Fabrication of three‐dimensional photonic crystals in quantum‐dot‐based materials

Controlling spontaneous emission (SE) is of fundamental importance to a diverse range of photonic applications including but not limited to quantum optics, low power displays, solar energy harvesting and optical communications. Characterized by photonic bandgap (PBG) property, three‐dimensional (3D) photonic crystals (PCs) have emerged as a promising synthetic material, which can manipulate photons in much the same way as a semiconductor does to electrons. Emission tunable nanocrystal quantum dots (QDs) are ideal point sources to be embedded into 3D PCs towards active devices. The challenge however lies in the combination of QDs with 3D PCs without degradation of their emission properties. Polymer materials stand out for this purpose due to their flexibility of incorporating active materials. Combining the versatile multi‐photon 3D micro‐fabrication techniques, active 3D PCs have been fabricated in polymer‐QD composites with demonstrated control of SE from QDs. With this milestone novel miniaturized photonic devices can thus be envisaged.     

Large-scale photonic crystals with inserted defects and their optical properties

Deliberately introducing defects into photonic crystals is an important way to functionalize the photonic crystals. We prepare a special large-scale three-dimensional(3D) photonic crystal(PC) with designed defects by an easy and low-cost method. The defect layer consists of photoresist strips or air-core strips. Field emission scanning electron microscopy(FESEM) shows that the 3D PC is of good quality and the defect layer is uniform. Different defect states shown in the ultraviolet-visible spectra are induced by the photoresist strip layer and air-core strip layer. The special large-scale 3D PC can be tested for integrated optical circuits, and the defects can act as optical waveguides.     

Surface plasmon polaritons mediated by surface modes in a metal-based photonic crystal complex structure

A hybrid metal–organic–photonic crystal (PC), a gold film with a SU8 film on its top followed by a three-dimensional (3D) PC, was designed to exercise additional control upon the photon behaviors. Attenuated total reflection measurements demonstrate that the 3D PC plays a crucial role in the formation of significant optical properties of the metal-based hybrid and the reflectivity minimum in its reflectivity curve is, mostly, a result of synergetic action of the coupling of surface plasmon polaritons to surface modes and additional guided modes yielded in the resonant cavity composed of the gold film and the PC.     

Diffractionless optical networking in an inverse opal photonic band gap micro-chip

We present a design for a photonic crystal (PC) all-optical micro-chip based on a three-dimensional (3D) inverse opal heterostructure intercalated with a two-dimensional (2D) triangular lattice photonic crystal slab. Within the 2D micro-chip layer, we demonstrate single-mode (diffractionless) waveguiding of light in air, throughout a bandwidth of more than 70 nm near 1.55 μm. This suggests that inverse opal photonic band gap (PBG) materials can facilitate on-chip optical networking functions over the telecommunication frequency band used in current-day optical fibers.     

Light confinement in 3D silicon doped with germanium (n-SixGe1−x) and silicon-on-insulator (SOI) photonic crystal structures

The numerical investigation of photonic band gaps (PBGs) for three-dimensional (3D) photonic crystals (PCs) of silicon doped with germanium (n-Si_xGe_1−x) and silicon-on-insulator (SOI) structures has been illustrated. The effect of germanium-doping (Ge-doping) concentration on the vertical confinement of the light and the band gap size has been presented. A 3D full vectorial plane wave was developed and employed to investigate design parameters of the 3D PC structure and to calculate dispersion relation for guided modes. Calculations of band structures for the triangular lattices of dielectric cylinders in air for quasi-3D PC structures have been performed.     

A Novel Woodpile Three-Dimensional Terahertz Photonic Crystal

A novel woodpile lattice structure is proposed. Based on plane wave expansion （PWE） method, the complete photonic band gaps （PBGs） of the novel woodpile three~dimensional （3D） terahertz （THz） photonic crystal （PC） with a decreasing symmetry relative to a face-centred-tetragonal （fct） symmetry are optimized by varying some structural parameters and the highest band gap ratio can reach 27.61%. Compared to the traditional woodpile lattice, the novel woodpile lattice has a wider range of the filling ratios to gain high quality PBGs, which provides greater convenience for the manufacturing process. The novel woodpile 3D PC will be very promising for materials of THz Junctional components.     

Switching control of spontaneous emission by polarized atoms in two-dimensional photonic crystals

We calculate the lifetime distribution function of an assembly of polarized atoms in two-dimensional (2D) photonic crystals (PCs) at different polarization orientations of atomic dipole moments. We reveal a switching effect of atomic spontaneous emission (SE) and find a significant change of atomic lifetime, up to a factor of 33, by tuning the polarized orientation of the atoms. These observations suggest that the tuning of the polarized orientation of atoms provides a new way for the effective control of atomic SE processes in 2D PCs.     

