共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Baudach J. Bonse W. Kautek 《Applied Physics A: Materials Science & Processing》1999,69(7):S395-S398
Some applications of polymer films require the microstructuring of partly uneven substrates. This cannot be achieved by conventional photolithography, usually performed with ultraviolet short-pulse lasers (excimer, fourth harmonic Nd:YAG). When processing thermally sensitive or undoped polymers with low optical absorption, the use of femtosecond laser pulses can improve the ablation precision, also reducing the heat-affected zone. Therefore, a Ti:sapphire laser system was employed to perform ablation experiments on polyimide (PI). The irradiated areas were evaluated by means of optical and scanning electron microscopy. Highly oriented ripple structures, which are related to the polarization state of the laser pulses, were observed in the cavities. The relationship between the ablation threshold fluence and the number of laser pulses applied to the same spot is described in accordance with an incubation model. 相似文献
2.
J. J. J. Kaakkunen J. Bekesi J. Ihlemann P. Simon 《Applied Physics A: Materials Science & Processing》2010,101(2):225-229
A new method for simple and economic fabrication of diffractive optical elements (DOEs) with three and four phase levels, by UV nanosecond (ns) laser ablation is presented. The technique is based on the combination of two sequentially generated complementary 2-level phase elements. During the fabrication, complete ablative removal of a highly absorbing silicon suboxide layer by pixelated backside illumination ensures the necessary high precision and optical quality. Full functionality of the new DOEs is demonstrated by fabricating micro-structures using UV femtosecond pulses. 相似文献
3.
N. Bärsch K. Körber A. Ostendorf K.H. Tönshoff 《Applied Physics A: Materials Science & Processing》2003,77(2):237-242
Although lasers are generally able to machine silicon, the major material in many microsystems applications, doing so without
influencing the physical properties of the bulk material remains an important challenge. Ultrafast lasers, in particular,
with their potential to precisely ablate all kinds of solid materials, are able to perform such processes with high efficiency
and accuracy. This article starts with an overview of the general interaction of ultrafast laser radiation with semiconductors,
explaining the absorption processes and different fluence regimes for the ablation of silicon. Major parameter influences,
especially for cutting processes in thin silicon, are described. By varying pulse energies, beam shaping methods, the beam
polarization, and temperatures, the cutting quality and speed can be significantly influenced. One important quality aspect,
besides kerf widths and surface roughness, is the amount of back-side chipping when cutting brittle materials. Achievements
in speed enhancement using linear focus shapes are presented, with cutting speeds up to five times higher than by conventional
spot-focusing. On the other hand, laser processes that cut with a spot focus offer the possibility of free-shape cutting,
which is explained using the example of wafers carrying silicon chips with highly increased package densities.
Received: 10 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-511/2788-100, E-mail: nb@lzh.de 相似文献
4.
The Talbot effect under illumination of double femtosecond laser pulses has been reported. Spectrums of double femtosecond laser pulses with phase differences are quite different from that of one single femtosecond laser pulse. Therefore, the Talbot images of the double femtosecond laser pulses with phase differences are different from that of one single femtosecond laser pulse. Specifically, for the phase difference corresponding to π, the Talbot image shows the largest difference from that of one single pulse. Experimental results are in good agreement with the theoretical analysis. The behaviors of Talbot images under double femtosecond laser pulses illumination cannot be obtained under one femtosecond laser pulse, monochromatic or polychromatic light illumination. Therefore, it is a new interesting optical phenomenon for the Talbot effect which should have potential applications. 相似文献
5.
E. Yu. Perlin K. A. Eliseev E. G. Idrisov Ya. T. Khalilov 《Optics and Spectroscopy》2012,112(6):850-856
A theory of nonlinear absorption of femtosecond light pulses by bulk crystals and nanostructures of differing dimensionality is developed. The pulse width is assumed to be small compared to the relaxation times of the electron and hole momenta. Expressions for the absorbed energy under conditions of multiphoton resonance are derived for transitions between discrete or band-related electron states and between sub-band states of size quantization in quantum wells and quantum wires. The dependence of the absorbed energy on the multiphoton resonance detuning and pulse width is analyzed. 相似文献
6.
A. V. Kuznetsov A. S. Kuzakov E. F. Martynovich 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(1):64-67
The formation of fluorescent channels with color centers in LiF crystals under the action of the multiple filamentation of femtosecond laser pulses is studied experimentally and theoretically for pulse powers around four orders of magnitude higher than the critical self-focusing value. 相似文献
7.
Xiaofeng Wang Tianqing Jia Xiaoxi Li Chengbin Li Donghai Feng Haiyi Sun Shizhen Xu Zhizhan Xu 《中国光学快报(英文版)》2005,3(10)
The ablation in zinc selenide (ZnSe) crystal is studied by using 150-fs, 800-nm laser system. The images of the ablation pit measured by scanning electronic microscope (SEM) show no thermal stress and melting dynamics. The threshold fluence is measured to be 0.7 J/cm2. The ultrafast ablation dynamics is studied by using pump and probe method. The result suggests that optical breakdown and ultrafast melting take place in ZnSe irradiated under femtosecond laser pulses. 相似文献
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9.
Korte F. Serbin J. Koch J. Egbert A. Fallnich C. Ostendorf A. Chichkov B.N. 《Applied Physics A: Materials Science & Processing》2003,77(2):229-235
Detailed investigations of the possibilities for using femtosecond lasers for the nanostructuring of metal layers and transparent
materials are reported. The aim is to develop a simple laser-based technology for fabricating two- and three-dimensional nanostructures
with structure sizes on the order of several hundred nanometers. This is required for many applications in photonics, for
the fabrication of photonic crystals and microoptical devices, for data storage, displays, etc. Measurements of thermionic
electron emission from metal targets, which provide valuable information on the dynamics of femtosecond laser ablation, are
discussed. Sub-wavelength microstructuring of metals is performed and the minimum structure size that can be fabricated in
transparent materials is identified. Two-photon polymerization of hybrid polymers is demonstrated as a promising femtosecond
laser-based nanofabrication technology.
