Investigation of the limit of lateral beam shifts on a symmetrical metal-cladding waveguide

This paper reports that Goos--H\"anchen (GH) shifts occurring on a symmetrical metal-cladding waveguide are experimentally identified. It was found that there exists a critical thickness of the upper metal layer, h_cr, above which negative shift is observed and, reversely, positive shift occurs. Both positive and negative GH shifts near the critical thickness do not vary dramatically and can achieve a maximum on the submillimeter scale, which is different from simulated results using the stationary-phase method. It also shows that this critical thickness, h_cr, can be obtained at the position for zero reflectivity by setting the intrinsic damping to be the same as the radiative damping. The GH effects observed near the critical thickness are produced by extreme distortion of the reflected beam profiles, which limits the amplitude of the GH shift and, further, the sensitivity of the GH optical sensor based on the symmetrical metal-cladding waveguide.     

Physical origin of large positive and negative lateral optical beam shifts in prism-waveguide coupling system

Large lateral beam shift in prism-waveguide coupling system is theoretically analyzed from the viewpoint of interference between multiple reflected beam constituents. It is shown that the reflected beam is a result of interference between two beams: the beam directly reflected from the prism and the total leaky beam coming from guided mode. The thickness of coupling layer determines the amplitude of the total leaky beam, and further determines the sign (positive or negative) of the reflected beam shift. Because of interference between two beams, intrinsic damping itself plays an important role in deciding the distortion of the reflected beam.     

Bistable and negative lateral shifts of the reflected light beam from Kretschmann configuration with nonlinear left-handed metamaterials

We study the bistable and negative lateral shifts of the reflected light beam from Kretschmann configuration containing left-handed metamaterials with self-focusing and self-defocusing Kerr-type nonlinearity. It is shown that the lateral shifts can be large and negative when the thickness of the middle metal film is smaller than the critical value. Taking the nonlinear effect into account, there exists a hysteretic response between the beam shift and the intensity of the incident light beam. These results suggest that the bistable and negative beam shifts can be modulated by nonlinear coefficients and intensity of incident beam, which might be used in integrated photonics and optical switches.     

Negative and positive lateral shift of a light beam reflected from a grounded slab

We consider the lateral shift (LS) of a light beam reflecting from a dielectric slab backed by a metal. It is found that the LS of the reflected beam can be negative while the intensity of reflected beam is almost equal to the incident one under a certain condition. The explanation for the negativity of the LS is given in terms of the interference of the reflected waves from the two interfaces. It is also shown that the LS can be enhanced or suppressed under some other conditions. The numerical calculation on the LS for a realistic Gaussian-shaped beam confirms our theoretical prediction.     

Giant negative and positive lateral shifts in graphene superlattices

Electronic analogy of Goos-Hänchen shift has been well established and investigated in various graphene-based nanostructures, including p-n interface, single and double barriers. In this paper, we have studied the giant negative and positive lateral shifts of the transmitted electron beam through graphene superlattices. It is found that the lateral shifts, depending on the location of new Dirac point, can be negative as well as positive near the band edges of zero-k? (non-Bragg) gap. We have also achieved the enhanced opposite shifts in the graphene superlattice with defect layer, since such structure possesses the defect mode inside the zero-k? gap. The modulations of negative and positive lateral shifts by incidence angles, width and potential height of defect layer may lead to potential applications in the graphene-based electron wave devices.     

Analysis of the positive or negative lateral shift of the reflected beam in Otto configuration under grazing incidence

We investigate the lateral shift of a TM-polarized light beam reflected from Otto configuration under grazing incidence. It is found that the lateral shift is strongly dependent on the thickness of the air-gap layer. By employing the pole-null representation, we demonstrate that the lateral shift is closely related to the null of the reflection function. The numerical simulations for a Gaussian beam are performed to demonstrate the validity of our theoretical analysis.     

Giant positive and negative lateral shifts from the Kretschmann-Raether configuration with a weakly absorbing left-handed slab

The lateral shift of a TE-polarized beam reflected from the Kretschmann-Raether structure with a weakly absorbing left-handed slab is studied theoretically. It is shown that the lateral shift can be very large negative as well as positive near the resonant condition. These large negative and positive shifts can be one order of magnitude much larger than the shift from the corresponding nonabsorbing slab. As the absorption factor increases, the incident angle of producing largest lateral shift increases when the thickness is kept unchanged but the thickness of the slab of producing largest lateral shift decreases when the incident angle is kept unchanged.     

Large positive and negative lateral optical beam shift due to long-range surface plasmon resonance

In this paper, we examine theoretically the beam shift at visible wavelengths on a long-range surface plasmon (LRSP) configuration by using the stationary-phase approach. We report that the lateral beam shift at the resonance of LRSP can be two orders of magnitude greater than a wavelength. It is also found that the sign of the lateral beam shift depends on the magnitude of the intrinsic damping relative to that of the radiative damping. Negative lateral beam shift occurs when the former is larger than the latter.     

Enhanced superprism effect based on positive/negative lateral shift of reflective beam in a Fabry-Perot filter

It is found that when a light beam is incident obliquely on a thin film Fabry-Perot filter (FPF) from different incident media (air or substrate), the reflective beam will be shifted in both the forward and the backward directions. Based on this inverted spatial dispersion effect, two thin film FPFs with different directional lateral shifts are assembled to get a thin film superprism with a wider dispersion band. The thin film samples are fabricated as well as tested, and the results are in approximate agreement with numerical simulation.     

