Photonic Bandgap Structures Research Articles

Electrically tunable photonic band gap structure in monodomain blue-phase liquid crystals

Photonic band gap materials have the ability to modulate light. When they can be dynamically controlled beyond static modulation, their versatility improves and they become very useful in scientific and industrial applications. The quality of photonic band gap materials depends on the tunable wavelength range, dynamic controllability, and wavelength selectivity in response to external cues. In this paper, we demonstrate an electrically tunable photonic band gap material that covers a wide range (241 nm) in the visible spectrum and is based on a monodomain blue-phase liquid crystal stabilized by nonmesogenic and chiral mesogenic monomers. With this approach, we can accurately tune a reflection wavelength that possesses a narrow bandwidth (27 nm) even under a high electric field. The switching is fully reversible owing to a relatively small hysteresis with a fast response time, and it also shows a wider viewing angle than that of cholesteric liquid crystals. We believe that the proposed material has the potential to tune color filters and bandpass filters.

Porous Si-SiO2 based UV Microcavities

Obtaining silicon-based photonic-structures in the ultraviolet range would expand the wavelength bandwidth of silicon technology, where it is normally forbidden. Herein, we fabricated porous silicon microcavities by electrochemical etching of alternating high and low refraction index layers; and were carefully subjected to two stages of dry oxidation at 350 °C for 30 minutes and 900 °C, with different oxidation times. In this way, we obtained oxidized porous silicon that induces a shift of a localized mode in the ultraviolet region. The presence of Si-O-Si bonds was made clear by FTIR absorbance spectra. High-quality oxidized microcavities were shown by SEM, where their mechanical stability was clearly visible. We used an effective medium model to predict the refractive index and optical properties of the microcavities. The model can use either two or three components (Si, SiO2, and air). The latter predicts that the microcavities are made almost completely of SiO2, implying less photon losses in the structure. The theoretical photonic-bandgap structure and localized photonic mode location showed that the experimental spectral peaks within the UV photonic bandgap are indeed localized modes. These results support that our oxidation process is very advantageous to obtain complex photonic structures in the UV region.

Innovative fiber Bragg grating filter based on a graphene photonic crystal microcavity.

We propose a new model for a fiber Bragg grating (FBG) filter based on one-dimensional defective photonic bandgap structures, which operates within telecom windows. The device is realized in an asymmetric $ {{\rm SiO}_2}/{{\rm TiO}_2} $SiO2/TiO2 photonic crystal (PC) microcavity with the defect layer of the graphene disk placed in the center of the structure. The theoretical analysis of the optical properties of the narrowband FBG filter is given based on the combination of the density matrix approach with the transfer matrix method. The effect of the incident angle and the polarization of the probe field on the transmittance spectra is calculated. Also, tuning the filtering wavelength and the number of guided modes is performed by changing the properties of PC's defect layer. It is shown that depending on the ratio of the coupling fields' intensity, the probe field absorption can be minimized and even be amplified in $ {\lambda _0} = 1550\;{\rm nm} $λ0=1550nm. The results show very promising potential for fabrication of FBG filters operating in the near-infrared regime for light wave communications.

Resonance Energy Transfer Rate in the Presence of a Cylindrical Photonic Band-gap Structure

The resonance energy transfer rate between an excited atom and a ground-state one depends on various factors such as the matching between the donor and acceptor wavelengths, location of the atoms, and the environment that surrounds them. We investigate the interatomic resonance energy transfer rate in the presence of a cylindrical dielectric multi-layer structure using the Green’s tensor formalism. The permittivities of the layers are interchanged periodically between low and high values, so as to create a photonic band-gap system in the radial direction. We present results for atoms situated in a cross section normal to the cylinder axis. The contrast between low and high permittivities is varied to elucidate the effect of the band-gap structure. Furthermore, the results are compared with those for atoms located near a perfectly reflecting c-ylinder.

