This PDF file contains the errata for “JNP Vol. 5 Issue 01 Paper 3565200” for JNP Vol. 5 Issue 01

This PDF file contains the errata for “JNP Vol. 5 Issue 01 Paper 3592487” for JNP Vol. 5 Issue 01

This PDF file contains the errata for “JNP Vol. 5 Issue 01 Paper 3626858” for JNP Vol. 5 Issue 01

This PDF file contains the editorial “Green Nanotechnology: Solutions for Sustainability and Energy in the Built Environment," by G. B. Smith and C. G. Granqvist for JNP Vol. 5 Issue 01

This PDF file contains the editorial “Book Review: Microfluidic Devices in Nanotechnology: Fundamental Concepts," by C. S. Kumar for JNP Vol. 5 Issue 01

A book review of a recently released title.

The reasons nanophotonics is proving central to meeting the need for large gains in energy efficiency and renewable energy supply are analyzed. It enables optimum management and use of environmental energy flows at low cost and on a sufficient scale by providing spectral, directional and temporal control in tune with radiant flows from the sun, and the local atmosphere. Benefits and problems involved in large scale manufacture and deployment are discussed including how managing and avoiding safety issues in some nanosystems will occur, a process long established in nature.

A short technical commentary on a specific topic.

A short technical commentary on a specific topic.

A short technical commentary on a specific topic.

A short technical commentary on a specific topic.

Theoretical consideration of electromagnetic scattering by single-wall carbon nanotubes (SWNTs) and SWNT arrays requires knowledge of the linear surface conductivity of an SWNT. An expression for the surface conductivity of an infinitely long SWNT was derived by Slepyan et al. [Phys. Rev. B 60, 17136-17149 (1999)]10.1103/PhysRevB.60.17136. The twin purposes of this tutorial are to succinctly discuss the derivation using the density matrix formalism and to provide ready-to-use expressions.

By the process of homogenization, judiciously designed nanocomposite materials can offer unprecedented degrees of material enhancement and/or novel material properties that may be usefully exploited in nanophotonic applications. Recently, there have been significant developments in the theory of such homogenized nanocomposite materials (HNMs), within the context of linear bianisotropic scenarios for particulate nanocomposites. These developments involve: the incorporation of depolarization dyadics, which represent component particles of nonzero volume, and the implementation of the strong-property-fluctuation theory wherein scattering interactions between neighboring component particles are treated on a statistical basis. Four recent areas of application are notable: (i) HNMs that support the propagation of plane waves with negative phase velocity (while their component materials do not); (ii) HNMs that support Voigt wave propagation (while their component materials do not); (iii) modeling the infiltration of certain sculptured thin films with a view to optical sensing applications; and (iv) simulation of the electromagnetic properties of vacuum in curved spacetime via HNMs as Tamm mediums. Forward homogenization is implemented in applications (i) and (ii); inverse homogenization is implemented in application (iv); and both forward and inverse homogenization are implemented in application (iii).

We have examined antireflection (AR) coatings for high reflectivity metals such as Al on the basis of the admittance diagram. The proposed AR coatings consist of bilayers of absorptive and dielectric materials. A wide variety of materials can be used for AR coatings by tuning the thicknesses of both the absorptive and the dielectric layers. The bilayered AR concept has been applied to reduce the reflectance of wire grid (WG) polarizers made of Al. An absorptive FeSi ₂ layer has been deposited by the glancing angle deposition technique immediately on the top of Al wires covered with a thin SiO ₂ layer. For the optimum combination of the thicknesses of FeSi ₂ and SiO ₂, the reflectance reduces to lower than a few percent independent of the polarization, whereas the transmission polarization properties remain favorable. We have demonstrated that Ge is also appropriate for the low-reflectivity WG polarizers as an absorptive material. Because low-reflectivity WG polarizers are completely composed of inorganic materials, they are useful for applications requiring thermal durability, such as liquid crystal projection displays.

The Dyakonov-Tamm wave combines the features of the Dyakonov wave and the Tamm electronic state. Dyakonov-Tamm waves guided by the planar interface of two dissimilar chiral sculptured thin films (STFs) were systematically examined. The interfaces result from the chiral STFs being dissimilar in (a) orientation about the helical axis, (b) structural handedness, (c) structural period, (d) vapor incidence angle, (e) material, or (f) various combinations thereof. A boundary-value problem for the propagation of Dyakonov-Tamm waves was formulated and numerically solved. Up to three physical solutions were obtained for any specific combination of constitutive properties of the two chiral STFs. Each solution indicates the existence of a Dyakonov-Tamm wave. If more than one solution exists, the corresponding Dyakonov-Tamm waves differ in phase speed and degree of localization to the interface. Fewer solutions were found when the two chiral STFs differ in many attributes.

