Modification of photonic properties in porphyrin-infiltrated opal crystals

Structural, optical and magnetic properties of porphyrin-infiltrated opal hybrid structures were investigated. Bulk samples of synthetic opal were grown by sedimentation technique from colloidal solution of SiO₂ spheres of diameter 250 nm. The structure of the samples was examined by atomic force microscopy. The photonic properties of crystals were investigated by optical measurements in transmission and reflection modes. The stop band was observed in the region 510–550 nm. The photonic properties of synthetic opal crystals were modified by infiltration with aqueous basic solution of iron–porphyrin (FeTPPS) of concentration 1.0 mM. In hybrid samples the absorption bands typical of FeTPPS were observed in the vicinity of the opal stop band. Magnetic properties of FeTPPS-infiltrated opal samples have been studied at 5–300 K in magnetic fields up to 5 T. The FeTPPS-infiltrated opal crystals can be considered as the structures perspective for magnetophotonic devices.     

Tetragonal photonic woodpile structures

The photonic properties of dielectric woodpile structures with face-centered-tetragonal (fct) and body-centered-tetragonal (bct) lattice symmetries are theoretically studied. Computational calculation of the photonic band structure reveals a photonic band gap between the second and third photonic band in both symmetries. A complete photonic band gap is not found in the bct structure due to a band gap shift with variable direction of lightflow. When the degree of layer disorder in fct woodpiles is increased, the stop bands slightly narrow and the attenuation of the optical transmission is reduced. Even so, layer-to-layer misalignment in dielectric woodpile structures may be tolerable up to 20–30% in most applications. The complete photonic band gap in fct woodpiles remains open with planar layer-to-layer disorder up to 60–70%.     

Structure of light scattering spectra in opal photonic crystals

Spectra of light losses are studied at a fixed angle of incidence of a collimated beam on the surface of an opal anisotropic photon crystal at various observation angles. It is shown that the structure of the forward-and backscattered light spectra is connected with the existence of several directional photonic forbidden bands. It is demonstrated that back scattering is enhanced and forward scattering is suppressed in the frequency region of photonic forbidden bands. It is suggested that a scattering band associated with photon localization at the photonic gap edge is observed.     

Periodic thin-film interference filters as one-dimensional photonic crystals

We review the photonic band gap-related properties of a simple periodic system of thin dielectric layers. Properties associated with forbidden and allowed bands of such one-dimensional photonic crystals are presented. A revision of the properties of forbidden bands leads to an omnidirectional Bragg mirror design. The anisotropy of allowed bands suggests the formation of photon-focusing caustics in one-dimensional photonic crystals.     

Inverted yablonovite fabricated by the direct laser writing method and its photonic structure

Three-dimensional photonic crystals with an inverted yablonovite structure have been fabricated by the direct laser writing method based on the two-photon polymerization of a photosensitive material. The correspondence of the structure of the samples to the inverted yablonovite lattice has been confirmed by scanning electron microscopy. The photonic band structure of inverted yablonovite, as well as a number of related photonic materials with an fcc lattice, has been calculated. It has been found that the photonic properties of opal and yablonovite are opposite: the complete photonic band gap appears in inverted opal and direct yablonovite and is absent in direct opal and inverted yablonovite. A method for the fabrication of ideal three-dimensional photonic structures having the complete photonic band gap in the infrared and visible spectral ranges has been discussed.     

Multiple Bragg diffraction in low-contrast photonic crystals based on synthetic opals

The phenomenon of multiple Bragg diffraction in low-contrast photonic crystals based on synthetic opals has been studied both experimentally and theoretically. The transmission and reflection spectra of opal films near the K point of the Brillouin zone of the face-centered cubic lattice in s-polarization exhibit the effect of anticrossing of dispersion curves corresponding to the (111) and ([`1]11)(\bar 111) photonic stop bands. The effect of quasi-Brewster suppression of stop bands is clearly pronounced in p-polarization. The experimental data are analyzed using the calculation of the band structure of opal with the inclusion of the polarization of incident light.     

