Sahar A. El-Naggar

Tunability of two dimensional n-doped semiconductor photonic crystals based on the Faraday effect

In this paper, we theoretically investigate the effect of an external magnetic field on the properties of photonic band structures in two-dimensional n-doped semiconductor photonic crystals. We used the frequency-dependent plane wave expansion method. The numerical results reveal that the external magnetic field has a significant effect on the permittivity of the semiconductor materials. Therefore, the photonic band structures can be strongly tuned and controlled. The proposed structure is a good candidate for many applications, including filters, switches, and modulators in optoelectronics and microwave devices.

The properties of cutoff frequency in two-dimensional superconductor photonic crystals

In this paper, by means of frequency-dependent plane wave expansion method we investigate the properties of photonic band structures in two-dimensional superconductor photonic crystals. Effects of cut-off frequency are investigated by various parameters such as filling factor, the lattice constant alteration, threshold frequency of the superconductor, and shape of the rods as well. We show that the cut-off frequency can be efficiently tuned by the operating temperature. Moreover, it can be tailored by changing the dielectric constant of the background and the threshold frequency of the superconductor material.

Complete band gaps of phononic crystal plates with square rods.

Much of previous work has been devoted in studying complete band gaps for bulk phononic crystal (PC). In this paper, we theoretically investigate the existence and widths of these gaps for PC plates. We focus our attention on steel rods of square cross sectional area embedded in epoxy matrix. The equations for calculating the dispersion relation for square rods in a square or a triangular lattice have been derived. Our analysis is based on super cell plane wave expansion (SC-PWE) method. The influence of inclusions filling factor and plate thickness on the existence and width of the phononic band gaps has been discussed. Our calculations show that there is a certain filling factor (f=0.55) below which arrangement of square rods in a triangular lattice is superior to the arrangement in a square lattice. A comparison between square and circular cross sectional rods reveals that the former has superior normalized gap width than the latter in case of a square lattice. This situation is switched in case of a triangular lattice. Moreover, a maximum normalized gap width of 0.7 can be achieved for PC plate of square rods embedded in a square lattice and having height 90% of the lattice constant.

Tuning the flow of light in two-dimensional metallic photonic crystals based on Faraday effect

Abstract In this paper, we investigate the tunability of two-dimensional metallic photonic crystals by an external magnetic field. Our theoretical analysis is based on the frequency-dependent plane wave expansion method. The numerical results show that the external magnetic field has a pronounced effect on the permittivity of the metals. Therefore, the photonic band structures can be strongly tuned and controlled by adjusting the external magnetic field. Our structure is a good candidate for many applications such as filters, optical switches and modulators.

Thermal properties and two-dimensional photonic band gaps

The effect of temperature on a two-dimensional square lattice photonic crystal composed of Si rods arranged in an air background was investigated theoretically using the plane-wave expansion method...

Dependency of the photonic band gaps in two-dimensional metallic photonic crystals on the shapes and orientations of rods

Photonic bands in two types of two-dimensional metallic photonic crystals (2-D MPCs), which are composed of dielectric rods embedded into a metallic background (type I MPCs) and metallic rods in a dielectric background (type II MPCs), are investigated theoretically using a method based on the frequency-dependent plane-wave expansion method. We discuss the maximization of the normalized gap width as a function of the rod shapes and orientations. In addition, we study the effect of dielectric constants of the rods and the background on the width of the photonic band gap. Four different shapes of rods-square, circular, diamond, and rectangular-are considered. The numerical results show that the type I MPCs have a higher normalized gap width than the type II MPCs. We observe that the rotation of the noncircular rods in the type I MPCs leads to a slight variation, less than 10%, in the normalized values of the gap width in the two lattice structures. However, rotating the metallic square rods arranged in a square lattice results in doubling of the normalized gap width. The normalized gap width can be tailored by changing the dielectric constant of the rods (background) in type I (type II) MPCs.

Modeling of a wide band pass optical filter based on 1D ternary dielectric?metallic?dielectric photonic crystals

We suggest ternary structures of dielectric?metal?dielectric photonic structures to be used as optical band pass filters. We theoretically study and evaluate the optical properties of these one-dimensional structures. ZnSe/metal/LiF and SiC/metal/SiO2 with three metals, namely silver, gold and copper, are suggested as the optical filters. We calculated the reflectance and the transmittance of electromagnetic waves (EMW) out of these structures using the transfer matrix method. These calculations take place for the case of normal and oblique incidences using actual measured values for the indices of refraction. Our calculations show that such photonic crystal (PC) filters have a well shaped pass band in the visible range and block efficiently ultraviolet and infrared EMW. Our results show that PCs having silver as the metal layer are preferred to those having gold and copper because of the high transmittance in the visible range. A SiC/Ag/SiO2 filter shows better performance than a ZnSe/Ag/LiF one from the transmittance and the shape of the band points of view. Such a filter shows a well shaped wide band over the range of incident angles from 0? to 80?.

Analytical study of carrier photogeneration and photocurrent in thin silicon solar cells with specular and diffuse back reflection

An analytical study of the effect of back reflection in thin silicon solar cells implementing a practical (nonideal) diffuse reflector at the back side is presented. Both the diffuse and specular reflection components are considered. The reflection properties of the back reflector are described by means of three parameters, which are interpreted in terms of a simple physical model. An exact expression for the generation profile resulting from specular and diffuse reflections is derived and its dependence on the reflector parameters is studied. A mechanism through which specular reflection can significantly enhance light trapping in the case of relatively weak diffuse reflection is proposed. The photocurrent boost doe to both types of reflections acting simultaneously is estimated.

Properties of defect modes in one-dimensional photonic crystals that contain single negative materials

Abstract. We examine the properties of the defect modes arising in the zero-effective phase (zero-φ) gap when a dielectric defect layer is introduced in a one-dimensional photonic crystal containing single negative materials. We show that the defect modes inside the zero-φ gap can be as sensitive to the incidence angle as those inside the Bragg gap. In addition, adjusting the properties of the dielectric defect layer can control the frequencies and the number of defect modes. We present a brief design of a polarization-independent spatial filter based on those defects. The proposed spatial filter can work at dual carrier frequencies with low-pass and wide-pass characteristics. Our results can help improve the performance of microwave devices independent of the source wave polarization.