| 1. |
- Bin Abdul Rahim, H. R., et al.
(författare)
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Applied light-side coupling with optimized spiral-patterned zinc oxide nanorod coatings for multiple optical channel alcohol vapor sensing
- 2016
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Ingår i: Journal of Nanophotonics. - : SPIE - International Society for Optical Engineering. - 1934-2608. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- The width of spiral-patterned zinc oxide (ZnO) nanorod coatings on plastic optical fiber (POF) was optimized theoretically for light-side coupling and found to be 5 mm. Structured ZnO nanorods were grown on large core POFs for the purpose of alcohol vapor sensing. The aim of the spiral patterns was to enhance signal transmission by reduction of the effective ZnO growth area, thereby minimizing light leakage due to backscattering. The sensing mechanism utilized changes in the output signal due to adsorption of methanol, ethanol, and isopropanol vapors. Three spectral bands consisting of red (620 to 750 nm), green (495 to 570 nm), and blue (450 to 495 nm) were applied in measurements. The range of relative intensity modulation (RIM) was determined to be for concentrations between 25 to 300 ppm. Methanol presented the strongest response compared to ethanol and isopropanol in all three spectral channels. With regard to alcohol detection RIM by spectral band, the green channel demonstrated the highest RIM values followed by the blue and red channels, respectively.
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| 2. |
- Dai, Daoxin, et al.
(författare)
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Ultrasmall integrated devices based on silicon nanowires for optical communications
- 2008
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Ingår i: JOURNAL OF NANOPHOTONICS. - : SPIE-Intl Soc Optical Eng. - 1934-2608. ; 2, s. 021780-
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Tidskriftsartikel (refereegranskat)abstract
- Planar lightwave circuits (PLCs) based on Si nanowires exhibit several serious problems due to the small cross sections of the nanowires. These problems include large scattering loss, large coupling loss to a single-mode fiber, and high dependency on polarization. Several solutions to these problems have emerged. Recent progress on Si-nanowire-based passive PLC devices encompasses arrayed waveguide grating (de) multiplexers, microring resonators, and multimode interference couplers.
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| 3. |
- Dalarsson, Mariana, et al.
(författare)
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Exact analytical solution for fields in gradient index metamaterials with different loss factors in negative and positive refractive index segments
- 2013
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Ingår i: Journal of Nanophotonics. - 1934-2608. ; 7, s. 073086-
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Tidskriftsartikel (refereegranskat)abstract
- Gradient refractive index metamaterials are of interest for various applications of transformation optics. Wave propagation through gradient index metamaterials using an exact analytical approach is investigated. Composite materials containing constituents with negative real and positive real indexes of refraction are considered. An exact analytical solution for the field distribution is obtained for the sinusoidal spatial variation of complex effective permittivity and permeability along a fixed direction, under the assumption that the wave impedance remains spatially uniform across the structure. Loss factors in the constituent materials can be different from each other corresponding to the realistic situations. Temporal dispersion can be arbitrary subject to the physical limitations imposed by the Kramers-Kronig relations. A numerical model based on the Z-transform is developed to verify the analytical results. The approach can be applied to arbitrary periodic refractive index profiles using the Fourier series method.
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| 4. |
- Dalarsson, Mariana, et al.
(författare)
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Lossy gradient index metamaterial with sinusoidal periodicity of refractive index : case of constant impedance throughout the structure
- 2011
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Ingår i: J NANOPHOTONICS. - : SPIE-Intl Soc Optical Eng. - 1934-2608. ; 5, s. 051804-
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Tidskriftsartikel (refereegranskat)abstract
- We used an exact analytical approach to investigate the electromagnetic wave propagation across an isotropic metamaterial composite with i. a sinusoidally periodic gradient of the real parts of the effective permittivity and permeability, ii. spatially uniform imaginary parts of the effective permittivity and permeability, and iii. spatially uniform impedance. The real part of the effective refractive index can be positive and negative along the direction of nonhomogeneity. A remarkably simple direct solution for the field distribution was obtained.
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| 5. |
- Fadil, Ahmed, et al.
(författare)
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Fabrication and improvement of nanopillar InGaN/GaN light-emitting diodes using nanosphere lithography
- 2015
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Ingår i: Journal of Nanophotonics. - 1934-2608. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Surface-patterning technologies have enabled the improvement of currently existing light-emitting diodes (LEDs) and can be used to overcome the issue of low quantum efficiency of green GaN-based LEDs. We have applied nanosphere lithography to fabricate nanopillars on InGaN/GaN quantum-well LEDs. By etching through the active region, it is possible to improve both the light extraction efficiency and, in addition, the internal quantum efficiency through the effects of lattice strain relaxation. Nanopillars of different sizes are fabricated and analyzed using Raman spectroscopy. We have shown that nanopillar LEDs can be significantly improved by applying a combination of ion-damage curing techniques, including thermal and acidic treatment, and have analyzed their effects using x-ray photoelectron spectroscopy. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
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| 6. |
- Fang, Mei, et al.
