Omnidirectional Total Reflection Research Articles

Enhancement of optical visible wavelength region selective reflector for photovoltaic cell applications using a ternary photonic crystal

In a recent study, the authors proposed an optical broadband angular reflector having a band selective feature and high reflectivity rate for possible applications in photovoltaic applications using a binary photonic crystal. The obtained 100% reflectivity regions for TE and TM modes were in bandwidths of 244 nm and 134 nm, respectively. In this paper, we show theoretically the enhancement of the omnidirectional total-reflection wavelength range by using a ternary photonic crystal. By introducing a 30 nm-layer of Si3N4 between every two layers, constituting a period of the lattice, the regions of 100% reflectivity for TE and TM modes are improved to bandwidths of 269.641 nm and 155.364 nm, respectively. The improvement in the omnidirectional region is about 16%.

Phosphorene pnp junctions as perfect electron waveguides

The current flow in phosphorene pnp junctions is studied. At the interfaces of the junction, omni-directional total reflection takes place, named anti-super-Klein tunneling, as this effect is not due to an energetically forbidden region but due to pseudo-spin blocking. The anti-super-Klein tunneling confines electrons within the junction, which thus represents a perfect lossless electron waveguide. Calculating the current flow by applying Green’s function method onto a tight-binding model of phosphorene, it is observed that narrow electron beams propagate in these waveguides like light beams in optical fibers. The perfect guiding is found for all steering angles of the electron beam as the total reflection does not rely on the existence of a critical angle. For low electron energies and narrow junctions, the guided modes of the waveguide are observed. The waveguide operates without any loss only for a specific orientation of the junction. For arbitrary orientations, minor leakage currents are found, which, however, decay for low electron energies and grazing incidence angles. It is shown that a crossroad-shaped pnp junction can be used to split and direct the current flow in phosphorene. The proposed device, a phosphorene pnp junction as a lossless electron waveguide may not only find applications in nanoelectronics but also in quantum information technology.

Electron Optics in Phosphorene pn Junctions: Negative Reflection and Anti-Super-Klein Tunneling.

Ballistic electrons in phosphorene pn junctions show optical-like phenomena. Phosphorene is modeled by a tight-binding Hamiltonian that describes its electronic structure at low energies, where the electrons behave in the armchair direction as massive Dirac Fermions and in the orthogonal zigzag direction as Schrödinger electrons. Applying the continuum approximation, we derive the electron optics laws in phosphorene pn junctions, which show very particular and unusual properties. Because of the anisotropy of the electronic structure, these laws depend strongly on the orientation of the junction with respect to the sublattice. Negative and anomalous reflection are observed for tilted junctions, whereas the typical specular reflection is found only if the junction is parallel to the zigzag or armchair edges. Moreover, omni-directional total reflection, called anti-super-Klein tunneling, is observed if the junction is parallel to the armchair edge. Applying the nonequilibrium Green's function method on the tight-binding model, we calculate numerically the current flow. The good agreement of both approaches confirms the atypical transport properties, which can be used in nanodevices to collimate and filter the electron flow or to switch its direction.

Rectifying electromagnetic waves by a single-layer dielectric particle array based on dual-particle coupling

