Brewster Condition Research Articles

Ultra-broadband reflectionless Brewster absorber protected by reciprocity

The Brewster’s law predicts zero reflection of p-polarization on a dielectric surface at a particular angle. However, when loss is introduced into the permittivity of the dielectric, the Brewster condition breaks down and reflection unavoidably appears. In this work, we found an exception to this long-standing dilemma by creating a class of nonmagnetic anisotropic metamaterials, where anomalous Brewster effects with independently tunable absorption and refraction emerge. This loss-independent Brewster effect is bestowed by the extra degrees of freedoms introduced by anisotropy and strictly protected by the reciprocity principle. The bandwidth can cover an extremely wide spectrum from dc to optical frequencies. Two examples of reflectionless Brewster absorbers with different Brewster angles are both demonstrated to achieve large absorbance in a wide spectrum via microwave experiments. Our work extends the scope of Brewster effect to the horizon of nonmagnetic absorptive materials, which promises an unprecedented wide bandwidth for reflectionless absorption with high efficiency.

Terahertz beam focusing through designed oblique metal-slit array

Manipulation of propagating beams is essential in applications, and the potentially arising phenomena offer attractive optical components. However, the design of optical components using only naturally occurring materials has approached physical limits, and artificial materials such as metamaterials and metasurfaces are a way forward to open the door to sophisticated optical components. This paper shows manipulation of terahertz beams through designed oblique metal-slit arrays where a common metal-slit array does not perform as a lens. The oblique metal-slit array has a refractive index determined as a function of a steep angle. The lens consists of multiple metal plates with a designed oblique angle, and a convex output structure produces a focusing effect. We also suggest that the Brewster phenomenon in the lens can simply enhance the electric field intensity at the focal point. The Brewster condition of the lens is correlated with a jagged edged face on the input side with an appropriate metal-slit spacing and thickness. The phenomenon would be applicable to numerous promising components and applications such as gain-enhancement optical components and perfect impedance-matching polarizers.

Extending omnidirectional reflection bands in one-dimensional photonic crystals

The presence of the Brewster point in one-dimensional photonic crystals restricts the possibility of achieving full omni-directional reflection at large incident wave vectors. We show that it is possible to achieve omnidirectional reflection in both rarefied and refracting incident media utilising periodic structures consisting of three or more distinct layers with differing refractive indices. In these ternary periodic structures the Brewster condition is not satisfied simultaneously at all interface and so strong reflection bands are achievable at any angle of incidence and polarisation state. Combining the ternary structure with layer chirping is necessary to open the full omnidirectional band.

Nonlocal optical effects on the Goos–Hänchen shifts at multilayered hyperbolic metamaterials

The lateral beam shift of light incident on a multilayered hyperbolic metamaterial (HMM) is investigated using a theoretical model which emphasizes the nonlocal optical response of the indefinite material. By applying an effective local response theory formulated recently in the literature, it is found that nonlocal effects only affect p polarized light in this Goos–Hänchen (GH) shift of the incident beam; leading to a blue-shifted peak for positive shifts at high frequencies and red-shifted dip for negative shifts at low frequencies in the GH shift spectrum. An account for the observed phenomenon is given by referring to the ‘Brewster condition’ for the reflected wave from the HMM. This observation thus provides a relatively direct probe for the nonlocal response of the HMM.

Performance of eliminating sun glints reflected off wave surface by polarization filtering under influence of waves

Abstract For the purpose of investigating influence of waves on the performance of eliminating glints reflected off wavy sea surface by polarization filtering, we viewed glints twinkled in glitter path using a simultaneous multi-channel polarization camera. By analyzing the recorded data, it is found that the waving of water surface do not make unlimited influence on polarization elimination performance. Then a semi-quantitative analysis method is introduced. Combing with simulation results, it is concluded that the influence level of waves on polarization elimination performance is determined by observation geometry primarily and then limited by receiver's field of view. When observation geometry is approach to the Brewster condition closer, polarization filtering will has batter performance which is represented by more decrease of intensity of glints and lower influence level of waves on reducing intensity of glints.