Robust Self-Healing Magnetically Induced Colloidal Photonic Crystal Hydrogels

As important biological functions of many creatures, structural colors and self-healing features play crucial roles in the survival of organisms. Inspired by these features, the intelligent self-healing colloidal photonic crystals (CPCs) materials with stable structural colors are constructed here by immobilizing magnetically assembling Fe3O4@SiO2 colloidal nanoparticles into a self-repairing hydrogel matrix. The self-repairing hydrogels, prepared by using biodegradable material poly(1-vinyl-2-pyrrolidinone-co-acrylamide) modified with O-carboxymethyl chitosan (O-CMC), exhibit an outstanding mechanical property with favorable toughness and elasticity. Interestingly, one-dimensional Fe3O4@SiO2 chain structures embedded in the framework can maintain the stability of the photonic band-gap structure and its resultant bright structural colors. Furthermore, O-CMC contained in the matrix can supply plentiful carboxyl, amino, and hydroxyl functional groups which can form abundant intermolecular hydrogen bonds, and thus give the robust self-healing capability to the CPC colored hydrogels. On the basis of such CPCs hydrogels with bright structural colors and robust self-healing properties, a 3D flower pattern has been designed to realize arbitrary 3D configurable modeling. This work might constitute a promising simple way to fabricate structural colored CPC materials with a longer functional life, and thus extend their practical applications.

Antenna Patch Design Using a Photonic Crystal Substrate at a Frequency of 1.6 THz

In this paper, the design of a macro strip patch antenna with a photonic crystal structure has been studied. The purpose of this study is to create a photonic band gap (PBG) structure that can be used to design macro strip antennas. With this method, we can increase the bandwidth several times and increase the antenna’s gain. The noise and radiation loss of the antenna will also be significantly reduced by the use of PGB technology. The bandwidth of the antenna is 0.6 GHz to 1.6 THz. At 1.4 THz, the gain is 7.703 dB. This antenna is widely used in high frequency microwave transmitter and microwave receiver systems.

Dressed optical vortex in a hot atomic medium

We experimentally observe the vortex six-wave mixing (SWM) signal carrying orbital angular momentum in a photonic band gap structure. First, we scan the probe detuning and the detuning of the dressing field to find an explanation for the intensity variation of four-wave mixing (FWM) intensity and the shift of forks in interference patterns. Then we change the power of the coupling field and obtain SWM images as well as its interference patterns to investigate the propagation characteristics, including spatial shift and splitting. We observe a change of fork quantity when decreasing the incident angle of the probe field. We suppose that the reflected signal is a combination of a linear probe and a nonlinear vortex FWM signal. By changing the incident angle of the field, the overlap condition between fields have changed correspondingly and the cross-Kerr effect of the coupling field on the linear vortex probe and third-order FWM become different, causing a separation in the center of the two components, which brings the inducement of additional forks.

Optimized optical nonreciprocal transmission in defective one-dimensional photonic bandgap structures with weak asymmetry

A novel and compact one-dimensional (1D) geometry for optical nonreciprocal transmission was proposed in this paper. Different from previous designs with high spatial asymmetry, by simply introducing a few dielectric periods of (BA) and (AB) into a typical nonlinear Fabry–Perot resonator with symmetric Bragg mirrors (AB)ND(BA)N, excellent optical nonreciprocal transmission properties can be achieved in the optical communication wavelength range. The optimized structure can be generally expressed as: (AB)ND(BA)M(AB)L, where M=N+1, L=1; M=N+2, L=2; M=N+3, L=3;…… and N≥6. The relationship between the bistability and the local field distribution of the Kerr defect layer D and the optical nonreciprocal transmission of the whole 1D system was analyzed theoretically. The direction- and incident wavelength-dependent shift of defect mode are confirmed to be responsible for the optimized optical nonreciprocity. The proposed optimized structures (AB)6D(BA)8(AB)2 and (AB)7D(BA)8(AB)1 are shown to have advantages over previously reported 1D designs with wide unidirectional transmission range (UTR) width (>3.1nm), high transmission for the forward incidence (>88%) and low transmission for the backward incidence (<1.22%) at lower input intensity (10 MW/cm2) with fewer layers (33 layers). Interestingly, the asymmetry degree of the proposed structures can be as low as 11.12%, which is only 1/4 or less of that of previous designs. The effects of the incident angle and polarization on the nonreciprocal transmission properties were also discussed for practical applications. These results are of great importance to the design of high-performance optical nonreciprocal devices, such as all-optical diodes, isolators and limiters.

Design of enhanced sensitivity gas sensors by using 1D defect ternary photonic band gap structures

In this paper, an approach to design enhanced sensitivity gas sensors by using one-dimensional (1D) defect ternary photonic band gap (PBG) material structure is demonstrated. It is shown that when the 1D defect binary PBG structure gas sensors are modified to 1D defect ternary PBG structure gas sensors, the sensitivity of the sensor enhances by 100%. Thus, by converting 1D defect binary PBG structures to 1D defect ternary PBG structures enhanced sensitivity gas sensors can be fabricated.