Metal thin film functional properties depend strongly on its nanostructure, which can be manipulated by varying nucleation and growth conditions. Hence, in order to control the nanostructure of aluminum thin films fabricated by RF magnetron sputtering, we made use of in-situ monitoring of electrical and optical properties of the growing layer as well as plasma characterization by mass and optical emission spectroscopy. The electrical conductivity and I-V characteristics were measured. The optical constants were obtained from optical monitoring based on spectral ellipsometry. The relevant models (based on one or two Lorentz oscillators and B-spline functions) were suggested to evaluate the data obtained from the monitoring techniques. The results of the in-situ monitoring were correlated with scanning electron microscope analyses. We demonstrated the monitoring was able to distinguish the growth mode in real-time. We could estimate the percolation threshold of the growing layer and control layer nanostructure. The nanostructure was effectively manipulated by RF power variation. Optical functions exhibiting plasmonic behavior in the UV range and a strong nonlinear character of I-V curves were obtained for an ultrathin Al film deposited at a lower growth rate.

We present a study on erbium (Er)-doped silicon (Si)-rich silicon oxide thin films grown by the magnetron cosputtering of three confocal cathodes according to the deposition temperature and the annealing treatment. It is shown that, through a careful tuning of both deposition and annealing temperatures, it is possible to engineer the fraction of agglomerated Si that may play the role of sensitizer toward Er ions. To investigate the different emitting centers present within the films according to the fraction of agglomerated Si, a cathodoluminescence experiment was made. We observe in all samples contributions from point-defect centers due to some oxygen vacancies and generally known as silicon-oxygen deficient centers (SiODC), at around 450-500 nm. The behavior of such contributions suggests the possible occurrence of an energy transfer from the SiODCs toward Er³⁺ ions. Photoluminescence experiments were carried out to characterize the energy transfer from Si nanoclusters toward Er³⁺ ions with a nonresonant wavelength (476 nm) that is unable to excite SiODCs and then exclude any role of these centers in the energy transfer process for the PL experiments. Accordingly, it is shown that structural differences have some effects on the optical properties that lead to better performance for high-temperature deposited material. This aspect is illustrated by the Er-PL efficiency that is found higher for 500°C-deposited, when compared to that for RT-deposited sample. Finally, it is shown that the Er-PL efficiency is gradually increasing as a function of the fraction of agglomerated silicon.

Silicon-based porous nanoparticles showing at the same time intense visible luminescence and magnetic response were fabricated. The hybrid luminescent/magnetic nanoparticles (hLMNPs) were fabricated by the electrodeposition of cobalt and iron into nanostructured porous silicon. These nanoparticles were subsequently functionalized and internalized into cells. The hybrid behavior of the hLMNPs is a relevant feature for the development of research tools as nontoxic cellular tracker for progenitor cells and consequently able to be used in many strategies of cellular therapy. Additionally, the hLMNPs can be functionalized with various biomolecules that will endow them with new functionalities.

A nonlinear theory for the optical properties of gold nanorods at various aspect ratios is used to calculate the refractive index sensitivity of surface plasmon resonance (M) which is found to be 100 to 1000 nm/RIU and proportional to the aspect ratio (R). Based on Gans theory, the calculated figure of merit, defined by the ratio of M and the resonance spectral width, has a range of 1.0 to 10 and has a maximum value at the optimum aspect ratio of 3.5 to 4.5. Numerical results are fit for analytic equations for the peak wavelength and sensitivity showing their nonlinear dependence on the surrounding medium refractive index (n) and R. The calculated optimal condition for the figure of merit provides useful guideline for the design of biosensors.

One symmetric and two asymmetric chevron thin films of silver were fabricated by bidepositing oppositely tilted nanorods sequentially via oblique angle deposition. The equivalent electromagnetic parameters of the films for s and p polarizations were retrieved at a wavelength of 639 nm for normal incidence using walk-off and polarization interferometers. Experimental results indicate that the symmetric chevron thin film has the strongest magnetic field reversal among the three different shapes. The coupling of the transverse magnetic field between two separate rods makes the equivalent permeability negative real.

This work presents a three-layered thin film system to generate broadband polarization conversion. The enhanced polarization conversion in the prism coupling system is analyzed as a constructive interference effect of polarization coupled states. According to our analysis, an antireflection film that is used to reduce the multireflection in the anisotropic film and a compensation film that is used to reduce dispersion of propagation phase difference are applied on both sides of an anisotropic thin film to cause broadband polarization conversion.

Fingerprint visualization obtained from physical evidence taken from crime scenes for subsequent comparison typically requires the use of physical and chemical techniques. One physical technique to visualize or develop sebaceous fingerprints on various surfaces employs the deposition of metals such as gold and zinc thereon. We have developed a different vacuum technology: the conformal-evaporated-film-by-rotation technique to deposit dense columnar thin films (CTFs) on latent fingerprints on different types of surfaces. Sample fingerprints, acting as nonplanar substrates, deposited on different surfaces were placed in a vacuum chamber with the fingerprint side facing a boat containing an evaporant material such as chalcogenide glass. Thermal evaporation of the solid material led to the formation of a dense CTF on the fingerprint, thereby capturing the topographical texture with high resolution. Our results show that it is possible to acquire the topology of latent fingerprints on nonporous surfaces. Additionally, deposition of CTFs on overlapping fingerprints suggested ours may be a technique for elucidating the sequence of deposition of the fingerprints at the scene.