Spatial and frequency domain effects of defects in 1D photonic crystal

The aim of this paper is to present the analysis of influence of defects in 1D photonic crystal (PC) on the density of states and simultaneously spontaneous emission, in both spatial and frequency domains. In our investigations we use an analytic model of 1D PC with defects. Our analysis reveals how presence of a defect causes a defect mode to appear. We show that a defect in 1D PC has local character, being negligible in regions of PC situated far from the defected elementary cell. We also analyze the effect of multiple defects, which lead to photonic band gap splitting.     

Superprism effect in 1D photonic crystal

It is shown that superprism effect can be observed not only in 2D and 3D photonic crystal but also in 1D photonic crystal. To observe the effect a diffraction grating should be put on the top of the 1D PC. It is shown that the band gap more dramatically appears in 1D PC than in 2D PC. This effect makes all PBG effects including superprism effect more pronounced and also weakens the influence of losses.     

二维光子晶体量子阱的光谱特性研究

研究了二维光子晶体量子阱的光谱特性,该量子阱结构由二维正方晶格圆柱晶胞光子晶体通过移去中间位置的介质圆柱层形成。由于光子晶体中的光子禁带充当了光子运动的势垒,类似于半导体量子阱中电子的行为,在光子晶体量子阱结构中会出现量子化的光子能态。文章利用平面波展开法计算了所用光子晶体的能带结构,利用传输矩阵方法计算了量子阱结构的透射光谱。计算结果表明,在光子禁带中出现了离散的透射峰,透射峰的强度随着势垒宽度的增加而减弱,个数随着势阱宽度的增加而增加,通过计算得到了其定量关系,并且讨论了透射峰频率与势阱宽度的关系。     

超薄金膜-发光层-光子晶体三明治结构的光学特性及荧光调制

结合垂直沉积自组装法和旋涂法制备了由超薄金膜、发光层和三维光子晶体组成的三明治结构。通过对样品的衰减全反射曲线进行测量和分析,发现该三明治结构的光学特性取决于光子晶体的质量,高质量三维光子晶体使得三明治结构的衰减全反射曲线在48°和63°两个位置出现了反射波谷,而低质量三维光子晶体的三明治结构的反射波谷完全消失。与薄金膜-发光层双层结构相比,该三明治结构的荧光特性曲线也出现了显著变化,单一辐射峰分裂为双峰,且位于600nm的辐射峰比位于620nm处的辐射峰要弱30%。     

Surface Plasmon Sensor Based on a Dual Dielectric–Silver Photonic Crystal

We present a new type of biosensor. The principle of operation of the device is similar to conventional surface plasmon sensors, except that the ordinary metallic film in surface plasmon sensors is replaced by a one-dimensional photonic bandgap array. The advantages of using a photonic bandgap structure, instead of a metallic film, include enhanced sensitivity, physical and chemical robustness, and the ability to engineer the optical response of the device. We propose and elaborate a biosensor based on a onedimensional (1D) photonic crystal (PC) with a surface plasmon resonance (SPR). In comparison with standard SPR sensors that use silver (Ag ) or gold (Au) films, PC–Ag–PC–Au structures have narrower resonance widths, lower minimum reflectance, and higher sensitivity, making them a much better choice for biosensing applications. Moreover, the structure is compact (H = 1.139 μm), providing a better option in biosensing in comparison with other PC-SPR and conventional SPR sensors.     

Efficient omnidirectional couplers achieved by anisotropic photonic crystal waveguides

Photonic crystals (PCs) have many potential applications because of their ability to control light-wave propagation. We have investigated omnidirectional couplers in two-dimensional anisotropic PC structures. The anisotropic PC coupler composed of an anisotropic-dielectric cylinder in air is studied by solving Maxwell's equations using the plane wave expansion method and finite-difference time-domain method. The photonic band structures are found to exhibit absolute bandgaps for the square lattices. Numerical simulations show that the incident light-waves at both transverse electric and transverse magnetic modes have efficient coupling in anisotropic PC coupler with square lattices. The guided modes and coupling length are analyzed by considering various line defect anisotropic PC waveguides and interaction regions of couplers. Such a mechanism of omnidirectional coupling should open up a new application for designing components in photonic integrated circuits.     

Comparison of photonic bandgaps of two-dimensional periodic and quasi-periodic photonic crystals with different relative permittivity dielectric

Photonic bandgaps (PBGs) of two-dimensional (2D) triangular-lattice and square-lattice and decagonal quasi-periodic photonic crystals (PCs) have been analyzed, with a given scatterer radius and dielectric relative permittivity changing from 1 to 30 within air-cylinders-in-dielectric and dielectric-cylinders-in-air constructions. The results have shown that 2D quasi-periodic PC is more likely to generate PBG and complete PBG than 2D periodic PC. For the given scatterer radius and two constructions, PBG widths of the two types of 2D PCs vary little, whereas the corresponding center frequencies decrease in smooth “hyperbola-like” curves with dielectric relative permittivity increasing monotonically. The present results will guide the design of PBG-type microstructure photonic devices.     

