共查询到20条相似文献,搜索用时 15 毫秒
1.
Yoshiki Nakata Yoshiki Matsuba Keiichi Murakawa Noriaki Miyanaga 《Applied Physics A: Materials Science & Processing》2014,117(1):207-210
Interference pattern of two different wavelengths, forming a four-sided pyramid consisting of eight beams, is discussed. Synchronization between two wavelengths having a multiple relationship, which corresponds to mixing of fundamental and second-harmonic generation wavelengths, forms a stationary interference pattern successfully. Phase shift variation of a beam changes the basic pattern of interference. This technique can be a new scheme for multi-wavelength material processing with periodic structure and will increase the variation of meta-atoms fabricated by interfering femtosecond laser processing. 相似文献
2.
We report on a simple method to obtain surface gratings using a Michelson interferometer and femtosecond laser radiation. In the optical setup used, two parallel laser beams are generated using a beam splitter and then focused using the same focusing lens. An interference pattern is created in the focal plane of the focusing lens, which can be used to pattern the surface of materials. The main advantage of this method is that the optical paths difference of the interfering beams is independent of the distance between the beams. As a result, the fringes period can be varied without a need for major realignment of the optical system and the time coincidence between the interfering beams can be easily monitored. The potential of the method was demonstrated by patterning surface gratings with different periods on titanium surfaces in air. 相似文献
3.
The thin bimetallic film systems Fe–Al, Fe–Ni, Ti–Al, and Ti–Ni were irradiated using a laser interference pattern with laser fluence values from 50 to 250 mJ/cm2. The thermal simulation was carried out to analyze the topographical effects. It was found that according to the laser fluence value, three different types of topographies can be obtained. For lower laser fluence values, the molten material in the lower layer induces deformation over the upper one obtaining a periodic pattern with a structure depth in the order of the layer thickness. If the laser fluence is high enough so that the upper layer reaches the melting point, this last is broken obtaining a high structured pattern consisting on a large depression and next two consecutive peaks. This threshold value can be estimated using the thermal simulation calculating the laser fluence at which the upper layer starts to melt. For higher laser fluence values, this pattern transforms into a periodical peak–valley structure with high structure depth. In both last two cases, the material at the interference peaks is removed. A model is suggested for explaining this behavior. 相似文献
4.
L. A. Ageev K. S. Beloshenko E. D. Makovetskiĭ V. K. Miloslavskiĭ 《Optics and Spectroscopy》2008,105(1):134-140
Instabilities in the operation of a two-mode He-Ne laser are observed with the help of interference of polarized beams. Two interference patterns created by two radiation modes alternatively appear. The contrast of the interference pattern increases under the action of an external constant magnetic field on the laser. If one of the interfering beams is delayed sufficiently long, the instability manifests itself in the motion of interference fringes in a direction that depends on which of the two beams is delayed. The particular features of the evolution of the interference pattern are explained based on interference equations for the two modes that take into account the orthogonality of the linear polarizations of the modes, as well as changes in their amplitudes and frequencies. 相似文献
5.
《Optics Communications》2002,201(1-3):21-28
Optically trapped objects are rotated controllably in the interference pattern between a Laguerre–Gaussian (LG) beam and a Gaussian beam. In this work the interference pattern is analysed and its properties as it propagates are modelled, showing the important role played by the Guoy-phase of the two interfering beams. An analysis of producing controlled rotation of the interference pattern using a glass plate is presented demonstrating the ease with which the rotation can be controlled. 相似文献
6.
Attila Tóth Sándor Borbély Károly Tőkési Ladislau Nagy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(11):1-5
We have investigated the ionization of the H atom by intense few-cycle laser pulses, in particular the intra-pulse interference effects, and their dependence on the carrier-envelope phase (CEP) of the laser pulse. In the final momentum distribution of the continuum electrons the imprint of two types of intra-pulse interference effects can be observed, namely the temporal and spatial interference. During the spatial interference electronic wave packets emitted at the same time, but following different paths interfere leading to an interference pattern measurable in the electron spectra. This can be also interpreted as the interference between a direct and a scattered wave, and the spatial interference pattern as the holographic mapping (HM) of the target. This HM pattern is strongly influenced by the carrier-envelope phase through the shape of the laser pulse. Here, we have studied how the shape of the HM pattern is modified by the CEP, and we have found an optimal CEP for the observation of HM. 相似文献
7.