Symmetrical temperature-chaos effect with positive and negative temperature shifts in a spin glass

Aging in a Heisenberg-like spin glass Ag(11 at. % Mn) is investigated by measurements of the zero-field-cooled magnetic relaxation at a constant temperature after small temperature shifts absolute value of Delta T/T(g) < 0.012. A crossover from fully accumulative to nonaccumulative aging is observed, and by converting time scales to length scales using the logarithmic growth law of the droplet model, we find quantitative evidence that positive and negative temperature shifts cause an equivalent restart of aging (rejuvenation) in terms of dynamical length scales. This result supports the existence of a unique overlap length between a pair of equilibrium states in the spin-glass system.     

Generation of radiation in tunnel-coupled waveguides with positive and negative refractive indices

The possibility of generating microwave radiation in tunnel-coupled planar waveguides, one of which is made of a metamaterial and is characterized by a negative refractive index in the corresponding frequency range, while the other waveguide is active and exhibits positive refractive index, is demonstrated. The model of a tunable distributed feedback laser, in which the dependence of the refractive index of the metamaterial on the external magnetic field allows controlling the oscillation frequency, is proposed.     

Lateral displacement of a Gaussian beam reflected from absorbing media

Lateral displacements of well-focused beams reflected from absorbing media are demonstrated in this paper. The incident beam is modeled as a tapered wave with a Gaussian spectrum. The field solutions are obtained on both sides of the interface by solving analytically from Maxwell's equations and by matching the boundary conditions at the interface. Numerical simulations are presented and the field values as well as the time-averaged power densities are computed. The influences of the polarization, the angle of incidence and the beam width on the displacement are discussed. The origin of the displacement lies in the absorption of the media, for which there is a phase shift between the incident and reflected waves. Because of this phase shift, the center of the reflected beam does not coincide with that of the incident one, similar to the Goos-Hänchen shift.     

Negative and positive Goos–Hänchen shifts of a light beam transmitted from an indefinite medium slab

We study the lateral shift of a light beam transmitted from an indefinite medium slab. The analytic expressions for the transmission coefficient and the lateral shift are obtained by using the stationary-phase method, and different conditions for the occurrence of a negative lateral shift are deduced. It is shown that the thickness of the indefinite medium strongly affects the properties of the lateral shift. For a larger thickness, the sign of the lateral shift depends only on the signs of the permittivity and permeability, while, for a smaller thickness, the sign of the lateral shift is determined by the combined effect of the incident angle of the light, the signs of the permittivity and permeability, and the thickness of the indefinite medium slab. In addition, the lateral shift at the transmitted resonance points is found to be enhanced greatly, and the sign of the lateral shift around the transmitted resonance points is strongly dependent on the permittivity and permeability of the indefinite medium. Some examples are given to validate the obtained theoretical results. PACS 41.20.Jb; 42.25.Gy; 42.25.Bs; 78.20.Ci; 78.68.+m     

Self-focusing of a Gaussian laser beam reflected from a thermocapillary liquid surface

Self-focusing of laser radiation reflected from the surface of liquid heavy hydrocarbons is reported. Close agreement of experimental data with theoretical previsions suggests that thermocapillarity is the main physical phenomenon involved. The focus appears at 40 cm of the sample surface after 1 s of irradiation at 350 mW.     

基于双面金属包覆光波导的传感器温度特性研究及实验验证

双面金属包覆波导结构(SMCW)是由一层介质波导层被两层金属膜层上下包覆的一种新型波导结构; 本文基于金属层和介质层材料的热-光效应和热膨胀作用, 研究了双面金属包覆波导结构的温度特性. 计算分析的结果表明, 金属膜层的厚度、金属的介电系数、波导层的厚度及其介电常数几乎都与温度变化成比例, 同时, 对双面金属包覆波导结构的波导功能起主要影响的是介质层的厚度值随温度的变化. 本文分别在光谱模式和角度模式下研究双面金属包覆波导结构的反射特性, 并将其应用于基于双面金属包覆波导结构的传感器, 其灵敏度约为21.89 pm/K(光谱模式)和1.449×10^-3 rad/K(角度模式). 最后, 本文对角度模式的模拟分析进行了实验验证, 实验验证结果与模拟分析结果基本一致, 实验所用SMCW样品的平均灵敏度约为0.517×10^-3 rad/K, 与模拟分析的灵敏度结果同一量级. 双面金属包覆波导结构的传感器对温度非常敏感, 且该结构的物理构造简单, 成本低, 具有非常大的潜在应用价值.     

Net lateral shift of reflected beam due to surface plasmon resonance in Kretschmann configuration

When surface plasmon resonance is excited in Kretschmann configuration, the maximum Goos–Hänchen shift occurs at the resonant angle which is associated with the minimum value of reflectivity, but the maximum angular shift occurs at two incident angles beside the resonant angle. When the reflected beam is detected at Rayleigh range, the maximum net lateral shift of the reflected beam does not encounter the resonant angle and its magnitude is lager than that of Goos–Hänchen shift. Numerical simulation shows that theory agrees well with numerical results when the beam width is large enough.     

Lateral shift and tunneling of optical beam reflected from gradient-induced inhomogeneity

Two effects have been analytically and numerically studied: Goos-Hänchen shift, which is acquired by an optical beam reflected from a gradient inhomogeneity, and tunneling of radiation through a narrow induced inhomogeneity. A possibility of increasing the lateral beam shift in comparison with total internal reflection from a homogeneous medium is revealed. The dependence of the tunneling coefficient on the inhomogeneity parameters is determined and the critical inhomogeneity width at which the tunneling effect arises is found.     

吸收媒质反射束Goos-Hnchen位移的直接计算公式

本文导出了从吸收媒质上反射的s和p两种偏振的Goos-Hnchen位移的一般表达式。若令消光系数等于零,它们就简化成McGuilk和Carniglia给出的仅用于非吸收媒质的公式。吸收媒质的位移,在任何不为零的入射角度时都有。在镓的表面上,位移有几个波长。