Porous silicon optical rugate filters are electrochemically fabricated to display reflectance peaks in the medium-wavelength infrared (MWIR) region from 4 to 8 μm. Etching conditions are adjusted to create filters with single and multiple infrared reflectance peaks overlapping specific infrared chemical absorbance bands. Additional infrared reflectance peaks are designed into the structures to provide internal optical reference channels. Samples containing optical reflectance features matching the absorbance band of CO₂ at 2350 cm−¹ are used to demonstrate gas sensing with optical filters, and a structure with a photonic stop band tuned to match the infrared absorbance band of the P=O functional group, found in G-series chemical warfare agents, is fabricated. With adequate electrolyte replenishment, the calibrated etch conditions generated reproducible spectral band features even for relatively long etch durations. This work represents the first example of a porous Si spectral filter prepared to match specific spectral features of molecules in the MWIR ("fingerprint") region.

Silver is widely used for fabrication of plasmonic devices because of its unique optical constants. The nanostructure of the Ag layer is mainly influenced during the initial stage of the silver nucleation. Therefore, we focus our attention on studying this stage of silver growth. Nanostructured ultrathin silver layers are prepared by means of magnetron sputtering. The initial stage of the nucleation and the layer growth is studied by optical monitoring, which is based on spectrophotometric measurement of the sample reflectivity. The measured data are compared to a model of layered structure. The noncontinual (Volmer-Weber) mode of the layer nucleation is clearly distinguished in the monitored data. Thus, we are able to estimate the point of noncontinual layer coalescence. The optical data are correlated with in situ monitoring of the electrical resistance. We find that the nucleation mode and resulting nanostructure can be significantly influenced by an ultrathin silver oxide interlayer.

The homogeneous and transport properties of a set of metallic fibers were studied. The existence of a plasma frequency was deduced and a precise formula for it was derived. A homogenized system for finite length ohmic wires was derived. Some numerical simulations were made to study the influence of disorder. The persistence of a low-frequency band gap was demonstrated numerically even in the case of a strong disorder. The existence of localized modes was explained in terms of the statistical properties of the medium.

Historically, the methods used to describe the electromagnetic response of random, three-dimensional (3D), metal-dielectric composites (MDCs) have been limited to approximations such as effective-medium theories that employ easily-obtained, macroscopic parameters. Full-wave numerical simulations such as finite-difference time domain (FDTD) calculations are difficult for random MDCs due to the fact that the nanoscale geometry of a random composite is generally difficult to ascertain after fabrication. We have developed a fabrication method for creating semicontinuous metal films with arbitrary thicknesses and a modeling technique for such films using realistic geometries. We extended our two-dimensional simulation method to obtain realistic geometries of 3D MDC samples, and we obtained the detailed near- and far-field electromagnetic responses of such composites using FDTD calculations. Our simulation results agree quantitatively well with the experimentally measured far-field spectra of the real samples.

This PDF file contains the editorial “Special Section Guest Editorial: Nanostructured thin films: Fabrication, characterization, and application” for JNP Vol. 5 Issue 01

Tailoring the parameters of a silver nanorod array for subwavelength imaging of arbitrary coherent sources is of recent interest. We evaluated the operational bandwidth of this type of superlens, and also the impact of source-offset in order to understand the level of tolerance offered by the superlens with regard to source location. The performance of the device was analyzed numerically both through analysis of transmission and reflection coefficients and by full-wave simulation for a particular sample source arrangement. We observed that such a device exhibited better imaging performances with the sources spread wider, offering a bandwidth of around 13.5%.

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.

We theoretically explored the feasibility of a tunable metamaterial using binary as well as core-shell nanoparticle dispersed liquid crystal cells in the infrared and optical regimes. Owing to the spatial variation of the permittivity of the liquid crystal host upon the application of a bias voltage, the host was decomposed into a layered medium and the effective refractive index recalculated for each layer due to the distribution of polaritonic and plasmonic nanoparticles. The scattering, extinction, and absorption of such a nanoparticle dispersed liquid crystal cell were also found. Depending on the applied voltage bias across the liquid crystal host, the types of nanoparticles used, and their radii and volume-filling fractions in the liquid crystal host, near-zero as well as negative index of refraction can be obtained over a range of frequencies, according to the effective medium theory.

We recently demonstrated a phase compensated metalens that cannot only achieve super-resolution, but also possesses the Fourier transform capability. The metalens consists of a metamaterial slab and a plasmonic waveguide coupler (PWC). We have now ascertained the requirements for the metamaterial and the detailed design principles for the PWCs. Simulations of metalenses with a new type of PWC geometry have confirmed that the new metalenses also possess super-resolution and the Fourier transform function. The hyperbolic metalens shows an anomalous focus shifting behavior, which may be used to design exotic optical systems with new functionalities.

