Characteristics Of Photonic Band Gaps Research Articles

Photonic band gaps in one-dimensional magnetized plasma photonic crystals with arbitrary magnetic declination

In this paper, the properties of photonic band gaps and dispersion relations of one-dimensional magnetized plasma photonic crystals composed of dielectric and magnetized plasma layers with arbitrary magnetic declination are theoretically investigated for TM polarized wave based on transfer matrix method. As TM wave propagates in one-dimensional magnetized plasma photonic crystals, the electromagnetic wave can be divided into two modes due to the influence of Lorentz force. The equations for effective dielectric functions of such two modes are theoretically deduced, and the transfer matrix equation and dispersion relations for TM wave are calculated. The influences of relative dielectric constant, plasma collision frequency, incidence angle, plasma filling factor, the angle between external magnetic field and +z axis, external magnetic field and plasma frequency on transmission, and dispersion relation are investigated, respectively, and some corresponding physical explanations are also given. From the numerical results, it has been shown that plasma collision frequency cannot change the locations of photonic band gaps for both modes, and also does not affect the reflection and transmission magnitudes. The characteristics of photonic band gaps for both modes can be obviously tuned by relative dielectric constant, incidence angle, plasma filling factor, the angle between external magnetic field and +z axis, external magnetic field and plasma frequency, respectively. These results would provide theoretical instructions for designing filters, microcavities, and fibers, etc.

The characteristics of photonic band gaps for three-dimensional unmagnetized dielectric plasma photonic crystals with simple-cubic lattice

In this paper, the characteristics of photonic band gaps (PBGs) for two types of three-dimensional unmagnetized dielectric plasma photonic crystals (PPCs) with simple-cubic lattices are theoretically studied based on a modified plane wave expansion (PWE) method. The first type (type-1) is a three-dimensional PPCs which dielectric spheres are arranged in the plasma background periodically with simple-cubic lattice, while the second one (type-2) is a complementary structure composed of plasma spheres in the dielectric background. Theoretical derivation of band structure of type-2 structure has been induced. We present the evolution of the locations and the midgap ratios of first two PBGs for two types of PPCs as functions of plasma frequency, filling factor, the relative dielectric constant and plasma collision frequency, respectively. The results show that not only the locations but also midgap ratios and bandwidths of first two PBGs for two types of PPCs can be tuned by plasma frequency, filling factor and the relative dielectric constant, respectively. However, the plasma collision frequency has no effect on the frequency ranges and midgap ratios of the first two PBGs for two types of PPCs.

The Research on Multi-Channel Narrow Band Filter Based on Dual-Periodical Photonic Crystal Heterostructures

A type of filter based on a one-dimensional (1-D) photonic crystal (PC) with dual-periodical heterostructures is designed. The characteristics of photonic band gap (PBG) are studied by transfer matrix method. The result showed that a PBG range from 512 nm to 960 nm appeared in the PC and five very narrow transmittance peaks exhibited in this gap. The authors put emphasis on the case of the PC with complex refractive index layers, as well as the meso-piezooptic effect of the strained PC. The investigation results show that the transmittance peaks gain if the imaginary part is negative. With the increase of the absolute of the imaginary part, the transmittance peaks increase firstly then decrease even occur attenuation lastly. However, the transmittance peaks are absorbed if the imaginary part is positive. On the case of the strained PC, the variation of transmittance peaks presents a shape of L as the stain increases. The conclusions provide theoretical guidance for the realization of multi-channel narrow band filter, filter with gain.

Characteristics of magneto-optic fiber Bragg gratings for use in optical signal processing

The characteristics of photonic bandgaps and the transmission/reflection of guided optical waves in the magneto-optic fiber Bragg grating (MFBG) are theoretically investigated for the first time. The polarization-mode conversion resulting from the Faraday effect may change the width of the pure bandgap, or even lead to a couple of photonic semitransparent frequency band (STB) for sufficiently large magneto-optical-to-grating coupling ratio (MGR). Within the STBs, the transmittivity and reflectivity are equal and then the MFBG can serve as a 3 dB light beam splitter. Based on the sensitivity of MFBG spectral lines to the magneto-optic (MO) coupling coefficient, a novel high-resolution magnetic field sensor capable of up to 0.01 nm/(kA/m) is predicted. According to the dependency of nonlinear transmission or reflection on the MO effects, a new class of MFBG-based nonlinear optical switches under an appropriate MO bias may also be achieved with applications to flexible and controllable optical signal processing.

