One-dimensional Photonic Bandgap Research Articles

Tunable absorption resonance in electromechanical one-dimensional metallodielectric photonic band gap structures

We present the results of an experimental study of an electromechanical, one-dimensional, metallodielectric photonic band gap structure. We monitor the reflectance as a function of the thickness of an air gap located inside the stack. The results suggest that, by changing the thickness of the air gap by approximately 20 nm, a large contrast can be achieved between high- and low-reflectance states, as reflectance switches from a fraction of a percent to about 70%. Using this approach, we are able to selectively remove a relatively narrow but tunable wavelength range from the reflected spectrum, thus making possible applications to accelerometers, linear optical switches, modulators, and other specialized filters in the visible range. The characteristic absorption spectrum can be controlled by varying air gap and dielectric layer thicknesses.

Optical bistability and multistability in one-dimensional photonic band gap structures

We study optical bistability and multistability in multilayer coupled-cavity thin film structures comprised of high-index and low-index materials. The reduction of the bistable threshold and necessary index change are studied as functions of structural parameters by explicitly mapping the evolution of transmission and phase. We find that the coupled-cavity structure has no clear advantage over single-cavity structures for bistable operation. However, there is an advantage in using coupled-cavity structures for multistability in that the threshold for multistability can be reduced.

Guided modes of one-dimensional photonic bandgap waveguides

Using a ray-optics model, we analyze the guided modes of a slab waveguide that consists of a low-index layer sandwiched between two photonic bandgap structures. Normalized band diagrams and dispersion curves for the TE and TM waves are investigated in detail, and a nomenclature system for the guided modes based on the mode-field patterns in the waveguide is proposed. The cutoff conditions and the confinement factors of the modes are discussed. The effects of varying the physical parameters of the waveguide on the dispersion characteristics of the modes are also analyzed.

Geometric phases for a three-level Λ -type system in one-dimensional photonic band gaps

The geometric phase of a three-level atom interacting with single-mode in the presence of the one-dimensional photonic band gap material is studied. We consider dipole emitters situated in the thin slab region between two semi-infinite one-dimensionally periodic photonic crystals, a situation reminiscent of planar cavity laser structures. It shows that the Pancharatnam phase depends crucially on the presence of the photonic band gap. This feature is attributed to the fact that in the photonic band gap region electromagnetic modes are not allowed to propagate into the dielectric slab and hence no interaction can take place in this region. The outcomes are illustrated with numerical simulations applied to GaAs.

Fabrication and analysis of one-dimensional defect-induced ultrawide photonic band gaps

An approach named the defect-induced extension of photonic band gaps (PBGs) is proposed, in which a stratified periodic structure is combined with another stratified structure containing defect layers. For comparison, three structures composed of TiO2 and SiO2 alternating layers, perfect, five-defect and combined-photonic crystals (PCs), were fabricated by using an electron-beam evaporation system. The measured PBG width of combined-PCs extended to 370 nm at the normal incidence, nearly three times more than that of perfect ones, 130 nm, but a few ripples are observed within the PBG. In order to elucidate the origin of the ripples, the influence of the refractive-index contrast on the reflectance was analyzed theoretically. When the refractive-index contrast nH∕nL≥1.7, the ripples are eliminated. More importantly, an overdoubled omnidirectional PBG is realized at nH∕nL=2.56, covering the visible region completely. This approach is considered to be based on the light localization and a heterostructure resulting from introducing the impurity band and compensating for it using PCs with a strictly periodic structure, in which the thickness of every layer remains unchanged. These characteristics distinguish it from other methods proposed before, with the fabrication much easier.

