Conventional Photonic Bandgap Research Articles

Particle Swarm Optimization Based Design of a Terahertz Antenna with a Modified Photonic Band Gap Substrate for 6G Future Wireless Communications

In this study, an antenna is proposed that operates at THz spectrum for sixth generation (6G) short-range future wireless communications. A modified photonic band gap (MPBG) substrate is employed to design an octagonal ring shaped microstrip patch antenna with wideband and high gain properties. Unlike the conventional photonic band gap (PBG) form, the proposed MPBG substrate structure is created by variable sized cylindrical air holes. The radii of each air cylinder in the row is determined with the help of particle swarm optimization (PSO) algorithm, where the goal is set to achieve the highest gain and impedance bandwidth (S_11≤-10 dB) possible. The simulation results of the antennas that are built on 1) non-PBG, 2) conventional PBG and 3) the proposed MPBG substrate structures are compared. It is observed that the radiation performance is most enhanced by implementing MPBG structure. In comparison to the antenna without PBG, the reported MPBG structure offers almost 300% gain and 11% bandwidth improvement. To summarize, the designed antenna with its proposed MPBG substrate structure achieves an excellent radiation performance within a wide operating bandwidth.

Frequency invariance, gain improvement, and fast design in 3D‐printed photonic band gap antennas with quadratic holes

AbstractThe use of photonic band gap (PBG) substrates with noncylindrical holes in microstrip antennas is little reported in the literature. In this article, a 3D printer was used to produce two PBG antennas in acrylonitrile‐butadiene‐styrene (ABS) substrate: one with cylindrical holes and the other with quadratic prism holes, both with the same volume in the holes and in the total composition. The proposed PBG antenna with quadratic prism holes maintains the same resonance frequency of antenna with cylindrical holes, that is, 2.64 GHz. In addition, the proposed antenna greatly reduces the project time in the simulation phase, which is very onerous in conventional PBG antennas. The PBG antennas improved the distribution of surface current and increased the gain in relation to the antenna without PBG. Thus, the obtained results were as follows: the gain and efficiency of radiation were 3.75 dB and 55% for the antenna without PBG, 4.5 dB and 60% for the antenna with cylindrical holes, and 5 dB and 62% for the antenna with quadratic holes. All antennas maintained an approximate bandwidth of 3%. These antennas were built, simulated, and measured. A schematic of the build structures, return loss, Smith's chart, radiation diagrams, and computational simulation time was analyzed throughout this article.

Unique loss characteristics in TE01 modes of conventional photonic bandgap fibers.

We report modeling that demonstrates the reduction of transmission loss and broadening of the bandwidth of a conventional hollow-core photonic bandgap fiber (PBF). Numerical investigation reveals that transmission loss of the high-order TE01 mode is lower than that of the fundamental HE11 mode in fibers with thick cladding walls. By comparing dispersion curves of PBFs with different core-wall thicknesses, we show that the TE01 mode has weaker coupling strength to a surface mode than the HE11 mode. This result opens the way for a wider transmission band and lower transmission loss in PBFs that are subject to the detrimental effects of surface modes.

Abnormal behaviour of one-dimensional photonic crystal with defect

The effect of introduction a defect in a conventional one-dimensional photonic band gap (PBG) structure in respect of the dispersion relation, reflectivity, group velocity and effective group index of such a structure has been studied. In particular, the dependence of various properties of such a structure on the angle of incidence of the electromagnetic waves has been given more importance in the present study. The study shows that inside the conventional PBG structure as well as defect PBG structure, the group velocity and effective group index become negative for certain ranges of normalized frequency. In a defect PBG structure, it is possible to achieve desired values (negative or positive) of group velocity and effective group index by choosing appropriate angle of incidence, whereas in conventional PBG structures, the maximum (negative and positive) values of group velocities and effective group index are found to be almost independent of the angle of incidence. This is a unique property of defect PBG structure which is different from the properties of conventional PBG structures. Because of this unique property, defect PBG structure may be widely used for construction super lenses, lasing without inversion and other optical systems in photonics.

A Compact Defected Ground Microstrip Device with Photonic Bandgap Effects

Filters and other devices using photonic bandgap (PBG) theory are typically implemented in microstrip lines by etching periodic holes on the ground plane of the microstrip. The period of such several holes corresponds to nearly half the guided wavelength of the transmission line. In this paper we study the effects of miniaturization of the PBG device by meandering the microstrip line about one single hole in the ground plane. A comparison of the S-parameters and dispersion behavior of the modified geometry and a conventional PBG device with a straight microstrip line shows that these devices have similar behaviors.

GaAs MMIC상에서 주기적으로 천공된 홀을 가지는 접지 금속막 구조를 이용한 전송선로 특성연구 및 코프레너 선로를 이용한 온칩 초소형 임피던스 변환기에의 응용

Abstract ： In this paper, basic characteristics of transmission line employing PPGM (periodically perforated ground metal) were investigated using theoretical and experimental analysis.According to the results, unlike the conventional PBG (photonic band gap) structures, the characteristic impedance of the transmission line employing PPGM structure showed a real value, which exhibited a very small dependency on frequency. The transmission line employing PPGM structure showed a loss (per quarter wave length) higher by 0.1 ∼0.2 dB than the conventional microstrip line. According to the investigation of the dependency of RF characteristic on ground condition, the RF characteristic of the transmission line employing PPGM structure was hardly affected by the ground condition in the frequency lower than Ku band, but fairly affected in the frequency higher than Ku band, which indicated that coplanar waveguide employing PPGM structure was optimal for RF characteristic and reduction of size. Considering above results, impedance transformer was developed using coplanar waveguide with PPGM structure for the first time, and good RF characteristics were observed from the impedance transformer. In case that λ/4 impedance transformer with a center frequency of 9 GHz was fabricated for a impedance transformation from 20 to10 Ω, the line width and length were 20 and 500 μm, respectively, and its size was only 0.64 % of the impedance transformer fabricated with conventional microstrip lines. Above results indicate that the transmission line employing PPGM is a promising candidate for a development of matching and passive elements on MMIC.

