Photonic Quasicrystals Research Articles

A Novel Photonic Quasicrystal Fiber with Broadband Large Negative Dispersion

A broadband highly dispersive fiber based on a dual-concentric-core photonic quasicrystal fiber (PQF) is designed for chromatic dispersion compensation. The fiber is composed of pure silica background and air-holes without doping. The fundamental supermode has a large negative dispersion value of about −9600 ps·nm−1·km−1 over an optical communication band around 1550 nm and a full width at half maximum (FWHM) of 40 nm. By adjusting the structural parameters, a dispersion of −2250 ps·nm−1·km−1 around 1550 nm with the FWHM exceeding 280 nm is obtained and the dispersion-bandwidth product can reach 630 GHz−1·km−1, which is the highest value of dispersion-bandwidth product from pure silica fibers reported so far.

Light Extraction Efficiency Enhancement of GaN-Based Light Emitting Diodes on n-GaN Layer Using a SiO2 Photonic Quasi-Crystal Overgrowth

In this paper, GaN-based LEDs with a SiO2 photonic quasi-crystal (PQC) pattern on an n-GaN layer by nano-imprint lithography (NIL) are fabricated and investigated. At a driving current of 20 mA on Transistor Outline (TO)-can package, the better light output power of LED III (d = 1.2 microm) was enhanced by a factor of 1.20. After 1000 h life test (55 degrees C/50 mA) condition, Normalized output power of LED with a SiO2 PQC pattern (LED III (d = 1.2 microm)) on an n-GaN layer only decreased by 5%. This results offer promising potential to enhance the light output power of commercial light-emitting devices using the technique of nano-imprint lithography.

Negative refraction and localized states of a classical wave in high-symmetry quasicrystals

Recently, negative refraction of electromagnetic waves in periodic photonic crystals has been demonstrated experimentally and sub-wavelength images observed. A theoretical and experimental investigation is reported of the electromagnetic wave transport in high-symmetry photonic quasicrystals (QCs). It is shown that negative refraction can appear in these transparent quasicrystalline photonic structures. It is interesting that highly symmetric two-dimensional photonic QCs possess a universal feature for non-near-field focus of two kinds of polarized waves (S wave and P wave). That is, the non-near-field focus for two kinds of polarized waves can be realized by using flat lenses, which consist of some high-symmetric two-dimensional photonic QCs with the same structures and parameters. In addition, some two-dimensional and three-dimensional localized states in defect-free photonic QCs have been found. It is evident that these unusual localized states can be explored by means of electron energy loss spectroscopy.

Analysis of one-dimensional Fibonacci-class quasicrystals using perturbation theory

In this work, we present a new and semi-analytical method to investigate one-dimensional Fibonacci-class photonic quasicrystals from waveguiding properties point of view. Usually, the exact treatment for obtaining band diagram in these situations is very hard and the numerical methods are used. In this paper, we investigate the waveguiding properties of one-dimensional quasicrystals by using perturbation method. In this direction, the band diagram and field distribution of this structure are investigated.

Stable structures with high topological charge in nonlinear photonic quasicrystals

Stable vortices with topological charge of 3 and 4 are examined numerically and analytically in photonic quasicrystals created by interference of 5 as well as 8 beams, in the cases of cubic as well as saturable nonlinearities. These structures are experimentally realizable, including a prototypical example of a stable charge 4 vortex. Direct numerical simulations corroborate the analytical and numerical linear stability analysis predictions.

Holographically formed three-dimensional Penrose-type photonic quasicrystal through a lab-made single diffractive optical element

Large-area three-dimensional Penrose-type photonic quasicrystals are fabricated through a holographic lithography method using a lab-made diffractive optical element and a single laser exposure. The diffractive optical element consists of five polymer gratings symmetrically orientated around a central opening. The fabricated Penrose-type photonic quasicrystal shows ten-fold rotational symmetry. The Laue diffraction pattern from the photonic quasi-crystal is observed to be similar to that of the traditional alloy quasi-crystal. A golden ratio of 1.618 is also observed for the radii of diffraction rings, which has not been observed before in artificial photonic quasicrystals.

