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Photonic crystals

Fei Wang, Bin Yang, Qingchun Yu, Dachun Liu, Wenhui Ma
Gd2O3-xSx:Er crystals were prepared through high-temperature solid-state reaction method in vacuum, with the vacuum synthesis mechanism determined by thermal analysis. The crystal structure and upconversion luminescence properties were investigated respectively by XRD, TEM and spectrophotometer. Well crystallized Gd2O2S:Er phosphors were prepared under 1000°C in vacuum with a certain excessive amount of sulfur content than stoichiometric. It is confirmed that with the increasing sulfur content the green emission was enhanced and red emission was weakened...
September 13, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Magda Białkowska, Irena Deperasińska, Artur Makarewicz, Bolesław Kozankiewicz
Highly terrylene doped single crystals of p-terphenyl, obtained by co-sublimation of both components, showed bright spots in the confocal fluorescence images. Polarization of the fluorescence excitation spectra, blinking and bleaching, and saturation behavior allowed us to attribute them to single molecules of terrylene anomalously embedded between two neighbor layers of the host crystal, in the (a,b) plane. Such an orientation of terrylene molecules results in much more efficient absorption and collection of the fluorescence photons than in the case of previously investigated molecules embedded in the substitution sites...
September 21, 2017: Journal of Chemical Physics
Lijuan Shen, Yuzhou Xia, Sen Lin, Shijing Liang, Ling Wu
Creating two-dimensional (2D) crystal-metal heterostructures with an ultrathin thickness has spurred increasing research endeavors in catalysis because of its fascinating opportunities in tuning the electronic state at the surface and enhancing the chemical reactivity. Here we report a novel and facile Nb(4+)-assisted strategy for the in situ growth of highly dispersed Pd nanoparticles (NPs) on monolayer HNb3O8 nanosheets (HNb3O8 NS) constituting a 2D Pd/HNb3O8 NS heterostructure composite without using extra reducing agents and stabilizing agents...
September 22, 2017: Nanoscale
Zhongyu Cai, Aniruddha Sasmal, Xinyu Liu, Sanford A Asher
Lectin proteins, such as the highly toxic lectin protein, ricin, and the immunochemically important lectin, jacalin, play significant roles in many biological functions. It is highly desirable to develop a simple but efficient method to selectively detect lectin proteins. Here we report the development of carbohydrate containing responsive hydrogel sensing materials for the selective detection of lectin proteins. The copolymerization of a vinyl linked carbohydrate monomer with acrylamide and acrylic acid forms a carbohydrate hydrogel that shows specific "multivalent" binding to lectin proteins...
September 22, 2017: ACS Sensors
Zhihong Zhang, Xiaozhi Xu, Lu Qiu, Shaoxin Wang, Tianwei Wu, Feng Ding, Hailin Peng, Kaihui Liu
The exceptional properties of graphene make it a promising candidate in the development of next-generation electronic, optoelectronic, photonic and photovoltaic devices. A holy grail in graphene research is the synthesis of large-sized single-crystal graphene, in which the absence of grain boundaries guarantees its excellent intrinsic properties and high performance in the devices. Nowadays, most attention has been drawn to the suppression of nucleation density by using low feeding gas during the growth process to allow only one nucleus to grow with enough space...
September 2017: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Weihong Gao, Muriel Rigout, Huw Owens
The work presented investigates how to produce structural colours on textile materials by applying a surface coating of silica nanoparticles (SNPs). Uniform SNPs with particle diameters in a controlled micron size range (207-350 nm) were synthesized using a Stöber-based solvent varying (SV) method which has been reported previously. Photonic crystals (PCs) were formed on the surface of a piece of textile fabric through a process of natural sedimentation self-assembly of the colloidal suspension containing uniform SNPs...
2017: Journal of Nanoparticle Research: An Interdisciplinary Forum for Nanoscale Science and Technology
Nikita Kostylev, Maxim Goryachev, Andrey D Bulanov, Vladimir A Gavva, Michael E Tobar
This corrects the article DOI: 10.1038/srep44813.
September 20, 2017: Scientific Reports
Cheng Xing, Yinzhou Yan, Chao Feng, Jiayu Xu, Peng Dong, Wei Guan, Yong Zeng, Yan Zhao, Yijian Jiang
Dielectric microspheres with extraordinary microscale optical properties, such as photonic nanojets, optical whispering-gallery modes (WGMs), and directional antennas, have drawn interest in many research fields. Microsphere-enhanced Raman spectroscopy (MERS) is an alternative approach for enhanced Raman detection by dielectric microstructures. Unfortunately, fabrication of microsphere monolayer arrays is the major challenge of MERS for practical applications on various specimen surfaces. Here we report a microsphere-embedded film (MF) by immersing a highly refractive microsphere monolayer array in the poly(dimethylsiloxane) (PDMS) film as a flexible MERS sensing platform for one- to three-dimensional (1D to 3D) specimen surfaces...
