Reflection Phase Shift Research Articles

Modeling and simulation of polarization errors in reflective fiber optic current sensor

Several key optical components in a reflective fiber optic current sensor (R-FOCS) show error characteristics, which induces linearly polarized light wave in polarization maintaining (PM) fiber and circularly polarized light wave in sensing fiber to be an elliptically polarized light wave. Therefore, nonreciprocal phase shift induced by magnetic field of the current is interrupted by the wrong polarization state. Focused on optical polarization error in R-FOCS, we analyze the characteristics of polarization errors associated with optical components in R-FOCS theoretically, and demonstrate the methods to build optical polarization error models by using Poincaré sphere and Jones matrix, respectively. Then, based on a model of polarization states in R-FOCS, we theoretically investigate the effect of several main error factors on optical polarization characteristics, including polarizing performance of polarizer, phase delay in quarter-wave retarder, splice angular between quarter-wave retarder and PM fiber, birefringence in sensing head and mirror reflection phase shift error. Finally, we quantify a nonreciprocal phase shift to be detected in R-FOCS with optical polarization error respectively, and propose measures.

Mapping Surface-Plasmon Polaritons and Cavity Modes in Extraordinary Optical Transmission

Transmission of light through periodic metal films with intensity considerably exceeding that predicted by aperture theory is referred to as extraordinary optical transmission (EOT). The mechanisms responsible for this effect have been investigated intensively during the past decade. Here, we show an elegant method of visualizing the operative physical mechanisms for model resonance systems. By numerically mapping the resonance loci, modal and plasmonic mechanisms emerge clearly with delineated regions of dominance. Thus, the photonic transmission resonances are parametrically correlated with localized electromagnetic fields forming pure surface-plasmon polaritons (SPPs), coexisting plasmonic and cavity-mode (CM) states, and pure CMs. This mapping method renders a consistent picture of the transitions between photonic states in terms of key parameters. It shows how the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> CM seamlessly morphs into the odd SPP mode as the film thickness diminishes. Similarly, the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> mode converts to the even SPP mode. At the intersection of these mode curves, an EOT-free gap forms due to their interaction. On account of a reflection phase shift of a slit-guided mode, an abrupt transition of the resonance loci in the SPP/CM region is observed.

Principal angles and principal azimuths of frustrated total internal reflection and optical tunneling by an embedded low-index thin film

The condition for obtaining a differential (or ellipsometric) quarter-wave retardation when p- and s-polarized light of wavelength λ experience frustrated total internal reflection (FTIR) and optical tunneling at angles of incidence ϕ ≥ the critical angle by a transparent thin film (medium 1) of low refractive index n1 and uniform thickness d, which is embedded in a transparent bulk medium 0 of high refractive index n0 takes the simple form: -tanh2 x = tan δp tan δs, in which x = 2πn1(d/λ)(N2sin2ϕ - 1)(1/2), N = n0/n1, and δp, δs are 01 interface Fresnel reflection phase shifts for the p and s polarizations. From this condition, the ranges of the principal angle and normalized film thickness d/λ are obtained explicitly. At a given principal angle, the associated principal azimuths ψr, ψt in reflection and transmission are determined by tan2ψr = -sin 2δs/sin 2δp and tan2ψt = -tan δp/tan δs, respectively. At a unique principal angle ϕe given by sin2ϕe = 2/(N2 + 1), ψr = ψt = 45° and linear-to-circular polarization conversion is achieved upon FTIR and optical tunneling simultaneously. The intensity transmittances of p- and s-polarized light at any principal angle are given by τp = tan δp/tan (δp - δs) and τs = -tan δs/tan (δp - δs), respectively. The efficiency of linear-to-circular polarization conversion in optical tunneling is maximum at ϕe.

Effects of reflector-induced interferences on light extraction of InGaN/GaN vertical light emitting diodes

We provide a large F–P cavity model to analyze the effects of reflector-induced interferences on light extraction of InGaN/GaN vertical light emitting diodes (VLEDs). It shows that the distance ( d) between the active region and the metal reflector has a significant influence on extraction efficiency due to interferences. The maximum in extraction efficiency corresponding to the optimal d is about three times the neighboring minimum. The reflector of different metals is considered in this model and the results show that the optimal d and the value of the maximum in the extraction efficiency are directly related to the type of metal, which can be attributed to varied reflection phase shift and reflectivity on different metals, respectively.