Metamaterials, composed of subwavelength building blocks with artificial electric/magnetic response, have attracted the intensive interest due to the unprecedented controllability of electromagnetic (EM) waves and the potential applications. Nonetheless, the resonance of the metallic building block induces a strong loss, severely limiting the performance. Dielectric particle based subwavelength structures provide an alternative choice for the manipulation of EM waves, meanwhile, circumventing the loss problem inevitable for metallic metamaterials, in particular, in optical regime. It is shown that this kind of metamaterial can be used to guide the surface wave with the dielectric particle chain, which is similar to the surface plasmon mediated wave guiding. The structure is also shown to be capable of implementing negative refraction with negligible loss theoretically and experimentally. In addition, the single-layer dielectric rod array can be used to achieve omnidirectional total reflection at subwavelength scale. To further extend the functionality of dielectric based metamaterials and make them more appropriate for integrated optics, a variety of experimentally feasible configurations should be designed. In this work, based on the Mie scattering theory and the multiple scattering theory, we investigate the manipulation of EM waves through a single-layer subwavelength dielectric rod array (SDRA) and particle coupled system. Our results show that by removing the central dielectric rod in the SDRA and at the beam focus, like a vacancy defect, a normal incident transverse electric polarized Gaussian beam is weakly transmitted with an efficiency of less than 12 percent. By further introducing a dielectric rod with optimized parameters on the incident side of the vacancy defect, an enhanced transmitted EM wave with an efficiency of 36 percent is exhibited, nearly triple that with a solely vacancy defect. By adding another identical dielectric rod symmetrically on the outgoing side of the vacancy defect, the transmitted EM field pattern can be clearly tailored due to the dual-particle coupling so that the forward scattering is intensified, similar to the beaming effect, although the total transmittance is not further improved. Interestingly, by use of dual-particle system composed of metallic rods a similar effect can be realized as well near the surface plasmon resonance, adding flexibility to design. It should be pointed out that one-way beam propagation can be possibly achieved by constructing an asymmetric dual-particle coupling system. More importantly, the proposed systems are simple and experimentally realizable, which makes them favorable for the on-chip beam steering, offering a possibility to improve the optical element design of the integration photonic circuit in the terahertz and optical range.

Tunable Omnidirectional Total Reflection Frequency Range in One-Dimensional Photonic Crystals Based on the Faraday Effect

Tunable Omnidirectional Total Reflection Frequency Range in One-Dimensional Photonic Crystals Based on the Faraday Effect

Tunable Omnidirectional Total Reflection Frequency Range in One-Dimensional Photonic Crystals Based on the Faraday Effect

We report that tunable omnidirectional total reflector can be realized theoretically with one-dimensional (1D) photonic crystals (PCs) by adding external magnetic fields. The 1D PCs consist of two alternating layers with SiO2 and InSb. We show that the 1D PCs have rather large omnidirectional photonic band gaps (omni-PBGs). After being added external magnetic fields the omni-PBGs will be tuned accordingly. The shift ranges of left and right circular polarizations are different. As a result, the omnidirectional reflector and omnidirectional circular polarizer can be realized.

Analysis of enlargement of the omnidirectional total reflection band in a special kind of photonic crystal based on the incident angle domain

A special kind of one-dimensional (1D) magnetic photonic crystal (MPC) is investigated. The refractive indices of the alternating layers in such a MPC are equal. As a result, the stop-band edges of TE mode coincide with those of TM mode, and the stop-bands for both modes expand as the incident angle increases. Based on the incident angle domain method, the omnidirectional total reflection (ODTR) band determined by the wave impedance ratio between the composites can be enlarged substantially using a heterostructure in which the stop-band edges of the sub-PCs can be completely adjacent at any incident angle. Moreover, the requirement of ODTR of each sub-PC is unnecessary, which extends the range of materials; that is, the wave impedance ratio between the composites and the refractive index ratio between the composites and the incident media can be much lower than that required in a single periodic structure.

Design of broad omnidirectional total reflectors based on one-dimensional dielectric and magnetic photonic crystals

Omnidirectional total reflectors based on one-dimensional dielectric and magnetic photonic crystals are investigated in this paper. We adopt the transmission matrix method to analyze the transmission properties of such reflectors and use the decimal genetic algorithm to obtain broad omnidirectional total reflection (ODTR) bandwidth. Finally, an omnidirectional total reflector with very broad ODTR bandwidth of 1.34 ω 0 is achieved.