September 19, 2017: ACS Applied Materials & Interfaces
Lijing Zhang, Bofan Liu, Jie Wang, Shengyang Tao, Qingfeng Yan
In this paper, we present a general fabrication strategy to achieve the structure control and the flexible photonic stop band regulation of (2+1) D photonic crystal heterostructures (PCHs) by layer-by-layer depositing the annealed colloidal crystal monolayers of different sphere size. The optical properties of the resulting (2+1) DPCHs with different lattice constants were systematically studied and a universal photonic stopband variation rule was proposed, which makes it possible to program any kind of stopband structure as required, such as dual- or multi-stopbands PCH and ultra-wide stopband PCH...
August 24, 2017: Journal of Colloid and Interface Science
Josey E Topolski, Jared O Kafader, Caroline Chick Jarrold
The anion photoelectron (PE) spectra of a range of small mono-cerium molecular species, along with the Ce2O4(-) and Ce3O6(-) stoichiometric clusters, are presented and analyzed with the support of density functional theory calculations. A common attribute of all of the neutral species is that the Ce centers in both the molecules and clusters are in the +4 oxidation state. In bulk ceria (CeO2), an unoccupied, narrow 4f band lies between the conventional valence (predominantly O 2p) and conduction (Ce 5d) bands...
September 14, 2017: Journal of Chemical Physics
Kai Guo, Søren M M Friis, Jesper B Christensen, Erik N Christensen, Xiaodong Shi, Yunhong Ding, Haiyan Ou, Karsten Rottwitt
We derive from Maxwell's equations full-vectorial nonlinear propagation equations of four-wave mixing valid in straight semiconductor-on-insulator waveguides. Special attention is given to the resulting effective mode area, which takes a convenient form known from studies in photonic crystal fibers, but has not been introduced in the context of integrated waveguides. We show that the difference between our full-vectorial effective mode area and the scalar equivalent often referred to in the literature may lead to mistakes when evaluating the nonlinear refractive index and optimizing designs of new waveguides...
September 15, 2017: Optics Letters
Andrey M Vyunishev, Pavel S Pankin, Sergey E Svyakhovskiy, Ivan V Timofeev, Stepan Ya Vetrov
We propose an elegant approach to produce photonic bandgap (PBG) structures with multiple photonic bandgaps by constructing quasiperiodic photonic crystals (QPPCs) composed of a superposition of photonic lattices with different periods. Generally, QPPC structures exhibit both aperiodicity and multiple PBGs due to their long-range order. They are described by a simple analytical expression, instead of quasiperiodic tiling approaches based on substitution rules. Here we describe the optical properties of QPPCs exhibiting two PBGs that can be tuned independently...
September 15, 2017: Optics Letters
Sagi Frishman, Meir Razvag, Aharon J Agranat
We present wavelength selective switching with a rise time of 25 ns implemented in a slab waveguide constructed in a KLTN:Cu crystal. The waveguide was fabricated by implantations of alpha particles at 2.1 MeV which produced a 0.5 μm thick cladding layer with reduced refractive index at 4.5 μm underneath the crystal surface. This demonstrates the feasibility of implementing electroholography in waveguides maintaining the performance obtained in bulk crystals, providing in potential the basis for constructing integrated photonic circuits which incorporate interconnected electroholographic wavelength selective switches and electrical wavelength tuning devices for employing wavelength addressing routing schemes in computer networks, in particular for relieving the bandwidth bottlenecks in data center networks...
September 15, 2017: Optics Letters
Jinhui Yuan, Zhe Kang, Feng Li, Xianting Zhang, Chao Mei, Guiyao Zhou, Xinzhu Sang, Qiang Wu, Binbin Yan, Xian Zhou, Kangping Zhong, Kuiru Wang, Chongxiu Yu, Gerald Farrell, Chao Lu, Hwa Yaw Tam, P K A Wai
In this Letter, we demonstrate experimentally for the first time, to the best of our knowledge, discrete ultraviolet (UV) wavelength generation by cascaded intermodal FWM when femtosecond pump pulses at 800 nm are launched into the deeply normal dispersion region of the fundamental guided mode of a multimode photonic crystal fiber (MPCF). For pump pulses at average input powers of Pav=450, 550, and 650 mW, the first anti-Stokes waves are generated at the visible wavelength of 538.1 nm through intermodal phase matching between the fundamental and second-order guided mode of the MPCF...