The nonlinear responses of a one-dimensional quasiperiodic Fibonacci structure containing single negative materials (linear mu-negative and Kerr-type nonlinear epsilon-negative layers) were investigated using the transfer matrix approach. Bistable behaviors were found in the considered Fibonacci structure. The results indicate that transmission in the zero phase gap regions is relatively insensitive to the angle of incidence, in comparison with the one in the Bragg gap. Transmissions associated with the zero phase gap especially peak at almost the same input intensity for different angles of incidence. The effect of the loss and the scaling on the characteristics of bistability were considered in both gaps. The zero phase gap soliton is insensitive to the angle of incidence and loss factor.

An introduction to the special section by the guest editors.

Specially designed surface micro- and nanostructures allow one to steer the bottom up self-organized growth of crystalline nanoaggregates from wide bandgap organic molecules, which possess extraordinary optoelectronic properties. Polarized light-emitting para-hexaphenylene nanofiber arrays exemplify such "self-growing" nanophotonic devices. The methodology behind this growth is an alternative to transfer of nanofiber arrays from specific growth substrates onto device platforms. We compared the optical properties of transferred and in situ grown nanofibers in terms of polarization function and emission homogeneity and also studied the temperature dependence of the emission spectra of transferred nanofiber arrays. Both types of nanofibers show the same spatial emission characteristics along their long axes and also the same polarization ratio. However, in nanofiber arrays, the polarization ratio decreases in the case of structured surface-grown nanofibers since the mutual orientation of the nanofibers is less perfect than for transferred fibers.

In order to show the potential of photonic techniques for realizing nanoscale computing, we examined the operation of DNA reactions by optical manipulation of microdroplets that contain DNA. The processing procedures are reconfigurable owing to flexibility in manipulating the microdroplets. The method is effective in, for example, implementing DNA computations in limited-volumes at multiple positions in parallel, enhancing an operation rate, and decreasing sample consumption, and it can be a promising technique applicable to photonic DNA computing. A reaction scheme using a pair of hairpin DNA and linear DNA was examined to confirm the method. The reaction scheme provides exchange of the sequence of a sticky-end of a DNA conformation, and it is usable for DNA computation. Microdroplets that contain DNA components were contacted to each other to start the reaction. By observing fluorescence intensity, we confirmed the reaction of sequence-change in the optically manipulated microdroplet. The experimental result also showed that different reactions are implemented at separate positions simultaneously.

Glass surface morphologies with defined shapes and roughness are realized by a two-step lithography-free process: deposition of an ∼10-nm-thin lithographically unstructured metallic layer onto the surface and reactive ion etching in an Ar/CF₄ high-density plasma. Because of nucleation or coalescence, the metallic layer is laterally structured during its deposition. Its morphology exhibits islands with dimensions of several tens of nanometers. These metal spots cause a locally varying etch velocity of the glass substrate, which results in surface structuring. The glass surface gets increasingly rougher with further etching. The mechanism of self-masking results in the formation of surface structures with typical heights and lateral dimensions of several hundred nanometers. Several metals, such as Ag, Al, Au, Cu, In, and Ni, can be employed as the sacrificial layer in this technology. Choice of the process parameters allows for a multitude of different glass roughness morphologies with individual defined and dosed optical scattering.

A wide array of nanotechnologies can be used to improve the efficiency of energy harvest from the Sun and the wind, and the efficiency of energy storage in secondary batteries, for use in smart grid and transportation applications. High-quality nanostructured copper indium gallium selenide thin films help produce high-efficiency photovoltaic modules. Various nanotechnologies are utilized to improve the efficiency of power-generating wind turbines, including nanoparticle-containing lubricants that reduce the friction generated from the rotation of the turbines, nanocoatings for de-icing and self-cleaning technologies, and advanced nanocomposites that provide lighter and stronger wind blades. A number of nanotechnologies can be beneficial in advanced high-capacity secondary batteries for smart grid and transportation applications. These technologies include nanostructured carbon-nanotube-based and silicon-nanowire-based electrodes with ultrahigh surface areas, as well as nanoengineered β-alumina ceramic electrolytes with well-controlled grains, grain boundaries, and crystal orientation, which are used to boost the energy and power densities in secondary batteries such as lithium-ion, sodium-sulfur, flow, and dry cell batteries.

Silicon photonics is the emerging optical interconnect technology where integrated nanophotonic components allow reaching high device density and improved optical functionalities. One key component is the optical microresonator. A particular kind of microresonator is the racetrack resonator where straight waveguide sections are used to achieve a large value of the coupling coefficient with a bus waveguide for any light polarization state. It is our aim to study the performances of racetrack resonators fabricated on silicon on insulator via CMOS processing. We experimentally investigated different multiple resonator designs where box-shaped filter characteristic, Vernier effect, and coupled resonator induced transparency effects are obtained. We demonstrate that racetrack resonators are instrumental to several different functions in nanophotonics and that the actual lithographic process is fully capable of building these structures.

An introduction to the special section by the guest editors.