Mode analysis of 2D photonic quasicrystals based on an approximate analytic model

In this work, we have developed a semi-analytical model based on perturbation theory for evaluating optical properties of photonic quasicrystals. Although numerical techniques are being used for determining characteristics of photonic quasicrystals, it is believed that analytical studies based on approximations help us to understand the physical properties and treatment of the structure more easily. Towards that end, the use of perturbation method can be beneficial in approximating the photonic band structure and mode profile in photonic quasicrystals made of low dielectric contrast materials with high accuracy. It is shown that error incurred by the approximation through the perturbation method can be estimated to be a few percent, in comparison to the more accurate finite difference time domain method. In addition, the effect of variation in the dielectric contrast on the photonic band structure of 2D 12-fold photonic quasicrystal has been studied and it is presented that by decreasing dielectric contrast a smaller photonic band gap is obtained, which is interesting for optical communication devices.

Tuning efficiency and sensitivity of guided resonances in photonic crystals and quasi-crystals: a comparative study

In this paper, we present a comparative study of the tuning efficiency and sensitivity of guided resonances (GRs) in photonic crystal (PC) holed slabs based on periodic and aperiodically-ordered unit cells, aimed at assessing the applicability of these important technology platforms to ultra-compact optical sensors and active devices. In particular, with specific reference to square-lattice periodic PCs and aperiodically-ordered Ammann-Beenker photonic quasi-crystals, we study the effects of the hole radius, slab thickness, and refractive index on the GR sensitivity and tunability with respect to variation in the hole refractive index. Finally, we carry out a theoretical and numerical analysis in order to correlate the GR shift with the field distribution of the unperturbed (air holes) structures. Our results indicate that the spatial arrangement of the holes may strongly influence the tuning and sensitivity efficiency, and may provide new degrees of freedom and tools for the design and optimization of novel photonic devices for both sensing and telecommunication applications.

High extraction efficiency GaN-based light-emitting diodes on embedded SiO2 nanorod array and nanoscale patterned sapphire substrate

In this paper, GaN-based LEDs with a nanoscale patterned sapphire substrate (NPSS) and a SiO2 photonic quasicrystal (PQC) structure on an n-GaN layer using nanoimprint lithography are fabricated and investigated. The light output power of LED with a NPSS and a SiO2 PQC structure on an n-GaN layer was 48% greater than that of conventional LED. Strong enhancement in output power is attributed to better epitaxial quality and higher reflectance resulted from NPSS and PQC structures. Transmission electron microscopy images reveal that threading dislocations are blocked or bended in the vicinities of NPSS layer. These results provide promising potential to increase output power for commercial light emitting devices.

Efficiency Improvement of GaN-Based LEDs With a $ \hbox{SiO}_{2}$ Nanorod Array and a Patterned Sapphire Substrate

The enhancement of light extraction from GaN-based light-emitting diodes (LEDs) with a patterned sapphire substrate (PSS) and a SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 12-fold photonic quasi-crystal (PQC) structure using nanoimprint lithography is presented. At a driving current of 20 mA on transistor-outline-can package, the light output powers of LED with a PSS and LED with a PSS and a SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> PQC structure are enhanced by 35% and 48%, compared with the conventional LED. In addition, the higher output power of the LED with a PSS and a SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> PQC structure is due to better reflectance on PSS and higher epitaxial quality on an n-GaN using a SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 12-fold PQC structure pattern. These results provide promising potential to increase output powers of commercial light-emitting devices.

Rhombicuboctahedral Three‐Dimensional Photonic Quasicrystals

The aesthetics of quasicrystals has fascinated mankind already for centuries. Numerous examples are known in one and two dimensions, yet in three dimensions only icosahedral quasicrystals have been realized and observed to date in any system, i.e., in man-made, natural, photonic, and phononic quasicrystals. We rationally construct the novel class of three-dimensional rhombicuboctahedral quasicrystals and realize it as polymer microstructure.