S. Liu I. Sherstov C. Lisdat H. Kn?ckel E. Tiemann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(3):369-377
A matter wave interferometer based on a molecular beam of K2 has been designed for observation of both exits: with molecules in the electronically excited state and in the ground state. In addition to the excited state fluorescence the molecular ground state population is detected with a further laser. Two transitions to different electronic states were employed for this purpose and their usefulness is compared. Under the present experimental conditions both interferometer exits show a superposition of different interference patterns due to the influence of transverse and longitudinal overlaps of the interfering matter waves. The interference patterns have been analyzed to be composed of a contribution caused by a two beam splitter Ramsey interference and Ramsey-Bordé pattern with four beam splitters. This overlap of interference signals influences the suitability of the matter wave interferometer for phase measurements of the interferences. 相似文献
8.
Acoustic microscopes can be used to measure Rayleigh and longitudinal or P-wave speeds in a specimen at microscopic resolution. The wave speeds are obtained from the interference pattern as a function of the defocus distance or V(z) curve. The received signal voltage amplitude Vis generated by two beams--the normally reflected central beam and a non-specularly reflected beam that strikes the fluid-solid interface at critical angle. It is shown in this paper that instead of analyzing the interference pattern between these two beams if we consider two other beams that follow the same path but travel through the coupling fluid multiple times before interfering then the V(z) curve generated by this higher order interference gives more accurate values for the material properties. The spacing distance between two successive dips of the V(z) curve is smaller for the higher order interference. The higher order interference, although weaker, gives more accurate results. Justification for the greater accuracy of the higher order interference is given in the paper. Material properties of silicon and bone are obtained by the new technique. Bones are microscopically heterogeneous and anisotropic. Anisotropic properties of homogeneous specimens can be obtained by the line focus acoustic microscope; however, it does not work when the specimen is microscopically heterogeneous. An attempt has been made here to obtain anisotropic properties of bones using point focus lens. 相似文献
9.
为了提高瞬态高温检测的精度,利用快速傅里叶变换(FFT)对散斑干涉条纹进行光谱分析,提出了通过光谱分布的偏移及幅值变化反演温度的方法。当激光照射应变材料时,瞬态高温使材料发生形变从而使散斑干涉条纹改变,被测表面形变前后获得的干涉条纹由面阵CCD采集。由于其对应的光谱密度分布函数也会发生相应的改变,即中心波长位置偏移及振幅变化,通过其改变反演材料的瞬态温度。在分析推导了瞬态温度变化、材料应变及干涉条纹变化之间的函数关系后,仿真分析得到了瞬态温度正比于压强系数、反比于温度系数。实验采用660 nm半导体激光器,SI6600型面阵CCD探测器,从获得的光谱分布函数中提取中心波长的偏移量,经计算和标定所得数据与传统的干涉测温方法进行对比,探测精度可达0.3%。相比传统的直接检测干涉条纹的变化量,由被测面形变量推导温度的方法精度提高近3倍。 相似文献
10.
Inspired by results of interfering signal and idler from a nondegenerate parametric amplifier we investigate the photon statistics of the resulting field after interference of two components subjected to double-mode two-photon absorption. This absorption process leads to a strong correlation of the participating modes, which can be used to generate fields with photon antibunching in interference experiments. In addition the photon number can be made small, which produces enhanced antibunching. 相似文献
11.