Optical manipulation of photonic defect-modes in cholesteric liquid crystals induced by direct laser-lithography

Manipulation of photonic defect-modes in cholesteric liquid crystals (ChLCs), which are one-dimensional pseudo photonic band-gap materials have been demonstrated by an external optical field. A structural defect in which the pitch length of the ChLC in the bulk and the defect are different was introduced by inducing local polymerization in a photo-polymerizable ChLC material by a direct laser-lithography process, and infiltrating a different ChLC material as the defect medium. When an azobenzene dye-doped ChLC was infiltrated in the defect, the trans– cis isomerization of the dye upon ultraviolet (UV) exposure caused the pitch to shorten, changing the contrast in the pitch lengths at the bulk and the defect, leading to a consequent shifting of the defect-mode. The all-optical manipulation was reversible and had high reproducibility.

Broadband super-resolving lens with high transparency in the visible range

The authors present a theoretical analysis of a super-resolving lens based on one-dimensional metal-dielectric photonic band gap composed of Ag∕GaP multilayers. The lens contains a total of ten optical skin depths of Ag, yet maintains a normal incidence transmittance of ∼50% for propagating waves over the super-resolving wavelength range of 500–650nm. The individual Ag layers are 22nm thick and can be readily fabricated in conventional deposition systems. The importance of antireflection coatings for the transmission of evanescent and propagating waves is illustrated by comparison to periodic and symmetric structures without the coatings.

Optical bistability in one-dimensional photonic band gap structures with coupled nonlinear defects

Using the transfer matrix method, we study the transmission property of one-dimensional photonic band gap structure with two coupled nonlinear defects separated by a linear middle layer and find that such composite structure exhibits a bistability that’s strongly dependent of the linear middle layer. The switching threshold values can be greatly reduced just by choosing the proper parameters of the linear middle layer.

Label-Free Quantitative Detection of Protein Using Macroporous Silicon Photonic Bandgap Biosensors

A label-free biosensor was demonstrated using macroporous silicon (pore size >100 nm) one-dimensional photonic band gap structures that are very sensitive to refractive index changes. In this study, we employed Tir-IBD (translocated Intimin receptor-Intimin binding domain) and Intimin-ECD (extracellular domain of Intimin) as the probe and target, respectively. These two recombinant proteins comprise the extracellular domains of two key proteins responsible for the pathogenicity of enteropathogenic Escherichia coli (EPEC). The optical response of the sensor was characterized so that the capture of Intimin-ECD could be quantitatively determined. Our result shows that the concentration sensitivity limit of the sensor is currently 4 microM of Intimin-ECD. This corresponds to a detection limit of approximately 130 fmol of Intimin-ECD. We have also investigated the dependence of the sensor performance on the Tir-IBD probe molecule concentration and the effect of immobilization on the Tir-IBD/Intimin-ECD equilibrium dissociation constant. A calibration curve generated from purified Intimin-ECD solutions was used to quantify the concentration of Intimin-ECD in an E. coli BL21 bacterial cell lysate, and results were validated using gel electrophoresis. This work demonstrates for the first time that a macroporous silicon microcavity sensor can be used to selectively and quantitatively detect a specific target protein with micromolar dissociation constant (Kd) in a milieu of bacterial proteins with minimal sample preparation.

Enhancement of omnidirectional total-reflection wavelength range by using one-dimensional ternary photonic bandgap material

Here we demonstrate by theoretical analysis a novel way to enhance the omnidirectional total-reflection wavelength range in one-dimensional photonic bandgap material by using a ternary periodic structure (i.e., three material layers constituting a period of the lattice). The omnidirectional total reflection range using a binary (BaF2/PbS) periodic structure was enhanced by 108 nm when the structure was modified by sandwiching a thin layer of ZrO2 between every two layers, constituting a period of the lattice. A shift of the omnidirectional range toward higher wavelengths was also observed. When the sandwiched layer was CeF3, the enhancement in the range was 120 nm. As the sandwiched layer is very thin, there will not be any significant increase in the size of the reflector, contrary to the case of heterostructured photonic crystals (PCs) where two or more PCs are clubbed together to achieve enhancement.

