共查询到20条相似文献,搜索用时 31 毫秒
1.
Hanninen I. Pitkonen M. Nikoskinen K.I. Sarvas J. 《Antennas and Propagation, IEEE Transactions on》2006,54(4):1167-1173
A method of moments (MoM) formulation is developed to analyze the backscattering properties of an anisotropic trihedral corner reflector, which is obtained by corrugating one or several of its interior faces. The proposed formulation treats the corrugated surface as ideally tuned to the incident wave frequency. The numerical analysis of the studied structures has been done using closed-form formulas and accurate numerical integration. The focus of the study reported in this paper has been the polarization responses of ideally tuned corrugated reflectors, which have interesting properties, particularly regarding elliptically or circularly polarized waves. We numerically verify that an appropriately corrugated reflector returns elliptically and circularly polarized waves with the same handedness as the incident wave. For a linearly polarized incident wave, the corner reflector is able to rotate them by 90/spl deg/. Also the effect of the direction of the corrugation to the backscattering properties is studied. 相似文献
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为了实现圆极化波到线极化波的高效率转换,提出了一种由两种圆极化波调制模块构成的复合结构单元频率选择表面圆-线极化转换器。采用天线-馈线-天线结构设计了左-左旋和左-右旋两种圆极化调制模,并将二者组合形成具有左旋圆极化波接收、左旋和右旋圆极化波同幅同相辐射功能的圆-线极化转换器。仿真与测试结果表明,该极化转换器能够将入射左旋极化波转换成线极化波,3 dB传输系数相对带宽大于19.8%,工作带宽内的圆-线极化转换率大于0.99。该极化转换器具有插入损耗低、设计原理易于推广等优势。 相似文献
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The polarized light acted as one of the non-contacted media could effectively tune the crystal structure to improve the physical properties. In this work, under polarized laser excitation, the molecular motion is driven inside the crystals, where the electronic structure of the crystal is affected to further change the spin and optical properties. However, decreasing the temperature to 77 K, the external polarized laser cannot produce direct molecular motion. Moreover, switching the incident laser from the linearly to circularly polarized state, the dependence of the molecular motion on the spin and optical properties show pronounced difference. 相似文献
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玻璃角反射器棱镜的偏振特性 总被引:4,自引:0,他引:4
当一束线偏振光轴向入射至玻璃角反射器棱镜(corner-cube refiector以下简称CCR)经过三次全内反射而反方向射出时,一般说来它将成为一束椭圆偏振光。仅存在二个特殊的偏振方位角,在这二个方位角偏振的线偏振光入射至玻璃CCR将得到线偏振的出射光,但偏振面已发生了转动。本文计算出了这二个特殊的方位角和出射光方位角的改变量,且为实验所证实。 相似文献
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Electrostriction is a cause of laser beam self-trapping and damage in transparent glass. It predominates over other self-focusing mechanisms, such as Kerr effect or thermal self-focusing, under certain conditions. This paper shows that self-focusing can occur even if the laser pulse is so short that no steady state is achieved, provided the pulse power is large enough. In the steady state, the threshold power for self-focusing is independent of beam size. In the transient region, the threshold power increases and becomes proportional to the square of the initial beam radius, in the limit of large radius beams or short pulses. The theoretical trapping threshold derived here is less than typical experimental thresholds for track formation in glass. 相似文献
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Power reflection and transmission coefficients are found for linearly and circularly polarized plane electromagnetic waves, normally incident on a plasma slab, moving uniformly along a magnetostatic field, normal to the slab boundaries. The solution is found by applying the boundary conditions in the rest frame, and then using relativistic transformations for the fields and the plasma parameters to find the reflection and transmission coefficients observed in the laboratory frame. The results for the circularly polarized incident waves are found in closed form. Numerical results are presented for linearly polarized incident waves. It is found that with an increase in the magnetostatic field, the absolute maximum of the reflection coefficient increases at different velocities. An increase in the magnetostatic field makes the slab more transparent at velocities for which the transmission coefficient with no magnetostatic field is very small. A dielectric-like behavior is observed for large magnetostatic fields. The sum of the power reflection and power transmission coefficients is found to be no longer equal to unity for velocity different from zero. 相似文献
