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2012

Volume 6 (partial)

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Review Papers

Select this Article OPEN ACCESS		Plasmonic nano-architectures for surface enhanced Raman scattering: a review G. V. Pavan Kumar J. Nanophoton. 6, 064503 (May 04, 2012); http://dx.doi.org/10.1117/1.JNP.6.064503 Online Publication Date: May 04, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract Surface enhanced Raman scattering (SERS) is an optical spectroscopy technique with single molecule sensitivity and chemical specificity. The electromagnetic enhancement mechanism of SERS is facilitated by the localized surface plasmons of metallic nanostructures utilized in experiments. The magnitude of the local optical field created by the plasmonic nanostructure depends on parameters such as size, shape, morphology, arrangement, and local environment of the nanostructure. By tuning these parameters, electromagnetic hot spots can be created to facilitate ultra-sensitive, subwavelength SERS detection platforms. In recent years, there have been a number of innovations in nanofabrication and synthesis of plasmonic nanostructures. This has led to a variety of plasmonic nano-architectures that can be harnessed for SERS. Recently investigated plasmonic nanostructures in the context of SERS include nanosphere dimers, individual nanocubes, nanotriangular arrays, nano-pyramid shells, individual and assembly of nanorods, nanowires, and nanotips, and some unconventional nano-architectures. Challenges in fundamental and application aspects of SERS remain for future research.

Select this Article OPEN ACCESS		Superconductivity with excitons and polaritons: review and extension Fabrice P. Laussy, Thomas Taylor, Ivan A. Shelykh, and Alexey V. Kavokin J. Nanophoton. 6, 064502 (May 07, 2012); http://dx.doi.org/10.1117/1.JNP.6.064502 Online Publication Date: May 07, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract A system where a Bose-Einstein condensate of exciton-polaritons coexists with a Fermi gas of electrons has been recently proposed as promising for realization of room-temperature superconductivity. In order to find the optimum conditions for exciton and exciton-polariton mediated superconductivity, we studied the attractive mechanism between electrons of a Cooper pair mediated by the exciton and exciton-polariton condensate. We also analyzed the gap equation that follows. We specifically examined microcavities with embedded n-doped quantum wells as well as coupled quantum wells hosting a condensate of spatially indirect excitons, put in contact with a two-dimensional electron gas. An effective potential of interaction between electrons was derived as a function of their exchanged energy ℏω, taking into account the retardation effect that allows two negatively charged carriers to feel an attraction. In the polariton case, the interaction is weakly attractive at long times, followed by a succession of strongly attractive and strongly repulsive windows. Strikingly, this allows high critical temperature solutions of the gap equation. An approximate three-steps potential is used to explain this result that is also obtained numerically. The case of polaritons can be compared with that of excitons, which realize the conventional scenario of high-T_c superconductivity where a large coupling strength accounts straightforwardly for the high critical temperatures. Excitons are less advantageous than polaritons but may be simpler systems to realize experimentally. It is concluded that engineering of the interaction in these peculiar Bose–Fermi mixtures is complex and sometimes counter-intuitive, but leaves much freedom for optimization, thereby promising the realization of high-temperature superconductivity in multilayered semiconductor structures.

Select this Article OPEN ACCESS		Synthesis, electromechanical characterization, and applications of graphene nanostructures Traian Dumitrică, Suneel Kodambaka, and Sukky Jun J. Nanophoton. 6, 064501 (Feb 24, 2012); http://dx.doi.org/10.1117/1.JNP.6.064501 Online Publication Date: Feb 24, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract The emerging field of graphene brings together scientists and engineers as the discovered fundamental properties and effects encountered in this new material can be rapidly exploited for practical applications. There is potential for a two-dimensional graphene-based technology and recent works have already demonstrated the utility of graphene in building nanoelectromechanical systems, complex electronic circuits, photodetectors and ultrafast lasers. The state-of-the-art of substrate-suported graphene growth, and the current fundamental understanding of the electromechanical properties of graphene and graphene nanoribbons, represent important knowledge for developing new applications.

