Fresnel Transmission Coefficients Research Articles

Damour–Solodukhin Wormhole as a Black Hole Mimicker: The Role of Observers’ Location

It has been recently argued that in semi-classical gravity, a minimal 2-sphere is not a horizon but a tiny throat of a wormhole, such as the Damour–Solodukhin wormhole (DSWH), with a free parameter λ≠0 separating it from a Schwarxzschild black hole (BH) (λ=0). As shown by DS, their horizonless WH can mimic many properties of a black hole (BH). Assuming that observing a BH mimicker is equivalent to observing a BH itself, we ask the question as to which identity of the object, a WH or a BH, an observer is likely to observe in a single experiment. To answer this, we introduce Tangherlini’s new concept of indeterminacy in the gravitational field by portraying the field as a refractive medium. We then postulate that the identity of the observed object will depend on the probabilistic outcome of photon motion probing the object. The probabilities will be described by Fresnel reflection (R) and transmission (T) coefficients derived by Tangherlini on the basis of a non-quantum statistical indeterminacy of photon motion in ordinary optical media. By adapting this approach to a gravitational “effective optical medium,” we obtain two intriguing results: (i) The Fresnel coefficients at the DSWH throat are independent of mass M but dependent solely on the parameter λ≠0. (ii) Depending on the location of the observer, what is a DSWH to one observer may appear as a BH to another observer for the same value of λ≠0.

Optical Phase Contrast Microscopy with Incoherent Vortex Phase

AbstractA novel, compact, and broadband optical phase contrast microscopy based on incoherent vortex topological quadrupole is theoretically proposed and experimentally realized. The topological quadrupole, generated in a thin uniaxial crystal, possesses four single‐charge optical vortexes, each of which can act as a two‐dimensional (2D) optical spatial differentiator. The incoherence of light‐emitting diode (LED) light will wash out the optical vortex and the spatial differentiation effect, which can be ingeniously overcome by choosing Kohler illumination and inserting a 1 mm‐thickness uniaxial crystal sandwiched with two polarizers before the camera. By adjusting the polarizers and the tilted angle of crystal to selectively utilize the geometric Berry phase and the angular gradient of Fresnel transmission coefficients of crystal, the 1D, 2D, and second‐order analog spatial differentiations with a spatial resolution better than 0.775 μm can be switched flexibly. A versatile phase contrast microscope is built, which is well compatible with the conventional microscopes. The uniformly incoherent illumination without laser speckle effects results in high‐quality spatial differentiation imaging. Biologically transparent living cells are thus imaged with high contrast.

Development of a novel approach for snow wetness estimation using hybrid polarimetric RISAT-1 SAR datasets in North-Western Himalayan region

Snow wetness estimates are critical inputs in the understanding of snow hydrological processes. With early warming in winters in the Himalayas, snowpack shows early signs of melting in February with increased snow wetness. Typically, in February, the snowpack comprises a mix of dry and wet snow layers. In the literature, methods for quantitative analysis of snow wetness are mostly based on fully polarimetric synthetic aperture radar (SAR) data. Methods based on the hybrid polarimetric SAR (PolSAR) data for snow monitoring are virtually inexistent. This study proposes a novel methodology for the estimation of snow wetness utilizing the C-band hybrid polarimetric RISAT-1 SAR dataset. Using radar remote sensing to analyze the behavior of such a snowpack requires information on the surface and volume scattering characteristics. The modeled generalized surface and volume scattering parameters (α), and (γ), based on the X-Bragg’s reflection coefficients and Fresnel transmission coefficients, are used for the inversion of surface and volume snow permittivities, respectively. The investigations are carried out for February 2014 for a study area in the Manali region in Himachal Pradesh, India. The retrieved snow estimates showed a coefficient of determination of 0.86 and a root mean square error of 0.667 with respect to in-situ measurements. Further, it was observed that the snow wetness estimates derived from the proposed method using RISAT-1 dataset outperformed the estimates based on fully polarimetric RADARSAT-2 dataset using the conventional Shi and Dozier method.

Limitations of the transmitted photonic spin Hall effect through layered structure

In this paper, we show theoretically that the spin-dependent transverse shift of the transmitted photonic spin Hall effect (SHE) through layered structure cannot exceed half of the incident beam waist. Exact conditions for obtaining the upper limit of the transmitted SHE are clarified in detail. In addition, different from the popular view in many investigations, we find that there is no positive correlation between the spin-dependent transverse displacement and the ratio between the Fresnel transmission coefficients (tp, ts). In contrast, the optimal transmission ratio is determined by the incident angle and the beam waist. Moreover, two conventional transmission structures are selected and studied in detail. The characteristics of the transverse displacements obtained are in very good agreement with our theoretical conclusions. These findings provide a deeper insight into the photonic spin Hall phenomena and offer a guide for future related research.