Extracting bottom reflection parameters from the vertical correlation of ambient noise in shallow water

A method is introduced to extract reflection characteristics at smaller angles from the vertical correlation of surface-generated noise in shallow water, since the relationship of the two is analyzed. By presenting the vertical correlations of the ambient noise data measured in one experiment in China, the geo-acoustics parameters are estimated. It is shown that these parameters are mutual coupled, therefore a segmentation inversion algorithm has been developed. The reflection phase shift is obtained according to curve fitting or empirical expressions, while the reflection energy is inferred subsequently. The simulation calculated using the inverted geo-acoustic parameters is in good agreement with the explosive sources measurement. There is a discrepancy of about 10% in the prediction values. It is effective for acoustic field prediction by extracting bottom reflection parameters from the noise vertical correlation. The advantage of using reflection parameters is not limited. In addition, it is simple and precision to predict acoustical field, as a result of containing interface scattering in the reflection loss.

Multipolar Plasmonic Resonances in Silver Nanowire Antennas Imaged with a Subnanometer Electron Probe

We detect short-range surface plasmon-polariton (SR-SPP) resonances setup in individual silver nanoantenna structures at high-spatial resolution with a scanning, subnanometer electron probe. Both even and odd multipolar resonant modes are resolved up to sixth order, and we measure their spatial distribution in relation to nanoantenna structures at energies down to 0.55 eV. Fabry-Perot type SR-SPP reflection phase shifts are calculated from direct measurements of antinode spacings in high-resolution plasmonic field maps. We observe resonant SR-SPP antinode bunching at nanoantenna terminals in high-order resonant modes, and antinode shifts in nonhomogeneous local environments. Finally, we achieve good agreement of our experimental SR-SPP maps with numerical calculations of photon excited near fields, using a novel integrated photon excitation geometry.

Simulation of optical performance of red top emitting organic light emitting devices based on phase-shift on reflection theory

In this paper, we study the phase shift of the reflection from a semitransparent electrode of a top-emitting organic light-emitting device (TOLED) which is able to adjust spectrum of TOLED. Based on the micro-cavity theory and the transfer matrix theory, a model is set up to simulate the red TOLED. The simulation results show that the modulation of the device is not only limited to organic layer thickness, but also related to the reflection phase shift. The phase shift of the reflection of top electrode is adjusted through changing the thickness of organic layer capped on the top electrode, thus the TOLED optical performance can be changed. This result provides a useful method of improving the performance of the device.

Broadband one-dimensional photonic crystal wave plate containing single-negative materials

The properties of the phase shift of wave reflected from one-dimensional photonic crystals consisting of periodic layers of single-negative (permittivity- or permeability-negative) materials are demonstrated. As the incident angle increases, the reflection phase shift of TE wave decreases, while that of TM wave increases. The phase shifts of both polarized waves vary smoothly as the frequency changes across the photonic crystal stop band. Consequently, the difference between the phase shift of TE and that of TM wave could remain constant in a rather wide frequency range inside the stop band. These properties are useful to design wave plate or retarder which can be used in wide spectral band. In addition, a broadband photonic crystal quarter-wave plate is proposed.

Phase properties of reflected light in photonic band gap

We find that the phase shifts of reflected light within band gap of two-dimensional photonic crystal (PC) are as follows: with frequency altering from the lower edge to the upper edge of first stop band, the reflection phase shift varies from −π to 0 for the PC’s unit cell with the high-index material near the center, while it varies from 0 to π for that with low-index material near the center. For the higher-order stop band, there exists a certain value of filling fraction, which makes the phase shifts in higher-order stop bands almost the same as that in the first stop band. When the filling fraction is far from that value, the phase shifts are significantly different. The further study on the Bloch modes demonstrates that their distribution of electric field and magnetic field determines the phase shifts. Moreover, we have found that, in the overlap area of transverse magnetic and transverse electric stop band, the phase difference between two polarizations of reflected light can remain invariant in a broad frequency region. Based on this property, the broadband and angle-insensitive phase retarders are designed. These interesting phase characteristics will bring about many potential applications.

Mode Characteristics for Square Resonators With a Metal Confinement Layer

Microsquare resonators laterally confined by SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Au/air multilayer structure are investigated by light ray method with reflection phase-shift of the multiple layers and two-dimensional (2-D) finite-difference time-domain (FDTD) technique. The reflectivity and phase shift of the mode light ray on the sides of the square resonator with the semiconductor/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Au/air multilayer structure are calculated for TE and TM modes by transfer matrix method. Based on the reflection phase shift and the reflectivity, the mode wavelength and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> factor are calculated by the resonant condition and the mirror loss, which are in agreement well with that obtained by the FDTD simulation. We find that the mode Q factor increases greatly with the increase of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer thickness d , especially as d < 0.3 ¿m . For the square resonator with side length 2 ¿m and refractive index 3.2, anticrossing mode couplings are found for confined TE modes at wavelength about 1.6 ¿m at d = 0.11 ¿m, and confined TM modes at d = 0.71 ¿m, respectively.