Spatially tunable laser emission in dye-doped cholesteric polymer films

A spatially tunable laser emission of the dye-doped cholesteric polymer film is demonstrated by generating a one-dimensional gradient photonic band gap which is cured by an ultraviolet light. A frequency-doubled pulsed Nd:YAG laser is used to pump the film. The lasing wavelength is tunable from 595to643nm by shifting the position of the film with respect to the pumping beam. Since the spatial distribution of the reflection band is fixed in the cholesteric polymer film, the tuning of the laser wavelength does not require any external field. Therefore, the film is portable and has many applications.

Tunable and Sensitive Biophotonic Waveguides Based on Photonic-Bandgap Microcavities

This paper presents a theoretical study of the single-mode and birefriengence condition of the silicon photonic wires using the imaginary distance beam propagation method. The photonic wires are suitable for integration with active one-dimensional silicon photonic bandgap waveguides. This inherently will reduce the propagation loss caused by the scattering factors within the photonic bandgap structure itself. To the best of our knowledge, we provide for the first time, a systematic study of the various physical parameters that can affect the Q-factor and transmission properties in such waveguides. In order to make this technology viable, the waveguides must be tunable, have low attenuation, possess high Q-factor, and can be switched. Can these be achieved simultaneously without changing the device width and height dimensions? Furthermore, can we meet these aims without placing unrealistic demands in fabrication? The electrical switching of this device is implemented using a p-i-n optical diode. The diode is predicted to require an on state power of 81 nW with rise and fall times of 0.2 and 0.043 ns, respectively. The length of the microcavity and the diameter of the air holes are finely tuned with reference to the Q-factor and transmission. It will be shown that for certain desired resonant wavelength, the Q-factor and transmission properties can be optimized by tuning the length of the cavity and the diameter of the two inner most air holes. This method allows ease of fabrication by not having to vary the waveguide width and height to obtain the tuning effects. Optical simulation was performed using the three-dimensional finite-difference time-domain simulation method

Design and analysis of one-dimensional resonant hexagonal holes photonic bandgap filter waveguide

We propose an one-dimensional (1-D) resonant hexagonal holes photonic bandgap (PBG) filter waveguide based on a silicon-on-insulator (SOI) substrate. In the 1-D resonant PBG filter waveguide, we use the technique of PBG and /4 phase shift to design our resonant PBG filter waveguide. According to the beam propagation method (BPM) simulation, the maximum transmission of the guided light is 89.91%, the quality factor is approximately 612.10, and the transmittance power uniformity over the 32 phase-shift wavelengths is about 1.3343 dB. The insertion loss is 0.4617 dB and reduces the size to 2.1 µm×57 µm on our designed resonant hexagonal holes PBG filter waveguide.

Optical properties and electric field enhancement in cholesteric liquid crystal containing different periodicities

We study a defect mode in a one-dimensional photonic band gap of a cholesteric liquid crystal (CLC) consisting of two helicoidal periodicities. The optical properties of this CLC are analyzed using 4×4 transfer matrix and finite difference time domain (FDTD) methods. In calculated transmission spectra of this CLC, one of the defect modes always appears at the band edge wavelength of the inner CLC having a different helix to that of two sides of CLCs. Furthermore, the electric field analysis of this CLC has also been demonstrated by the FDTD method. At the defect mode wavelength, the electric field enhancement is found to be significant larger than a normal CLC.

Surface electromagnetic waves in Fibonacci superlattices: Theoretical and experimental results

We study theoretically and experimentally the existence and behavior of the localized surface modes in one-dimensional (1D) quasiperiodic photonic band gap structures. These structures are made of segments and loops arranged according to a Fibonacci sequence. The experiments are carried out by using coaxial cables in the frequency region of a few tens of MHz. We consider 1D periodic structures (superlattice) where each cell is a well-defined Fibonacci generation. In these structures, we generalize a theoretical rule on the surface modes, namely when one considers two semi-infinite superlattices obtained by the cleavage of an infinite superlattice, it exists exactly one surface mode in each gap. This mode is localized on the surface either of one or the other semi-infinite superlattice. We discuss the existence of various types of surface modes and their spatial localization. The experimental observation of these modes is carried out by measuring the transmission through a guide along which a finite superlattice (i.e., constituted of a finite number of quasiperiodic cells) is grafted vertically. The surface modes appear as maxima of the transmission spectrum. These experiments are in good agreement with the theoretical model based on the formalism of the Green function.