Enhancement of light output power of GaN-based light-emitting diodes using a SiO2 nano-scale structure on a p-GaN surface

GaN (gallium nitride)-based light-emitting diodes (LEDs) with a nano-scale SiO2 structure between a transparent indium-tin oxide (ITO) layer and p-GaN were fabricated. The forward voltage at 20 mA for a GaN-based LED with a SiO2 nano-scale structure was slightly higher than that of a conventional GaN-based LED because the total area of the p-type metal contact between the transparent ITO layer and p-GaN was smaller. However, the light output power for the GaN-based LED with a nano-scale structured SiO2 at 20 mA was 24% higher than that for a conventional GaN-based LED structure. This increase in the light output power is mostly attributed to the scattering of light from the SiO2 photonic quasi-crystal (PQC) layer.

Čerenkov-type second-harmonic generation with fundamental beams of different polarizations

We analyze the conical second-harmonic generation via Cerenkov-type phase matching in two-dimensional decagonal nonlinear photonic quasi-crystals for linear, circular, and elliptical polarized fundamental beams. Depending on the polarization state, we observe either centrosymmetric or noncentrosymmetric intensity modulation of the second-harmonic rings. We explain this effect by employing the concept of effective quadratic nonlinearity combined with the hexagonal symmetry of the individual ferroelectric domains.

Three‐Dimensional Nanostructures for Photonics

AbstractRecent progress in direct laser writing of three‐dimensional (3D) polymer nanostructures for photonics is reviewed. This technology has reached a level of maturity at which it can be considered as the 3D analogue of planar electron‐beam lithography. Combined with atomic‐layer deposition and/or chemical‐vapor deposition of dielectrics—the 3D analogues of planar evaporation technologies, the 3D polymer templates can be converted or inverted into 3D high‐refractive‐index‐contrast nanostructures. Examples discussed in this review include positive and inverse 3D silicon‐based woodpile photonic crystals possessing complete photonic bandgaps, novel optical resonator designs within these structures, 3D chiral photonic crystals for polarization‐state manipulation, and 3D icosahedral photonic quasicrystals. The latter represent a particularly complex 3D nanostructure.

Resonant transmission of electromagnetic waves through two-dimensional photonic quasicrystals

We present numerical simulations of electromagnetic millimeter-wave propagation in a two-dimensional lattice of dielectric rods arranged in a tenfold Penrose tiling. We find (i) isotropic photonic band gap as expected for quasicrystals and (ii) localized states. We demonstrate that the high frequency edge of the second band gap is characterized by a very small refractive index (fast light). We study the transmission of electromagnetic waves in the frequency range corresponding to fast light and demonstrate that it is related to tunneling through localized states. We use the fast light phenomenon to design a focusing device—a planoconcave lens.

Double Photonic Quasi-Crystal Structure Effect on GaN-Based Vertical-Injection Light-Emitting Diodes

GaN-based thin-film vertical-injection light-emitting diodes (VLEDs) with a double 12-fold photonic quasi-crystal (PQC) structure formed using nanoimprint lithography (NIL) and inductively coupled plasma reactive-ion etching (ICP-RIE) are fabricated and presented. At a driving current of 20 mA and with a chip size of 350 ×350 µm2, our thin-film LED with a double-12-fold-PQC structure gave a light output power of 40.5 mW, which is an increase of 77% when compared with the output power of a VLED without a PQC structure at a peak wavelength of 460 nm. In addition, the corresponding light radiation patterns show a narrow beam shape due to the strong guided light extraction on the n-GaN surface and the reflected light effect of the PQC structure formed in the vertical direction on the p-GaN surface.

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.

Localized modes in defect-free two-dimensional circular photonic crystals

The localization of electromagnetic waves in defect-free circular photonic crystals (CPCs) is investigated using a multiple-scattering method. It is shown that electromagnetic waves of certain freqencies are localized in some special regions inside a perfect CPC with a high order of rotational symmetry. Localized modes with a high Q factor, greater than 10{sup 6}, are obtained. In particular, some unique localized modes such as circular modes and localized modes for both polarized waves are found in the present system, which are completely different from those in defect-free photonic quasicrystals and periodic structures. Their physical properties are also analyzed.

加工误差对准晶光子晶体绝对带隙的影响

加工误差对准晶光子晶体绝对带隙的影响

介质柱形状对准晶光子晶体带隙特性的影响

介质柱形状对准晶光子晶体带隙特性的影响