Characteristics of photonic band gaps in woodpile three-dimensional terahertz photonic crystals

Based on plane wave expansion method, complete photonic band gaps (PBGs) of a woodpile three-dimensional (3-D) terahertz (THz) photonic crystal (PC) with face-centered-tetragonal (fct) symmetry are optimized by varying structural parameters and the highest band gap ratio can reach 26.71%. In order to further optimize the complete PBGs, we propose a novel woodpile lattice with comparatively decreased symmetry and the highest band gap ratio can be increased to 27.61%. The woodpile THz PCs with two different symmetries both have a wide range of filling ratios to gain high quality complete PBGs, making the manufacturing process convenient. Woodpile 3-D PCs will be very promising materials for THz functional components.

Microwave-Assisted Self-Organization of Colloidal Particles in Confining Aqueous Droplets

Monodisperse aqueous emulsion droplets encapsulating colloidal particles were produced in the oil phase, and controlled microwave irradiation of the aqueous drop phase created spherical colloidal crystals by so-called evaporation-induced self-organization of the colloidal particles. Unlike usual colloidal crystals, colloidal crystals in spherical symmetry (or photonic balls) possessed photonic band gaps for the normal incident light independent of the position all over the spherical surface. While the consolidation of colloidal particles in emulsion droplets in an oven took several hours, the present microwave-assisted evaporation could reduce the time for complete evaporation to a few tens of minutes. Under the microwave irradiation, the aqueous phase in emulsions was superheated selectively and the evaporation rate of water could be controlled easily by adjusting the microwave intensity. The result showed that the packing quality of colloidal crystals obtained by the microwave-assisted self-organization was good enough to show photonic band gap characteristics. The reflectance of our photonic balls responded precisely to any change in physical properties including the size of colloidal particles, refractive index mismatch, and angle of the incident beam. In particular, for polymeric particles, the photonic band gap could be tuned by the intensity of microwave irradiation, and the reflection color was red-shifted with stronger microwave irradiation. Finally, for better photonic band gap properties, inverted photonic balls were prepared by using the spherical colloidal crystals as sacrificial templates.

Numerical analysis of PBG via structures using FDTD algorithm

PurposeTo study the photonic band‐gap (PBG) characteristics constructed by periodic conducting vias on various guided transmission‐line structures.Design/methodology/approachThe finite difference time domain (FDTD) method is adopted to analyze various PBG via structures. Conventionally, PBG characteristics on guided‐wave structures, such as microstrip lines or coplanar waveguides (CPW), are constructed through a series of perforations on the ground plane(s). PBG characteristics can, however, also be realized through periodic arrangements of conducting vias located on the respective ground planes.FindingsThrough studies of the scattering parameters, it has been found that all analyzed PBG via structures exhibit strong band‐gap characteristics in a particular frequency range. Different harmonic patterns are also observed when the dimensional sizes of the conducting vias vary with respect to the PBG period.Research limitations/implicationsResearch has been mainly limited to study solely the PBG via structures, guided‐wave transmission lines. More studies may be conducted in analyzing the overall performance when they are combined with other microwave components.Practical implicationsThe proposed PBG via structures can be applied to various microwave areas, ranging from signal suppressions in microelectronics and mobile communications, to electro‐magnetic interference studies in other practical electronic circuit structures.Originality/valueThe ideas of applying conducting vias on the guided‐wave transmission lines and the proposed via patterns to induce the PBG characteristics are the research's claim to originality one.

Photonic band gap effect in one-dimensional plasma dielectric photonic crystals

Propagation of electromagnetic waves in one-dimensional plasma dielectric photonic crystals, the superlattice structure consisting of alternating plasma and dielectric materials, is studied theoretically using transfer matrix method. Numerical calculation is presented for plasma-air finite and infinite periodic structures. The results of photonic band gap characteristics are discussed in terms of plasma density, plasma width, and number of unit cells ( N).