共查询到20条相似文献,搜索用时 31 毫秒
1.
基于金属-光敏硅组合圆环提出了一种光可调太赫兹超表面,可用于实现多功能的波前操控。该超表面单元由正反两面的结构层和中间介质层组成,其中结构层是开口方向相反的金属环,开口处由光敏硅进行填充。在光照强度较低时,超表面可以将入射的圆极化波转换为交叉极化的透射波;随着光照强度升高,透射波将逐渐被完全抑制。根据几何相位原理,通过旋转金属-光敏硅组合圆环,透射的交叉极化波会携带额外的相位因子,并可实现完全的2π范围相位覆盖。通过合理排列超表面单元结构,可以对透射波的波前实现任意操控。利用提出的光可调超表面,在较低光照条件下实现了高效的异常折射、透镜以及轨道角动量产生器;在较高光照条件下,抑制了其透射效率,可有条件地选择应用功能,表现出较好的灵活性。提出的光可调超表面在太赫兹成像、通信、雷达等方面具有较大的潜在应用价值。 相似文献
2.
从光束角谱理论出发建立了描述光自旋霍尔效应的傍轴传输模型, 利用这一模型分析了光自旋霍尔效应中的交叉偏振特性. 通过分析交叉偏振效应强度和入射角变化的规律, 发现交叉偏振效应越强, 光自旋霍尔效应中的自旋分裂越大. 为便于实验观察, 将入射角选在光自旋霍尔效应较强的布儒斯特角附近, 观测到了强的交叉偏振效应. 增大交叉偏振分量的同时减小初始偏振分量, 可显著增强光自旋霍尔效应. 这一调控方法为研制基于光自旋霍尔效应的新型光子器件提供了理论基础. 相似文献
3.
《Photonics and Nanostructures》2009,7(1):12-18
Calculations of angular-dependent reflectance and polarimetry spectra of nanoporous anodic alumina-based two-dimensional photonic crystal slabs are presented. The calculations are obtained using a scattering matrix numerical model that gives the polarization change as a function of the incidence angle and of the wavelength. The results reveal that the incident light can couple to several modes propagating in the photonic crystal slab at different angles with respect to the sample surface, and that the number of these modes increases with increasing pore depth. Two different lattice structures are studied: triangular and square. For the triangular lattice the off-diagonal components of the Jones Matrix show a certain amount of cross-polarization, while for the square lattice, there is no cross-polarization. 相似文献
4.
Antiferromagnetic resonance has been detected optically by monitoring the intensity of light transmitted through a crystal of KMnF3 at 2 K. At resonance, the intensity of the transmitted light decreases, implying that the absorption is enhanced by increases in magnon density. 相似文献
5.
J. C. Hebden 《Optics & Laser Technology》1995,27(4)
An object consisting of small inhomogeneities embedded in a highly scattering solution was imaged using measurements of the time-resolved transmitted intensity of picosecond pulses of near-infrared light. Data acquisition involved translating the object in two orthogonal directions across the beam, and recording the temporal distribution of transmitted light at a series of discrete positions. Images were constructed from the total transmitted light, the first four moments of the temporal distribution, and from parameters derived from a comparison of the distribution with an analytical model, based on the diffusion approximation to the radiative transfer theory. The results show that the optical properties along a line-of-sight between source and detector influence some of these characteristics more than others. 相似文献
6.
与通常利用二阶强度关联测量实现时域鬼成像不同,本文利用时域热光源借助干涉仪通过一阶关联实现时域成像.基于空域光束的近轴衍射和时域窄带脉冲在色散介质中色散之间的空间-时间二象性,在时域脉冲响应函数的基础上得到了表征一阶关联时域成像的强度表达式,分析研究了光源脉冲宽度和相干时间对成像可见度和分辨率的影响.结果一方面表明基于热光场一阶关联的时域成像在不需要额外色散补偿或消除条件下可以实现时域物体信号的再现,另一方面表明当光源脉冲宽度一定时,成像可见度随光源脉冲相干时间的增加而增加,但是成像分辨率逐渐降低,其中当光源脉冲宽度约为100 ps,相干时间约为0.5 ps时,间隔为20 ps,宽度为8 ps的时域矩形波型物体的成像质量(兼顾可见度和分辨率)较好.该结果对于基于热光一阶关联的时域成像在时序信号测量中的应用具有重要意义. 相似文献
7.
