Two-dimensional Photonic Bandgap Research Articles

Optical properties in 2D photonic crystal structure using fullerene and azafullerene thin films

Theoretical calculations via a transfer matrix method were performed to investigate the possibility of fullerene films acting as two-dimensional (2D) photonic band gap crystals. The response within and out of the periodic structure of 2D photonic crystals consisting of air rods drilled into C60 or (C59N)2 films was studied. PBG was found around 0.85–1.24eV in the near infrared region. We find that fullerene-based networks could be good candidates for absolute inhibition of transmission in the near infrared range for given orientations.

Modeling and design of two-dimensional guided-wave photonic band-gap devices

The model of two-dimensional (2-D) guided-wave photonic band-gap structures based on the Bloch-Floquet theory is proposed for the first time for both infinite and finite length devices. The efficient computation of dispersion curves and field distribution is carried out in very short computer time. Both guided and radiated modes can be easily identified to give a physical insight, even in defective structures. The accuracy of the model has been tested through the design of a very compact narrow-band 2-D guided-wave photonic band-gap filter at 1.55 /spl mu/m. The filter has a channel isolation of 22 dB, a large number of channel (>80) with a channel spacing of 50 GHz, and a very short length (24 /spl mu/m).

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.

High resolution and aspect ratio two-dimensional photonic band-gap crystal

This paper reports the challenges resolved to realize high aspect ratio pillar-type two-dimensional photonic band-gap crystal (PhC), designed for application at the optical communication wavelengths. Specifically, the issue of a drastically reduced process window of deep UV lithography and deep reactive ion etching, for a super dense array of submicron size pillars with a diameter of 230nm and a spacing of 340nm is treated. A rigorous design of experiments yielded high-resolution PhCs with precise lattice dimensions even near regions of “defect structures” designed for device operations. At the same time, in the etching process, the stringent requirement of an etch angle needed for successful realization of such a super dense array of submicron size PhC lattice was also satisfied to yield sidewalls of high verticality, aspect ratios greater than 50, and scallop-depths of 12nm.

Vacuum Rabi splitting with a single quantum dot in a photonic crystal nanocavity

Cavity quantum electrodynamics (QED) systems allow the study of a variety of fundamental quantum-optics phenomena, such as entanglement, quantum decoherence and the quantum-classical boundary. Such systems also provide test beds for quantum information science. Nearly all strongly coupled cavity QED experiments have used a single atom in a high-quality-factor (high-Q) cavity. Here we report the experimental realization of a strongly coupled system in the solid state: a single quantum dot embedded in the spacer of a nanocavity, showing vacuum-field Rabi splitting exceeding the decoherence linewidths of both the nanocavity and the quantum dot. This requires a small-volume cavity and an atomic-like two-level system. The photonic crystal slab nanocavity--which traps photons when a defect is introduced inside the two-dimensional photonic bandgap by leaving out one or more holes--has both high Q and small modal volume V, as required for strong light-matter interactions. The quantum dot has two discrete energy levels with a transition dipole moment much larger than that of an atom, and it is fixed in the nanocavity during growth.

Tunable photonic bandgap structures for optical interconnects

As continued progress towards faster, low power consuming microelectronic devices becomes increasing difficult due to the scaling challenges of electrical interconnects, it becomes even more critical to explore alternative technologies. Tunable porous silicon photonic bandgap structures are viable building blocks for optical interconnects, which present a possible long term solution to the interconnect problem. Forming the structures on a silicon platform provides the advantage of easier integration with current semiconductor processing techniques. In this work, tuning of the optical properties is controlled by liquid crystals (LCs) that are infiltrated into the silicon matrix. Active tuning is demonstrated both out-of-plane, with one-dimensional porous silicon photonic bandgap microcavities, and in-plane, using two-dimensional porous silicon photonic bandgap structures.

Spontaneous emission trapping and steering in a two-dimensional photonic bandgap structure

We study the superradiant decay of an ensemble of inverted two-level atoms embedded into a 2D photonic crystal with lateral confinement of the radiation. We show that the transfer of the optical excitation propagates along the Bragg planes and is manifested by strong energy localization.