Mode Analysis for Equilateral-Triangle-Resonator Microlasers with Metal Confinement Layers

Mode characteristics are analyzed for electrically injected equilateral-triangle-resonator (ETR) semiconductor microlasers, which are laterally confined by insulating barrier SiO2 and electrode metals Ti-Au. For the ETR without metal layers, the totally confined mode field patterns are derived based on the reflection phase shifts, and the Q -factors are calculated from the far-field emission of the analytical near field distribution, which are agreement very well with the numerical results of the finite-difference time-domain (FDTD) simulation. The polarization dependence reflections for light rays incident on semiconductor- SiO2-Ti-Au multi-layer structures are accounted in considering the confinement of TE and TM modes in the ETR with the metal layers. The reflectivity will greatly reduce with a Ti layer between SiO2 and Au for light rays with incident angle less than 30deg especially for the TE mode, even the thickness of the Ti layer is only 10 nm. If the ETR is laterally confined by SiO2 -Au layers without the Ti layer, the Fabry-PEacuterot type modes with an incident angle of zero on one side of the ETR can also have high Q-factor. The FDTD simulation for the ETR confined by metal layers verifies the above analysis based on multi-layer reflections. The output spectra with mode intervals of whispering-gallery modes and Fabry-Perot type modes are observed from different ETR lasers with side length of 10 mum, respectively.

A novel design of the sensor head for avoiding the influence of the reflection phase shift in optical current transducer

We propose a novel structure of the sensor head for optical current transducer (OCT), which consists of a bulk magneto-optic glass with graded index (GRIN) and a ferromagnetic ring acting as magnetic field concentrator. According to the transmission properties of the light in GRIN medium, under certain conditions the light beam propagates along a periodical curved track inside the sensor head and hence is unable to achieve the medium–air interface. Hence, this sensor head can effectively avoid the system error caused by reflection phase shift in the traditional bulk glass optical current transducer (BGOCT). Moreover, the track equation of the light beam, the effective optical path, and the effective range of the incident angle are analyzed and numerically simulated. The results show that the sensitivity of the proposed sensor head can be further improved by appropriately increasing the incident angle and the refractive index difference as well as coating a polarization-maintaining reflective film on the surface of the magneto-optic glass.

Optical current sensor immune to reflection phase shift based on graded-index magneto-optical glass

We propose a new design of bulk glass optical current sensor immune to reflection phase shift, in which an annular graded-index magneto-optical glass with a small prism is used as a sensing head, and the inner and outer layers of the glass possess gradient refractive indices, while the center layer is uniform. Our theoretical analyses show that under certain conditions the light beam will no longer reach the interface between the magneto-optical glass and air during the propagation in the sensing head. Therefore the reflection phase shift could be avoided essentially, resulting in dramatic enhancement of the sensitivity. The influences of the geometrical parameters on the beam traces and the effective range of the initial angle are specified by numerical simulations.

Directive metamaterial-based subwavelength resonant cavity antennas – Applications for beam steering

This article presents the use of composite resonant metamaterials for the design of highly directive subwavelength cavity antennas. These metamaterials, composed of planar metallic patterns periodically organized on dielectric substrates, exhibit frequency dispersive phase characteristics. Different models of metamaterial-based surfaces (metasurfaces), introducing a zero degree reflection phase shift to incident waves, are firstly studied where the bandwidth and operation frequency are predicted. These surfaces are then applied in a resonant Fabry-Perot type cavity and a ray optics analysis is used to design different models of ultra-compact high-gain microstrip printed antennas. Another surface presenting a variable reflection phase by the use of a non-periodic metamaterial-based metallic strips array is designed for a passive low-profile steering beam antenna application. Finally, the incorporation of active electronic components on the metasurfaces, allowing an electronic control of the phase responses, is applied to an operation frequency reconfigurable cavity and a beam steering cavity. All these cavity antennas operate on subwavelength modes, the smallest cavity thickness being of the order of lambda/60. To cite this article: A. Outir et al., C R. Physique 10 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Open Perturbatively Long-Range Integrable GL(&lt;I&gt;N&lt;/I&gt;) Spin Chains

We construct the most general perturbatively long-range integrable spin chain with spins transforming in the fundamental representation of gl(N) and open boundary conditions. In addition to the previously determined bulk moduli we find a new set of parameters determining the reflection phase shift. We also consider finite-size contributions and comment on their determination.