Energy and momentum conservation upon reflection of a solitary pulse in a bounded magnetized plasma

When the nature of a magnetosonic pulse propagating in a bounded magnetized plasma slab is successively transformed from compression to rarefaction and vice versa upon reflection at a plasma-vacuum interface, both the energy and the longitudinal electromagnetic (EM) momentum of the plasma-pulse system are found to oscillate between two states. Simple analytical models and particle-in-cell simulations show that these oscillations are associated with EM radiation to and from the surrounding magnetized vacuum. For partial reflection supplemental losses in total pulse energy and mechanical momentum are identified and shown to follow, respectively, Fresnel's transmission coefficients for the energy and the magnetic perturbation. This mechanical momentum loss upon partial reflection is traced to the momentarily nonzero volume-integrated Lorentz force, which in turn supports that mechanical and EM momentum transfers are, respectively, associated with the magnetic and electric parts of the momentum flux density.

Spin Hall effect of transmitted light for graphene–silica aerogel photonic crystal in terahertz region

Photonic spin Hall effect (SHE) holds great potential applications for the development of spin-based nanophotonic devices. Due to the weak spin–orbit interaction, it is highly desirable to tune and enhance the photonic SHE. However, such a goal remains elusive, especially for the transmitted light. Here, we present the significant enhancement of SHE behavior for transmitted light in terahertz region by introducing the graphene monolayers into adjacent silica aerogel layers of photonic crystal. The spin shift is quite sensitive to the period number and Fermi energy of graphene layers. We find that the value of spin shift is mainly decided by the phase of Fresnel transmission coefficients. In addition, two different tuned regions have been revealed: one is the low frequency region in which the significant feature is the giant spin shift over broad angle and frequency ranges, and the other is the high frequency region where the spin shift can be gradually enhanced as the period number increases. These findings pave the way to achieve the enhanced SHE for transmitted light in terahertz region and may open the possibility for manipulating the photonic SHE.

Dielectric surface coated with thin partially-reflecting mirror – A revisit to Fresnel laws

New forms of Fresnel reflection and transmission coefficients were derived in the case of oblique optical incidence at the interface of dielectric medium coated with thin partially-reflecting mirror. This essentially required the application of modified boundary conditions for both the electric and magnetic fields. The expressions for power reflectivity (of the mirror) were obtained for both the transverse electric (TE) and transverse magnetic (TM) waves considering the cases of dielectric and metallic coatings. The reflectance and transmittance of the coated surface were also examined corresponding to different values of mirror reflectivity. It is expected that the forms of Fresnel coefficients would be useful in modeling optical and optoelectronic mirror-based devices.

Modelling of early winter snow density using fully polarimetric C-band SAR data in the Indian Himalayas

The seasonal snow cover contributes significantly to the water resource in the Indian Himalayas, and snow density is one of the vital parameters in the determination of the hydrological potential of snow. The application of conventional methods for snow density retrieval using fully polarimetric SAR data is constrained by the properties of snow primarily due to the melt and frost cycles, as compared to fresh dry snow. The surface component of backscatter is significant in case of melt and frost. In the conventional decomposition based methods, the surface component is not considered for the inversion of permittivity, as proposed in this study. In this paper, we also propose a methodology for the estimation of snow density using bi-temporal fully polarimetric C-band RADARSAT-2 synthetic aperture radar (SAR) data. We utilize the relation between the differential modified Mueller matrix components, the attenuation constants, and the Fresnel transmission coefficients. The permittivity of snow is derived using the inversion of the Fresnel transmission coefficients which is used to determine the snow density using a state of the art empirical relation. The snow density estimates from the proposed method are compared with other methods based on coherency matrix decomposition and evaluated against in-situ measurements collected during a field campaign carried out in Dhundi in the state of Himachal Pradesh in India. The snow density estimates using the proposed method are observed to correlate with the in-situ measurements and were also found to be better than the decomposition based methods.

Analytical Fresnel laws for curved dielectric interfaces

Fresnel laws and the corresponding Fresnel reflection and transmission coefficients provide the quantitative information of the amount of reflected and transmitted (refracted) light in dependence on its angle of incidence. They are at the core of ray optics at planar interfaces. However, the well-known Fresnel formulae do not hold at curved interfaces and deviations are appreciable when the radius of curvature becomes of the order of several wavelengths of the incident light. This is of particular importance for optical microcavities that play a significant role in many modern research fields. Their convexly curved interfaces modify Fresnel’s law in a characteristic manner. Most notably, the onset of total internal reflection is shifted to angles larger than critical incidence (Martina and Henning 2002 Phys. Rev. E 65 045603). Here, we derive analytical Fresnel formulae for the opposite type of interface curvature, namely concavely curved refractive index boundaries, that have not been available so far. The accessibility of curvature-dependent Fresnel coefficients facilitates the analytical, ray-optics based description of light in complex mesoscopic optical structures that will be important in future nano- and microphotonic applications.