Two-dimensional metallo-dielectric photonic crystals embedded in anodic porous alumina for optical wavelengths

A theoretical study is presented for hexagonal lattice metallic pillar photonic crystals in anodic porous alumina with a lattice constant of 500nm. The objective of the investigation is to design a two-dimensional metallo-dielectric photonic crystal with an anodic porous alumina template. Optical responses are calculated for silver pillars of radii 100nm, and 200nm in porous alumina. The nature of their stop bands and attenuation in the near-infrared region is investigated. Calculations reveal that two-dimensional photonic band gaps for the TM polarization exist at visible wavelengths when the radius is 200nm.

Optical properties of two-dimensional photonic-bandgap crystals characterized by spectral ellipsometry

In this paper, we demonstrate a simple and non-destructive measuring method for both TE and TM bandgaps of two-dimensional (2D) silicon photonic bandgap (PBG) structures by using reflected spectral ellipsometry. Although this method measures the reflected light from samples, the transmitted signal of PBG layer can be measured by using reflecting signals. With large incident angles, planar PBG modulation effects and bandgap information can be obtained. To verify this method, we fabricated silicon arrays for 2D PBG by using electron-beam lithography. From SEM images, we can verify the geometry especially the radius of the cells, which is related to the bandgaps. With a specific set of radii and dielectric constants, we can get the band diagram with plane-wave expansion method. There are several bandgaps of both TE and TM modes, which can be used to detect multiple bandgaps by spectral ellipsometry.

Focused electron beam induced deposition of a periodic transparent nano-optic pattern

In this paper we describe the fabrication of a two-dimensional photonic band gap structure by focused electron beam induced deposition. Structure geometry is computed in order to create a light-trapping effect at 632 nm wavelength. Deposits produced using tetraethyl orthosilicate (SiO 4 C 8 H 20 ) as precursor were studied to determine their chemical composition and geometrical dimensions. The deposited material has a refractive index n ̃ =1.85+ i 3.9×10 −4 at 632 nm. Transmission electron microscopy revealed deposits obtained at low currents (100 pA) are amorphous. The structure was deposited on a quartz prism, coated with a transparent conducting antimony-doped tin oxide layer to minimize electron beam drifts and distortions. Multiple beam re-alignments during the deposition assured drift compensation. Optical characterisation of the photonic band gap effect is currently under investigation.

Optical properties of two-dimensional photonic-bandgap crystals characterized by spectral ellipsometry

In this paper, we demonstrate a simple and non-destructive measuring method for both TE and TM bandgaps of two-dimensional (2D) silicon photonic bandgap (PBG) structures by using reflected spectral ellipsometry. Although this method measures the reflected light from samples, the transmitted signal of PBG layer can be measured by using reflecting signals. With large incident angles, planar PBG modulation effects and bandgap information can be obtained. To verify this method, we fabricated silicon arrays for 2D PBG by using electron-beam lithography. From SEM images, we can verify the geometry especially the radius of the cells, which is related to the bandgaps. With a specific set of radii and dielectric constants, we can get the band diagram with plane-wave expansion method. There are several bandgaps of both TE and TM modes, which can be used to detect multiple bandgaps by spectral ellipsometry.

Focused electron beam induced deposition of a periodic transparent nano-optic pattern

In this paper we describe the fabrication of a two-dimensional photonic band gap structure by focused electron beam induced deposition. Structure geometry is computed in order to create a light-trapping effect at 632 nm wavelength. Deposits produced using tetraethyl orthosilicate (SiO 4C 8H 20) as precursor were studied to determine their chemical composition and geometrical dimensions. The deposited material has a refractive index n ̃ =1.85+ i 3.9×10 −4 at 632 nm. Transmission electron microscopy revealed deposits obtained at low currents (100 pA) are amorphous. The structure was deposited on a quartz prism, coated with a transparent conducting antimony-doped tin oxide layer to minimize electron beam drifts and distortions. Multiple beam re-alignments during the deposition assured drift compensation. Optical characterisation of the photonic band gap effect is currently under investigation.

Rapid photon flux switching in two-dimensional photonic crystals

We have investigated the out-of-plane propagation of light in two-dimensional photonic band-gap crystals consisting of long dielectric nanorods. Defects, which sufficiently break the crystal symmetry, can produce photonic states localized at the defect sites. We show that this localization can result in a sharp transition between the state of the out-of-plane light propagation through the entire photonic crystal, and the state in which light propagates only along the defect channels. This switching can be induced by slight changes of the dielectric constant at the defect sites. We propose a practical way of achieving this, and suggest applications.