Received: 20 November 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-511/2788-100, E-mail: ch@lzh.de 相似文献
10.
L. D. Pietanza G. Colonna S. Longo M. Capitelli 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):369-389
Different models for relaxation dynamics of electrons and phonons in a thin
metal film heated by femto-pico second laser pulses have been discussed. The
traditional two-temperature approach reveals to be inaccurate due to
deviations of electrons and phonons from Fermi-Dirac and Bose-Einstein
distributions, respectively. Coupled Boltzmann kinetic equations have been
adapted for the quantum statistics to study the energy distribution of
electrons and phonons in metals. Theoretical details have been discussed and
a new solution method has been proposed overcoming numerical problems and
improving stability, allowing the study of the dynamics until the complete
relaxation. Numerical results have been compared with photoemission
spectroscopy experimental data. 相似文献
11.
Received: 17 December 1998 相似文献
12.
Using molecular-dynamics, we study the thermodynamic evolution of a simple two-dimensional Lennard–Jones system during laser ablation for pulse durations ranging from 200 fs to 400 ps. We briefly review results previously obtained for fs pulses where the evolution of the material was shown to be solely a function of the locally absorbed energy (provided that only thermal effects are important), i.e., is adiabatic. For longer pulses (100 and 400 ps) the situation becomes more complex, as the relaxation path also depends on the position in the target and on the timescale on which expansion occurs. We show that, in contrast to fs pulses, the material ejected following ps laser irradiation does not enter the liquid–vapor metastable region before ablation occurs, hence showing that phase explosion is not the dominant mechanism in this regime. Following on from previous work, we propose that trivial fragmentation is the main ablation mechanism. PACS 79.20.Ds; 79.20.Ap; 61.80.Az 相似文献
13.
Spatially localized femtosecond pulses have been produced by a combination of scanning near-field optical microscopy with ultrashort pulse lasers. With these pulses direct ablative writing on metal surfaces is demonstrated. Possible applications of this technique for nanostructuring, repair, and production of lithographic masks are discussed. 相似文献
14.
An inherent property of the ultrashort pulse lasers used presently for materials processing is that the main pulse is accompanied by an amplified spontaneous emission background. The temporal quality of the pulses is characterized by the temporal contrast. Due to the 5-6 orders of magnitude difference in the duration of the main pulse and the pedestal, high intensity contrast does not mean necessarily high enough difference in the respective energies. In materials processing applications consideration of the energy contrast is advisable. The importance of the contrast in determining the ablation process is exemplified by the dependence of the ablation rate of boron carbide on the cleanness of the pulses of a high brightness hybrid dye/excimer laser system. It is shown that serious consideration of the effects of the nanosecond background is mandatory when evaluating the results. 相似文献
15.
The physical process of forming a modified region in soda-lime glass was investigated using 1 kHz intense femtosecond laser pulses from a Ti: sapphire laser at 775 nm. Through the modifications induced by the femtosecond laser radiation using selective chemical etching techniques, we fabricated reproducible and defined microstructures and further studied their morphologies and etching properties. Moreover, a possible physical mechanism for the femtosecond laser modification in soda-lime glass was proposed. 相似文献
16.
实验通过二极管记录透射光信号随脉冲个数变化关系以及观测样品烧蚀形貌来研究不同实验条件对激光烧蚀的影响。使用的样品是厚度为50 m铝箔。实验中通过研究不同变量:激光焦点与样品的相对位置、激光的能量、背景气体压强以及脉冲形状对烧蚀加工过程和结果的影响,从而获得较好烧蚀效果的条件,达到控制烧蚀加工过程的目的。特别是通过使用不同形状的脉冲和具有一定规律的脉冲序列对样品进行烧蚀,发现某些形状的整形脉冲烧蚀结果明显优于变换极限脉冲。说明脉冲整形作为一种新的技术可以在激光精细钻孔领域得到更深入的研究和应用。 相似文献
17.
David J. Hwang Kuniaki Hiromatsu Hirofumi Hidai Costas P. Grigoropoulos 《Applied Physics A: Materials Science & Processing》2009,94(3):555-558
Straight through-holes of high aspect ratio have been fabricated in glass by femtosecond laser pulses, utilizing unique characteristics
of ultrafast lasers such as volumetric multi-photon absorption and nonlinear self-focusing. In this study, interestingly,
the drilling process was initiated and progressed in a self-regulated manner, while the laser focus was fixed through the
specimen at the neighborhood of the rear surface that was in contact with liquid during the entire drilling process. The deposition
of laser energy along the nonlinearly extended focal range and the guided drilling along the pre-defined region are explained
based on time-resolved optical transmission and emission measurements. 相似文献
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Ultrafast temperature relaxation processes in Au film including two temperature relaxation and thermal diffusion relaxation with femtosecond laser pulse excitation were investigated numerically by Finite Element Method (FEM). With the temperature dependent thermal parameters, the full 2D temperature field evolution in picosecond and nanosecond domains were obtained. It is proposed that the heat transfer depth can be alternatively localized or enhanced by the distinct temperature relaxation mechanisms. Moreover, the effect of laser parameters and Au film thickness and surface reflectivity on the two temperature relaxation time were analysed. 相似文献