CdSe infiltrated TiO2 based omnidirectional photonic crystals for visible light control

Control of light emission by engineering the electromagnetic vacuum is important in photonics for fundamental understanding as well as in applications. Omnidirectional photonic crystals such as logpile photonic crystals provide a very interesting system to study such phenomena. Here, we describe the first steps towards achieving systematic and reproducible control of light using titanium dioxide (TiO₂) logpile photonic crystals (PC) with incorporated cadmium chalcogenide (CdSe) quantum dots (QDs) (λ  600 nm) to potentially modify QD photoluminescence (PL). We present a technique for coating a monolayer of the QDs on the PC rods based on 3-mercaptopropyltrimethoxysilanol linkage and measured the resulting PL response. Comparison of the PL spectra to a finite difference time domain model shows the need for further localization of QDs and fabrication of additional PC unit cells to observe PL modification.     

一维Al/SrF2低温超导体-电介质光子晶体能带结构

基于二流体电子模型和平面波展开法,计算了一维Al/SrF2超导体-电介质光子晶体的能带结构.结果表明:随着超导层厚度的增加,第一光子带隙中心频率和截止频率均发生蓝移,且第一带隙宽度逐渐增加到一个峰值后又逐渐变窄.更重要的是,在低于临界温度的超低温环境中,温度的微小变化,对该类光子晶体的带隙宽度、中心频率以及截止频率均有...     

3D harnessing of light with 2.5D photonic crystals

It is emphasized that two‐dimensional photonic crystals (2D PC) have not only a great potential for the development of 2D nanophotonics in the inplane waveguided configuration, but that they may also open the way to other brilliant developments, with an extension to out‐of‐plane operation, along a 2.5D nanophotonics approach. In this 2.5D approach, a 1D–2D high index contrast lateral structuration is combined with a 1D high index contrast vertical structuration, using multilayer membrane stacks including 1D–2D photonic crystal membranes, thus resulting in so‐called 2.5D PC. As a specific illustration of recent achievements along this approach, new families of VCSEL structures are presented.     

Analysis of vertical coupling between a 2D photonic crystal cavity and a hydrogenated-amorphous-silicon-wire waveguide

We present an efficient means of light extraction from two-dimensional photonic crystal (2D PC) cavities with SiO₂ cladding. We propose a vertically coupled system consisting of a 2D PC cavity and a hydrogenated-amorphous-silicon (a-Si:H)-wire waveguide, which we theoretically investigate using the 3D finite-difference time-domain method. Light can be extracted with an efficiency of greater than 95% to both output ports of the a-Si:H-wire waveguide or extracted with an efficiency of greater than 90% to a single output port of the a-Si:H-wire waveguide with a reflector.     

Prediction of photonic crystal emitter efficiency using an optimized fuzzy learning approach

Photonic crystals (PC) have attracted much attention over the last decade for their unique ability to control light propagation. Researchers suggested the use of metallic photonic crystal with network topology as high efficiency thermal emitters. A necessary precursor to the deployment of such crystals in practical systems is fast accurate prediction of the emission characteristics and efficiency from a photonic lattice. Conventional models that simulate the photonic response of PC are computationally expensive and can take up to a few hours on several parallel processors to realize the emitter efficiency for a given PC structure. Therefore, a practical design process with trial and error cannot be done in a reasonable amount of time.In this article we suggest the use of a fuzzy learning approach to establish a model that can be used to predict emitter efficiency from such systems. The widely studied metallic PC Lincoln log structure is used as a case study. We show that the proposed method can estimate the efficiency of any PC Lincoln log structure much faster than any existing method and is by no means bound to this specific geometry. The case study presented here was chosen only because of recent high interest in it and the abundance of literature data on the example structure. The learning process using Fuzzy set Theory is explained. A multi-objective optimization method to enhance the fuzzy learning process is also outlined. An exemplar case showing the ability of the proposed model to predict the emitter efficiency of a tungsten PC with a bandgap at (10–11.5 μm) is illustrated. We show that once the fuzzy learning is performed, the proposed method can predict the emitter efficiency with 95% accuracy without the need for any expensive computations.     

Design of air-guiding honeycomb photonic bandgap fiber

We introduce a design procedure for hollow-core photonic bandgap (PBG) fiber with a cladding made of air-silica honeycomb photonic crystal (PC). It is found that air-guiding can be realized in both fundamental and secondary PBG regions of the cladding PC. Dispersion and radiation loss of the fundamental mode for two types of fiber structure are theoretically calculated. The fibers show promising waveguiding ability.