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1.
Focused proton beam writing has been utilized to fabricate optical channel waveguides in Nd:GGG crystals. The 1?MeV proton beam irradiation creates a local modified region with positive refractive index changes at the end of the proton trajectory, in which the channel waveguide could confine the light field in a symmetric way. Room-temperature laser emission has been achieved at 1063.7?nm, with absorbed pump power of 61?mW (at 808?nm). The obtained slope efficiency of the Nd:GGG waveguide laser system is as high as 66%, which is, to our best knowledge, the highest value for integrated lasers from ion beam processed channel waveguide systems. 相似文献
2.
《中国光学快报(英文版)》2016,(3)
Diffractive optics is an important technique for beam shaping with high light efficiency and strong diffraction pattern flexibility. Since the diffraction angle is limited by the unit size of the diffractive optical element(DOE),the size of the required diffraction pattern is always rather small. In this Letter, refractive/diffractive hybrid optical elements(RDHOEs) consisting of a DOE and a lens are used to realize beam shaping for a large diffraction pattern. The lens, as the component of the RDHOEs, can not only be concave but also convex,and the double sampling Fresnel diffraction algorithm is developed for the design of these two types of RDHOEs.The simulation and experimental results provide solid evidence to demonstrate the proposed method with the pure phase spatial light modulator. 相似文献
3.
S. N. Vlasov M. A. Shapiro E. V. Sheinina 《Radiophysics and Quantum Electronics》1988,31(12):1070-1075
Institute of Applied Physics, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 31, No. 12, pp. 1482–1487, December, 1988. 相似文献
4.
A.Y. Vorobyev V.M. Kuzmichev N.G. Kokody P. Kohns J. Dai Chunlei Guo 《Applied Physics A: Materials Science & Processing》2006,82(2):357-362
A comparative study of residual thermal effects in aluminum following ns- and fs-laser ablation shows a surprisingly similar
trend in their behavior, despite many differences between ns and fs laser-matter interactions. At laser fluences above the
ablation threshold where plasmas are produced and at a sufficiently high ambient gas pressure, an enhanced coupling of pulsed
laser energy to the sample occurs. This effect appears to be a universal phenomenon for both ns- and fs-laser ablation in
gas media. Furthermore, in contrast to the common belief that residual thermal energy is negligible in fs-laser ablation,
our study shows that up to 70% of the incident pulse energy can be retained in the sample following single-pulse fs-laserablation
in 1-atm air. In both ns- and fs-laser ablation, the major factors governing thermal energy coupling to the sample are the
laser fluence and ambient gas pressure. Residual thermal energy deposition decreases with reducing ambient gas pressure.
PACS 78.20; 81.05.Bx 相似文献
5.
Complex-wave diffraction by the joints of circular two-layer uniformly filled waveguides is examined.Nizhny Novgorod State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 4, pp. 458–470, April, 1994. 相似文献
6.
The central spot of COS beam (CS-COS) can be obtained from COS beam by using the zero field truncation technique. The transversal intensity distributions of CS-COS through three different kinds of aperture functions are simulated numerically from the near field to the far field. It is shown that the CS-COS has the property of eliminating the diffraction fringes in the whole propagation process if a suitable aperture is introduced. 相似文献
7.
Beam parameters including mode-field half-width, divergence half-angle and beam propagation factor are investigated and their relations are derived. Moreover, the beam parameters of end diffraction-limited beam from TE0 propagating mode are given and influence of change of the near-field distribution on them is researched too. 相似文献
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9.
The multi-layers coupled-wave theory is extended to systematically investigate the pulse shaping and diffraction properties
of a system of multi-layers reflection volume holographic gratings (MRVHG) under ultrashort laser pulse (ULP) readout. The
combined effects that the grating parameters such as the number and thickness of layers and gaps between them and the pulse
duration of the input ULP have on the pulse shaping properties are considered. The pulse profiles of the diffracted and transmitted
beams, the diffraction bandwidth, and the total diffraction efficiency are presented. The calculated results we have derived
permit an optimal choice of grating parameters for the pulse shaping and process applications. 相似文献
10.
LD激光束准直整形模块的研制 总被引:1,自引:0,他引:1
SDL-5400型号GaAlAs LD激光器产生的是单模高斯光束,在相互垂直方向上光束发散角不相等,且存在像散。为得到共腰的圆形光斑,由复参数q和ABCD定律,设计出两相互垂直的柱面透镜和棱镜对准直整形模块,通过CCD标定方法,得到经准直整形后的LD激光束在弧矢方向上的远场发散角为0.53mrad,子午方向为0.64mrad。 相似文献
11.