Characterization of the MgO/GaSe0.5S0.5 heterojunction designed for visible light communications

In this study an optoelectronic design is reported and characterized. The device is made of p-type MgO solved in sodium silicate binder and n-type GaSe0.5S0.5 heterojunction. It is described by means of X-ray diffraction, optical absorption and reflection in the incident light wavelength range of 190–1100nm and by means of dark and 406nm laser excited current (I)–voltage (V) characteristics. The optical reflectance was also measured as a function of angle of incidence of light in the range of 35–80°. The structural analysis revealed no change in the existing phases of the device composers. In addition, it was observed that for pure sodium silicate and for a 67% content of MgO solved in sodium silicate binder (33%), the heterojunction exhibits a valence band shift of 0.40 and 0.70eV, respectively. The painting of MgO improved the light absorbability significantly. On the other hand, the angle-dependent reflectance measurements on the crystal displayed a Brewster condition at 70o. The MgO/ GaSe0.5S0.5 heterojunction exhibited no Brewster condition when irradiated from the MgO side. Moreover, for the crystal and the MgO/GaSe0.5S0.5 heterojunction, the dielectric spectral analysis revealed a pronounced increase in the quality factor of the device. The I–V characteristics of the device revealed typical optoelectronic properties with high photo-response that could amplify the dark current 24 times when irradiated with 5mW power laser light. The structural, optical, dielectric and electrical features of the MgO/GaSe0.5S0.5 heterojunction nominate it for use in visible light communication technology.

Optical dynamics of MgO/Ga4Se3S interface

Abstract A new p–n interface made of p-type MgO as an optical window to the n-type Ga4Se3S crystals is investigated by means of optical reflectance, transmittance and absorbance in the incident light wavelength ( λ ) range of 200–1100 nm. The reflectivity spectral analysis as a function of angle of incidence for MgO, Ga4Se3S and the Ga4Se3S/MgO layers revealed Brewster angles of 75°, 80° and 70° with the corresponding dielectric constants of 13.93, 32.16 and e MgO = 7.55 e Ga 4 Se 3 S , respectively. To remove Brewster condition of reflection and obtain maximum absorption, the light must be incident from the MgO side. A novel light absorbability is observed. Namely, for all λ λ values, while the crystal absorbance decreases significantly, the bilayer absorbance increased by four times in the visible range and three times in the IR range of spectrum. In the MgO layer, two distinct sets of band tails of the localized states with the widths of 2.30 and 1.26 eV are determined from the absorption spectral analysis. These band tails shift up to 2.32 and 1.44 eV when the interface is constructed. In addition, an indirect energy band gaps (Eg) which are located at 3.10, 2.13 and 1.90 eV for the MgO, Ga4Se3S and the Ga4Se3S/MgO layers, respectively, are determined. The Eg value of the crystal shifts by a 0.23 eV upon bilayer construction. The reflection properties, the band tails, the energy gaps and related shifts make the Ga4Se3S/MgO interface attractive for fabrication of solar cells, narrow barrier resonant tunneling diodes or quantum dots, and as an optical detector for tunable types of lasers.

Influence of the orientation of optical axis on the transmission properties of one-dimensional photonic crystals containing uniaxial indefinite metamaterial

The transmission properties of a one-dimensional photonic crystal containing uniaxial indefinite metamaterial are investigated using the transfer matrix method. It is shown that the photonic bandgaps of the structure strongly depend on the orientation of the optical axis of the indefinite metamaterial. The results show that it is possible to obtain the Brewster condition for both TE and TM polarizations. This condition noticeably affects the profiles of the electromagnetic field inside the one-dimensional periodic structure.

Omnidirectional constant transmission and negative Brewster angle at planar interfaces associated with a uniaxial medium

This paper presents our detailedly theoretical analyses on omnidirectional constant transmission and negative Brewster angle at planar interfaces associated with a uniaxial medium. The amplitude reflection and transmission coefficients at planar interfaces associated with uniaxial media are derived by examining the boundary condition and the dispersion relation. It is found that under certain conditions, the coefficients are constants independent of the incident angle. Another interesting phenomenon is that an interface between isotropic and uniaxial media can exhibit negative refraction under Brewster condition. Our results offer considerable potential device applications of uniaxial media.

