Open-Loop Folded Ring Mimics Photonic Band-Gap Device

Summary form only given. The microstrip dipole antennas have found widespread application according to their desirable properties such as good electrical performance, conformal structure, relatively low cost, of compact size and being lightweight, which are very attractive in cellular telephone systems, wireless local loop networks, and wireless data transmission systems. Concurrently, the photonic band gap (PBG) structure, also called electromagnetic crystals, is a periodic structure in which the propagation of the electromagnetic waves within a certain frequency band is prohibited. The microstrip feed lines incorporating a photonic band gap (PBG) structure have shown great potential application in antenna design. These structures have slow wave and band stop characteristics, and can prohibit certain band of frequencies and reduce the physical dimension of the microstrip structure. In this paper, one dimensional (1D) novel microstrip photonic band gap (PBG) cells are proposed.

We present a photonic band gap (PBG) structure design for terahertz (THz) wave parametric generation, which has crystal layer fabrication tolerance of a few micrometers and can be made with traditional polishing methods. This PBG structure consists of two component materials with a small refractive index difference at near infrared pump wavelengths and a large refractive index difference for THz waves. With this design the PBG device has optical properties very close to that of a bulk crystal in the near infrared, but photonic crystal features in the THz range, such as structural dispersion, which allows placement of the phase matched pump wavelength in the near infrared to eliminate two-photon absorption of the pump and signal beams. The added design flexibility also allows the use of the most efficient crystal orientations. Potential applications of this THz PBG structure are discussed.

Laser-assisted chemical vapor deposition (LCVD), in combination with 3-D self-assembly of colloidal silica particles, was used to fabricate 3-D photonic bandgap (PBG) structures. Multilayer of colloidal silica particles was formed on silicon substrates using the isothermal heating evaporation approach. A continuous wave (CW) CO2 laser (10.6 µm wavelength) was used as the energy source in the LCVD process. A silica-core-silicon-shell PBG structure was obtained. This technique is capable of fabricating structures with various PBGs by obtaining different silicon shell thickness with different LCVD parameters. This enables us to engineer the position and width of PBGs by flexibly controlling the core-shell geometry. Face-centered cubic (FCC) PBG structures were composed by “effective atom” of silica-core-silicon-shell. In this study, a series of PBG structures with designed PBGs were obtained with different experimental conditions. Incidence-angle-resolved spectroscopic ellipsometer was used to identify specific PBGs. The refractive indices of the “effective atom” with different silicon-shell thickness were calculated using Bruggeman composite model. The plain-wave expansion was used to simulate the photonic dispersion diagrams, which agreed with the experimental results.

Photonic band-gap (PBG) materials have recently attracted significant interest in the microwave region to suppress surface waves and to improve component performance. In this article, the NY-FDTD (nonYee grid higher order finite difference time-domain) formulation of a PBG structure in an anisotropic medium is derived, and then applied to compute the dispersion curves of 2D PBG structures. The numerical results for the isotropic medium are in good agreement with that from the traditional FDTD method. Then, the dispersion curves for anisotropic media are provided respectively. Which show that both the TM wave in the PBG structure with a magnetic-anisotropic medium and the TE wave in a PBG structure with an electric-anisotropic medium, possess an enhanced bandwidth of the first band-gap and also an increment of the number of bandgaps, compared to that of a PBG with isotropic medium.

We present the theoretical design and cold test of a 17 GHz photonic band gap (PBG) cavity with improved coupling from an external rectangular waveguide. The PBG cavity is made of a triangular lattice of metal rods with a defect (missing rod) in the center. The ${\mathrm{TM}}_{010}$-like defect mode was chosen as the operating mode. Experimental results are presented demonstrating that critical coupling into the cavity can be achieved by partial withdrawal or removal of some rods from the lattice, a result that agrees with simulations. A detailed design of the PBG accelerator structure is compared with a conventional (pillbox) cavity. One advantage of the PBG cavity is that its resonance frequency is much less perturbed by the input/output coupling structure than in a comparable pillbox cavity. The PBG structure is attractive for future accelerator applications.