Resonant crystal band gap metamaterials in the microwave regime and their exotic amplification of evanescent waves

The authors realize resonant crystal band gap metamaterials (CBMs) using circuit structures in the microwave regime, which behave quite differently from the conventional photonic band gap structures. They show that a periodic array of series inductor and shunt capacitor is equivalent to a CBM similar to a magnetic plasma at higher frequency band, and a periodic array of series capacitor and shunt inductor behaves like a CBM similar to an electric plasma at lower frequency band. The equivalent medium parameters have been derived in both cases, which show the existence of conjugate loss in imaginary parts. When two such structures are cascaded together, the authors demonstrate that evanescent waves are amplified and transmitted in a very narrow frequency band under the antimatching condition. Such a feature can be used to design extremely narrow band filters. Theoretical predictions, circuit simulations, and experimental results are presented to validate their conclusions.

Anomalous behavior of group velocity and index of refraction in a defect photonic band gap structure

In the present paper, we have made an analysis to observe the effect of introduction of defect on dispersion relation, group velocity, and effective group index in a conventional photonic band gap (PBG) structure. The study shows that inside the PBG materials group velocity and effective group index becomes negative in both types (conventional as well as defect PBG structure) of structure at a certain range of frequencies. Also, near the edges of the bands it attains very high values of index of refraction. A defect PBG structure gives a very unique feature that group velocity becomes exactly zero at a particular value of frequency and also becomes several hundred times greater than the velocity of light which is not attainable with the conventional PBG structure. Defect PBG structures with such peculiar characteristics are seen in lasing without inversion, in construction of perfect lens, in trapping of photon and other optical devices.

Second-harmonic generation at angular incidence in a negative-positive index photonic band-gap structure

In the spectral region where the refractive index of the negative index material is approximately zero, at oblique incidence, the linear transmission of a finite structure composed of alternating layers of negative and positive index materials manifests the formation of a new type of band gap with exceptionally narrow band-edge resonances. In particular, for TM-polarized (transverse magnetic) incident waves, field values that can be achieved at the band edge may be much higher compared to field values achievable in standard photonic band-gap structures. We exploit the unique properties of these band-edge resonances for applications to nonlinear frequency conversion, second-harmonic generation, in particular. The simultaneous availability of high field localization and phase matching conditions may be exploited to achieve second-harmonic conversion efficiencies far better than those achievable in conventional photonic band-gap structures. Moreover, we study the role played by absorption within the negative index material, and find that the process remains efficient even for relatively high values of the absorption coefficient.

Experimental verification of zero order bandgap in a layered stack of left-handed and right-handed materials

A theoretically, predicted bandgap corresponding to the zero volume-averaged refractive index is verified experimentally by measuring the scattering parameters of a one-dimensional layered stack composed of left-handed and right-handed materials. The unique property of the zero-n gap, also denoted zero order bandgap, is verified by experiments, showing that unlike a conventional photonic band gap, the frequency corresponding to the zero order gap remains unchanged when the periodicity is altered.

Harmonic suppression with photonic bandgap and defected ground structure for a microstrip patch antenna

This letter presents a microstrip patch antenna integrated with two-dimensional photonic bandgap (PBG) and one-dimensional defected ground structure (DGS) jointly in ground plane. It is demonstrated that application of both PBG and DGS eliminates the second and third harmonics and improves the return loss level. Moreover, the combination use of PBG and DGS decreases the occupied area by 70% compared to the conventional PBG patch antenna.

Parallel PBG microstrip line

A novel photonic bandgap (PBG) microstrip line is proposed for 50Ω conventional microstrip line. The proposed structure is fabricated with a periodic rectangle etched on the edge of the conductor line, and a flat and low-rippled passband is obtained. The characteristics of the novel PBG microstrip line are improved, as compared those of the conventional PBG microstrip line with holes etched in the conductor line or in the ground plane. The width of the stopband or passband can be changed according to the requirements. The measurement data of this novel PBG microstrip line agree well with the simulations. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 548–550, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20875

A novel PBG structure for filter application

This paper presents the design, simulation and test results of a novel photonic band-gap (PBG) structure for filter application. The proposed PBG structure is a 50Ω meander microstrip line with a single rectangular ground-etched pattern instead of conventional periodic ground-etched pattern. The simulated results, verified by the test results, demonstrate that this proposed structure provides less ripple in the lower pass-band with an increased rejection bandwidth of about 20%, as compared to a conventional PBG filter with same fill-factor. This single etched ground pattern enables easier fabrication and packaging, as compared to conventional multiple ground-etched patterns. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 188–190, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21302

Photonic Band Gaps in Two Dimensional Photonic Quasicrystals

It is generally believed that long range periodic order is instrumental in the formation of a photonic band gap. Using a spectral method that scales linearly with the system size, we found that sizable spectral gaps for each polarization in 2D can be found in aperiodic arrangements of dielectrics that resemble quasicrystalline tiling. Since the aperiodic arrangement has many inequivalent sites, the defect properties of these systems are more complex and interesting than conventional photonic band gap systems.