Photonic Bandgap Structures Research Articles

Nonlinear optical performance of periodic structures made from composites of polymers and Co3O4 nanoparticles

The nonlinear optical performance of specially designed periodic structures made from composites of optical polymers and Co3O4 nanoparticles is investigated. The refractive indices of the alternating layers are designed to be close and no photonic band gap (PBG) is formed at low power density. Under high power illumination, the index difference becomes large because of the high optical nonlinearities of the Co3O4 nanoparticles. Consequently, enhanced nonlinear optical performance is obtained with the formation and the strengthening of the PBG. Nonlinear reflection and nonlinear transmission as well as reduced nonlinear threshold are observed in the PBG structures.

Ultracompact Silicon/Polymer Laser with an Absorption-Insensitive Nanophotonic Resonator

A planar nanophotonic Fabry-Perot-like resonator that can defy strong absorption of about 20 000 cm(-1) in the cavity material is demonstrated. Visible laser emission is observed from two silicon subwavelength-sized high index contrast gratings with embedded polymer gain material. The size of the laser is reduced by an order of magnitude compared to established designs based on photonic bandgap structures. As silicon constitutes the most common carrier for electronics, the cost-efficient integration of compact laser sources for visible wavelengths comes within reach.

PBG structures of novel two-dimensional annular photonic crystals with triangular lattice

The photonic band gap (PBG) structures of four types of annular photonic crystals (PCs) with inner-scatter of rectangular, square, hexagonal and circle shapes are respectively calculated by the plane wave expansion method. The optimal samples with the largest gap-midgap ratio for each structure are obtained by scanning the four parameters: filling ratio f, dielectric constant ɛ1, rotating angle θ of inner-scatters and outside radius R of the air ring. The results show that the band gap can be further maximized by adjusting the structural parameters, and a wide PBG with the gap-midgap ratio of 20.4% is gained in the annular photonic crystal with rectangular inner-scatters.

Porous silicon and porous polymer substrates for optical chemical sensors

Mesoporous materials, such as porous silicon and porous polymer gratings (Bragg structures), offer an attractive platform for the encapsulation of chemical and biological recognition elements. These materials include the advantages of high surface to volume ratio, biocompatibility, functionality with various recognition elements, and the ability to modify the material surface/volume properties and porosity. Two porous structures were used for chemical and biological sensing: porous silicon and porous polymer photonic bandgap structures. Specifically, a new dry etching manufacturing technique employing xenon difluoride (XeF2) based etching was used to produce porous silicon Porous silicon continues to be extensively researched for various optical and electronic devices and applications in chemical and biological sensing are abundant. The dry etching technique to manufacture porous silicon offers a simple and efficient alternative to the traditional wet electrochemical etching using hydrofluoric acid. This new porous silicon material was characterized for its pore size and morphology using top and cross-sectional views from scanning electron microscopy. Its optical properties were determined by angular dependence of reflectance measurements. A new class of holographically ordered porous polymer gratings that are an extension of holographic polymer dispersed liquid crystal (H-PDLC) structures. As an alternative structure and fabrication process, porous polymer gratings that include a volatile solvent as the phase separation fluid was fabricated. Porous silicon and porous polymer materials were used as substrates to encapsulate gaseous oxygen (O2) responsive luminophores in their nanostructured pores. These substrate materials behave as optical interference filters that allow efficient and selective detection of the wavelengths of interest in optical sensors.

Control of absorption spectrum of a one-dimensional resonant photonic crystal

The crystal under consideration is a layered structure consisting of alternating layers of two materials, one of which is a resonantly absorbing gas. It is shown that the combination of the dispersion of an atomic gas with the dispersion of a photonic-bandgap structures allows one to efficiently control the transmission spectra of s- and p-polarized modes in these combined systems. It is found that the spectrum is highly sensitive to the position of the gas resonance frequency with respect to the bandgap edge and to a change in the gas pressure. The transmission, reflection, and absorption spectra of the resonant photonic crystal are studied at an angle of incidence equal to the Brewster angle of a seed photonic crystal. Possible applications of the found particular features of the dispersion of resonant photonic crystals are discussed.