We identified nanostructured devices sustaining out-of-plane nondiffracting beams with near-grazing propagation and a transverse beamwidth clearly surpassing the diffraction limit of half a wavelength. This type of device consists of a planar multilayered metal-dielectric structure with a finite number of films deposited on a solid transparent substrate. We assumed that the nondiffracting beam is launched from the substrate. The construction of the subwavelength diffraction-free beam is attended by plane waves which are resonantly transmitted through the stratified medium. Therefore, light confinement and wave amplification occurs simultaneously. We performed an optimization process concerning the layers width as free parameters in order to reach the most efficient optical resonances with uniform transmission. The value of the propagation constant and the focal placement are initially arbitrary, which can be chosen according to its practical realization. Possible applications include optical trapping, biosensing, and nonlinear optics.

Investigating the propagation of electromagnetic radiation in linear and nonlinear materials (with third-order nonlinearity), we derived a general expression for the dwell time valid for all linear media, as well as its relation with the group delay. The obtained results indicate that, for a nonmagnetic lossless material, the group delay reduces to the sum of the dwell time and the self-interference time. Calculations confirmed the occurrence of the Hartman effect in negative-refractive-index metamaterials (the dwell time saturates with increasing obstacle length), as well as the negative group delay in a certain spectral regime. Analysis of the Goos-Hänchen shift, in case of an obstacle made of negative-refractive-index metamaterial embedded in a dielectric with saturable nonlinearity, showed that there is no impact on the dwell time, while various effects on the group delay may be achieved, including its reduction or even preservation for nonzero incident angles.

We used optical tweezers to rotate bacterial cells relative to the optical axis. We rapidly oscillate the optical tweezers along an axis normal to the laser beam, thereby obtaining a linear trap. When the linear trap is longer than a trapped rod-shaped bacterial cell, the cell is aligned along the trap axis. Decreasing the length of the trap, we found that the cell rotates away from the image plane toward the optical axis. In the limit of a nonoscillating trap, the cell aligns along the optical axis. A defocused-edge detection method was devised to measure the orientation of the rotated cell from the corresponding phase-contrast images. Our technique can be used to image three-dimensional sub-cellular structures from different viewpoints and therefore may become a useful tool in fluorescence microscopy.

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.

The influence of the substrate temperature on the effective optical behavior of Ag-SiO₂ composites obtained by electron beam evaporation was studied. Optical characterization of the composites was performed by means of spectroscopic ellipsometry measurements. The effective dielectric function of the composites, modeled using a multiple oscillator approach, could be widely tuned by controlling the deposition temperature. The spectral dependence of the composite absorption appeared to be better described with a Gaussian line shape than with the classical Lorentz oscillator model. The description of the effective dielectric function using standard effective medium theories failed and the experimental results could be explained only in the general framework of the Bergman spectral density theory.

Gradient refractive index lens-like media are implemented using two-dimensional graded photonic crystals. They were considered as effectively homogeneous media in the long-wavelength approximation. Specified distribution of the gradient refractive index was realized using rods with spatially varying radii and applied for a design of a focusing and imaging lens. The validity of the proposed method was confirmed using full-wave numerical simulations. Planar versions of the presented lenses can find applications in integrated nanophotonics.

The three-dimensional (3D) point spread function (PSF) of multilayered flat lenses was proposed in order to characterize the diffractive behavior of these subwavelength image formers. We computed the polarization-dependent scalar 3D PSF for a wide range of slab widths and for different dissipative metamaterials. In terms similar to the Rayleigh criterion we determined unambiguously the limit of resolution featuring this type of image-forming device. We investigated the significant reduction of the limit of resolution by increasing the number of layers, which may drop nearly 1 order of magnitude. However, this super-resolving effect is obtained in detriment of reducing the depth of field. Limitations exist on the formation of 3D images.

The dc photocurrent spectra of the indium tin oxide/poly(3,4-ethylene- dioxythiophene):poly(styrenesulfonate)/poly (2-methoxy-5-(2´-ethylhexyloxy)-1,4-phenylene- vinylene)Al (ITO/PEDOT:PSS/MEH-PPV/Al) device are measured for three different MEH-PPV thin-film thicknesses in a wide range of bias voltages and for several incident light intensities. The device operation is modeled based on a singlet exciton diffusion and hole polaron drift and diffusion. The Poole-Frenkel transport and the bimolecular Langevine recombination for hole polarons are assumed. The extrinsic photocarrier generation through singlet exciton dissociation on the electrodes and charge transfer in bulk of the polymer film is discussed. We considered three intrinsic charge-carrier photogeneration mechanisms: exciton-exciton annihilation, hot-exciton dissociation, and field dissociation. It is shown that the photocurrent is dominated by the field dissociation of singlet excitons. Experimental results compared to model predictions indicate that absorption coefficient of the MEH-PPV film is thickness dependent. This surprising result is experimentally investigated and confirmed. Excellent agreement between theory and experiment for all the measured photocurrent spectra is achieved.

The optical properties of few-layer graphene (FLG) films were measured in the ultraviolet and visible spectrum using a spectroscopic ellipsometer equipped with a 50-μm nominal microspot size. The FLG thickness was found by atomic force microscopy. Measurements revealed that the microspot is larger than the FLG flake. The ellipsometric data was interpreted using the island-film model. Comparison with graphite and recently published graphene data showed reasonable agreement, but with some features that could not be explained. The error margin for the optical constants was estimated to be ±10%.