Investigation of Photonic Band Gaps of One-Dimensional Heterostructure Magnetic Photonic Crystals

Multiple structures in one-dimensional photonic crystals have great potentials for ultrawide omnireflectors and tunable switches. In this paper, we study the propagation of electromagnetic waves in a one-dimensional heterostructure magnetic photonic crystal for both TE and TM incidence polarizations by means of the transfer matrix method. Results show that by stacking two magnetic photonic crystals as a heterostructure magnetic photonic crystal the omnidirectional total reflection frequency range for any polarization enlarged due to overlapping of photonic band gaps of both magnetic photonic crystals. Omnidirectional band gaps in the heterostructure magnetic photonic crystal is enhanced rather than that in a single magnetic photonic crystal.

Anomalous phenomena of electromagnetic wave propagation in metamaterials for arbitrary orientation of optical axis

When there is an angle between the anisotropic metamaterials' optical axis and the electromagneticwave propagation axis, anomalous omnidirectional total reflection and anomalous negative refraction are discovered at the interface. The functional relation between incident angle and refractive angle of energy flow is obtained. According to this relation, we can restructure the refractive angle as negative or positive readily by selecting suitable permittivity and permeability tensors. And under these conditions, an anomalous transmittance emerges，such that when incident angle is less than a value, especially in the vicinity of vertical incident, the transmittance is minimum or even zero. According to these characteristics, a new slab spatial filter is put forward. Compared with the traditional space filter system, this new spatial filter's volume is smaller. And these characteristics can also be used to build a reflector of low spatial frequency.

Improving selective thermal emission properties of three-dimensional macroporous silicon through porosity tuning

We present a theoretical and experimental study on the effect of progressive porosity increase, through multiple oxidation/oxide removal steps, upon the optical characteristics in three-dimensional macroporous silicon. It is shown that, by increasing porosity, optical features can be pushed toward higher frequencies. Optimum porosities exist where normal or omnidirectional total reflection bandwidths are maximized, doubling the initial values. Results are confirmed experimentally through angle-resolved reflectance and thermal emission measurements.

Photonic structures based on dielectric and magnetic one-dimensional photonic crystals for wide omnidirectional total reflection

Omnidirectional total reflection (ODTR) has a wide variety of applications, such as in optical communication, electromagnetic energy transportation, and solar energy engineering. We propose a type of photonic structure made of dielectric and magnetic 1D photonic crystals (PCs). Simulations by the optical transmission matrix method demonstrate that such structures can achieve ODTR in a wide wavelength range. In such structures, the total reflections of the s-polarization part and p-polarization part of the incident wave are caused by the 1D dielectric sub-PC and the 1D magnetic sub-PC, respectively.

ENHANCEMENT OF OMNIDIRECTIONAL REFLECTION IN PHOTONIC CRYSTAL HETEROSTRUCTURES

In this paper we have theoretically studied the omnidirectional total reflection frequency range of a multilayered dielectric heterostructures. Three structures of Na3AlF6/Ge multilayer have been studied. The thickness of the two layers of the first and second structure is differing from each other and the third photonic structure is the combination of first and second structures. Using the Transfer Matrix Method (TMM) and the Bloch theorem, the reflectivity of one dimensional periodic structure for TEand TM-modes at different angles of incidence is calculated. From the analysis it is found that the proposed structure has very wide range of omnidirectional total frequency bands for both polarizations.

Polarization-sensitive propagation in an anisotropic metamaterial with double-sheeted hyperboloid dispersion relation

The polarization-sensitive propagation in the anisotropic metamaterial (AMM) with double-sheeted hyperboloid dispersion relation is investigated from a purely wave propagation point of view. We show that TE and TM polarized waves present significantly different characteristics which depend on the polarization. The omnidirectional total reflection and oblique total transmission can occur in the interface associated with the AMM. If appropriate conditions are satisfied, one polarized wave exhibits the total refraction, while the other presents the total reflection. We find that the opposite amphoteric refractions can be realized by rotating the principle axis of AMM, such that one polarized wave performs the negative refraction, while the other undergoes positive refraction. The polarization-sensitive characteristics allow us to construct two types of efficient polarizing beam splitters under certain achievable conditions.