Circularly Polarized Laser Emission Induced by Supramolecular Chirality in Cholesteric Liquid Crystals

This paper describes the circularly polarized spectroscopic studies on absorption and emission of an achiral fluorescent dye embedded in cholesteric liquid crystals (CLCs). Optical excitation of the dye-doped CLC cell with a linearly polarized laser brought about the two laser emission peaks at longer and shorter reflection band edges of the CLC host through the internal laser feedback effect of the one-dimensional CLC photonic band-gap. At this stage, the optically excited laser emissions showed circularly polarized characteristic, even though the excitation beam was linearly polarized. The circularly polarized direction of the laser emission was determined by molecular chirality of only few mol% of the enantiomeric chiral dopant in this molecular system.

Dynamic pattern of finite-pulsed beams inside one-dimensional photonic band gap materials

The dynamics of two-dimensional electromagnetic (EM) pulses through one-dimensional photonic crystals (1DPC) has been theoretically studied. Employing the time expectation integral over the Poynting vector as the arrival time [Phys. Rev. Lett. 84, 2370, (2000)], we show that the superluminal tunneling process of EM pulses is the propagation of the net forward-going Poynting vector through the 1DPC, and the Hartman effect is due to the saturation effect of the arrival time (smaller and smaller time accumulated) of the net forward energy flow caused by the interference effect of the forward and the backward field (from the interfaces of each layer) happened in the region before the 1DPC and in the front part of the 1DPC.

Nonlinear optical response of photonic bandgap structures containing PbSe quantum dots

New nanocomposite materials with large optical nonlinearity are important for the development and miniaturizing of active components and integrated circuits for all-optical signal processing and computing. To enable on-chip integration with silicon microelectronics nonlinear signal processing components compatible with silicon nanophotonics need to be developed. In this paper, we study the nonlinear optical response of silicon-based photonic bandgap (PBG) structures filled with PbSe quantum dot (QD) materials and experimentally demonstrate the feasibility of a new class of nonlinear nanophotonic devices for all-optical signal processing based on such microstructures. Active tuning is demonstrated for both out-of-plane components, with one-dimensional porous silicon PBG microcavities and in-plane components, using one-dimensional PBG waveguide-based microresonators.

Photonic band gap control in one-dimensional dielectric Bragg structures

One-dimensional photonic band gap structures have been studied for applications in many branches of physics. Numerical and experimental studies of wave scattering and interference inside one-dimensional photonic band gap structures based on a rectangular waveguide filled with a double-sided corrugated dielectric are presented. The experimental data and theoretical predictions obtained are compared and discussed. It is shown experimentally that variation of the relative phase of the one-dimensional perturbations with respect to each other results in a change of the band gap parameters in accordance with the predictions.

Nonlinear wave interaction in photonic band gap materials

We present detailed analytical and numerical studies of nonlinear wave interaction processes in one-dimensional (1D) photonic band gap (PBG) materials with a Kerr nonlinearity. We demonstrate that some of these processes provide efficient mechanisms for dynamically controlling so-called gap-solitons. We derive analytical expressions that accurately determine the phase shifts experienced by nonlinear waves for a large class of non-resonant interaction processes. We also present comprehensive numerical studies of inelastic interactions, and show that rather distinct regimes of interaction exist. The predicted effects should be experimentally observable, and can be utilized for probing the existence and parameters of gap solitons. Our results are directly applicable to other nonlinear periodic structures such as Bose–Einstein condensates in optical lattices.