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https://www.readbyqxmd.com/read/28630910/ferroelastic-modulation-and-the-bloch-formalism
#1
Angelo Mascarenhas, Brian Fluegel, Lekhnath Bhusal
The key to the development of advanced materials is to understand their electronic structure-property relationship. Utilization of this understanding to design new electronic materials with desired properties led to modern epitaxial growth approaches for synthesizing artificial lattices, which for almost half a century have become the mainstay of electronic and photonic technologies. In contrast to previous scalar modulation approaches, we now study synthetic crystal lattices that have a tensor artificial modulation and develop a theory for photons and conduction band states in these lattices in a regime with an unusual departure from the familiar consequences of translational symmetry and Bloch's theorem...
June 2017: Science Advances
https://www.readbyqxmd.com/read/28630799/optimized-process-for-fabrication-of-free-standing-silicon-nanophotonic-devices
#2
Paul Seidler
A detailed procedure is presented for fabrication of free-standing silicon photonic devices that accurately reproduces design dimensions while minimizing surface roughness. By reducing charging effects during inductively coupled-plasma reactive ion etching, undercutting in small, high-aspect ratio openings is reduced. Slot structures with a width as small as 40 nm and an aspect ratio of 5.5:1 can be produced with a nearly straight, vertical sidewall profile. Subsequent removal of an underlying sacrificial silicon dioxide layer by wet-etching to create free-standing devices is performed under conditions which suppress attack of the silicon...
May 2017: Journal of Vacuum Science and Technology. B, Nanotechnology & Microelectronics: Materials, Processing, Measurement, & Phenomena: JVST B
https://www.readbyqxmd.com/read/28630678/on-the-colour-of-wing-scales-in-butterflies-iridescence-and-preferred-orientation-of-single-gyroid-photonic-crystals
#3
Robert W Corkery, Eric C Tyrode
Lycaenid butterflies from the genera Callophrys, Cyanophrys and Thecla have evolved remarkable biophotonic gyroid nanostructures within their wing scales that have only recently been replicated by nanoscale additive manufacturing. These nanostructures selectively reflect parts of the visible spectrum to give their characteristic non-iridescent, matte-green appearance, despite a distinct blue-green-yellow iridescence predicted for individual crystals from theory. It has been hypothesized that the organism must achieve its uniform appearance by growing crystals with some restrictions on the possible distribution of orientations, yet preferential orientation observed in Callophrys rubi confirms that this distribution need not be uniform...
August 6, 2017: Interface Focus
https://www.readbyqxmd.com/read/28630672/circularly-polarized-reflection-from-the-scarab-beetle-chalcothea-smaragdina-light-scattering-by-a-dual-photonic-structure
#4
Luke T McDonald, Ewan D Finlayson, Bodo D Wilts, Pete Vukusic
Helicoidal architectures comprising various polysaccharides, such as chitin and cellulose, have been reported in biological systems. In some cases, these architectures exhibit stunning optical properties analogous to ordered cholesteric liquid crystal phases. In this work, we characterize the circularly polarized reflectance and optical scattering from the cuticle of the beetle Chalcothea smaragdina (Coleoptera: Scarabaeidae: Cetoniinae) using optical experiments, simulations and structural analysis. The selective reflection of left-handed circularly polarized light is attributed to a Bouligand-type helicoidal morphology within the beetle's exocuticle...
August 6, 2017: Interface Focus
https://www.readbyqxmd.com/read/28629209/fabrication-of-nanoshell-based-3d-periodic-structures-by-templating-process-using-solution-derived-zno
#5
Shinji Araki, Yasuaki Ishikawa, Xudongfang Wang, Mutsunori Uenuma, Donghwi Cho, Seokwoo Jeon, Yukiharu Uraoka
Fabrication methods for a 3D periodic nanostructure with excellent and unique properties for various applications, such as photonic and phononic crystals, have attracted considerable interest. Templating processes using colloidal crystals have been proposed to create nanoshell-based 3D structures over a large area with ease. However, there are technical limitations in structural design, resulting in difficulties for structural flexibility. Here, we demonstrate a combination of proximity field nanopatterning and infiltration processes using solution-derived ZnO for a nanoshell-based 3D periodic structure with high structural flexibility and controllability...