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The relative contributions of the Kerr, electrostrictive, and thermal effects to the self-focusing thresholds of borosilicate crown glass, fused silica, and dense flint glass have been estimated from an analysis of damage-threshold data for linearly polarized and circularly polarized radiation. The measurements were made with a Nd:glass laser operating in the TEM00 mode with a temporal pulsewidth of 25 ns. The Kerr effect appears to be the largest effect. The thermal effect is also significant. The electrostrictive effect is smallest. Reasonable values of the absorption coefficient are calculated from the thermal contribution. The results are in qualitative agreement with the work of others. 相似文献
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In liquids with optically anisotropic molecules the largest nonlinear polarization, cubic in the field amplitudes, corresponds to the intensity dependent index of refraction. The resulting self-focusing of the laser beam is in turn responsible for the anomalous gain of the stimulated Raman emission. The stimulated Brillouin effect in these self-focusing fluids has the same threshold condition as the stimulated Raman effect. In both cases the condition is that self-focusing occurs within the cell length. The anomalous frequency broadening in these same liquids depends on the parameter(omega_{L} - omega'_{L})tau_{c} , where ωL andomega'_{L} are two frequencies occurring in the laser beam and τc is a correlation time for molecular reorientation. In agreement with this theory, more broadening was observed at higher temperatures, although the Raman gain has the opposite trend. 相似文献
9.
偏振光飞秒双脉冲微加工 总被引:3,自引:1,他引:2
利用具有纳焦能量、高重复频率的偏振光飞秒双脉冲对金属铬膜样品进行微加工,样品表面都会产生微突起状结构,它们的宽度在0~400 ps的双脉冲时延范围内没有明显的变化,但高度却都在1~10 ps的双脉冲时延范围内呈现明显的下降,在此时延范围之外并没有明显的变化。通过加工样品的扫描电子显微镜(SEM)图片发现,对于偏振光,利用双脉冲方法,可以获得更好的加工质量。并且线偏振光得到的微突起状结构比较细长,在入射光束的偏振方向上有所伸长;圆偏振光得到的微突起状结构比较接近圆形。即在低脉冲能量、高重复频率情况下,具体的微加工特征形貌与入射光束的偏振状态有关。 相似文献
10.
圆偏振光和线偏振光散射特性分析与比较 总被引:8,自引:0,他引:8
本文对圆偏振态和线偏振态两种光束在激射粒子场散射中的散射特性进行了对比和分析。散射粒子直径分别为:1.24μm、0.494μm、0.36μm、0.123μm、0.065μm。以粒子与水技不同比例混合液,作为散射粒子场.所得结果表明,散射光强度总是相对入射光束的偏振面呈对称分布;散射光强度对散射粒子大小敏感而与入射光偏振态无关;散射光中垂直偏振分量在两种光入射下存在完全不同的状态分布。 相似文献
11.
This work investigates symmetry‐breaking deformation of azo molecular glass microspheres induced by interfering circularly polarized light, and related particle shape manipulation as well as 3D patterning. The isolated microspheres and microsphere monolayers are obtained from an azo molecular glass (IA‐Chol) by the solution dispersion method and soft‐lithography, respectively. Unique symmetry‐breaking deformation is observed for the microspheres upon exposure to the spatially modulated light field, which is produced by interference of two orthogonally polarized laser beams with the right‐circular polarization (RCP) and left‐circular polarization (LCP). Two distinct deformation modes are developed upon the irradiation with the interfering beams in RCP:LCP and LCP:RCP superposition manners, respectively. The unique morphologies with the symmetry‐breaking characteristics are caused by mass transfer induced by the light irradiation. For the microsphere monolayers, the deformations of the microspheres not only capture and record the polarization states of the light field, but also create various surface patterns combining the symmetry‐breaking deformations and periodic surface modulation. A variety of unique surface patterns are obtained by irradiation with the interfering circularly polarized waves with the orthogonal and also the same‐handed polarizations. The material and methodology developed in this study are promising for applications in sensing, optics, responsive surfaces, and others. 相似文献
12.