David Kuebel 《Optics Communications》2009,282(17):3397-17129
A definition of the degree of cross-polarization in the space-time domain is introduced which is based on considerations of the correlations of intensity fluctuations of an electromagnetic beam at two points. Some general properties of this quantity are discussed. For the special cases of fully coherent and fully polarized light it is shown that the degree of cross-polarization exhibits a relationship between the states of polarization at the two points. 相似文献
8.
The femtosecond temporal speckle field of a random medium is
studied theoretically and experimentally. Femtosecond temporal
speckle arises from the interference of multiple randomly scattered
electric fields. The femtosecond temporal speckle field is measured with
a cross-correlation frequency-resolved optical gating method. The
spatial average of the speckle field yields a smooth transmitted
profile. The speckle field is a circular complex Gaussian variable
because the scattered light beams from different trajectories have
no correlation with each other. The field and the intensity profiles
of individual speckle spots fluctuate randomly in time. The ensemble
average of the temporal intensity profiles converges, thereby
yielding the photon travel time probability distribution
function. 相似文献
9.
光通过纳米颗粒随机散射体透射光强的计算及分析 总被引:5,自引:0,他引:5
光通过随机散射体后透射光强的估算,对于提取散射体内部无法直接测量或者无法直接观察的信息至关重要。在分析平行光束通过纳米圆形颗粒随机散射体出射面上光强组成的基础上推导了透射光强的计算公式,并指出多重散射理论、一阶多重散射理论和朗伯-比尔定律在一定近似程度上可以相对精确地估算透射光强。这三种方法的估算结果之间会出现四种相对关系。根据这些相对关系,分析了光在散射体内部传输时散射过程的特征以及各种散射过程对出射面光强的贡献大小。 相似文献
10.
A two-beam random interferometer is demonstrated where coupling is facilitated by a scattering medium. A modulation observed in the normalized second-order intensity frequency correlation of the transmitted light is attributed to the relative temporal delay of the two beams and is insensitive to beam alignment and spacing. 相似文献
11.
We have studied anisotropic Bragg diffraction of light by ultrasonic shear waves in an optically isotropic plane-parallel
layer. We have established the analytical dependences of the relative intensities and polarization azimuths of reflected and
transmitted diffracted waves on the intensity of the ultrasound, the layer thickness, the angle of incidence, and the polarization
azimuth of the incident light. We show that rotation of the plane of polarization of the diffracted wave is determined by
the different Fresnel reflection of the s and p polarized components of the incident light in the plane-parallel layer. We
have determined that in mismatched acousto-optic structures, deep amplitude modulation of transmitted and reflected light
is possible which is an order of magnitude greater than the usual modulation in matched structures. 相似文献
12.
空气隙偏光镜对单模高斯光束光强分布影响的分析 总被引:8,自引:0,他引:8
根据光在格兰泰勒棱镜和格兰傅科棱镜空气隙胶合层中的干涉效应,分析了空气隙偏光棱镜对单模高斯光束光强分布的影响;结果表明:对于某一波长的入射光,当空气隙的厚度一定时,透射光强随光在空气隙介面上入射角的变化作周期性振荡;当入射角一定时,透射光强随空气隙厚度的变化作周期性变化;且透射高斯光束的形状也随光的入射角以及空气隙厚度的改变发生变化;且无论是透射光强的周期性振荡,还是透射高斯光束的形状的变化,格兰泰勒棱镜的影响均小于格兰傅科棱镜;这说明前者的综合性能优于后者。 相似文献
13.
Transient electromagnetically induced transparency spectroscopy of 87Rb atoms in buffer gas
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Zi-Shan Xu 《中国物理 B》2022,31(7):73201-073201
We study the transient response dynamics of 87Rb atomic vapor buffered in 8 torr Ne gas through an electromagnetically induced transparency configured in $\varLambda$-scheme. Experimentally, the temporal transmission spectra versus probe detuning by switching on and off the coupling one show complex structures. The transmitted probe light intensity drops to a minimum value when the coupling light turns off, showing a strong absorption. Even at the moment of turning on the coupling light at a subsequent delayed time, the atomic medium shows a fast transient response. To account for the transient switching feature, in the time-dependent optical Bloch equation, we must take the transverse relaxation dephasing process of atomic vapor into account, as well as the fluorescence relaxation along with the optical absorption. This work supplies a technique to quantify the transverse relaxation time scale and to sensitively monitor its variation along the environment by observing the transient dynamics of coherent medium, which is helpful in characterizing the coherent feature of the atomic medium. 相似文献
14.