September 15, 2017: Optics Letters
N Akamatsu, K Hisano, R Tatsumi, M Aizawa, C J Barrett, A Shishido
Tunable photonic crystals exhibiting optical properties that respond reversibly to external stimuli have been developed using liquid crystal networks (LCNs) and liquid crystal elastomers (LCEs). These tunable photonic crystals possess an inverse opal structure and are photo-responsive, but circumvent the usual requirement to contain dye molecules in the structure that often limit their applicability and cause optical degradation. Herein, we report tunable photonic crystal films that reversibly tune the reflection peak wavelength under thermo-, photo- and mechano-stimuli, through bilayering a stimuli-responsive LCN including azobenzene units with a colourless inverse opal film composed of non-responsive, flexible durable polymers...
September 13, 2017: Soft Matter
Chengxin Luan, Yueshuang Xu, Fanfan Fu, Huan Wang, Qionghua Xu, Baoan Chen, Yuanjin Zhao
Barcodes have a demonstrated value for multiplex high-throughput bioassays. The tendency of this technology is to pursue high sensitivity target screening. Herein, we presented a new type of inverse opal-structured poly(N-isopropylacrylamide) (pNIPAM) hydrogel photonic crystal (PhC) barcodes with the function of fluorescent signal self-amplification for the detection. During the bio-reaction process at body temperature, the pNIPAM hydrogel barcodes kept swelling, and their inverse opal structure with interconnected pores provided unblocked channels for the targets to diffuse into the voids of the barcodes and react...
September 13, 2017: Nanoscale
Raghavender Medishetty, Lydia Nemec, Venkatram Nalla, Sebastian Henke, Marek Samoc, Karsten Reuter, Roland A Fischer
Multi-photon absorption (MPA) is among the most prominent nonlinear optical (NLO) effects and has applications, for example in telecommunications, defense, photonics and bio-medicines. Established MPA materials include dyes, quantum dots, organometallics and conjugated polymers, most often dispersed in solution. We demonstrate how metal-organic frameworks (MOFs), a novel NLO solid-state materials class, can be designed for exceptionally strong MPA behavior. MOFs consisting of zirconium- and hafnium-oxo-clusters and featuring a chromophore linker based on the tetraphenylethene (TPE) molecule exhibit record high two-photon absorption (2PA) cross section values, up to 3600 GM...
September 12, 2017: Angewandte Chemie
S Assali, J Lähnemann, T T T Vu, K D Jöns, L Gagliano, M A Verheijen, N Akopian, E P A M Bakkers, J E M Haverkort
One of the major challenges in the growth of quantum well and quantum dot heterostructures is the realization of atomically sharp interfaces. Nanowires provide a new opportunity to engineer the band structure as they facilitate the controlled switching of the crystal structure between the zinc-blende (ZB) and wurtzite (WZ) phases. Such a crystal phase switching results in the formation of crystal phase quantum wells (CPQWs) and quantum dots (CPQDs). For GaP CPQWs, the inherent electric fields due to the discontinuity of the spontaneous polarization at the WZ/ZB junctions lead to the confinement of both types of charge carriers at the opposite interfaces of the WZ/ZB/WZ structure...
September 18, 2017: Nano Letters
Jue Hou, Mingzhu Li, Yanlin Song
Colloidal photonic crystals (PCs) have been well developed because they are easy-to-prepare, cost-effective, and versatile to be modified and functionalized. Patterned colloidal PCs contributes a novel approach to constructing high-performance PC devices with unique structures and specific functions. In this review, an overview of the strategies for fabricating patterned colloidal PCs, including patterned substrate induced assembly, inkjet printing, and selective immobilization and modification is presented...
September 11, 2017: Angewandte Chemie
Tao Lu, Hui Pan, Jun Ma, Yao Li, Shenmin Zhu, Di Zhang
Stimuli-responsive photonic crystals (PCs) trigged by light would provide a novel intuitive and quantitative method for noninvasive detection. Inspired by the flame-detecting aptitude of fire beetles and the hierarchical photonic structures of butterfly wings, we herein developed near-infrared stimuli-responsive PCs through coupling photothermal Fe3O4 nanoparticles with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM), with hierarchical photonic structured butterfly wing scales as the template. The nanoparticles within 10 s transferred near-infrared radiation into heat that triggered the phase transition of PNIPAM; this almost immediately posed an anticipated effect on the PNIPAM refractive index and resulted in a composite spectrum change of ∼26 nm, leading to the direct visual readout...
September 19, 2017: ACS Applied Materials & Interfaces
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