基于超表面对光波的振幅、相位和偏振进行调控来实现聚焦与成像的超透镜受到广泛关注。设计了一种聚焦强度可调的高数值孔径的双焦点超透镜,并进行了理论分析和仿真验证。仿真结果表明,该超透镜能有效地将圆偏振入射光聚焦到半高宽为0.44λ的光斑上,对应的数值孔径高达0.95。此外,通过改变入射光的偏振态,可以灵活地调制两个焦点的相对强度,而不同于以往的双焦点超透镜需要对光强进行重新组合。更重要的是,当圆偏振光入射时,它的聚焦效率可达65%,可适用在0.8~1.2 THz的较宽频率范围和0°~20°的入射角内,同时该工作为多焦点超透镜的设计提供了重要思路,也将在多成像系统、光学层析成像技术等许多领域具有较高的应用价值。 相似文献
13.
A study has been made of the interaction of two crosspolarized plane electromagnetic waves with six-layered spherical models of a mammalian head. The numerical results indicate that the absorbed powers induced inside small animal and human heads by incident circularly polarized waves and linearly polarized waves are very similar except that the absorbed power in the planes transverse to the direction of propagation is uniform for the cross-polarized wave. It is also shown that the average absorbed power depends strongly on the frequency and head size involved. The maximum absorbed powers in a given size spherical head vary only slightly with frequency for the two frequencies studied. However, since a greater amount of the absorbed power occurs in the inner sphere representing the brain of a human head when 918 MHz rather than 2450 MHz is used, the former constitutes a greater health hazard to man at the same incident power. 相似文献
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A simple technique, time division circular polarization (TDCP), is described which permits the simultaneous measurement of attenuation and depolarization for two orthogonal linearly polarized waves and two orthogonal circularly polarized waves in a slowly varying linear propagation medium using only a single frequency beacon switched between two linearly polarized antenna ports. 相似文献
18.
Self-switching with a nonlinear birefringent loop mirror 总被引:1,自引:0,他引:1
We investigate switching characteristics of the nonlinear birefringent loop mirror which consists of a symmetric directional coupler, a birefringent fiber, and a symmetry-breaking element that converts linearly polarized light to circularly polarized light, and vice versa. The condition for total reflection in the linear regime is obtained using the Jones matrix formalism, The switching curves have been obtained through numerical computations both in the nondispersive pulse regime and in the soliton-like pulse regime. Parameter values suitable for practical applications of our device as an intensity filter are obtained 相似文献
19.
The problem of how a slab of random medium affects the propagation and polarization of an arbitrarily polarized obliquely incident electromagnetic wave is investigated. The general formulation is given by using vector radiative transfer theory. The multiple scattering solution is compared with the analytical first-order solution when the optical distance is small and the comparison shows that the results are consistent with each other. The multiple scattering results for a left-handed circularly polarized incident wave show that the transmitted wave is still right-handed near the backscattering direction. The scattering signature obtained shows that for normal incidence one can obtain a maximum backscattered power if an arbitrarily oriented linearly polarized incident wave is chosen and that for an incident angle of 30°, a minimum backscattered power can be obtained if a linearly polarized incident wave is oriented at 45° or 135° 相似文献
20.
Xiang Tong Li Natansohn A. Kobayashi S. Rochon P. 《Quantum Electronics, IEEE Journal of》2000,36(7):824-827
We have developed a liquid crystal (LC) device that is totally controlled using light. The initial alignment is made by optically buffing the azopolymer film with two coherent argon laser beams. Surface relief gratings have been optically induced on an assembled cell filled with LC. A single linearly polarized argon laser beam is then employed to irradiate the sample and photoinduce a twisted alignment structure. This can then be erased by a circularly polarized beam. The alignment information can also be erased by heating to the glass transition temperature of the azopolymer film 相似文献