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Research Papers

Select this Article		Photoluminescence of Er-doped ZnO nanoparticle films via direct and indirect excitation Zhengda Pan, Akira Ueda, Haiyang Xu, Sui K. Hark, Steven H. Morgan, and Richard Mu J. Nanophoton. 6, 063508 (May 21, 2012); http://dx.doi.org/10.1117/1.JNP.6.063508 Online Publication Date: May 21, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract Photoluminescence (PL) of Er-doped ZnO nanoparticle films was studied. The films were grown on silicon (100) or fused silica substrates using e-beam evaporation and subsequently annealed at 700 °C in air for an hour. PL was measured at two excitation wavelengths, 325 and 514.5 nm. The 325 nm was used for exciting the host semiconductor ZnO while 514.5 nm was used for directly exciting Er³⁺ ions in the ZnO host. Er³⁺ luminescence was observed from annealed films using either indirect (325 nm) or direct (514.5 nm) excitations. It has been found that the indirect excitation is significantly more efficient than the direct excitation in producing 1.54 μm photoluminescence. With indirect excitation, the Er³⁺ luminescence observed is attributed to energy transfer from ZnO host to the Er³⁺ ions doped. Energy transfer from e-h pairs resulting from ZnO host excitation may provide efficient routes for exciting Er³⁺ ions inside nano-crystalline particles of the films.

Select this Article		Al-doped ZnO aligned nanorod arrays: significant implications for optic and opto-electronic applications Terence Holloway, Rajeh Mundle, Hareesh Dondapati, Messaoud Bahoura, and Aswini K. Pradhan J. Nanophoton. 6, 063507 (Apr 26, 2012); http://dx.doi.org/10.1117/1.JNP.6.063507 Online Publication Date: Apr 26, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract We investigated the optical and optoelectronic properties of vertically aligned Al:ZnO nanorod arrays synthesized by the hydrothermal technique at a considerably low temperature on a sputtered Al:ZnO seed layer. The nanorod arrays maintained remarkable alignment along the c-axis over a large area. The seed layers and nanorod arrays showed various optical band gaps. Investigation of the optoelectronic properties of nanorod arrays on Al:ZnO/p-Si seed layer with SiO₂ revealed that the photocurrent is significantly reduced in nanorod arrays on a AZO/SiO₂/p-Si heterojunction due to multiple scattering phenomena associated with nanorod arrays. This research may open up venues for various optical and opto-electronic applications where highly aligned nanostructures are desired.

Select this Article		Suppression of losses in negative refractive index metamaterials by means of bichromatic parametric irradiation Adil-Gerai Kussow and Alkim Akyurtlu J. Nanophoton. 6, 063506 (Mar 23, 2012); http://dx.doi.org/10.1117/1.JNP.6.063506 Online Publication Date: Mar 23, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract If two parametrically-coupled fields, with the frequency of the probe p wave twice the frequency of the support s wave, are applied to a metal plasma, the non-linearity of the Boltzmann equation affects the permittivity. Based on the solution of the Boltzmann equation for the bichromatic problem, an analytical expression for the permittivity was derived. The amplitudes and the relative phase of the p and s waves can be adjusted to suppress the dielectric loss to almost zero within a narrow frequency band. If this frequency band overlaps with a negative-refractive-index band of a composite metamaterial, which contains a metallic component, the optical losses can be reduced by a factor of ∼ 30, with a figure of merit exceeding 100. An isotropic metamaterial comprising spherical Au and SiC nanoparticles can show that effect.

Select this Article		Nanomechanically suspended low-loss silicon nanowire waveguide as in-plane displacement sensor Xiongyeu Chew, Guangya Zhou, and Fook Siong Chau J. Nanophoton. 6, 063505 (Mar 29, 2012); http://dx.doi.org/10.1117/1.JNP.6.063505 Online Publication Date: Mar 29, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract We have devised an air-suspended nano-optomechanical structure that is capable of precisely detecting in-plane motion up to a precision of subnanometer level. To achieve the detection, we utilized a basic silicon photonic building block (i.e., a nanowire waveguide directional coupler) in conjunction with nanoelectromechanical systems (NEMS). We numerically optimized the design and experimentally demonstrated a displacement sensitivity of 8.83×10⁻⁵ V/nm⁻¹ with a low noise-level resolution of 0.172 nm/√Hz in a 1 Hz bandwidth centered at 950 Hz. As the waveguide coupler design does not segmentize nanowire waveguides, we eliminated the undesirable insertion losses and coupling losses irrelevant to the measurand. Furthermore the design is simple, ultracompact, and can be easily integrated with on-chip photonic systems, which may be beneficial for applications that require a compact displacement sensor with high accuracy and precision.