(författare)
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Designing photonic band gaps in SiO(2)-based face-centered cubic-structured crystals
- 2011
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Ingår i: Journal of nanophotonics. - : SPIE-Intl Soc Optical Eng. - 1934-2608. ; 5, s. 053514-
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Tidskriftsartikel (refereegranskat)abstract
- We designed face-centered cubic-structured (fcc) photonic crystals whose lattice parameters were tuned by varying the size of the constituent spherical silica particles in the range 100 to 520 nm. From wide-angle optical transmission investigations and Gaussian fitting of the absorbance spectra over UV-Vis-Near IR range, we found that in these crystals the Bragg wavelengths of the photonic band gaps (PBGs) corresponding to the reflected crystal planes linearly increase with the size of the spheres as expected. From this data, the average refractive index along the different crystal planes of the fcc structure was found to be in the 1.24 to 1.32 range. The Bragg wavelengths were tuned between 400 and 1100 nm. Thus, photonic crystals of the same structure can be designed to tune the Bragg wavelengths of PBGs by selecting the sphere size. These studies open up possibilities to design a new class of "smart" photonic crystals consisting of dielectric entities of sub-micron silica spheres with added functionality from magnetic or piezoelectric nanoparticles embedded in them.
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| 7. |
- Hu, Rui, et al.
(författare)
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Tunable multicolored hybrid metallic nanoparticles for live human cancer cell imaging
- 2010
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Ingår i: JOURNAL OF NANOPHOTONICS. - : SPIE-Intl Soc Optical Eng. - 1934-2608. ; 4, s. 041545-
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Tidskriftsartikel (refereegranskat)abstract
- Gold/silver core/shell nanorods with precisely tunable resonance peaks covering the visible and near-infrared wavelength range were obtained using a simple wet-chemical synthesis approach. These nanoparticles surfaces can be further modified to improve their biocompatibility and stability in biological media. After conjugating with some biomolecules, these functionalized nanoparticles were used as multicolored optical probes for targeted dark field imaging of live human cancer cells. These experiments suggest that the gold/silver core/shell nanoparticles can serve as a potential platform for multichanneled and ultrasensitive bioimaging.
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| 8. |
- Moskalenko, S. A., et al.
(författare)
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Dispersion laws of the two-dimensional cavity magnetoexciton-polaritons
- 2016
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Ingår i: Journal of Nanophotonics. - : SPIE - International Society for Optical Engineering. - 1934-2608. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- The energy spectrum of the two-dimensional cavity magnetoexciton-polaritons has been investigated previously, using exact solutions for the Landau quantization (LQ) of conduction electrons and heavy holes (hhs) provided by the Rashba method. Two lowest LQ levels for electrons and three lowest Landau levels for hhs lead to the construction of the six lowest magnetoexciton sates. They consist of two dipole-active, two quadrupole-active, and the two forbidden quantum transitions from the ground state of the crystal to the magnetoexciton states. The interaction of the four optical-active magnetoexciton states with the cavity-mode photons with a given circular polarization and with well-defined incidence direction leads to the creation of five magnetoexciton-polariton branches. The fifth-order dispersion equation is examined by using numerical calculations and the second-order dispersion equation is solved analytically, taking into account only one dipole-active magnetoexciton state in the point of the in-plane wave vector k→ ||=0. The effective polariton mass on the lower polariton branch, the Rabi frequency, and the corresponding Hopfield coefficients are determined in dependence on the magnetic-field strength, the Rashba spin-orbit coupling parameters, and the electron and hole g-factors.
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| 9. |
- Moskalenko, Sveatoslav A., et al.
(författare)
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Two-dimensional magnetoexciton-polariton
- 2012
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Ingår i: JOURNAL OF NANOPHOTONICS. - 1934-2608. ; 6, s. 061806-
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Tidskriftsartikel (refereegranskat)abstract
- The Hamiltonian describing the interaction of the two-dimensional (2-D) magnetoexcitons with photons propagating with arbitrary-oriented wave vectors in the three-dimensional (3-D) space is deduced. The magnetoexcitons are characterized by the numbers n(e) and n(h) of the electron and hole Landau quantizations, by circular polarization (sigma) over right arrow (M) of the holes in the p-type valence bands and by in-plane wave vectors (k) over right arrow (parallel to). The photons are characterized by the wave vectors (k) over right arrow with in-plane component (k) over right arrow (parallel to) and perpendicular component k(z), which is quantized in the case of microresonator. The interaction is governed by the conservation law of the in-plane components (k) over right arrow (parallel to)of the magnetoexcitons and photons and by the rotational symmetry around the axis perpendicular to the layer, which leads to the alignment of the magnetoexcitons under the influence of the photons with circular polarization (sigma) over right arrow (+/-)((k) over right arrow) and with probability proportional to vertical bar (sigma) over right arrow (+/-)((k) over right arrow) . (sigma) over right arrow (M)*vertical bar(2.)
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| 10. |
- Ozturk, Z. Fatih, et al.
(författare)
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Field enhancement at metallic interfaces due to quantum confinement
- 2011
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Ingår i: J NANOPHOTONICS. - : SPIE-Intl Soc Optical Eng. - 1934-2608. ; 5, s. 051602-
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Tidskriftsartikel (refereegranskat)abstract
- We point out an apparently overlooked consequence of the boundary conditions obeyed by the electric displacement vector at air-metal interfaces: the continuity of the normal component combined with the quantum mechanical penetration of the electron gas in the air implies the existence of a surface on which the dielectric function vanishes. This, in turn, leads to an enhancement of the normal component of the total electric field. We study this effect for a planar metal surface, with the inhomogeneous electron density accounted for by a Jellium model. We also illustrate the effect for equilateral triangular nanoislands via numerical solutions of the appropriate Maxwell equations, and show that the field enhancement is several orders of magnitude larger than what the conventional theory predicts.
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