| 1. |
- Talneau, A., et al.
(författare)
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Modal behavior of single-line photonic crystal guiding structures on InP substrate
- 2004
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Ingår i: Photonics and Nanostructures - Fundamentals and Applications. - : Elsevier BV. - 1569-4410 .- 1569-4429. ; 2:1, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- We have experimentally investigated the modal behaviour and the polarization dependence of the transmission through single-missing-row photonic crystal (PC) straight guides, bends and combiners, fabricated on InP substrate. A photonic crystal-based taper has been included to funnel light in these strongly confined structures. Two-dimensional finite-difference time-domain simulations have been performed and favorably compared with the measurements. It is found that the scattering process occurring at a bend/combiner transition plays a key role on the overall transmission.
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| 2. |
- Elhadi Adam, Rania Elhadi, et al.
(författare)
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Synthesis of ZnO nanoparticles by co-precipitation method for solar driven photodegradation of Congo red dye at different pH
- 2018
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Ingår i: PHOTONICS AND NANOSTRUCTURES-FUNDAMENTALS AND APPLICATIONS. - : ELSEVIER SCIENCE BV. - 1569-4410. ; 32, s. 11-18
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Tidskriftsartikel (refereegranskat)abstract
- Solar driven photocatalytic processes to remove organic pollutants from wastewater and other aqueous solutions is very important and useful due to its environmental benefits regarding sustainability aspect. In this article, we report a study on the use of bare zinc oxide (ZnO) nanoparticles (NPs) prepared by the chemical low temperature co-precipitation method and used as a catalyst to degrade the Congo red dye from aqueous solution using solar radiation. We performed the photocatalytic experiments for degradation of Congo red dye under solar radiation at different pH values. The results showed that the ZnO NPs are effective under solar radiation for degradation of Congo red dye. Even when the pH was varied down to 4 or raised to 10, the degradation was observed to be slightly improved. This result is due to the excess of radicals species, which enhance the photocatalytic process. In general, the observed degradation efficiency of the ZnO NPs is due to the deep level defects within the band gap that were introduced during the growth process of the ZnO NPs, which enhance the absorption wavelength band towards the visible light region. Recycling of the ZnO NPs for 3 successive runs have indicated the feasibility of reusing the NPs for several times. This implies that by using bare ZnO NPs an efficient approach for degradation of toxic waste can be achieved. Radical scavengers were used to evaluate the role of the radicals in the reaction mechanism.
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| 3. |
- Fransson, Jonas, et al.
(författare)
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Transport through quasi-degenerate states in coupled quantum dots
- 2004
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Ingår i: Photonics and Nanostructures - Fundamentals and Applications. - : Elsevier BV. - 1569-4410. ; 2:1, s. 11-21
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Tidskriftsartikel (refereegranskat)abstract
- By means of a general method for treating mesoscopic systems with strong internal correlations, transport properties through a set of quasi-degenerate transitions in the interacting region, or active element (AE), are considered. It is shown that the behaviour of the AE drastically changes as the couplings to the contacts are varied from the strong to the weak coupling limit. These changes strongly influence the transport properties of the system, from a single increase of the current to a staircase form with unequally large steps. In the present study, kinematic interactions, non-equilibrium populations numbers and dependence on the bias voltage has been included in the treatment of the local properties of the AE. Analytical results for the equilibrium situation are presented as well as a derivation of the corresponding non-equilibrium quantities. Results from self-consistent numerical calculations of the considered case are presented.
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| 4. |
- Kulbickas, A., et al.
(författare)
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Optical study and structure modelling of PPI liquid crystalline dendrimer derivatives
- 2007
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Ingår i: Photonics and Nanostructures-Fundamentals and Applications. - : Elsevier BV. - 1569-4410. ; 5:4, s. 178-183
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Tidskriftsartikel (refereegranskat)abstract
- Optical study of two families of poly(propylene imine) (PPI) dendrimers (G = 1-5) are reported. The enlarging of the chain number (generations) of the PPI dendrimer leads to the spectra shift to IR region in solvent until 8 and 19 nm for both families, respectively. The theoretical modelling of the dendrimer structure was performed. The geometric characterization of dendrimer structure demonstrates that the preferable free space for encapsulation is periphery of the PPI dendrimer.
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| 5. |
- Suarez, I., et al.
(författare)
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Simulation of surface-modified porous silicon photonic crystals for biosensing applications
- 2012
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Ingår i: Photonics and Nanostructures - Fundamentals and Applications. - : Elsevier BV. - 1569-4410. ; 10:3, s. 304-311
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Tidskriftsartikel (refereegranskat)abstract
- In this work realistic biosensing structures based on the integration of porous silicon photonic crystals with polymer coating technology are presented. Microcavities and rugate filters are chosen as the photonic crystal configuration. The deposition of a polymer layer on the pore walls of these structures is proposed to improve the selectivity and sensitivity of the sensing function. A complete effective refractive index model including the polymer layer, the target and external effects like silicon oxidation has been developed in order to accurately simulate the structures. It is expected that the proposed structures could be used as low cost, highly integrated and highly sensitive biological sensors.