Geometric properties of optimal photonic crystals

Photonic crystals can be designed to control and confine light. Since the introduction of the concept by Yablonovitch and John two decades ago, there has been a quest for the optimal structure, i.e., the periodic arrangement of dielectric and air that maximizes the photonic band gap. Based on numerical optimization studies, we have discovered some surprisingly simple geometric properties of optimal planar band gap structures. We conjecture that optimal structures for gaps between bands n and n+1 correspond to n elliptic rods with centers defined by the generators of an optimal centroidal Voronoi tessellation (transverse magnetic polarization) and to the walls of this tessellation (transverse electric polarization).     

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.     

高质量三维胶体光子晶体中慢光速与超光速的实验研究

利用飞秒脉冲自相关技术研究了高质量三维胶体光子晶体中的慢光速和超光速效应.实验中使用的胶体光子晶体是采用压力控制的绝热沉积技术（PCIHVD）制备的、由聚苯乙烯小球组成的人工蛋白石结构.由于其中的缺陷和位错密度很低,它们具有很高的通带透过率和陡峭的能带边缘.测量了从通带到带边直至带隙中央群速度的变化,在只有20层左右小球的样品中观察到低至0.43c的慢光速以及高至1.34c的超光速现象.此外,利用时域有限差分（FDTD）方法对短脉冲在三维光子晶体中的群速度进行了数值模拟,并且和 关键词： 三维胶体光子晶体 慢光速 超光速 脉冲自相关     

中红外完全带隙Si反蛋白石光子晶体的制备与光学性能研究

通过溶剂蒸发对流自组装法制备SiO2胶体晶体,采用低压化学气相沉积法填充Si,制备得到Si反蛋白石(opal)三维光子晶体.采用扫描电子显微镜对Si反opal的显微形貌进行表征,采用平面波展开法理论模拟Si反opal的光子带隙,采用傅里叶变换红外光谱仪测试其光学性能.研究结果表明:Si在SiO2微球空隙内填充致密均匀,显微红外光谱测试的光子带隙反射峰位置及带宽与理论计算基本符合.变角度反射光谱测试表明,Si反opal沿不同角度入射时在中心波长3319nm处均存在明显的反射峰,证明其具有完全光子带隙,带隙位于中红外大气窗口区域.     

Mid infrared band gap properties of 3-dimensional silicon inverse opal photonic crystal

By the solvent vaporization convection self-assembly method, 1.86 μm silica microspheres were assembled into a colloidal crystal template with long-range order. High refractive index silicon was then filled in the voids of the silica template by the low pressure chemical vapor deposition method. A 3-dimensional silicon inverse opal photonic crystal was obtained with a photonic band gap simulated by a plane wave expansion method. Its micro modality and photonic band gap properties were characterized by scanning electron microscopy and Fourier transform IR spectrometer. There was a good agreement between the measured spectra and the simulated results. The tilt-angle reflectance spectra showed that an obvious reflection peak at 3319 nm stayed in existence with different incidence directions. This result proved that silicon inverse opal has a complete photonic band gap in the mid infrared range. This study opens up an opportunity to create Si-based photonic crystal devices for atmosphere mid infrared photodetection.     

Effective photonic pseudogap of a two-phase composite opaline photonic crystal

We report the observation of suppression of the green photoluminescence from an optically active ZnO-infiltrated composite opal fabricated by electrodeposition templated on a self-assembled polystyrene opal. This is interpreted to be the consequence of an effective photonic pseudogap formed by the composite opaline photonic crystal. The effective pseudogap’s effect on emission of the composite opal, one ‘raw’ and one ‘inverted’, is simply the addition of the effect of each component opal, with no noticeable interaction effect, thus suggesting a simple route for engineering the photonic behavior of heterogeneous photonic crystals. PACS 42.70.Qs; 78.55.-m; 78.66.Hf     

Hypersonic modulation of light in three-dimensional photonic and phononic band-gap materials

The elastic coupling between the a-SiO2 spheres composing opal films brings forth three-dimensional periodic structures which besides a photonic stop band are predicted to also exhibit complete phononic band gaps. The influence of elastic crystal vibrations on the photonic band structure has been studied by injection of coherent hypersonic wave packets generated in a metal transducer by subpicosecond laser pulses. These studies show that light with energies close to the photonic band gap can be efficiently modulated by hypersonic waves.     