Formation of colorimetric fingerprints on nano-patterned deterministic aperiodic surfaces

Periodic gratings and photonic bandgap structures have been studied for decades in optical technologies. The translational invariance of periodic gratings gives rise to well-known angular and frequency filtering of the incident radiation resulting in well-defined scattered colors in response to broadband illumination. Here, we demonstrate the formation of highly complex structural color patterns, or colorimetric fingerprints, in two-dimensional (2D) deterministic aperiodic gratings using dark field scattering microscopy. The origin of colorimetric fingerprints is explained by rigorous full-wave numerical simulations based on the generalized Mie theory. We show that unlike periodic gratings, aperiodic nanopatterned surfaces feature a broadband frequency response with wide angular intensity distributions governed by the distinctive Fourier properties of the aperiodic structures. Finally, we will discuss a range of potential applications of colorimetric fingerprints for optical sensing and spectroscopy.

Photonic bandgap infrared spectrometer

We propose and demonstrate an infrared (IR) absorption spectrometer, made with a spatially variable photonic bandgap (PBG) structure, a blackbody source, and a simple IR detector, to identify the IR molecular fingerprints of analyte molecules. The PBG-based structure consists of thermally evaporated, IR transparent, high-refractive-index chalcogenide quarter-wave stacks (QWS) with a cavity layer. Spatial variation of the very sharp transmission peak due to the QWS cavity mode allows the structure to be used as a variable IR filter. Our proposed IR-PBG spectrometer can be used for detection and identification of volatile organic compounds.

Gyrotropic band gap optical sensors

Faraday-effect-active photonic band gap structures fabricated in iron garnet films are shown to provide a platform for optical sensing based on refractive index detection. Strong near-band gap-edge polarization rotations serve as a sensitive probe to cover-index changes in birefringent magneto-optic waveguides. A wide index range from air to n=1.6 is explored. Device sensitivity is found to improve with cover index increase. Theoretical analysis of Bloch modes polarization state shows large near stop-band edge rotations and strong sensitivity to cover index. The combined effects of geometrical waveguide birefringence and Faraday rotation contribute to the strength of the sensor response.

Modulation of bistable lateral shifts in a one-dimensional nonlinear photonic crystal consisting of indefinite metamaterials

Nonlinear propagation characteristics are investigated theoretically in a one-dimensional photonic band-gap structure containing indefinite metamaterials. It is found that optical bistability can be achieved at very low threshold values of normalized input intensity in this composite structure when the indefinite metamaterial is a cut-off, anticut-off, and never cut-off medium. It is also found that there exists corresponding bistable lateral shift which is strongly dependent on the parameters of indefinite metamaterials.

The slowing of light in one-dimensional hybrid periodic and non-periodic photoniccrystals

Studied in the present paper are the transmission properties, the group velocity, the totalphase, the phase time and the slowing-down factor of one-dimensional periodic photonicbandgap structures. The effects of the periodicity and non-periodicity of photonicstructures and of the number of layers on the slowing down of light in these structures arealso discussed. The group velocity of non-periodic (Fibonacci, Thue–Morse and Cantor)and hybrid (periodic/non-periodic) photonic bandgap structures are studied and comparedto those of periodic structures. We show that the slowing-down factors at the edge of thebandgaps are higher for the hybrid (periodic/non-periodic) multilayer systems.The proposed structures have been modelled using the transfer matrix method.

Photon scattering by a three-level emitter in a one-dimensional waveguide

We discuss the scattering of photons from a three-level emitter in a one-dimensional waveguide, where the transport is governed by the interference of spontaneously emitted and directly transmitted waves. The scattering problem is solved in closed form for different level structures. Several possible applications are discussed: the state of the emitter can be switched deterministically by Raman scattering, thus enabling applications in quantum computing such as a single-photon transistor. An array of emitters gives rise to a photonic band gap structure, which can be tuned by a classical driving laser. A disordered array leads to Anderson localization of photons, where the localization length can again be controlled by an external driving.