Composite periodic structures, also named photonic band gap (PBG) materials, have attracted a lot of attention due to their controllable dispersive properties that allow a wide range of applications in novel antenna structures and frequency selective surfaces. Up to now, the analysis of PBG structures has been performed by numerical methods. Therefore optimizing the performance of a particular PBG design usually requires a case-by-case, trial and error method which is both CPU-time consuming and physically obscure. In order to bypass these limitations and isolate the response of the medium from the device in use, an effective description for PBG crystals is needed far beyond the quasistatic limit of traditional effective medium theories. Such an effective description for a metalo-dielectric photonic band gap (PBG) material with disk inclusions has been developed analytically. In this paper, we generalize this approach by presenting the effective permittivity and permeability functions for inclusions of a general canonical shape. This is useful in optimising the band gap formation as a function of the shape of the implants. We focus on flat inclusions of infinitesimal thickness that create thin planar geometries which are relevant for microwave devices.

One-dimensional (1-D) photonic bandgap (PBG) structures remain one of the most practical ways of applying the PBG concepts to the solution of many urgent problems in laser physics and optical technologies. The sol-gel method is an inexpensive and flexible liquid phase processing technique that is suitable for the deposition of multilayer stacks. The multilayer stacks can be designed as 1-D PBG structures, such as distributed Bragg reflectors (DBR), or single and coupled microcavities, as reported in this work. Spin-coated TiO2 and SiO2 layers acted as the high and low refractive index materials, respectively. Each layer was heat-treated at a high temperature (~1000 degree(s)C) for a short period of time (~90 s) in order to increase the index contrast, while preserving relatively smooth interfaces between the consecutive layers. Ellipsometry, X-ray diffraction, micro-Raman spectroscopy, transmittance/reflectance spectroscopy, and atomic force microscopy were used to characterize both the individual layers and the whole structures. Strong PBG properties are demonstrated, with an omni-directional stop band for a 5.5-pair DBR ((lambda) equals 550 - 600 nm, gap to mid-gap ratio equals 7.6%) and sharp pass bands within the stop bands for the microcavities.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this work, the photonic band gap (PBG) structure in a one-dimensional ferroelectric photonic crystal (PC) is theoretically investigated. We consider a PC, air/(AB)N/air, in which layer A is a dielectric of MgO and layer B is taken to be a ferroelectric of Ba0.55Sr0.45TiO3 (BSTO). With an extremely high value in the dielectric constant in BSTO, the calculated photonic band structure at microwave frequencies exhibits some interesting features that are significantly different from those in a usual dielectric-dielectric PC. First, the photonic transmission band consists of multiple and nearly discrete transmission peaks. Second, the calculated bandwidth of the PBG is nearly unchanged as the angle of incidence varies in the TE wave. The bandwidth will slightly reduce for the TM mode. Thus, a wide omnidirectional PBG can be obtained. Additionally, the effect of the thickness of the ferroelectric layer on the PBG is much more pronounced compared to the dielectric layer thickness. That is, the increase of ferroelectric thickness can significantly decrease the PBG bandwidth.

In this paper, hybrid integration of planar microstrip line and Photonic Band Gap (PBG) structure is proposed for the dielectric characterization of liquids. To implement the PBG structure of the microstrip line, a microfluidic channel with periodic form is introduced into the substrate and filled with different liquids. Based on this configuration, the operation principle of the sensor is based on a frequency shift due to the variation in the center of the bandgap, which in turn changes with the variation of the permittivity of LUT filled in the microfluidic channel. The proposed sensor exploits the behavior of the bandgap as a reflector to construct a resonant structure sensitive to the variation in LUT permittivity. The dimensions of the planar structure are optimized to achieve high precision and discrimination capability. The different empirical expressions describing the complex permittivity with the measured parameters were carried out. To validate the proposed concept, the sensor prototype is designed, fabricated, and tested. The frequency shift related to a change of 3.2 in LUT permittivity corresponds to 180 MHz around 6 GHz. The resonant-mode sensor spans a permittivity range from 1 to 80 with a precision better than 7.2%. The proposed sensor is simple in design and low cost, which may be applied in different applications at the industrial.

A novel one-dimensional (1-D) photonic bandgap (PBG) structure for microstrip lines is proposed. This new circuit is consisting of cross-gaps and base-to-base triangles etched in the ground plane of microstrip line. The PBG structures were designed and fabricated with different dimensions. It has been shown that the stopband characteristics may be controlled by tuning the geometrical dimensions. Also, multiple-frequency-tuned PBG structure has been derived by increasing the geometrical dimension.