Enhancement in sensitivity of blood glucose sensor by using 1D defect ternary photonic band gap structures

This paper demonstrates a novel way to enhance sensitivity of a blood glucose sensor made up of one-dimensional (1D) defect binary photonic band gap (PBG) structure by converting it to 1D defect ternary PBG structure. On conversion of the structure from binary to ternary, the glucose concentration sensitive output transmission spectrum shift in the structure enhances by 25% and the sensitivity enhancement is 4.71 nm/RIU. Due to high sensitivity of 1D defect ternary PBG structure, fast and more accurate determination of concentration of glucose in blood can be achieved.

Experimental study of an evanescent-field biosensor based on 1D photonic bandgap structures.

A photonic bandgap (PBG) biosensor has been developed for the label-free detection of proteins. As the sensing in this type of structures is governed by the interaction between the evanescent field going into the cladding and the target analytes, scanning near-field optical microscopy has been used to characterize the profile of that evanescent field. The study confirms the strong exponential decrease of the signal as it goes into the cladding. This means that biorecognition events must occur as close to the PBG structure surface as possible in order to obtain the maximum sensing response. Within this context, the PBG biosensor has been biofunctionalized with half-antibodies specific to bovine serum albumin (BSA) using a UV-induced immobilization procedure. The use of half-antibodies allows one to reduce the thickness of the biorecognition volume down to ca. 2.5 nm, thus leading to a higher interaction with the evanescent field, as well as a proper orientation of their binding sites towards the target sample. Then, the biofunctionalized PBG biosensor has been used to perform a direct and real-time detection of the target BSA antigen.

Band-edge field enhanced nonlinear cross-polarized wave generation in photonic band-gap structure.

We report on the enhancement of nonlinear cross-polarized wave (XPW) generation in a one-dimensional photonic band-gap structure, which is composed of two periodic arrangements of barium-fluoride and silicon-dioxide through numerical simulations. By detuning the pump-field wavelength to the band-edge position of the photonic band-gap spectrum, the electric field at this wavelength would be resonant and then the field enhancement mechanism arises immediately. Under band-edge field enhancement condition, we found that the conversion efficiencies of XPW generation was implicitly enhanced even without phase-matched condition from the exact angle of crystallographic axis orientation.

High gain miniaturised photonic band gap terahertz antenna for size-limited applications

ABSTRACT Graphene has special properties that can be utilised in the design of terahertz (THz) range antennas for wireless network applications. A graphene-based photonic band gap (PBG) THz Patch Antenna is proposed. A reduced size antenna showing better performance is reported by utilisation of graphene with a PBG structure. PBG structures in the presence of a graphene patch with and without a slotted ground are also analysed. The proposed antenna is miniaturised still maintaining good gain (7.99 dB) and good directivity (8.42 dB) in comparison to work reported in the literature. Volume of the proposed antenna is reduced to 0.05 mm3 which is suitable for size-limited future applications such as Wireless Networks on Chip and Wireless Nano-Sensor Networks.

Design and Performance of a Multipurpose 2-D Photonic Crystal Device Based on Y Couplers

This paper reports on the design of a multipurpose photonic device based on 2-D photonic crystals which uses Y couplers in its structure that is very efficient when employed as a switch in optical communication systems and possesses a very high sensitivity not only if used as a biophotonic sensor to detect refractive index changes but also as a pressure sensor to sense pressure changes. The performance of the device is analyzed in terms of photonic bandgap structure, transmission power, electrical field distribution, resonance wavelength, and sensitivity by making use of the methods of the plane wave expansion (PWE) and the finite-difference time-domain (FDTD). The design is optimized to allow maximum power transmission so no constraints are imposed on the device detector and to achieve high sensitivity in biosensors’ applications allowing, thus, not only sensing very low analyte concentrations but also nondestructively detecting and analyzing nanoparticles. We propose here a highly efficient switching/coupling device suitable for current optical communication systems with a transmission power that could reach 98.16%. If the same platform is used as a biosensor, it has a refractive index sensitivity of 1055 nm/RIU, the highest value so far reported in the literature. If used as a pressure sensor, it has a sensitivity of 23.057 nm/GPa in the pressure range 0 to 1 GPa, which is second highest sensitivity so far reported.

Design and simulation of DGS based multi band filter for wireless applications

In this paper an efficient high performing cost-effective, compact size BPF is designed for wireless application is designed. There are various technologies have been introduced from time to time to address these concerns which also include those in the field of microwave filters like Photonic Band Gap structures (PBG), defected ground structures (DGS), fractals, metamaterial and so on to resonate for multiband frequencies. The simulated structure resonates at 1.01, 1.69, 1.93, 2.83, and 3.38 GHz.