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28628907/whispering-gallery-mode-esr-spectroscopy-and-parameters-measurement-in-single-crystal-srlaalo4-at-millikelvin-temperature
#6
M A Hosain, J-M Le Floch, J Krupka, M E Tobar
A cylindrical single crystal SrLaAlO4 Whispering Gallery mode dielectric resonator was cooled to millikelvin temperature using a dilution refrigerator. By controlling a DC-magnetic field, impurity ions' spins were coupled to a variety of modes allowing the measurement of hybrid spin-photon systems. This Electron Spin Resonance mapping technique allowed us to detect Cu(2+),Fe(3+) and Mn(4+) impurity ions (at the level of parts per million (ppm) to parts per billion (ppb)), verified by the measurement of the spin parameters along with their site symmetry...
June 11, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28625344/confined-photonic-mode-propagation-observed-in-photoemission-electron-microscopy
#7
Theodore Stenmark, R C Word, R Könenkamp
Using photoemission electron microscopy (PEEM) we present a comparative analysis of the wavelength dependence of propagating fields in a simple optical slab waveguide and a thin film photonic crystal W1-type waveguide. We utilize an interferometric imaging approach for light in the near-ultraviolet regime where a 2-photon process is required to produce photoelectron emission. The typical spatial resolution in these experiments is < 30nm. Electromagnetic theory and finite element simulations are shown to be in good agreement with the experimental observations...
June 13, 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/28621978/self-similar-nanocavity-design-with-ultrasmall-mode-volume-for-single-photon-nonlinearities
#8
Hyeongrak Choi, Mikkel Heuck, Dirk Englund
We propose a photonic crystal nanocavity design with self-similar electromagnetic boundary conditions, achieving ultrasmall mode volume (V_{eff}). The electric energy density of a cavity mode can be maximized in the air or dielectric region, depending on the choice of boundary conditions. We illustrate the design concept with a silicon-air one-dimensional photon crystal cavity that reaches an ultrasmall mode volume of V_{eff}∼7.01×10^{-5}λ^{3} at λ∼1550  nm. We show that the extreme light concentration in our design can enable ultrastrong Kerr nonlinearities, even at the single-photon level...
June 2, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28618569/chaos-in-the-band-structure-of-a-soft-sinai-lattice
#9
Max D Porter, Aaron Barr, Ariel Barr, L E Reichl
We study the effect of broken spatial and dynamical symmetries on the band structure of two lattices with unit cells that are soft versions of the classic Sinai billiard. We find significant signatures of chaos in the band structure of these lattices, in energy regimes where the underlying classical unit cell undergoes a transition to chaos. Broken dynamical symmetries and the presence of chaos can diminish the feasibility of changing and controlling band structure in a wide variety of two-dimensional lattice-based devices, including two-dimensional solids, optical lattices, and photonic crystals...
May 2017: Physical Review. E
https://www.readbyqxmd.com/read/28618539/highly-efficient-optical-director-reorientation-of-liquid-crystalline-polymer-induced-by-dye-additives
#10
I A Budagovsky, V N Ochkin, S A Shvetsov, A S Zolot'ko, A Yu Bobrovsky, N I Boiko, V P Shibaev
Light-induced director orientation of polymeric liquid-crystalline systems was investigated. The materials under study were composed of a nematic liquid-crystalline polymer (NLCP) and a small amount (0.05-0.5 wt.%) of conformationally active (azobenzene) or stable (anthraquinone) dye impurity. Light action on the homogeneously aligned polymer films above glass transition temperature leads to the director reorientation and, consequently, to a change in the extraordinary refractive index. The effect is associated with the dye molecule excitation and related change of intermolecular forces...