对Airy光束的特性做进一步探讨, 一方面对无限宽Airy光束的重心问题给出新的理论说明, 另一方面着重对有限宽情形下的Airy光束的奇特性质进行探讨. 文中采用反证法给出无衍射的讨论, 同时结合数值模拟给出高斯函数及矩形函数限定下的有限宽Airy光束的场分布, 并由此得到其重心位置的轨迹: 重心位置是不变的, 不可能整体自由加速. 最终得到有限宽Airy光束既不可能在自由空间加速, 也不可能是无衍射光束.
关键词:
Airy光束
无衍射
自加速
数值模拟 相似文献
12.
The problem of the guided mode reflection from the planar dielectric waveguide end is studied by the finite difference time domain method. The influence of facet deformations on the scattering characteristics is considered. The reflectivity problem for the system with the nonlinear dielectric waveguide insert is examined. 相似文献
13.
Electromagnetic-wave excitation by a vertical electric dipole located inside a flat waveguide containing a vertical circular metal cylinder is examined. An exact solution is obtained, and the diffracted field inside the waveguide is analyzed. Algorithms are provided for electromagnetic-field calculation in a Rayleigh approximation and in a short-wave approximation. Results of numerical calculations of fields and directivity characteristics are presented. The effect of the cylinder on the radiation power of the dipole in the waveguide is analyzed.Nizhny Novgorod State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 11, pp. 965–976, November, 1993. 相似文献
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Optical heterodyne interfering is used to measure the Doppler shift of diffraction beam of moving plane grating. By introducing Doppler shift in reference beam and contrasting the final beat frequency, the Doppler shift is measured to be normal when incident light and diffraction light are in the same side of the normal of periodic plane grating, which shows that abnormal Doppler shift can not occur on the material with “negative refraction phenomenon” caused by periodicity. Periodic two-dimensional photonic crystal with the property of abnormal Doppler shift has equivalent negative refractive index, and the abnormal properties of left-handed materials are not only caused by periodicity. 相似文献
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17.
Propagation of a Gaussian beam in an absorbing waveguide is analyzed for cubic-quintic and saturable media taking into account both linear and nonlinear absorption. A “collective variable approach” technique, based on trial functions, is used to solve the general nonlinear Schrodinger equation. In the absence of losses, we construct a diagram which defines regions of oscillatory and diffractive beam propagation for both types of media, and also a diagram that compares bistable behavior in such media. We show that if the linear and nonlinear absorption coefficients are small, the behavior of the oscillations of the beam width on propagation allows one to distinguish between cubic-quintic and saturable media. By reversing the sign of the linear absorption, we analyze the behavior of the beam propagation in media with gain and nonlinear absorption. In cubic-quintic media, the energy reaches a plateau for certain ratios of gain to losses, whereas for saturable media, the energy increases throughout the beam propagation. 相似文献
18.
The production of high aspect ratio microstructures is a potential growth area. The combination of deep X-ray lithography with electroforming and micromolding (i.e. LIGA) is one of the main techniques used to produce 3D microstructures. The new technique of proton micromachining employs focused MeV protons in a direct write process which is complementary to LIGA. During ion exposure of positive photoresist like PMMA, scission of molecular chains occurs. These degraded polymer chains are removed by the developer. The aim of this paper is to investigate the capabilities of proton micromachining as a lithographic technique. We show the realization of sub-surface channels, or microtunnels, which have been fabricated in only one exposure and without cutting or resurfacing the material. Using our Van-de-Graaff accelerator, the resist (PMMA) has been exposed with high-energy protons (2.5 MeV). The range of charged particles in matter is well-defined and depends on the energy. Therefore, it is possible to obtain a dose which is sufficient to develop the bottom part of the ion paths but not the top part. Thus, by selecting the energy and the exposure time, a big variety of microtunnels can be realized. 相似文献
19.
We study the mode coupling among the local normal modes of couplers formed from planar parabolic graded-index tapered optical waveguides with the propagating beam method. Our results indicate that couplers whose radiia (z) depend on axial length as
\Lambda /2$$
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, have many desirable properties not possessed by other couplers. 相似文献