Select this Article		Silicon-on-insulator photonic crystal miniature devices with slow light enhanced third-order nonlinearities Swati Rawal, Ravindra K. Sinha, and Richard M. De La Rue J. Nanophoton. 6, 063504 (Mar 12, 2012); http://dx.doi.org/10.1117/1.JNP.6.063504 Online Publication Date: Mar 12, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract The effects of the slow-down factor on third-order nonlinear effects in silicon-on-insulator photonic crystal channel waveguides were investigated. In the slow light regime, with a group index equal to 99, these nonlinear effects are enhanced but the enhancement produced depends on the input peak power level. Simulations indicate the possibility of soliton-like propagation of 1 ps pulses at an input peak power level of 50 mW inside such a photonic crystal waveguide. The increase in the induced phase shift produced by lower group velocities can be used to decrease the size and power requirements needed to operate devices such as optical switches, logic gates, and wavelength translators.

Select this Article OPEN ACCESS		Electroluminescence from Er³⁺ incorporated into silicon oxide thin film on silicon in a scanning tunneling microscope Jan Fiala, Hiroo Omi, and Takehiko Tawara J. Nanophoton. 6, 063503 (Mar 05, 2012); http://dx.doi.org/10.1117/1.JNP.6.063503 Online Publication Date: Mar 05, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract A scanning tunneling microscope (STM) with an electrically conductive and optically transparent probe was used to study electroluminescence induced by tunneling electrons from erbium oxide (Er₃O₃) deposited on SiO₂/Si(100). Erbium was primarily incorporated into SiO₂ on silicon substrate to create impurities and overcome a high band gap. Subsequently, emissions of photons in the visible/near-infrared region, because of the excitation of higher Er states, are realized electrically without the need to apply high voltage. The STM-induced photon emission exhibits an asymmetric character with respect to the applied bias, which is explained by the direct recombination and impact ionization processes. The observed electroluminescence spectrum was decomposed to identify single inter-band transitions that could be related to erbium states. STM-induced electron emission measurements were also performed, revealing a band gap of around 2.8 eV. This corresponds to the x = 0.91 rate factor of the SiO_x layer created during the annealing process on silicon.

Select this Article		Electrical characteristics of InAs self-assembled quantum dots embedded in GaAs using admittance spectroscopy Azzouz Sellai, Piotr Kruszewski, Abdelmadjid Mesli, Anthony R. Peaker, and Mohamed Missous J. Nanophoton. 6, 063502 (Feb 24, 2012); http://dx.doi.org/10.1117/1.JNP.6.063502 Online Publication Date: Feb 24, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract GaAs based structures in which are embedded InAs self-assembled quantum dots are studied using admittance measurements taken over a large frequency spectrum and for several temperatures. The presence of quantum dots is evidenced in the capacitance-voltage characteristics by one, or more, plateau-like structures related to the processes of charging and discharging of the quantum dots. Concurrently, the measured conductance exhibits a peak in a certain bias range that coincides with the plateau-like structure in the capacitance but only for temperatures below 150 K. The conductance dependence on both the temperature and applied bias is attributed to two mechanisms of carrier escape/capture mechanisms from the InAs embedded quantum dots into/out of the hosting GaAs; a thermally activated process for temperatures above 80 K and a perceptibly nonthermal tunneling process for temperatures below 40 K. The conductance data is used to estimate rates and activation energies in association with the electron escape mechanisms from the quantum dots.

Select this Article		Improved surface-enhanced Raman scattering of insulin fibril templated colloidal gold nanoparticles on silicon Chiung-Wen Hsieh, Pei-Ying Lin, and Shuchen Hsieh J. Nanophoton. 6, 063501 (Mar 12, 2012); http://dx.doi.org/10.1117/1.JNP.6.063501 Online Publication Date: Mar 12, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract Insulin fibrils were used as a biotemplate to attach gold nanoparticles to silicon wafer surfaces for application as surface-enhanced Raman scattering (SERS) substrates. Gold nanoparticles (NP) attach to the insulin fibrils through electrostatic interactions forming chains of discreet NPs. A combination of 4-aminothiophenol and 4-Mercaptobenzoic acid were used as probe molecules to evaluate the Raman signal enhancement that was 10⁴ to 10⁶. The SERS signal was strongly enhanced on these surfaces due to the close inter-particle spacing of the patterned gold NPs.