May 2017: Physical Review. E
https://www.readbyqxmd.com/read/28618525/influence-of-liquid-crystalline-phases-on-the-tunability-of-a-random-laser
#11
José Trull, Josep Salud, Sergio Diez-Berart, David O López
In this paper, we report the temperature behavior of an optimized disordered photonic system-based liquid crystal by means of heat capacity and refractive index measurements. The scattering system is formed by a porous borosilicate glass random matrix (about 60%) infiltrated with a smectogenic liquid crystal (about 16%) and a small amount of laser dye (0.1%). The rest of the scattering system is about 24% air, giving rise to a high refractive index contrast scattering system. Such a system has the functionality to change the refractive index contrast with temperature due to the liquid crystal temperature behavior...
May 2017: Physical Review. E
https://www.readbyqxmd.com/read/28616943/a-colloidal-quantum-dot-photonic-crystal-phosphor-nanostructural-engineering-of-the-phosphor-for-enhanced-color-conversion
#12
Kyungtaek Min, Hyunho Jung, Yeonsang Park, Kyung-Sang Cho, Young-Geun Roh, Sung Woo Hwang, Heonsu Jeon
Phosphors, long-known color-converting photonic agents, are gaining increasing attention owing to the interest in white LEDs and related applications. Conventional material-based approaches to phosphors focus on obtaining the desired absorption/emission wavelengths and/or improving quantum efficiency. Here, we report a novel approach for enhancing the performance of phosphors: structural modification of phosphors. We incorporated inorganic colloidal quantum dots (CQDs) into a lateral one-dimensional (1D) photonic crystal (PhC) thin-film structure, with its photonic band-edge (PBE) modes matching the energy of 'excitation photons' (rather than 'emitted photons', as in most other PBE application devices)...
June 15, 2017: Nanoscale
https://www.readbyqxmd.com/read/28616133/naked-eye-detection-of-multiple-tumor-related-mrnas-from-patients-with-photonic-crystal-micropattern-supported-dual-modal-upconversion-bioprobes
#13
Xiaoxia Hu, Yingqian Wang, Haoyang Liu, Jie Wang, Yaning Tan, Fubing Wang, Quan Yuan, Weihong Tan
Development of a portable device for the detection of multiple mRNAs is a significant need in the early diagnosis of cancer. We have designed a biochip-based mRNA detection device by combining a hydrophilic-hydrophobic micropattern with upconversion luminescence (UCL) probes. The device achieves highly sensitive detection, using the naked eye, of multiple mRNAs among patient samples. The high sensitivity is attributed to enrichment of the target concentration and a fluorescence enhancement effect. In addition, since the photonic crystal (PC) dot biochip is functionalized with dual-wavelength excitation UCL probes, two kinds of mRNAs in the heterogeneous biological samples are detected simultaneously, and the corresponding luminescence signals are captured using an unmodified camera phone...
January 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28614340/self-referenced-frequency-combs-using-high-efficiency-silicon-nitride-waveguides
#14
David R Carlson, Daniel D Hickstein, Alex Lind, Stefan Droste, Daron Westly, Nima Nader, Ian Coddington, Nathan R Newbury, Kartik Srinivasan, Scott A Diddams, Scott B Papp
We utilize silicon-nitride waveguides to self-reference a telecom-wavelength fiber frequency comb through supercontinuum generation, using 11.3 mW of optical power incident on the chip. This is approximately 10 times lower than conventional approaches using nonlinear fibers and is enabled by low-loss (<2  dB) input coupling and the high nonlinearity of silicon nitride, which can provide two octaves of spectral broadening with incident energies of only 110 pJ. Following supercontinuum generation, self-referencing is accomplished by mixing 780-nm dispersive-wave light with the frequency-doubled output of the fiber laser...
June 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28614328/compressible-1d-photonic-crystal-nanolasers-with-wide-wavelength-tuning
#15
Tsan-Wen Lu, Chia-Cheng Wu, Chun Wang, Po-Tsung Lee
We propose and demonstrate a tunable photonic crystal nanolaser consisting of 1D periodic nanorods wrapped in deformable polydimethylsiloxane. In addition to low-threshold and long-term lasing stability, the nanolaser also displays reproducible and reliable wavelength tuning with a large tunability of 7.7 nm under 1% compression. By further associating with stretching, a very wide wavelength-tunable range of 155 nm that almost spans the entire S+C+L telecommunication bands is successfully demonstrated with a single nanolaser device...