正负折射率材料组成的一维光子晶体的能带及电场

计算了由正负折射率材料交替排列组成的一维光子晶体的能带及电场，发现其能带不同于由普通正折射率材料组成的光子晶体的能带.当选择合适的参数时，由正负折射率材料组成的光子晶体的TE模或TM模有完全光子带隙出现，这在普通光子晶体中不出现.导带中的电场波函数与普通光子晶体相比具有很强的局域性.对于负折射率材料层为色散介质的情况，计算了在不同的具有正负折射率区域能带.     

Anomalous coherent backscattering of light from opal photonic crystals

We studied coherent backscattering (CBS) of light from opal photonic crystals with incomplete band gaps. We observed a dramatic broadening of the CBS cone for incident angles close to the Bragg condition in the crystals. We modify the conventional CBS theory to incorporate Bragg attenuation resulting from the photonic band structure. By fitting the CBS data with the modified theory, we extract both the disorder-induced light mean-free path and the Bragg attenuation length of the inherent opal photonic crystal.     

Controlling the photoluminescence spectroscopy of quinacrine dihydrochloride by SiO_2 inverse opal photonic crystal

Manipulation of the photoluminescence spectra of light-emitting materials doped in three-dimensional （3D） inverse opal photonic crystals is investigated. Quinacrine dihydrochloride molecules doped highly ordered SiO2 inverse opal is successfully synthesized by co-assembly combined with double-substrate vertical infiltrate method. The quinacrine dihydrochloride-doped and-undoped SiO2 inverse opals each exhibit an apparent photonic band gap （PBG） in the visible light region. Significant suppression of the emission is observed when the PBG is overlapped with the quinacrine dihydrochloride emission bands. The mechanism of suppression effect of PBG in inverse opal on the fluorescence intensity of quinacrine dihydrochloride molecules is studied.     

低温等离子体增强化学气相沉积法制备Ge反opal三维光子晶体及其光学性能

通过溶剂蒸发对流自组装法制备SiO2三维有序胶体晶体模板,采用等离子体增强化学气相沉积法在200℃低温条件下填充高折射率材料Ge,获得了Ge反opal三维光子晶体.实现了低于GeH4热分解温度的低温填充.通过扫描电镜、X射线衍射仪和傅里叶变换显微红外光谱仪对Ge反opal的形貌、成分和光学性能进行了表征.结果表明:沉积得到无定型态Ge,退火后形成多晶Ge,Ge在SiO2微球空隙内填充致密均匀.Ge反opal的反射光谱有明显的光学反射峰,表现出光子带隙效应,其带隙中心波长为1650nm和2640nm,测试的光学性能与理论计算基本符合.采用SU-8光刻胶薄膜也进行了Ge沉积,证实了SU-8模板可以耐受这一沉积温度.低温沉积降低了Ge的填充温度,可以直接采用不耐高温的高分子材料作为初始模板,单次复型制备得到多种构型的完全带隙三维光子晶体.     

Enhanced photoluminescence from three-dimensional ZnO photonic crystals

We have fabricated optically active ZnO inverse opals by infiltrating polystyrene (PS) opal templates using an electrodeposition process. Compared with bare ZnO films also prepared by electrodeposition, the three-dimensional (3D) ordered ZnO structure exhibits markedly enhanced photoluminescence. The effect of photonic band gap on PL spectra is also clearly observed from the ZnO inverse opal structure.     

蛋白石型光子晶体红外隐身材料的制备

基于光子晶体的红外隐身材料,主要采取一维层层堆叠结构和三维木堆结构等来实现对红外波段电磁波辐射性能的调控.本文报道了一种操作简易、成本低廉的光子晶体红外隐身材料制备方法.通过优化的垂直沉积法,微米级SiO_2胶体微球自组装成高质量的蛋白石型光子晶体结构.对SiO_2胶体微球进行优选,成功制备了禁带位于2.8—3.5μm,8.0—10.0μm的SiO_2胶体晶体蛋白石型光子晶体材料.该材料可改变目标相应波段的红外辐射特征,具有目标红外波段的隐身效果.     

The photonic analogue of the graded heterostructure: Analysis using the envelope approximation

We develop and deploy an envelope function formalism in order to study graded photonic crystals – periodic photonic media whose features vary continuously with position. We use the method to reduce the properties of the uniform crystals to the spectral position of their band edges and an effective mass-like term. These are employed within the Schrödinger-like equation derived herein to determine the behaviour of light inside a specific graded photonic crystal created using depth-dependent infiltration of an artificial opal.