Spatial solitons in periodic nanostructures

We present the first principle theory of the existence and stability of TE and TM spatial solitons in a subwavelength periodic semiconductor-dielectric structure. We have found that for the wavelength 1550nm and the interface separation close to and less than 100nm the band structure of the linear TE and TM waves becomes similar to the band structure of a homogeneous medium. The properties of TE solitons change accordingly. However, the transverse profiles of the TM solitons continue to reflect the subwavelength geometry of the structure and develop dominant intensity peaks inside the low index dielectric slots. Our stability analysis based on the linearized Maxwell equations indicates that the nonlinear TM waves can be approximated as the evanescently coupled modes of the slot waveguides with the low index dielectric core and the high index semiconductor cladding. Transition to the regime where the slot waveguides start to determine properties of TM waves is associated with the so called Brewster condition.

Theoretical analysis of two nonpolarizing beam splitters in asymmetrical glass cubes

The design principle for a nonpolarizing beam splitter based on the Brewster condition in a cube is introduced. Nonpolarizing beam splitters in an asymmetrical glass cube are proposed and theoretically investigated, and applied examples are given. To realize 50% reflectance and 50% transmittance at specified wavelengths for both polarization components with an error of less than 2%, two measurements are taken by adjusting the refractive index of the substrate material and optimizing the thicknesses of each film in the design procedures. The simulated results show that the targets are achieved using the method reported here.

宽带偏振薄膜的设计

The reflection and transmittance of s- and p-polarized lights should be treated separately at nonzero angle incidence. By choosing two special film materials whose refractive indices meet the Brewster condition in a given incident angle, the reflection of p-polarized light can be eliminated. When the two materials are fabricated into multilayer stacks, the reflection of s-polarized light can be largely increased while the reflection of p-polarized light keeps low. According to this principle, a film polarizer with bandwidth of 198 nm or even more is designed.

New designs and characteristics analysis of non-polarizing beam splitters

When used at oblique angles of incidence, the reflectance and transmittance of thin films exhibit strong polarization effects, particularly for the films inside a glass cube, which results from the fact that the tangential components of the electric and magnetic fields are continuous across each layer interface. However, for many applications, the polarization effects are undesirable and should be reduced. In the present paper, a method for designing a non-polarizing beam splitter (NPBS) in a cube is introduced, based on the Brewster condition. Applied examples of the NPBSs designed employing this method are also researched within specified wavelength ranges. Moreover, the effects of some important parameters, including the incident angle and the material indices, on the NPBS are investigated. Optical property simulations are presented.

Unattenuated light transmission through the interface between two materials with different indices of refraction using magnetic metamaterials

We report on the application of a magnetic composite metamaterial. The magnetic response of the metamaterial in the light region of the spectrum can realize the Brewster condition for $s$-polarized light. By introducing a uniaxial magnetic metamaterial consisting of stacked two-dimensional arrays of split-ring resonators, the Brewster effect can be produced for both $p$ and $s$ polarizations simultaneously. We also propose optical components that can interconnect two materials of different refractive index and that can transmit the light across the material boundary without any reflection at the interface.

Brewster angle and optical tunneling in one-dimensional photonic crystals composed of left- and right-handed materials

The band structure of periodic multilayers that include left- and right-handed materials is studied under the formalism of equivalent layers. Although the band structure of these systems looks quite complicated, it is shown that bandgaps and bulk bands follow a simple behavior that can be explained in terms of the phase thickness of one period and the Brewster condition that can be satisfied in both polarizations. The optical tunneling is explained in terms of optical holes that are points where the gaps narrow and close owing to the zero optical thickness of the period under given conditions. It is shown that optical tunneling can be present also under nonnormal incidence.

