金属有机化学气相沉积法在欧泊空隙中生长磷化铟的影响因素

制备磷化铟(InP)反欧泊三维光子晶体的关键是提高InP在欧泊空隙中的填充率。使用低压金属有机化学气相沉积(MOCVD)系统在人工欧泊空隙中生长了InP晶体,分析了影响InP在欧泊空隙中填充的因素及确定了InP的最佳生长条件。实验和理论分析的结果较为符合。磷化铟在人工欧泊空隙中的填充率越高,二氧化硅球和空隙间的折射率差越大,人工欧泊光子晶体光学性能的变化就越显著;周期生长、低压、使用和InP失配小的衬底以及异质同构现象有助于InP在欧泊空隙中的填充。在优化的生长条件下制备了填充率较高的SiO₂-InP光子晶体。研究结果为制备InP反欧泊结构积累了有益的经验。     

Photonic crystals for applications in photoelectrochemical processes: Photoelectrochemical solar cells with inverse opal topology

Photonic crystal structures, that present strong light localization effects near photonic band gap frequency regions, can be very useful to maximize chemical processes of phototoactive materials. One example is the use of photonic crystals to improve solar energy harvesting in photoelectrochemical solar cells. Here, we describe the optical monitoring synthesis of macroporous materials, with inverse opal topology, made of transition metal and rare-earth oxide nanoparticles. Through the optical properties we can obtain information concerning both infiltration and over layer growth. Finally, we report on the efficiency improvement of photoelectrochemical cells when titania inverse opal topology is used.     

Nanostructural effects on optical properties of tungsten inverse opal

Tungsten (W) photonic crystals are very attractive because of their potential applications in the conventional lighting field. In this work we show that W nanostructures have dominative effects on optical properties of W inverse opal. The nanoparticle structure of W phase can cause intensive optical absorption and breakdown of the photonic band gap; on the contrary, W inverse opal made from bulk and compact W phase would have weak absorption and possess a good photonic band gap. The results will throw a new light on the study and application of W photonic crystals and development of other photonic crystal and black-body materials. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

Fabrication of 3D inverse opal structured photonic crystal by using wedge-shaped cell method

A simple and low cost fabrication method for three dimensional inverse opal structured photonic crystal by using wedge-shaped cell (WSC) was suggested and demonstrated. The key idea of our method in the infiltration process was that the opal template was attached on the upper plate of the WSC, by which we could prevent the surface sedimentation of suspension. The micro shape and the transmission spectrum of the fabricated inverse opal structured photonic crystal were measured and discussed.     

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.     

Photoluminescence in Gd2O3: Er3+, Yb3+ upconversion inverse opal

Photoluminescence properties of Gd₂O₃: Er³⁺, Yb³⁺ upconversion inverse opal photonic crystals were investigated. The photoluminescence spectra of the inverse opal show strong dependence on upconversion emission intensity and the corresponding photonic band-gaps of the inverse opal. Significant suppression of the green or red upconversion emission was observed if the photonic band-gap overlaps with the Er³⁺ ions emission band. The color purity of the red or green emission was improved in the inverse opal by the suppression of green or red UC emission. We believe that the present work will be valuable for not only the foundational study of upconversion emission modification but also new optical devices in upconversion lighting and display.     

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.     

红外区金属氧化物反蛋白石光子晶体的安德森定域化研究

根据Mie散射理论,在低浓度近似下,对中红外区由金属氧化物构成的反蛋白石光子晶体的禁带的存在区域,即光子定域化区进行了研究。发现在浓度为10%,此类晶体在中红外区将出现多个光子禁带区域,并且计算了影响定域化区域的各种因素。由此可知利用材料在剩余射线带内折射率小于1的特性,我们可以制备出中红外区和远红外区存在禁带的光子晶体。这一结果为反蛋白石晶体的研究提供了理论方法。     

Directional emission from rare earth ions in inverse photonic crystals

Angular distribution of the photoluminescence from trivalent rare earth ions (Eu³⁺) embedded inside a magnesium silicate photonic crystal with an inverse opal structure is experimentally and theoretically studied. The emission at frequencies near the first stop-band of the photonic crystal is shown to exhibit strong angular modulation. The angle-dependent Eu³⁺ photoluminescence is numerically simulated by evaluating the fractional density of optical states in the photonic crystal, with diffuse scattering on structural imperfections taken into account. Experimental data for the emission properties of thin inverse opal films are shown to be in agreement with the simulation results. PACS 42.70.Qs; 78.55.-m     

Photonic band gap and upconversion emission properties of Yb,Er co-doped lead lanthanum titanate inverse opal photonic crystals

Upconversion (UC) emission properties of Yb, Er co-doped lead lanthanum titanate inverse opal photonic crystals were investigated. The results showed that the photonic band gap has a significant influence on the upconversion emission of Yb, Er co-doped lead lanthanum titanate inverse opal photonic crystals. Significant suppression of the upconversion emission was detected if the photonic band gap overlapped with the Er³⁺ ions emission band.     

