self-defocusing of the laser radiation in anisotropic semiconductors. This effect influences
the breaking of semiconductors by nanosecond and picosecond laser pulses. The LID of dopant atoms, caused by the electrostatic
interaction between the ions of these atoms and the space charge of drifting electrons, changes differently the luminescence
spectra on the input and output surfaces of crystals and also results in the appearance of a dark spot on the output surface
of some ZnSe crystals after irradiation by a continuous-wave CO2 laser.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 8, pp. 674–683, August 2005. 相似文献
18.
Mark Frogley Gianfelice Cinque James Dynes Mattias Beck Jrme Faist Chris Phillips 《Infrared Physics & Technology》2008,51(5):454-457
Time-resolved IR spectroscopy is a powerful non-destructive technique for probing electron dynamics and plasmonics in semiconductors. We present recent experiments in which intense IR laser pulses are used to induce “quantum-optical” phenomena, including gain without population inversion and slow light, in semiconductor nanostructures. The potential advantages of IR Synchrotron radiation to probe these systems are discussed. 相似文献
19.
M. B. Agranat S. I. Ashitkov V. E. Fortov S. I. Anisimov A. M. Dykhne P. S. Kondratenko 《Journal of Experimental and Theoretical Physics》1999,88(2):370-376
The formation of periodic surface structures by ultrashort laser pulses was observed experimentally and explained theoretically.
The experiments were performed on graphite with picosecond laser pulses. The spatial period of the structures is of the order
of the wavelength of the incident radiation, and the orientation of the structures is correlated with the direction of polarization
of the light. The key point of the theoretical model proposed is resonance excitation of surface electromagnetic waves, which
under conditions such that the temperature of the electronic subsystem is decoupled from the temperature of the crystal lattice
causes a “temperature grating” to be written on the flat solid surface of the sample while the laser pulse is being applied
on account of the temperature dependence of the surface impedance. The formation of a periodic surface profile from the temperature
grating occurs by the volume expansion of a melted layer near the surface of the material. For typical values of the surface
tension and viscosity for metals, there is not enough time for the periodic profile to be resorbed before the liquid layer
solidifies. The formation of periodic surface structures is delayed in time relative to the laser pulse.
Zh. éksp. Teor. Fiz. 115, 675–688 (February 1999) 相似文献
20.
Haifeng Yang Haidong He Enlan Zhao Jiguo Qian Jingbin Hao Wei Tang Hua Zhu 《Journal of Russian Laser Research》2013,34(4):362-368
We report on the fabrication of surface nanoparticles and micro/nanograting structures on bulk pure aluminum in air using a 150 fs, 775 nm femtosecond laser. We investigate the size of the generated surface nanoparticles under irradiation with different femtosecond laser pulses. Smaller nanoparticles can be induced by a larger number of laser pulses and a lower laser fluence. In addition, we observe the formation of micro/nanogratings when the laser focus is scanned across a pure aluminum surface in air. We obtain micro- and nano-grating composite structures on a pure aluminum surface by adjusting the laser fluence and scan velocity. Femtosecond laser surface ablation of bulk pure aluminum in air is potentially a promising technique for efficient fabrication of surface nanostructures. 相似文献