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Special Section on Nanostructured Thin Films: From Theoretical Aspects to Practical Applications

Select this Article		Effect of surface functionalization of porous silicon microcavities on biosensing performance Marta Martin, Laurent Massif, Elias Estephan, Maribelle Saab, Thierry Cloitre, Christian Larroque, Vivechana Agarwal, Frederic J. G. Cuisinier, Guy Le Lay, and Csilla Gergely J. Nanophoton. 6, 061506 (May 10, 2012); http://dx.doi.org/10.1117/1.JNP.6.061506 Online Publication Date: May 10, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract Surface functionalization methods were investigated for their effects on the sensing performances of porous silicon (p-Si) microcavities when used for detection of biomolecules. These microcavities were fabricated to reveal reflectivity pass-band spectra in the visible and near-infrared spectral regime. In one approach, the devices were thermally oxidized and functionalized to ensure covalent binding of molecules. In the second approach, the as-etched p-Si surface was modified with adhesion peptides, isolated via phage display, that present high binding capacity for silicon. Functionalization and molecular binding events were monitored via reflectometric interference spectra as shifts in the resonance peaks of the cavity structure due to changes in the refractive index when a biomolecule is attached to the large internal surface of p-Si. Improved sensitivity was obtained owing to the peptide interface linkers between the p-Si and biological molecules compared to the silanized devices. Investigating the formation of peptide–Si interface layer via X-ray photoelectron spectroscopy, scanning tunneling microscopy, and scanning electron microscopy, we found that peptides form nanometer-thin layers on the Si surface and that their binding energy depends on the sequence of the peptide.

Select this Article		Green nanophotonics Geoff B. Smith J. Nanophoton. 6, 061505 (May 10, 2012); http://dx.doi.org/10.1117/1.JNP.6.061505 Online Publication Date: May 10, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract Nanotechnology, in particular nanophotonics, is proving essential to achieving green outcomes of sustainability and renewable energy at the production scales needed. Nanomaterials enable optimization of optical, opto-electrical, and thermal responses. Optical harmonization of material responses to environmental energy flows involves large changes in spectral response over limited wavelength bands and tailoring to environmental dynamics. The latter includes engineering angle of incidence dependencies and switchable (or chromogenic) responses. Nanomaterials can be made at sufficient scale and low enough cost to be economical and have high impact on a short time scale. Issues to be addressed include human safety and property changes induced during manufacture, handling, and outdoor use. Unexpected advantages have arisen in this work such as the savings and environmental benefits of cool roofs extending beyond the more obvious benefit of reduced heat flows from the roof into the building. We explore some of the likely elements involved in harmonizing nature and technology with applications of nanophotonics to reduce the use of energy in buildings.

Select this Article		Homogenization of a metallic metamaterial and electrostatic resonances Didier Felbacq, Brahim Guizal, Frédéric Zolla, and Emmanuel Kling J. Nanophoton. 6, 061504 (May 10, 2012); http://dx.doi.org/10.1117/1.JNP.6.061504 Online Publication Date: May 10, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract The homogenization of arrays of metallic rods was studied. Using standard homogenization theory, the effective permittivity was obtained. The onset of resonances was evidenced and showned to be linked with the negative sign of the real part of the permittivity. Numerical computations were performed to test the homogeneous model.

Select this Article		Ultrathin silicon solar cells with enhanced photocurrents assisted by plasmonic nanostructures Sanshui Xiao, Erik Stassen, and N. Asger Mortensen J. Nanophoton. 6, 061503 (Mar 12, 2012); http://dx.doi.org/10.1117/1.JNP.6.061503 Online Publication Date: Mar 12, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract Thin-film photovoltaics offers the potential for a significant cost reduction compared to traditional photovoltaics. However, the performance of thin-film solar cells is limited by poor light absorption. We have devised an ultra-thin-film silicon solar cell configuration assisted by plasmonic nanostructures. By placing a one-dimensional plasmonic nanograting on the bottom of the solar cell, the generated photocurrent for a 200 nm-thickness crystalline silicon solar cell can be enhanced by 90% in the considered wavelength range, while keeping insensitive to the incident angle. These results are paving a promising way for the realization of high-efficiency thin-film solar cells.