Reflection by and transmission through an ENZ interface

We have studied the reflection and transmission of traveling and evanescent plane waves, incident upon an ENZ material. The Fresnel reflection and transmission coefficients were obtained in the ENZ limit. For a p polarized incident wave, the transmission coefficient vanishes, except very close to normal incidence. The reflection coefficient is -1 for both traveling and evanescent waves. It is shown, however, that there is a finite electric field in the ENZ material, even though the transmission coefficient is zero. This field is either linearly polarized or circularly polarized. The magnetic field in the medium for p polarized illumination is zero, and therefore there can be no energy flow through the material. For s polarization, the magnetic field in the medium is circularly polarized, and energy can flow through the material, parallel to the interface.

Plane Wave Diffraction by Arbitrary-Angled Lossless Wedges: High-Frequency and Time-Domain Solutions

This paper concerns the diffraction phenomenon originated by a uniform plane wave impacting an arbitrary-angled lossless dielectric wedge with planar surfaces. The high-frequency diffraction coefficients are obtained by performing uniform asymptotic evaluations of the radiation integrals resulting from the physical optics approximation of the electric and magnetic equivalent surface currents located on the inner and outer faces of the wedge. The final expressions are in closed form and contain the standard transition function of the uniform theory of diffraction and the Fresnel reflection and transmission coefficients related to the geometrical optics propagation mechanisms. Moreover, they allow a simple physical interpretation of each contribution and they are easy to use and to implement in a computer code. The knowledge of such diffraction coefficients in the frequency domain permits to apply the inverse Laplace transform to obtain the time-domain counterparts, which enable the evaluation of the transient diffracted field originated by an arbitrary function plane wave.

Fresnel Reflection and Transmission Coefficients for Temporally Dispersive Attenuative Media

AbstractGeneralized Fresnel reflection and transmission coefficients are derived for both time‐harmonic TE(s)‐ and TM(p)‐polarized plane wave fields incident upon a planar interface separating two attenuative linear media, each described by a frequency‐dependent complex‐valued dielectric permittivity , magnetic permeability , and electric conductivity while maintaining the real‐valued form of Snell's law. The resultant effects of material loss on both the reflected and transmitted fields are presented, including the condition for the appearance of a polarizing angle.

Modeling variation coefficient of wave-induced underwater irradiance for clear ocean and its application to find the optimal detector size.

In measuring the coefficient of variation (CV) of underwater wave-induced sunlight irradiance, the spatial integration of irradiance signals due to the finite aperture size of an irradiance detector usually causes underestimation of the measured variance. Because this spatial integration effect is strongly coupled with ocean wave features, inherent optical properties (IOPs) of water, and atmospheric radiance conditions, direct deconvolution techniques from measured irradiance signals can lead to serious signal-to-noise degradation in a noisy upper ocean. On the other hand, choosing a small detector to guarantee CV accuracy is expensive. We address the intrinsic dependence of the CV on the detector size and choice of optimal detector size for measuring irradiance variability in a turbid ocean environment. We present a new theoretical model to directly obtain the form of the CV of the wave-induced scalar irradiance as the function of the detector size, ocean surface wave parameters, and IOPs of ocean water. The model is derived under the small-angle scattering approximation and the first-order assumption of Snell's law and Fresnel transmission coefficient. We demonstrate the validity and efficacy of the model for weakly roughened Gaussian ocean surface conditions, by comparison with Monte Carlo radiative transfer simulations. The model shows that the CV of wave-induced irradiance reaches an asymptotic with decreasing the detector size, thereby providing an optimal or maximum detector size for given IOP and environmental conditions.

Efficient and Accurate Computation of Electric Field Dyadic Green’s Function in Layered Media

Concise and explicit formulas for dyadic Green's functions, representing the electric and magnetic fields due to a dipole source placed in layered media, are derived in this paper. First, the electric and magnetic fields in the spectral domain for the half space are expressed using Fresnel reflection and transmission coefficients. Each component of electric field in the spectral domain constitutes the spectral Green's function in layered media. The Green's function in the spatial domain is then recovered involving Sommerfeld integrals for each component in the spectral domain. By using Bessel identities, the number of Sommerfeld integrals are reduced, resulting in much simpler and more efficient formulas for numerical implementation compared with previous results. This approach is extended to the three-layer Green's function. In addition, the singular part of the Green's function is naturally separated out so that integral equation methods developed for free space Green's functions can be used with minimal modification. Numerical results are included to show efficiency and accuracy of the derived formulas.

Ray-wave correspondence in chaotic dielectric billiards.