Planar quarter wave stacks prepared from chalcogenide Ge–Se and polymer polystyrene thin films

Planar quarter wave stacks based on amorphous chalcogenide Ge–Se alternating with polymer polystyrene (PS) thin films are reported as Bragg reflectors for near-infrared region. Chalcogenide films were prepared using a thermal evaporation (TE) while polymer films were deposited using a spin-coating technique. The film thicknesses, d∼165 nm for Ge 25Se 75 ( n=2.35) and d∼250 nm for polymer film ( n=1.53), were calculated to center the reflection band round 1550 nm, whose wavelengths are used in telecommunication. Optical properties of prepared multilayer stacks were determined in the range 400–2200 nm using spectral ellipsometry, optical transmission and reflection measurements. Total reflection for normal incidence of unpolarized light was observed from 1530 to 1740 nm for 8 Ge–Se+7 PS thin film stacks prepared on silicon wafer. In addition to total reflection of light with normal incidence, the omnidirectional total reflection of TE-polarized light from 8 Ge–Se+7 PS thin film stacks was observed. Reflection band maxima shifted with varying incident angles, i.e., 1420–1680 nm for 45° deflection from the normal and 1300–1630 nm for 70° deflection from the normal.

Total reflection of electromagnetic waves propagating from an isotropic medium to an indefinite metamaterial

The existence conditions for total reflection and the corresponding critical angle at the interface separating an isotropic medium and an indefinite metamaterial for TE- and TM-polarized electromagnetic waves are obtained. For different kinds of indefinite metamaterial, there appear different total reflection phenomena. Particularly, the anomalous total reflection in which the incident angle is smaller than the critical angle and the Brewster’s angle can be smaller than the critical angle can occur for anti-cutoff medium. Furthermore, the omnidirectional total reflection exists for the always cutoff medium and anti-cutoff medium. The total reflection depends on the thickness of indefinite metamaterial when the indefinite metamaterial is finite, and the photon tunneling phenomenon can occur when the thickness of indefinite metamaterial is smaller than wavelength.

Enhancement of omnidirectional total-reflection wavelength range by using one-dimensional ternary photonic bandgap material

Here we demonstrate by theoretical analysis a novel way to enhance the omnidirectional total-reflection wavelength range in one-dimensional photonic bandgap material by using a ternary periodic structure (i.e., three material layers constituting a period of the lattice). The omnidirectional total reflection range using a binary (BaF2/PbS) periodic structure was enhanced by 108 nm when the structure was modified by sandwiching a thin layer of ZrO2 between every two layers, constituting a period of the lattice. A shift of the omnidirectional range toward higher wavelengths was also observed. When the sandwiched layer was CeF3, the enhancement in the range was 120 nm. As the sandwiched layer is very thin, there will not be any significant increase in the size of the reflector, contrary to the case of heterostructured photonic crystals (PCs) where two or more PCs are clubbed together to achieve enhancement.

Omnidirectional total reflection for liquid surface waves propagating over a bottom with one-dimensional periodic undulations

We study theoretically the propagation of liquid surface waves over a bottom with one-dimensional (1D) periodic undulations. We find a general criterion for omnidirectional total reflection in such a system. Numerical simulations based on a transfer matrix method demonstrate unambiguously the existence of omnidirectional total reflection for liquid surface waves propagating over a bottom with 1D periodic undulations.

Enlargement of omnidirectional total reflection frequency range in one-dimensional photonic crystals by using photonic heterostructures

We show theoretically that the omnidirectional total reflection frequency range of a multilayer dielectric reflector can be substantially enlarged as desired by using photonic heterostructures. This photonic heterostructure consists of different one-dimensional (1D) photonic crystals. The constituent 1D photonic crystals have to be properly chosen such that their omnidirectional photonic band gaps of the adjacent photonic crystals overlap each other.