Interferograms of Votex FWM Beam for Nonlinear Spatial Filter in Photonic Band Gap

We analyze the properties and interferograms of vortex four-wave mixing (FWM) beams by varying the incident angle of the probe field. Based on the properties, we propose the model of a new type of nonlinear spatial filter without diffraction using a Bragg grating in the nonlinear FWM process. We show the evolutions of shapes and interferograms of probe transmission signal (PTS) and FWM by scanning the probe detuning, and demonstrate the Kerr nonlinearity can manipulate the shapes and spatial location of vortex PTS and FWM images. Further, we can determine the center position of the new type of nonlinear filter through interference patterns and use the Kerr nonlinearity of related fields to control the nonlinear filter precisely. In addition, the interferograms of the reflected signal from the photonic band gap (PBG) structure are studied both in experiment and theory. We demonstrate that the number of fork-like patterns of reflected signal changes from one to three, revealing that the superposition of first-order and third-order beams in the reflected signal from PBG structure creates an inverted fork-like pattern.

Characteristic Features of Multilayer Photonic Bandgap Fiber Fabrication

We have demonstrated a modified chemical vapor deposition (MCVD) process for the fabrication of multilayer photonic bandgap fiber based on high-purity silica glass. Sequential growth of layers differing in melting point has been shown to lead to distortion of the layers in the resulting photonic bandgap structure and a sharp rise in optical loss as a result of deviations from Bragg’s reflection conditions. By optimizing the chemical composition of the layers in the photonic bandgap structure, we were able to suppress excessive optical losses and reach the optical loss limit, which is only determined by the guidance properties of the photonic bandgap structure itself.

Effect of Excitation Beam Divergence on the Goos–Hänchen Shift Enhanced by Bloch Surface Waves

The Goos–Hänchen (GH) shift is simulated and experimentally studied when the Bloch surface wave is excited in the forbidden band of a one-dimensional photonic band-gap structure for an excitation beam with different divergence. By changing the beam waist radius, a correspondingly changed Goos–Hänchen shift curve can be observed, where with a larger waist radius and the corresponding less divergence of the excitation beam, a greater GH shift that is closer to the Artmann estimation is obtained. The experimental demonstration of this phenomenon agrees well with the theoretical simulation.

Porous photonic crystal structure for sensing applications

A multilayer photonic band gap structure is proposed for sensing applications in visible wavelength range. The structure is designed by introducing alternate layers of dielectric material on a glass substrate. To ease the analyte infiltration and to improve the sensitivity, porosity is introduced deliberately within each layer. Extensive analysis is carried out to optimize the number of dielectric layers, their thickness, and percentage of porosity. The transmission/reflection spectral characteristic and sensitivity of the proposed structure are analyzed by a three-dimensional finite difference time domain method. The porosity value and structural parameters are optimized to obtain highest possible sensitivity. The proposed structure exhibits a 0.05-nm shift in reflection/transmission wavelength with corresponding refractive index change of 10 − 3. Analyte can also be distinguished by seeing the sample color change with naked eyes. Thus, multiparametric characterization of the proposed structure demonstrates its potential for sensing applications.

On-Demand Design of Tunable Complete Photonic Band Gaps based on Bloch Mode Analysis

The fundamental property of photonic crystals is the band gap effect, which arises from the periodic dielectric modulation of electromagnetic waves and plays an indispensable role in manipulating light. Ever since the first photonic-bandgap structure was discovered, the ability to tune its bandgap across a wide wavelength range has been highly desirable. Therefore, obtaining photonic crystals possessing large on-demand bandgaps has been an ever-attractive study but has remained a challenge. Here we present an analytical design method for achieving high-order two-dimensional photonic crystals with tunable photonic band gaps on-demand. Based on the Bloch mode analysis for periodic structures, we are able to determine the geometric structure of the unit cell that will realize a nearly optimal photonic band gap for one polarization between the appointed adjacent bands. More importantly, this method generates a complete bandgap for all polarizations, with frequencies tuned by the number of photonic bands below the gap. The lowest dielectric contrast needed to generate a photonic band gap, as well as conditions for generating complete bandgaps, are investigated. Our work first highlights the systematic approach to complete photonic band gaps design based on Bloch mode analysis. The physical principles behind our work are then generalized to other photonic lattices.