Non‐uniform Chebyshev distributed chirped dumbbell‐shaped photonic bandgap structure (PBGs) low‐pass filter

PurposeThe purpose of this paper is to introduce a non‐uniform Chebyshev distributed low‐pass filter (LPF) with dumbbell‐shaped photonic bandgap structure (PBGs), implemented in the 50 Ω microstrip line, with improved defected ground structure.Design/methodology/approachThe non‐uniform distribution of PBGs and dumbbell‐shaped DGS of PBGs have been discussed in open literatures. In this study, the influence of FF of PBGs in dumbbell‐shaped PBG is represented.FindingsBy varying filling factor (FF) of the periodic structure from 0.25 to 0.8 of the dumbbell squares can generate better rejection band than uniform dumbbell LPF. Different FF of each square can produce different band rejection range and then yields the LPF with different cutoff. By using chirp adjustment of distance between PBGs, the band rejection performance can be optimized.Originality/valueIt can be seen that the chirped and non‐uniform dumbbell‐shaped PBGs generate excellent bandgap performances in linearly varying period (chirped devices) than those of structures with constant period (non‐chirped or uniform devices).

X-ray spontaneous emission control by 1-dimensional photonic bandgap structure

The possibility of controlling the X-ray spontaneous emission of atoms embedded in a 1-dimensional photonic bandgap structure by the so-called Purcell effect, is studied. Calculations of the spontaneously emitted power are presented from Fermi’s golden rule in the framework of the Wigner-time approach extended to absorbing media. Numerical simulations are compared to experimental results for the case of the K emission from silicon atoms excited by electrons within a Mo/Si multilayer Bragg reflector. The inhibition or enhancement of X-ray emission from such structures appear to be feasible.

Room-temperature single photon sources with definite circular and linear polarizations

We report experimental results of two room-temperature single photon sources with definite polarization based on emitters embedded in either cholesteric or nematic liquid crystal hosts. In the first case, a cholesteric 1-D photonic bandgap microcavity provides circular polarization of definite handedness of single photons from single colloidal semiconductor quantum dots (nanocrystals). In these experiments, the spectral position of the quantum dot fluorescence maximum is at the bandedge of a photonic bandgap structure. The host does not destroy fluorescence antibunching of single emitters. In the second case, photons with definite linear polarization are obtained from single dye molecules doped in a planar-aligned nematic liquid crystal host. The combination of sources with definite linear and circular polarization states of single photons can be used in a practical implementation of the BB84 quantum key distribution protocol.

Measurement of wakefields in a 17 GHz photonic bandgap accelerator structure

We report the experimental measurement of wakefields in a 17.14 GHz metallic photonic bandgap accelerator structure and its comparison with theory. Damping of wakefields is a critical issue in the next generation of high gradient electron accelerators, and photonic bandgap (PBG) structures have unique properties for suppressing and damping wakefields. In the experiments the wakefields were generated by passing an 18 MeV electron beam through the six cell 17.14 GHz structure. The wakefield radiation was measured at two locations: the structure output port, and at a window viewing port located at the side of the structure.The electron beam consisted of a train of bunches spaced at 17.14 GHz, so that only radiation at 17.14 GHz and its harmonics was observed. Wakefields at up to the fifth harmonic (85.7 GHz) were detected by a heterodyne receiver system. The wakefield power levels were measured at 17 and 34 GHz for average currents between 20 and 300 mA. The results were compared with full wakefield simulations using the code ANALYST. The measured power level at 17 GHz was in excellent agreement with the theoretical estimate, but the measured power at 34 GHz was significantly lower than the theoretical estimate. At both 17 and 34 GHz the measured power level increased as the beam current squared, as expected from theory. The experimental results demonstrate the weak excitation of high order mode wakefields in a photonic bandgap structure.

Multilevel Green's function interpolation method for analysis of 3-D frequency selective structures using volume/surface integral equation

In this paper, we present the multilevel Green's function interpolation method (MLGFIM) for analyses of three-dimensional doubly periodic structures consisting of dielectric media and conducting objects. The volume integral equation (VIE) and surface integral equation (SIE) are adopted, respectively, for the inhomogeneous dielectric and conducting objects in a unit cell. Conformal basis functions defined on curvilinear hexahedron and quadrilateral elements are used to solve the volume/surface integral equation (VSIE). Periodic boundary conditions are introduced at the boundaries of the unit cell. Computation of the space-domain Green's function is accelerated by means of Ewald's transformation. A periodic octary-cube-tree scheme is developed to allow adaptation of the MLGFIM for analyses of doubly periodic structures. The proposed algorithm is first validated by comparison with published data in the open literature. More complex periodic structures, such as dielectric coated conducting shells, folded dielectric structures, photonic bandgap structures, and split ring resonators (SRRs), are then simulated to illustrate that the MLGFIM has a computational complexity of O(N) when applied to periodic structures.