Yoshiki Nakata Noriaki Miyanaga 《Applied Physics A: Materials Science & Processing》2010,98(2):401-405
Combined structures composed of a micron-sized periodic structure and a nano-sized quasi-periodic ripple structure were generated
by a single process of multiple shots of an interfering femtosecond laser. The former structure was generated by an interference
pattern and controlled by a number of beams. The latter structure was generated by a multiple shot method. As a result, multiple
periodic structures were generated. The periodicity of the structures was analyzed by two-dimensional (2D) fast Fourier transform
(FFT). The most probable period of ripple structure was downsized to 177 nm by restricting irradiated region by a TM wave
interference pattern. The smallest period was 105 nm. The dispersion angle of a ripple decreased to about 50%. The period
and direction of the ripples were for a first time controlled by using interference. 相似文献
12.
In this paper, the contrast enhancement produced by the subtraction of two sets of double pulse electronic speckle pattern interferometry (ESPI) addition fringes is investigated. It is shown that in most practical cases this process will produce a second set of interference fringes in addition to those which can be directly related to the vibration mode of interest. The formation of this second fringe pattern is explained by theory and computer simulation. Finally, the results are verified using an ESPI system with a pulsed Nd: YAG laser. 相似文献
13.
Photodetachment microscopy of a hydrogen negative ion in an electric field near a metal surface 下载免费PDF全文
According to the semi-classical theory, we study the photodetachment microscopy of H- in the electric field near a metal surface. During the photodetachment, the electron is photo-detached by a laser and the electron is drawn toward a position-sensitive detector. The electron flux distribution is measured as a function of position. Two classical paths lead the ion to any point in the classically allowed region on the detector, and waves traveling along these paths produce an interference pattern. If the metal surface perpendicular to the electric field is added, we find that the interference pattern is related not only to the electron energy and the electric-field strength, but also to the ion-surface distance. In addition, the laser polarization also has a great influence on the electron flux distribution. We present calculations predicting the interference pattern that may be seen in experiment. We hope that our study can provide a new understanding of the electron flux distribution of negative ions in an external field and surface, and can guide future experimental research on negative ion photo-detachment microscopy. 相似文献
14.
We propose a scheme to achieve super-resolution of interference pattern with independent laser beams. We perform an experimental observation of a double-slit interference with two orthogonally polarized laser beams. The resolution of the interference pattern measured by a two-photon detection is doubled provided the two beams illuminate the double-slit with certain incident angles. The scheme is simple and can favour both high intensity and perfect visibility. 相似文献
15.
Nataraja Sekhar Yadavalli Marina Saphiannikova Nino Lomadze Leonid M. Goldenberg Svetlana Santer 《Applied Physics A: Materials Science & Processing》2013,113(2):263-272
In this paper, we report on in-situ atomic force microscopy (AFM) studies of topographical changes in azobenzene-containing photosensitive polymer films that are irradiated with light interference patterns. We have developed an experimental setup consisting of an AFM combined with two-beam interferometry that permits us to switch between different polarization states of the two interfering beams while scanning the illuminated area of the polymer film, acquiring corresponding changes in topography in-situ. This way, we are able to analyze how the change in topography is related to the variation of the electrical field vector within the interference pattern. It is for the first time that with a rather simple experimental approach a rigorous assignment can be achieved. By performing in-situ measurements we found that for a certain polarization combination of two interfering beams [namely for the SP (?, ?) polarization pattern] the topography forms surface relief grating with only half the period of the interference patterns. Exploiting this phenomenon we are able to fabricate surface relief structures with characteristic features measuring only 140 nm, by using far field optics with a wavelength of 491 nm. We believe that this relatively simple method could be extremely valuable to, for instance, produce structural features below the diffraction limit at high-throughput, and this could significantly contribute to the search of new fabrication strategies in electronics and photonics industry. 相似文献
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We discuss a recent experiment with interfering neutron beams in the gravitational field of the earth, and show how the explanation of the interference pattern can be obtained by an application of the equivalence principle to the one-particle states. The calculation is carried out in the coordinate system where the gravitational field has been transformed away. 相似文献
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