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| 6. |
- Xiao, Sanshui, et al.
(författare)
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High-Q microcavities realized in a circular photonic crystal slab
- 2005
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Ingår i: Photonics and Nanostructures-Fundamentals and Applications. - : Elsevier BV. - 1569-4410. ; 3:2-3, s. 134-138
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Tidskriftsartikel (refereegranskat)abstract
- A series of microcavities in circular photonic crystal slabs are studied in this paper. It is shown that high quality factors can be obtained for such microcavities. For a cavity with three inner layers of air holes missing, Q factor larger than 105 can be obtained. It is also worth noting there exists resonant modes with high quality factors, even for the defect-free circular photonic crystal slab, due to gradual change of the average effective index.
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| 7. |
- Yusof, Haziezol Helmi Mohd, et al.
(författare)
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Optical dynamic range maximization for humidity sensing by controlling growth of zinc oxide nanorods
- 2018
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Ingår i: PHOTONICS AND NANOSTRUCTURES-FUNDAMENTALS AND APPLICATIONS. - : ELSEVIER SCIENCE BV. - 1569-4410. ; 30, s. 57-64
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Tidskriftsartikel (refereegranskat)abstract
- An experimental study of the dynamic range maximization with Zinc Oxide (ZnO) nanorods coated glass substrates for humidity and vapor sensing is reported. Growth time of the nanorods and the length of the coated segments were controlled to study the differences between a reference environmental condition (normal humidity or dry condition) and water vapor concentrations. In order to achieve long dynamic range of detection with respect to nanorods coverage, several substrates with triangular patterns of ZnO nanostructures were fabricated by selective hydrothermal growth over different durations of time (5 h, 10 h and 15 h). It was found that maximum dynamic range for the humidity sensing occurs for the combination parameters of normalized length (Z) of 0.23 and normalized scattering coefficient (zeta) of 0.3. A reduction in transmittance by 38% at humidity levels of 80% with reference point as 50% humidity was observed. The results could be correlated to a first order approximation model that assumes uniform growth and the optimum operating conditions for humidity sensing device. This study provides an option to correlate ZnO growth conditions for different vapor sensing applications which can set a platform for compact sensors where modulation of light intensity is followed. rights reserved.
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| 8. |
- Zakomirnyi, Vadim, et al.
(författare)
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Titanium nitride nanoparticles as an alternative platform for plasmonic waveguides in the visible and telecommunication wavelength ranges
- 2018
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Ingår i: Photonics and Nanostructures - Fundamentals and Applications. - : Elsevier. - 1569-4410. ; 30, s. 50-56
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Tidskriftsartikel (refereegranskat)abstract
- We propose to utilize titanium nitride (TiN) as an alternative material for linear periodic chains (LPCs) of nanoparticles (NPs) which support surface plasmon polariton (SPP) propagation. Dispersion and transmission properties of LPCs have been examined within the framework of the dipole approximation for NPs with various shapes: spheres, prolate and oblate spheroids. It is shown that LPCs of TiN NPs support high-Q eigenmodes for an SPP attenuation that is comparable with LPCs from conventional plasmonic materials such as Au or Ag, with the advantage that the refractory properties and cheap fabrication of TiN nanostructures are more preferable in practical implementations compared to Au and Ag. We show that the SPP decay in TiN LPCs remains almost the same even at extremely high temperatures which is impossible to reach with conventional plasmonic materials. Finally, we show that the bandwidth of TiN LPCs from non-spherical particles can be tuned from the visible to the telecommunication wavelength range by switching the SPP polarization, which is an attractive feature for integrating these structures into modern photonic devices.
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| 9. |
- Zhang, Ziyang, et al.
(författare)
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Coupled mode analysis of in-plane channel drop filters with resonant mirrors
- 2005
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Ingår i: Photonics and Nanostructures-Fundamentals and Applications. - : Elsevier BV. - 1569-4410. ; 3:2-3, s. 84-89
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Tidskriftsartikel (refereegranskat)abstract
- A channel drop filter system that consists of two waveguides and three cavities is studied. One cavity couples with both waveguides, while the other two work as resonant mirrors to reflect the selected channel back into the system. The operation of this configuration is analyzed, using coupled mode theory. The conditions to achieve 100% in-plane channel transfer are derived. A method to suppress the side lobes of reflection and backward drop is also proposed. The direct coupling between the cavities is not required. The analysis is verified by two-dimensional finite difference time domain simulations in 2D hexagonal photonic crystals.
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