Frustrated total internal reflection from thin-layer structures with a metal film

Formulas of the model of a conducting surface for calculating the reflection coefficient and phase shift of light reflected from a thin metal film at the interface between two dielectrics under the conditions of frustrated total internal reflection are analyzed. The effect of additional dielectric layers is discussed.

利用Gires-Tournois标准具的色散特性来获得窄线宽激光

A longer laser resonator length is benefit for laser linewidth, but harmful for single-frequency operation. A novel way is suggested to narrow the bandwidth of a Fabry-Perot (FP) cavity through increasing the derivative of one round-trip phase shift with respect to the frequency. It can be implemented by replacing one of two FP mirrors with a Gires-Tournois etalon (GTE), called FPGT, as a dispersion element. FPGT resonator has additional axial modes due to the GTE reflection phase shift. Theoretical analyses show that the bandwidth of additional axial modes can be 1% of that of a conventional FP cavity. A distributed feedback (DFB) laser diode can employ FPGT resonator to achieve ultra-narrow linewidth laser. It is shown that the effect of refractivity fluctuation in the gain medium on the linewidth is little, and kilohertz linewidth is achievable for such a device.

Omnidirectional narrow bandpass filter based on metal-dielectric thin films

We show that a metal-dielectric Fabry-Perot (FP) structure can exhibit an omnidirectional transmission for p-polarized light, which means a passband is independent of the incidence angle of light. The omnidirectional passband occurs when the sum of the reflection phase shift at the metal-spacer interface and the propagation shift in the spacer region is almost 2pi for every incidence angle. We numerically and experimentally demonstrate such an omnidirectional narrow bandpass filter in an air/Ag/ZnS/Ag/glass structure. Moreover, we introduce an antireflection coating on both sides of the metal-dielectric FP structure. The transmittance will increase obviously, while the omnidirectional property remains the same.

A Shallow-Water Reverberation Model Based on Perturbation Theory

A shallow-water reverberation model is developed based on Bass perturbation theory. The key component for shallow-water reverberation modeling, the modal backscattering matrix (MBSM), has been investigated and the explicit analytic expressions of the MBSM both for the scattering due to interface roughness and due to sediment volume inhomogeneities are derived. For rough interface scattering, it is shown that the angular dependence and the frequency dependence of the MBSM can be separated: the angular dependence is given by sin <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (? <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> P/2)sin <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (? <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> P/2), where ? <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> is the modal grazing angle and P is a bottom parameter related to the bottom reflection phase shift, and the frequency dependence is given by k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4-n</sup> , where n depends on the power spectrum of the roughness, for instance, n = 3 for Goff-Jordan spectrum. The difference between the scattering due to sediment volume inhomogeneities and the scattering due to rough interface is that there is an extra factor contributed by the vertical correlation and the exponential attenuation of the modal function weighting on the vertical direction in the sediment medium. This extra factor has some important impacts: (1) there will be, in general, a coupled angular-frequency behavior, (2) the angular pattern will decrease more rapidly at small grazing angle area, and (3) the angular pattern is no longer separable. It is shown that only for a ?thin? layer (or low frequency), the scattering due to volume inhomogeneities will have a similar behavior as the scattering due to rough interface. The significant feature of the angular pattern for both kinds of scattering is a marked departure from Lambert's law at small grazing angle area. The explicit analytic expression of the MBSM, and the differences between the two kinds of bottom scattering, given in this paper, provide the opportunity for a comprehensive model-data comparison and a better understanding of the scattering mechanism.

Anomalous Conductance Oscillations and Half-Metallicity in Atomic Ag-O Chains

Using spin density functional theory, we study the electronic and magnetic properties of atomically thin, suspended chains containing silver and oxygen atoms in an alternating sequence. Chains longer than 4 atoms develop a half-metallic ground state implying fully spin-polarized charge carriers. The conductances of the chains exhibit weak even-odd oscillations around an anomalously low value of 0.1G0 (G0=2e2/h) which coincide with the averaged experimental conductance in the long chain limit. The unusual conductance properties are explained in terms of a resonating-chain model, which takes the reflection probability and phase shift of a single bulk-chain interface as the only input. The model also explains the conductance oscillations for other metallic chains.