The electronic structure and optical properties of a one-electron quantum dot (QD) were investigated by assuming a spherically symmetric confining potential of finite depth. In this particular case CdSe is surrounded by ZnS. The energy eigenvalues and wave functions dependence on QD dimension were calculated by using effective mass approximation. We also calculated energies of s, p, and d states, oscillator strengths, and the linear and third-order nonlinear intersubband optical absorption coefficients as a function of the QD dimension, incident photon energy, and incident optical intensity for the 1s-1p, 1p-1d, and 1p-2s transitions. Even in a simple composition, QD correct calculation of oscillator strength differs from the simplified approach in the most sensitive QD radius region below one Bohr radius.

We designed a nanoscale optical communication device for use as an electro-optical modulator, an all-optical modulator, or an all-optical cascadable logic gate. The device is based on electrostatic forces and has the shape of a parallel plate capacitor. Careful planning of the dimensions allows for operation frequencies of up to hundreds of megahertz and a contrast of more than 3 dB. The device can be implemented for AND, NOT, and NAND gates.

The design of aperture shape is a promising approach for enhanced transmission through a subwavelength aperture. We designed split-ring-resonator (SRR)-shaped apertures in order to increase the transmission through subwavelength apertures by making use of the strong localization of the electromagnetic field in SRR-shaped apertures. We obtained a promising result of 104-fold enhancement by utilizing SRR-shaped apertures. It is possible to use these proposed structures at optical frequencies by making several modifications such as decreasing the sharpness of edges and increasing the gap width. Since SRRs are already being realized at optical frequencies, our proposed SRR-shaped aperture structures are promising candidates for novel applications.

A forward-projection algorithm based on Radon transform for two-dimensional surface plasmon imaging was devised to achieve nanoscale precision in determining the surface plasmon signal. A diverging laser beam at the chosen frequency was used to overcome the angular scanning in the well-known Kretschmann configuration. Multichannel sensing with improved resolution was realized. The technique was also used to find the lateral resolution of the sensor using a patterned layer of 40-nm thick SiO₂ layer on top of the metallic surface. As a surface plasmon resonance signal detector, the use of the proposed Radon transform algorithm shows nanoprecision accuracy in cases of single and multichannel sensing. The method also provides the filtered output of the signal without any extra modification and therefore, it is nonsensitive to noise.

A detailed investigation on planar two dimensional metallodielectric dipole arrays with enhanced near-fields for sensing applications was carried out. Two approaches for enhancing the near-fields and increasing the quality factor were studied. The reactive power stored in the vicinity of the array at resonance increases rapidly with increasing periodicity. Higher quality factors are produced as a result. The excitation of the odd mode in the presence of a perturbation gives rise to a sharp resonance with near-field enhanced by at least an order of magnitude compared to unperturbed arrays. The trade-off between near-field enhancement and thermal losses was also studied, and the effect of supporting dielectric layers on thermal losses and quality factors were examined. Secondary transmissions due to the dielectric alone were found to enhance and reduce cyclically the quality factor as a function of the thickness of the dielectric material. The performance of a perturbed frequency selective surface in sensing nearby materials was investigated. Finally, unperturbed and perturbed arrays working at infrared frequencies were demonstrated experimentally.

Ellipsometry and infrared polarized reflection spectroscopy at oblique incidence of golden split-ring resonators were simulated and discussed. The ellipsometric spectra were related to the reflection spectra for the two polarization of the incident wave, s- and p-, with electric field being normal and parallel to the plane of incidence, respectively. Near-field and bulk current distribution at the resonances proved that they correspond to the multiple plasmonic modes of the split-ring resonators. The calculated magnetic moment showed that at oblique incidence both magnetic and electric field induce the magnetic resonances.

The electrochemical deposition technique was used for the preparation of Cu-doped ZnO-nanowire-based emitters. Nanowires of high structural and optical quality were epitaxially grown on p-GaN single crystalline film substrates. We found that the emission is directional with a wavelength that is tuned and redshifted toward the visible region by doping with Cu in nanowires. Furthermore, Cu-doped ZnO-nanowires show an enhancement of the transition probability under magnetic field.

The transfer matrix of a dielectric slab under propagation of a Gaussian beam was formulated. The derived matrix was applied for a one-dimensional photonic crystal (1DPC) structure and the transmittance spectrum and photonic bandgap (PBG) properties were investigated. An r-dependent (r is the radial coordinate of the Gaussian beam) PBG was obtained. With the increase of r, a redshift and a decrease in the PBG are observed. Higher PBGs experience more shift. Also properties of the photonic crystal (PC) structure with defect layer were investigated and displacement to red and decrease of the defect mode peak height, with an increase of r, were observed. The extra optical path that the outer rays travel due to the oblique propagation compared to the central ray in a Gaussian beam is responsible for these effects. For long Rayleigh ranges our results for the Gaussian beam were the same as that for plane wave.