15.
In this paper, relaxation behavior of transmitted light through thin ferrofluid film under an applied magnetic field is measured.
The results show that the intensity of transmitted light through a ferrofluid film increases quickly as soon as an external
magnetic field is applied then weakens with time. If uniformity of the field is poor, the transmission of light continuously
decreases in a measured duration. Otherwise, the transmission of light will tend increasingly towards a stable value after
it decreases to a minimum value while the gradient of the field is low. The relaxation time would increase to an order of
some hundreds seconds magnitude and is dependent on the strength of magnetic field and viscosity of the ferrofluids. The field-induced
relaxation behaviors of transmitted light through ferrofluids correspond to anisotropic microstructure of the ferrofluids
under applied magnetic field.
PACS 75.50.Mm; 78.20.Ls 相似文献
16.
17.
Controlling the phase delay of light transmitted through double-layer metallic subwavelength slit arrays 总被引:1,自引:0,他引:1
Marcet Z Paster JW Carr DW Bower JE Cirelli RA Klemens F Mansfield WM Miner JF Pai CS Chan HB 《Optics letters》2008,33(13):1410-1412
We demonstrate that the phase of light transmitted through double-layer subwavelength metallic slit arrays can be controlled through lateral shift of the two layers. Our samples consist of two aluminum layers, each of which contains an array of subwavelength slits. The two layers are placed in sufficient proximity to allow coupling of the evanescent fields at resonance. By changing the lateral shift between the layers from zero to half the period, the phase of the transmitted electromagnetic field is increased by pi, while the transmitted intensity remains high. Such a controllable phase delay could open new capabilities for nanophotonic devices that cannot be achieved with single-layer structures. 相似文献
18.
Maciej Antkowiak Rafał Kotyński Krassimir Panajotov Francis Berghmans Hugo Thienpont 《Optical and Quantum Electronics》2007,39(4-6):455-467
We study numerically the temporal and spatial dynamics of light in Bragg gratings in highly nonlinear photonic crystal fibre
for a CW input signal. Our numerical model is based on the plane wave mode solver and a set of nonlinear coupled-mode equations
which we solve using a variation of implicit fourth order Runge-Kutta method. We observe not only bistability of the intensity
versus transmitted and reflected light but also complex dynamics. We demonstrate that for values of input intensity above
the bistable region the steady state may undergo a supercritical Hopf bifurcation. For some ranges of the input intensity
we also observe a coexistence of two periodic attractors. The dynamics found, in particular the features in the bifurcation
diagram, strongly depend on the parameters of the fibre. Consequently, we suggest that by proper design of the photonic crystal
in the cladding we can adjust such nonlinear features of the Bragg gratings as the width of the bistable region, the intensity
at which the bifurcation occurs and also the characteristics of the dynamics at high values of input intensity. 相似文献
19.
胶质红外量子点优异的光学性能使其荧光特性具有广泛的应用前景,在实际应用中通常需要封装成薄膜形态以保持稳定的荧光特性。然而,分散形式的改变可能会导致量子点荧光效率降低以及荧光角度特性变化。因此,建立了红外量子点荧光强度探测系统,对胶质红外量子点薄膜在不同角度激发光入射时产生的荧光分布情况进行研究。实验及分析结果表明,激发光与样品表面夹角大小在10°~170°之间的较大范围内入射时,在反射及透射荧光区域均可探测到荧光峰值强度70%~80%以上的荧光出射,在这一范围内的反射荧光与透射荧光强度差异和荧光强度随激发光入射角度的变化规律分别与样品中量子点的浓度以及分布形态有关。同时,随着入射激光能量的增强,样品出射荧光强度对于入射角度变化的“平坦”范围进一步扩大。 相似文献
20.
The concept of the degree of cross-polarization is extended from stochastic electromagnetic stationary beams to stochastic electromagnetic pulsed beams, and the propagation properties of the degree of cross-polarization of stochastic spatially and spectrally partially coherent electromagnetic pulsed beams is studied. The influence of pulse duration and temporal coherence length on the degree of cross-polarization P is emphasized. It is shown that P exhibits an oscillatory behavior in free-space propagation. An increase in the pulse duration or a decrease in the temporal coherence length can weaken the oscillation of P. The validity of the results is interpreted physically. 相似文献