Select this Article		Monitoring the reactivity of Ag nanoparticles in oxygen atmosphere by using in situ and real-time optical spectroscopy Vivek Antad, Lionel Simonot, David Babonneau, Sophie Camelio, Frédéric Pailloux, and Philippe Guérin J. Nanophoton. 6, 061502 (Apr 06, 2012); http://dx.doi.org/10.1117/1.JNP.6.061502 Online Publication Date: Apr 06, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract Surface differential reflectance spectroscopy (SDRS) is sensitive enough to observe the minute changes in the surface plasmon resonance (SPR) of noble metal nanoparticles (NPs), which is extremely dependent on the morphology and organization of the NPs as well as on the chemical atmosphere surrounding them. Taking this SPR as a signature, we have studied the reactivity of Ag NPs using a dedicated in situ SDRS setup adapted on a magnetron sputtering deposition machine. This configuration allowed us to analyze the SPR modifications in real-time, not only during the growth of Ag NPs, but also during their exposure to molecular O₂ and during their capping by a dielectric (Si₃N₄) matrix. Real-time SDRS analysis reveals that, upon exposure of the Ag NPs to O₂, their SPR characteristics (position, amplitude, and width of the absorption band) alter immediately, indicating the instantaneous reactive interactions between Ag NPs and adsorbed O₂ molecules. In addition, during the deposition of the Si₃N₄ matrix, real-time SDRS reveals possible breaking of Ag–O₂ interactions. Moreover, with increasing Ag NP size, SPR modifications are seen to be reduced in O₂ atmosphere, suggesting the diminution of Ag–O₂ reactive interactions in the bigger NPs compared to the smaller ones.

Select this Article		Design of an achromatic optical coating waveplate Yi-Jun Jen, Meng-Jie Lin, Ching-Wei Yu, Chia-Feng Lin, and Shun-Kai Yu J. Nanophoton. 6, 061501 (Mar 13, 2012); http://dx.doi.org/10.1117/1.JNP.6.061501 Online Publication Date: Mar 13, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract We propose a design method of an achromatic waveplate that comprises anisotropic thin films as a multi-cell layered system. Each cell is a symmetrical three-layered ABA structure with equivalent refractive indices and phase thicknesses. A merit function defined as the rate of change of the phase retardation with respect to wavelength is introduced to control the variation of phase retardation by selecting proper birefringence and thickness for each film. The allowed thickness of each birefringent film is investigated for different requirement about the uniformity of phase retardation. An achromatic waveplate with a smaller number of cells is demonstrated by arranging the two composed films made of different materials with high contrast of refractive index between them. The arrangement of a matching layer, which is associated with the performance of the achromatic waveplate, is also discussed.

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Commemorative Papers

Select this Article		Liquid crystal active nanophotonics and plasmonics: from science to devices Editorial Note: This paper was invited to commemorate the promotion of Ibrahim Abdulhalim to SPIE Fellow. Ibrahim Abdulhalim J. Nanophoton. 6, 061001 (Apr 23, 2012); http://dx.doi.org/10.1117/1.JNP.6.061001 Online Publication Date: Apr 23, 2012 Full Text: Read Online (HTML) \| Download PDF
	+ -	Show Abstract Liquid crystals (LCs) are made of molecules and layers of small nm sizes, hence by their nature they fall in the categories of nanoscale science, engineering, and technology. Their interaction with solid nanostructures has been a subject of interest since the early days of LC research, as their surface alignment processes are strongly related to the formation of nanogrooves upon mechanical rubbing, nanocolumns by the oblique deposition technique, nanopores in etched surfaces, and the formation of self-assembled nanolayers on solid surfaces. The field has been boosted after the latest developments in nanotechnology both in theoretical simulations and in the possible fabrication of nanoscale structures, such as subwavelength gratings, nanoporous materials, and nanoparticles. A new field of research has emerged that combines LCs with nanostructures. Because LC materials are switchable, a new family of active plasmonic and nanophotonic devices is emerging. Interesting fundamental research phenomena are being reported, as well as the development of improved devices. The interaction of LCs with nanostructures is not only of fundamental interest but can also be applied for novel devices.

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Commentaries

Select this Article OPEN ACCESS		Commentary: Silicon nanocrystals and their role in photonics José R. Rodríguez Núñez and Jonathan G. C. Veinot J. Nanophoton. 6, 060302 (Mar 21, 2012); http://dx.doi.org/10.1117/1.JNP.6.060302 Online Publication Date: Mar 21, 2012 Full Text: Read Online (HTML) \| Download PDF
		Abstract Unavailable

Select this Article OPEN ACCESS		Commentary: Single-molecule fluorescence spectroscopy Digambara Patra J. Nanophoton. 6, 060301 (Mar 13, 2012); http://dx.doi.org/10.1117/1.JNP.6.060301 Online Publication Date: Mar 13, 2012 Full Text: Read Online (HTML) \| Download PDF
		Abstract Unavailable

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