This paper reviews the main properties and applications of nanomembrane-based plasmonic structures, including some results presented here for the first time. Artificial nanomembranes are a novel building block in micro- and nanosystems technologies. They represent quasi-two-dimensional (2D) freestanding structures thinner than 100 nm and with giant aspect ratios that often exceed 1,000,000. They may be fabricated as various quasi-2D metal-dielectric nanocomposites with tailorable properties; they are fully symmetric in an electromagnetic sense and support long-range surface plasmon polaritons. This makes nanomembranes a convenient platform for different plasmonic structures such as subwavelength plasmonic crystals and metamaterials and applications such as plasmon waveguides and ultrasensitive bio/chemical sensors. Among other advantages of nanomembrane plasmonics is the feasibility to fabricate flexible, transferable plasmonic guides applicable to different substrates and dynamically tunable through stretching. There are various approaches to multifunctionalization of nanomembranes for plasmonics, including the use of transparent conductive oxide nanoparticles, but also the incorporation of switchable ion channels. Since the natural counterpart of the artificial nanomembranes are cell membranes, the multifunctionalization of synthetic nanomembranes ensures the introduction of bionic principles into plasmonics, at the same time extending the toolbox of the available nanostructures, materials and functions.

Electron transport through an InGaAs resonant tunneling structure with Rashba spin-orbit interaction and magnetic field parallel to the growth direction was studied theoretically. A nonequilibrium Green's function model was used, wherein interface roughness and longitudinal optical phonon scattering are treated in the self-consistent first Born approximation. The model predicts the main features of the two-dimensional magnetopolaron density of states and the secondary peaks in the I-V curve due to both resonant elastic and inelastic scattering. The I-V curves were studied at magnetic fields around the magnetophonon resonance and the elastic and inelastic contributions identified. At these fields (5 to 7 T), the current spin polarization was found to be dominated by the Zeeman effect and significant even in the presence of scattering events.

We theoretically investigated the optical properties of the lesser known (3.4.6.4) Archimedean photonic crystal. The structure is two dimensional and made of dielectric GaAs rods in air. The calculations of the band structures, equifrequency contours, and simulations of the wave propagation through the structure were performed by the plane wave expansion and finite-difference time-domain methods. With analysis of the gap map and equifrequency contours we obtained frequency ranges for best performance for wave guiding. For those frequency ranges, we designed a new type of waveguide for possible applications in integrated optics. In addition, negative refraction was exhibited by the structure.

Based on the experimental results and comparison between analytical and rigorous calculations, we have found that dual-surface plasmon (SP) waves are excited at both interfaces of a periodic array of thin metallic nanoslits: one at the grating-substrate interface and one at the grating-superstrate interface. Dual plasmons are excited for each diffraction order at two different wavelengths when the substrate differs from the superstrate. The splitting of the plasmons was investigated as a function of the refractive index difference between the substrate and superstrate. Verification of the extended nature of the double SPs is presented by comparing the rigorous calculation and analytic dispersion relation of extended SPs.

Slow light has been extensively studied in coupled arrays of passive optical resonators, and several applications have been demonstrated. We developed a theoretical framework for the design and analysis of arrays consisting of active resonators, in particular vertical cavity surface emitting lasers (VCESLs), which have potential applications as a flexible photonic platform. Building upon this framework, several such applications were analyzed for both one- and two-dimensional coupled VCSEL arrays. In particular, the use of two-dimensional VCSEL arrays holds great potential for several interesting applications such as tunable optical waveguides or optical splitters.

A new (nonrelativistic) model for electron-beam dynamics in a free-electron laser undulator was formulated using the method of linear invariants of quantum-mechanical charge particle. The magnetic field varies periodically along the undulator. We obtained an exact solution for this quantum-mechanical problem described by quadratic Hamiltonian. The time-evolutions of the tree independent quantum fluctuations [cov(q,p), var(q), and var(p)] of the electrons were determined. The quantum behavior shows covariance states which are different from the well-known coherent and squeezed states. On the basis of the quantum approach applied here, further exploration of Madey formula for Δλ of emitted photons was done and the low limit of the electron energy was determined, below which the quantum uncertainty prevails the energy spread of the beam.

A new dielectric Fabry-Perot cavity is considered for enhanced optical absorption in a thin semiconductor layer embedded within the resonant cavity. In this design, the front (furthest from the illuminated side) mirror is a grating structure with nearly perfect retroreflection. Proof of concept, including semianalytical calculation, and computer-aided design and simulation is performed for application in a midinfrared wavelength band based on a HgCdTe absorbing layer. The results indicate that this new type of cavity meets the combined challenges of significantly increasing the absorption efficiency and reducing the overall complexity and size of the entire device, in comparison to a conventional resonant cavity, in which both mirrors are formed from quarter-wavelength multilayer stacks.