Based on the reformulation of the boundary integral equations recently derived by Creagh, Hamdin, and Tanner [J. Phys. A: Math. Theor. 46, 435203 (2013)] together with semiclassical (short wavelength) approximation, we theoretically show that low-loss resonances of a fully chaotic dielectric billiard can be related with ray dynamical orbits whose intensities are weighted by the Fresnel reflection and transmission coefficients. In addition, it is revealed that intensity localization spots observed in the phase-space representation of an individual resonance wave function are ray-dynamically correlated.

Development of a snow wetness inversion algorithm using polarimetric scattering power decomposition model

In this paper, a new snow wetness estimation model is proposed for full-polarimetric Synthetic Aperture Radar (SAR) data. Surface and volume are the dominant scattering components in wet-snow conditions. The generalized four component polarimetric decomposition with unitary transformation (G4U) based generalized surface and volume parameters are utilized to invert snow surface and volume dielectric constants using the Bragg coefficients and Fresnel transmission coefficients respectively. The snow surface and volume wetness are then estimated using an empirical relationship. The effective snow wetness is derived from the weighted averaged surface and volume snow wetness. The weights are derived from the normalized surface and volume scattering powers obtained from the generalized full-polarimetric SAR decomposition method. Six Radarsat-2 fine resolution full-polarimetric datasets acquired over Himachal Pradesh, India along with the near-real time in situ measurements were used to validate the proposed model. The snow wetness derived from the SAR data by the proposed model with in situ measurements indicated that the absolute error at 95% confidence interval is 1.3% by volume.

Enhanced spin Hall effect of transmitted light through a thin epsilon-near-zero slab.

Spin Hall effect (SHE) of transmitted light is small even near the Brewster angle in general case, e.g., at the air-glass interface. However, we find that the SHE can be enhanced when a linearly polarized Gaussian beam transmits through a thin epsilon-near-zero slab due to the difference between the Fresnel transmission coefficients t(p) and t(s). For a vertically polarized incident beam, the spin-dependent transverse displacement of transmitted beam is enhanced near the Brewster angle, while it takes large value over a large angle scale for a horizontally polarized incident beam.

A Longitudinally Polarized Beam Generated by a Binary Axicon

Based on theoretical analysis and numerical modeling, we show the possibility of generating an extended longitudinally polarized light beam by a high-aperture binary axicon. Modeling was performed, in view the method of integral plane-wave decomposition in a Mansuripur modification with account for the Fresnel transmission coefficient, as well as based on the solution of the Helmholz equation using the finite element method. We show that, depending on the type and polarization of the illuminating beam, the structure of the generated beam and the relative energy of the electric-field longitudinal component change. The well-defined longitudinally polarized light needle with the greatest content of the longitudinal component is generated at the diffraction of radially polarized radiation on a high numerical-aperture axicon.

Estimation of snow density using full-polarimetric Synthetic Aperture Radar (SAR) data

In this paper, a new snow density estimation methodology is proposed for full-polarimetric Synthetic Aperture Radar (SAR) data. The generalized four component polarimetric decomposition with unitary transformation (G4U) based generalized volume parameter is utilized to invert snowpack dielectric constant using the Fresnel transmission coefficients. The snow density is then estimated using an empirical relationship. Six Radarsat-2 fine resolution full-polarimetric C-band datasets were acquired over Himachal Pradesh, India. The near-real time in-situ measurements were collected with the satellite pass to validate the proposed method. The mean absolute error (MAE) of the proposed method is 0.027gcm−3 and the root mean square error (RMSE) is 0.032gcm−3. The snow density variation within a season were also analyzed using multi-temporal Radarsat-2 data.

Efficient Algorithm for the Evaluation of the Physical Optics Scattering by NURBS Surfaces With Relatively General Boundary Condition

An adaptive integration algorithm is presented for the computation of the Physical Optics (PO) electric and magnetic field scattered by electrically large objects modeled by Non-Uniform Rational B-Splines (NURBS). The algorithm is the customization of a more general-purpose result that has been recently published. By using a unique formulation both impenetrable (e.g., impedance surfaces, coated conductors) as well as transparent thin sheet materials (e.g., thin dielectric panels, or frequency selective surfaces) are treated, via their Fresnel reflection and transmission coefficients. The PO radiation integral is evaluated over the NURBS parametric domain. Since most of the computer-aided geometric design (CAGD) tools are based on NURBS, the proposed algorithm allows a straightforward electromagnetic analysis of the structures by exploiting the standard available geometrical description, with no need of generating new geometrical models. Furthermore, the proposed adaptive sampling requires a number of integration points that is found to be drastically smaller than that resulting from standard Nyquist-based sampling integration algorithms. Such reduction of the sampling points is achieved by resorting to high-frequency technique concepts and allows a significant reduction of the CPU computational burden. Therefore the algorithm is efficient and particulary suitable for the electromagnetic characterization of real-life electrically large objects.