Reconfigurable Optically Induced Quasicrystallographic Three‐Dimensional Complex Nonlinear Photonic Lattice Structures

Complex reconfigurable 3D photonic quasicrystals (PQCs) are fabricated in nonlinear photorefractive strontium barium niobate by an optical phase engineering-based single-step optical induction approach (see image). The approach demonstrates the embedded potential to use these structures as a reconfigurable platform for the investigation of advanced nonlinear light-matter interaction, or as templates fabricated in various photosensitive materials for photonic bandgap structures.

Phononic and photonic band gap structures: modelling and applications

Photonic crystals (PhCs) are artificial materials with a permittivity which is a periodic function of the position, with a period comparable to the wavelength of light. The most interesting characteristic of such materials is the presence of photonic band gaps (PBGs). PhCs have very interesting properties of light confinement and localization together with the strong reduction of the device size, orders of magnitude less than the conventional photonic devices, allowing a potential very high scale of integration. These structures possess unique characteristics enabling to operate as optical waveguides, high Q resonators, selective filters, lens or superprism. The ability to mould and guide light leads naturally to novel applications in several fields.Band gap formation in periodic structures also pertains to elastic wave propagation. Composite materials with elastic coefficients which are periodic functions of the position are named phononic crystals. They have properties similar to those of photonic crystals and corresponding applications too. By properly choosing the parameters one may obtain phononic crystals (PhnCs) with specific frequency gaps. An elastic wave, whose frequency lies within an absolute gap of a phononic crystal, will be completely reflected by it. This property allows realizing non-absorbing mirrors of elastic waves and vibration-free cavities which might be useful in high-precision mechanical systems operating in a given frequency range. Moreover, one can use elastic waves to study phenomena such as those associated with disorder, in more or less the same manner as with electromagnetic waves.The authors present in this paper an introductory survey of the basic concepts of these new technologies with particular emphasis on their main applications, together with a description of some modelling approaches.

Enhanced Incidence Angle Based Spectrum Tuning by Using One-Dimensional Ternary Photonic Band Gap Structures

This paper demonstrates a novel way to enhance the incident angle based output spectrum tuning in one-dimensional (1D) photonic band gap (PBG) material by using a ternary periodic structure (i.e., three material layers constituting a period of lattice). The incidence angle sensitive wavelength band shift of binary periodic structure was significantly enhanced when the structure was modified to ternary periodic structure by sandwiching a thin new material layer between every two layers, constituting a period of lattice. When the thickness of sandwiched layer was increased, further enhancement in tunable wavelength band shift was observed. These 1D ternary PBG structures can be substituted in place of 1D binary PBG structures for enhancing the tuning performance of optical filters.

Fabrication of silicon inverse opal photonic crystal with a complete photonic band gap in mid infrared range and its optical properties

SiO2 colloidal crystal template was fabricated by the solvent vaporization convection self-assembly method. The low pressure chemical vapor deposition method was then used to fill the voids of the silica colloidal crystal template with high refractive index silicon, thus silicon inverse opal photonic crystal was obtained. The modality structure silicon inverse opal was characterized by scanning electron microscopy. Its photonic bandgap structure was calculated based on plane wave expansion method. Its photonic bandgap properties were characterized by Fourier transform infrared spectroscopy. The results showed that silicon is homogeneously distributed inside the voids of silica template. The wavelength and bandwidth of photonic bandgap measured by microscopic infrared spectrometer agree with the calculated one. The tilt-angle reflectance spectra along the different incidence angles showed that the refection peaks with the band center wavelength of 3319 nm always existed. This result proved that silicon inverse opal has the complete photonic bandgap. The bandgap lies in the range of mid infrared atmosphere window.