Sensitive absorption detection for micro-column liquid chromatography by ultraviolet forward-scattering degenerate four-wave mixing

The performance of forward-scattering degenerate four-wave mixing (F-D4WM) in the mid-ultraviolet (UV) region (351 nm) as a detection technique for micro-column liquid chromatography (μLC) is studied, using nitro-substituted polycyclic aromatic hydrocarbons (NO 2-PAHs) and amino-substituted anthraquinones (AAQs) as test compounds. When using round capillaries, the concentration limits of detection (LOD) for the NO 2-PAHs were 20–70-fold better compared with absorption detection using a U-shaped detector cell. The final result is influenced by photochemical degradation during 351 nm F-D4WM detection. Furthermore, it is demonstrated that the use of recently commercially available square capillaries (i.e., capillaries with both a square cross section and a square bore) instead of round ones is quite suitable for F-D4WM detection. The square capillary (internal dimensions, 75×75 μm 2; external dimensions 300×300 μm 2) did not cause significant chromatographic band broadening in μLC. The angle of incidence of the laser light should be 56°, thus fulfilling the Brewster condition at the air–quartz boundary. Using this approach for the AAQs, compounds not prone to significant photodegradation under the experimental conditions, a further 4-fold improvement was achieved. As a result, the overall gain in concentration LOD for 2-amino-9,10-anthraquinone (molar absorptivity 4000 M −1 cm −1 at 351 nm) was from 4 to 0.05 μM, and baseline irregulations were reduced.

Nonspecular first-order effects in Kretschmann's configuration

Abstract First-order nonspecular effects for Gaussian beams reflected on the first interface of a system formed by two interfaces of isotropic materials are studied. The complex lateral displacement is analytically determined and the validity of the approximations made is analysed. It is shown that the lateral displacement is independent of the beam waist and the approximation results suitable even for very narrow beams near Brewster's condition. With a dielectric-metal-dielectric configuration (Kretschmann's) and under resonance conditions, lateral displacements of up to 25% of the beam width can be obtained.

Nonspecular first-order effects in Kretschmann's configuration

First-order nonspecular effects for Gaussian beams reflected on the first interface of a system formed by two interfaces of isotropic materials are studied. The complex lateral displacement is analytically determined and the validity of the approximations made is analysed. It is shown that the lateral displacement is independent of the beam waist and the approximation results suitable even for very narrow beams near Brewster's condition. With a dielectric-metal-dielectric configuration (Kretschmann's) and under resonance conditions, lateral displacements of up to 25% of the beam width can be obtained.

Forward-scattering degenerate four-wave mixing as a potential laser-based absorption detection method in liquid separation systems: Coupling to conventional-size liquid chromatography

An explorative study on the compatibility of liquid separation systems, such as (micro) liquid chromatography (LC) and capillary electrophoresis (CE), and forward-scattering degenerate four-wave mixing (F-D4WM) as a detection method is presented. F-D4WM is a laser-based technique showing some analogy with holographic spectroscopy: a signal on a theoretical dark background is observed as a result of light absorption by an analyte. Parameters considered are solvent composition focussing on acetonitrile, methanol and water; mobile phases in LC and CE), detector cell construction, and influences of laser beam powers. A specially designed detector cell has been developed to meet the Brewster condition, both at the air-quartz and the quartz-liquid boundaries. For practical reasons, the tested cell has an optical pathlength of 1 mm; reduction to 100 μm is required to apply the cell in microseparations. The F-D4WM technique has been involved for detection in a conventional-size, reversed-phase LC separation of 1- and 2-aminoanthraquinones. The detection limit obtained (for the 1 mm cell) is 2 × 10 −5 absorbance units. The experiments indicate that further reduction of background deserves explicit attention.

Manifestly covariant formalism for electromagnetism in chiral media.

A formalism of electromagnetism covariant under the complex rotation group is first described and then discussed thoroughly, in the case of two-dimensional electromagnetic fields, in homogeneous, isotropic chiral media. As a result, we obtain the generalized Descartes-Snell laws, the Fresnel relations for reflection and refraction, as well as the Brewster condition for plane waves incident on a surface of discontinuity between chiral and achiral media.