Sculpting the vacuum in a photonic band gap micro-chip

We describe the engineering of the electromagnetic vacuum in a 2D–3D photonic bandgap (PBG) hetero-structure. This facilitates the development of novel active devices and the observation of novel quantum electrodynamic phenomena. We consider a specific architecture suitable as an all-optical micro-transistor capable of novel ultra-fast response with low switching power requirements. This relies on a unique collective atomic switching and population inversion achieved by coherent resonant pumping in a suitably engineered vacuum. Specific waveguide architectures within the 3D PBG micro-chip provide local density-of-states (LDOS) peaks near their cutoff frequency. These provide “building blocks” for electromagnetic vacuum engineering without recourse to conventional high Q-factor micro-cavities. For the all-optical micro-transistor, a fork shape LDOS within the micro-chip is desirable, using trimodal waveguide architecture. We delineate the functional robustness of these architectures to disorder caused by manufacturing errors within the PBG micro-chip.     

中红外区二氧化钛反蛋白石光子晶体的光子定域化研究

为了得到二氧化钛反蛋白石光子晶体中影响光子定域化的规律,基于Mie散射理论和低浓度近似,对光子定域化参量进行了数值计算与理论分析,发现在该氧化物的剩余射线区内,入射波长和散射体大小对光子定域化有明显的影响.结果表明,在散射体浓度为10%,相对折射率大于3.8时,在中红外区13.3~15.3 μm范围内出现了光子定域化现象,并随着散射体半径的增大,定域化区向长波方向移动;同时,定域化参量先增大后减小.研究结果为实验上在该类光子晶体中实现光子定域化现象提供了理论参考.     

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.     

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.     

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.     

Design of photonic bands for opal-based photonic crystals

To make a device from an opal—or otherwise—the photonic bands and the optical properties derived from them are needed. Knowing the effects of different parameters defining the opal geometry and different possible modifications of its structure are needed, too. An accurate definition of the device will be required to obtain a good performance. With this aim, the optics of light with a wavevector in the vicinity of the L point in the Brillouin zone and its coupling to bare opals band structure are presented. An important aspect is the transition from finite to infinite crystal and the study of size effects on the bands. It is possible to substantially alter the photonic band structure of an opal-based system, while maintaining the lattice structure, simply by growing layers of other materials with an appropriate refractive index. Here, it is shown how, by the growth of accurately controlled thin layers of silicon and germanium, and further processing, one can induce the opening of two complete photonic band gaps (PBGs) in an opal structure. Finally, the possibility to fabricate a simple device consisting in a planar waveguide will be shown. By means of a very simple and inexpensive procedure, engineered planar defects acting as microcavities have been realized. These can be viewed as a particular case of a much more general class of heterostructures that can be grown by combining opal vertical deposition and chemical vapour deposition of oxides. A further step is made by applying electron beam lithography to provide lateral definition and facilitate three-dimensional structuring.     

三维光子晶体的带隙分析

平面波展开法分析了三维光子晶体的带隙 ,并用于光学通信系统。     

Preparation and upconversion emission properties of TiO2 :Yb, Er inverse opals

Inverse opal photonic crystals of Y b³⁺, Er³⁺ co-doped TiO₂ (TiO₂:Yb, Er) were prepared by a self-assembly technique in combination with a sol-gel method. Upconversion (UC) luminescence properties of the inverse opals were investigated. The results show that photonic bandgap has significant influence on the upconversion emission of the TiO₂:Yb, Er inverse opal photonic crystals. Significant suppression of the upconversion emission was detected if the photonic bandgap overlapped with the Er³⁺ ions emission band.     

A novel technique to measure the sucrose concentration in hydrogel sucrose solution using two dimensional photonic crystal structures

We propose a novel technique to measure the concentration of sucrose in PAm-hydrogel sucrose solution using two dimensional photonic crystal structures consists of air holes. PAm-hydrogel is an organic hydrogels, which is used as biomedical applications. The principle of measurement is based on the linear variation of photonic band gap with the change of dielectric constant of the solution infiltrated in air holes of photonic crystal structure. Plane wave expansion method is used to find the band gap and linear variation (R² = 0.9949) of photonic band gap with respect to sucrose concentration is observed. Besides this, an excellent linear variation (R² = 0.9949) of transmitted intensity of light with respect to sucrose concentration is also seen. Since the simulation is based on optical principle, it gives accurate results. This suggests the possible use of 2-D photonic crystal structure as a sucrose sensor. Experimental procedure for measuring the concentration of sucrose is also mentioned.     

Design of Narrowband Optical Filters Using Binary Number Sequence Photonic Crystals

A theory to design narrow band optical filters by using a new photonic crystal structure is presented. This new photonic crystal structure is composed of low index layers and high index layers arranged in mod. 4 up and down binary number sequence. The new structure exhibits narrow transmission peaks in the forbidden frequency gap region with high optical transmission (greater than 99.98%) at C.W.D.M. (Coarse Wavelength Division Multiplexing) center wavelengths. The proposed filters use only 8 layers. These new binary number sequence photonic crystal narrowband optical filters are much smaller in size, lower in cost and easier to fabricate as compared to narrowband photonic crystal optical filters based on defect Fractal Cantor multilayers, suggested recently by a group of researchers.