June 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28614327/super-resolution-in-diffractive-imaging-from-hemispherical-elastic-light-scattering-data
#16
Sergiy Lysenko, Valeriy Sterligov, Manuel Gonçalves, Armando Rúa, Iaroslav Gritsayenko, Félix Fernández
Angle-resolved hemispherical elastic light scattering techniques have been used to reconstruct the surface profile of two-dimensional photonic crystals with submicron resolution and metrological precision. Iterative algorithms permit subsequent calculation of a surface autocorrelation function with additional numerical approximation of the power spectrum and then yield final reconstruction of the surface shape. The proposed method enables filtering out unwanted scattering background, precluding the convergence of phase-retrieval algorithms...
June 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28608953/simultaneous-visualization-and-quantitation-of-multiple-steroid-hormones-based-on-signal-amplified-biosensing-with-duplex-molecular-recognition
#17
Yaning Tan, Xiaoxia Hu, Meng Liu, Xinwen Liu, Xiaobo Lv, Zhihao Li, Jie Wang, Quan Yuan
The simultaneous quantitation of multiple steroid hormones in real-time is of great importance for medical diagnosis. In this study, a portable hormone biosensor based on duplex molecular recognition coupled with a signal-amplified substrate was successfully developed for the simultaneous visualization and quantitation of multiple steroid hormones. Aptamer-functionalized upconversion nanoparticles (UCNPs) with different emission peaks are immobilized on the photonic crystal (PC) substrate as the nanoprobes, leading to the specific and simultaneous assay of multiple steroid hormones...
June 13, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28608889/nanoscale-triplet-exciton-diffusion-via-imaging-of-up-conversion-emission-from-single-hybrid-nanoparticles-in-molecular-crystals
#18
Kaishi Narushima, Shuzo Hirata, Martin Vacha
Up-conversion materials composed of donor and acceptor molecules which convert low energy photons into higher energy ones by triplet-triplet annihilation can improve the sensitivity of photocatalysts or the efficiency of solar cells. The use of crystalline materials can lead to a decrease in the up-conversion threshold intensity due to increased diffusion length LT of triplet excitons. Here, we demonstrate direct microscopic imaging of triplet exciton diffusion in polycrystalline films. The generation of high local density of triplet states is achieved by functionalizing alumina nanospheres with donor molecules and dispersing them in the acceptor films...
June 13, 2017: Nanoscale
https://www.readbyqxmd.com/read/28608691/impact-of-reabsorption-on-the-emission-spectra-and-recombination-dynamics-of-hybrid-perovskite-single-crystals
#19
Hiba Diab, Christophe Arnold, Ferdinand Lédée, Gaëlle Trippé-Allard, Géraud Delport, Christèle Vilar, Fabien Bretenaker, Julien Barjon, Jean-Sébastien Lauret, Emmanuelle Deleporte, Damien Garrot
Understanding the surface properties of organic-inorganic lead-based perovskites is of high importance to improve the device's performance. Here, we have investigated the differences between surface and bulk optical properties of CH3NH3PbBr3 single crystals. Depth-resolved cathodoluminescence was used to probe the near-surface region on a depth of a few microns. In addition, we have studied the transmitted luminescence through thicknesses between 50 and 600 μm. In both experiments, the expected spectral shift due to the reabsorption effect has been precisely calculated...
June 15, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28604861/interfacial-and-volumetric-sensitivity-of-the-dry-sintering-process-of-polymer-colloidal-crystals-a-thermal-transport-and-photonic-bandgap-study
#20
Fabian A Nutz, Markus Retsch
We introduce the in situ characterization of the dry sintering process of face-centred cubic colloidal crystals by two complementary techniques: thermal transport and photonic stopband characterization. Therefore, we employed time-dependent, isothermal laser flash analysis and specular reflectivity experiments close to the glass transition temperature of the colloidal crystal. Both methods yield distinctly different time constants of the film formation process. This discrepancy can be attributed to a volume- (photonic stopband) and interface-driven (thermal transport) sensitivity of the respective characterization method...
June 21, 2017: Physical Chemistry Chemical Physics: PCCP
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