Periodic structures, some of which are known as photonic band-gap (PBG) crystals, offer new dimensions of freedom in controlling the behavior of electromagnetic waves in modern microwave and millimeter wave circuits and antennas. This paper summarizes several novel structures developed recently at the authors' group, as well as some of their applications. The structures described include: (1) Dielectric-based PBG microstrip lines; (2) PBG ground plane for microstrip lines; (3) PBG-based high-Q image guide resonator; (4) Compact 2D PBG lattice for surface wave suppression in microstrip patch antennas; and (5) Uniplanar compact PBG (UC-PBG) structure and its unique characteristics such as slow-wave effect, wide stopband, leakage suppression as well as perfect magnetic surface impedance.

We propose coherently generated photonic heterostructures using a functional photonic superstructure. In the absence of a laser field (control field), such a structure exhibits a conventional passive (off-resonant) photonic band gap. When a region(s) of such a structure is illuminated by the control field, coherent enhancement of refractive index increases the refractive index perturbations of that region, while electromagnetically induced transparency keeps it lossless. This forms a photonic heterostructure consisting of a passive (unilluminated region) and an active (illuminated region) photonic band gap structures. Using such a superstructure, we study a coherently generated photonic quantum well structure wherein two active photonic band gaps sandwich a passive region. We show that, since the active photonic band gaps are roughly twice wider than the passive band gap, they form two photonic barriers around the transparency band located at the longer wavelength side of the passive photonic band gap. This leads to formation of resonant transparency states or photonic subbands, similar to the conduction or valence subbands in electronic quantum well structures. We show that the energies and linewidths of such photonic subbands can be coherently controlled by just adjusting the control field beam.

In a certain spectral range the extinction coefficient K in n-i-p-i layers becomes negative at the high excitation levels. It results in the appearance of the light amplification. The extinction coefficient in n-i-p-i layers depends on the wavelength and the difference in the quasi-Fermi levels /spl Delta/F. We considered the model, when a pump, which can be electrical as well as optical, excites uniformly all active layers and calculated light transmission characteristics versus /spl Delta/F which is the same within all active layers. In the present work we consider the optical mechanism of the pump, and solve the nonlinear problem of the pump light propagation through the photonic band gap (PBG) structure and the linear problem of a probe light transmission through the same structure with excited active layers.

Photonic band gap (PBG) structures have originally been explored in electro-optics. During the last five years, 2D planar PBG circuits have also been used at microwave frequencies. PBG structures behave as high impedance surfaces and suppress surface waves in one or more frequency ranges. Until now, these circuits have only been reliably modeled by numerical methods. A new equivalent circuit model is proposed. The model is based on the transmission line theory and periodic structures. The model is simple, but limited as it only allows for determination of the stop bands for the two principal directions of wave propagation. Nevertheless, it is a useful first step in the design of PBG structures. If this model is coupled with a simple numerical modeling using the FDTD method, it predicts the complete characteristics of the structure. The proposed analytical and numerical modeling is applied to improve the performance of a broadband circularly polarized patch antenna.

This paper highlights some applications areas of Photonic BandGap (PBG) or Electromagnetic BandGap (EBG) technology at (sub)millimetre wave frequencies. PBG structures are periodic dielectric or metallic materials which give them the property of permitting or preventing the propagation of electromagnetic waves at a known frequency. They are usually made of dielectric or metallic materials with 1, 2 and 3-D periodicity. PBG structures have numerous promising applications, including special antennas, broadband absorbers, frequency selective surfaces (FSS), single structure-multi-channel filter... Indeed, PBG materials working at centimetre or millimetre frequencies have generated a growing interest for antenna's applications to design a new kind of high gain antenna with a low cumbersome. These materials are used for their frequency properties and their ability to enhance the behaviour of a single patch antenna in order to have a higher gain. The frequency bandgap depends on the permittivity of the dielectric materials used and its Q factor, their dimensions, their periodicity and the incidence angle of electromagnetic waves. In 1987, two researchers, Eli Yablonovitch [1] of the University of Los Angeles and Sajeev John of the University of Toronto, had the idea to trap photons inside a crystalline structure. They had widened the concept of BRAGG's mirrors to the microwave frequencies and that for different propagation's direction.