Experimental studies of the influence of distributed power losses on the transparency of two-dimensional surface photonic band-gap structures.

Two-dimensional (2D) surface photonic band-gap (SPBG) structures have been suggested to realize 2D distributed feedback. The 2D SPBG structures can be obtained by providing 2D periodic perturbations of the waveguide surface. Such a structure can be used in a wide variety of applications including microwave electronics and integrated optics. The theoretically predicted effect of the transparency of the 2D SPBG structure when distributed Ohmic losses inside the structure are relatively high in comparison with the wave coupling coefficient has been observed in a series of experiments. The results obtained are in good agreement with theoretical predictions.

As-S and As-Se based photonic band gap fiber for IR laser transmission

IR transmissive As-S glass and As-Se glass triangular photonic band gap fiber structures are theoretically modeled. The potential for propagation of air-guided modes in the defect regions of these fibers is demonstrated by the large out of plane two-dimensional photonic band gaps found in these structures. Fiber design for IR light propagation is discussed.

Alumina nanowire arrays standing on a porous anodic alumina membrane

Alumina nanowire arrays standing on the surface of a porous anodic alumina membranehave been achieved by first forming a porous anodic alumina membrane with parallelY-branched nanochannels by reducing the applied anodizing voltage by a factor of in the anodization process of high-purity Al foil, and then chemically etching theY-branched nanochannel alumina membrane in an aqueous phosphoric acid solution. Thenovel nanostructures may be used for two-dimensional photonic bandgap structuralmaterials.

Fabrication of individually seeded nanowire arrays by vapour–liquid–solid growth

We report on a method of synthesizing arrays of individually seeded nanowires. Anelectron beam lithography and metal lift-off method was used to pattern InP(111)Bsubstrates with catalysing gold particles. Vertical nanowire arrays were then grown from the gold particles, using metal–organic vapourphase epitaxy. The lithographic nature of the method allows individual control over eachnanowire. Possible applications for such deterministic and uniform arrays include producingarrays of nanowire devices, two-dimensional photonic band gap structures and fieldemission displays, amongst others.

Periodic defects in 2d-pbg materials: full-wave analysis and design

In this paper, an accurate and efficient characterization of two-dimensional photonic bandgap structures with periodic defects is performed, which exploits a full-wave diffraction theory developed for one-dimensional gratings. The high convergence rate of the proposed technique is demonstrated. Results are presented for both TE and TM polarizations, showing the efficiencies as a function of wavelength, incidence angle, geometrical and physical parameters. A comparison with other theoretical results reported in the literature is shown with a good agreement. The transmission properties of photonic crystals with periodic defects are studied, investigating the effects of the variation of geometrical and physical parameters; design efficiency maps and formulas are given; moreover, the application of the analyzed structures as filters is discussed.

Analysis of bandgap characteristics of two-dimensional periodic structures by using the source-model technique.

We introduce a solution based on the source-model technique for periodic structures for the problem of electromagnetic scattering by a two-dimensional photonic bandgap crystal slab illuminated by a transverse-magnetic plane wave. The proposed technique takes advantage of the periodicity of the slab by solving the problem within the unit cell of the periodic structure. The results imply the existence of a frequency bandgap and provide a valuable insight into the relationship between the dimensions of a finite periodic structure and its frequency bandgap characteristics. A comparison shows a discrepancy between the frequency bandgap obtained for a very thick slab and the bandgap obtained by solving the corresponding two-dimensionally infinite periodic structure. The final part of the paper is devoted to explaining in detail this apparent discrepancy.

Asymptotic analysis of dispersion characteristics in two-dimensional metallic photonic band gap structures

We present a self-consistent technique for the asymptotic analysis of dispersion curves in two-dimensional metallic photonic band gap structures representing square and triangular arrays of metal rods. The technique is applicable for the structures with rod radii (a), which are small compared to the distance between the rods (b) and to the wavelength (λ). The induced current and charge distributions on the rods are expressed self-consistently in terms of the electromagnetic wave field. The dispersion characteristics are calculated for the TE and TM modes. The results are in agreement with those obtained previously using the Photonic Band Gap Structure Simulator code.