The hybrid optically and electrically controllable field effect transistor is a novel device whose current-voltage (I-V) curve can be controlled by optical or electrical modulation of metallic nanoparticles. The basic structure of this transistor is similar to that of a junction gate field effect transistor, where the conventional gate contact is replaced by an array of nanoparticles located on the upper side of the p-n junction and parallel to the channel direction, whereas the source and the drain contacts remain the same. The deposition of the nanoparticles is achieved by self-assembly using the focused-ion-beam technology. The displacement of the nanoparticles along the air gap is performed either optically or electrically. Optical control is based on a special type of optical tweezers realized by guiding and confining light into a nanosize void structure in which the nanoparticle is placed. Electrical control via an external electric field tunes the nanoparticles. Control of the I-V curve controls the logic function of the device.

This PDF file contains the editorial “Special Section Guest Editorial: Selected Papers from the 3rd Mediterranean Conference on Nanophotonics” for JNP Vol. 5 Issue 01

Growth dynamics of thin-films involves both shadowing and re-emission effects. Shadowing can originate from obliquely incident atoms being preferentially deposited on hills of the surface, which leads to a long range geometrical effect, as well as from an atomic shadowing process that can occur even during normal angle deposition. Re-emission effect is a result of nonsticking atoms, which can bounce off from hills and deposit on valleys of the surface. In the case of an energetic incident flux, re-emission can also originate from a resputtering process that includes a surface atom being knocked off by an incident ion/atom followed by redeposition to another surface point. Due to their long-range nonlocal nature, both the shadowing effect (which tries to roughen the surface) and re-emission effect (which has a smoothening effect) have been shown to be more dominant over local effects such as surface diffusion, and have been proven to be critical processes in accurately determining the dynamic evolution of surface roughness. Recent Monte Carlo simulation methods that involve shadowing, re-emission, surface diffusion, and noise effects successfully predicted many experimentally relevant surface roughness evolution results reported in the literature. For example, root-mean-square surface roughness (ω) of Monte Carlo simulated thin-films have evolved with time t according to a power law behavior ω ∼ tβ, with β values ranging from about 0 to 1 for a growth with strong re-emission effects (i.e., low sticking coefficients) and a growth with dominant shadowing effects (i.e., with high sticking coefficients), respectively. Potential future thin-film growth modeling studies are also discussed.These include advanced simulation approaches that can incorporate atomistic details of physical and chemical processes and a recently developed network growth model that can potentially capture some universal aspects of thin-film growth dynamics independent of the details of growth process.

Depending on the size of the smallest feature, the interaction of light with structured materials can be very different. This fundamental problem is treated by different theories. If first order theories are sufficient to describe the scattering from low roughness surfaces, second order or even higher order theories must be used for high roughness surfaces. Random surface structures can then be designed to distribute the light in different propagation directions. For complex structures such as black silicon, which reflects very little light, the theory needs further development. When the material is periodically structured, we speak about photonic crystals or metamaterials. Different theoretical approaches have been developed and experimental techniques are rapidly progressing. However, some work still remains to understand the full potential of this field. When the material is structured in dimension much smaller than the wavelength, the notion of complex refractive index must be revisited. Plasmon resonance can be excited by a progressing wave on metallic nanoparticles inducing a shaping of the absorption band and of the dispersion of the extinction coefficient. This addresses the problem of the permittivity of such metallic nanoparticles. The coupling between several metallic nanoparticles induces a field enhancement in the surrounding media, which can increase phenomena like scattering, absorption, luminescence, or Raman scattering. For semiconductor nanoparticles, electron confinement also induces a modulated absorption spectra. The refractive index is then modified. The bandgap of the material is changed because of the discretization of the electron energy, which can be controlled by the nanometers size particles. Such quantum dots behave like atoms and become luminescent.

We numerically analyze the generation of near-field light at a 50-nm-wide slit used for two-step photoionization detection of alkali-metal atoms with high spatial resolution, considering the influence of rounding the slit edges. In the case where near-field light is generated via total-internal reflection of s-polarized light introduced along the slit, the intensity decreases with increasing the radius of curvature of the slit edge. Finite-difference time-domain simulations indicate that the electric field is concentrated in the upper left and right corners of the slit when the radius of curvature is small, but the enhancement is resolved due to edging down. Assuming that the intensity of an Ar⁺ laser beam with a wavelength of 476.5 nm is 5 × 10⁴ W/cm², the radius of curvature of the edge of less than 15 nm is required for the ionization efficiency exceeding 10 % of slow ⁸⁷Rb atoms with the incident speed of 10 cm/s. The throughput of near-field light increases with wavelength for the s-polarization, but decreases with wavelength for the p-polarization.

We report recent progress toward on-chip single photon emission and detection in the near infrared utilizing semiconductor nanowires. Our single photon emitter is based on a single InAsP quantum dot embedded in a p-n junction defined along the growth axis of an InP nanowire. Under forward bias, light is emitted from the single quantum dot by electrical injection of electrons and holes. The optical quality of the quantum dot emission is shown to improve when surrounding the dot material by a small intrinsic section of InP. Finally, we report large multiplication factors in excess of 1000 from a single-Si-nanowire avalanche photodiode comprised of p-doped, intrinsic, and n-doped sections. The large multiplication factor obtained from a single Si nanowire opens up the possibility to detect a single photon at the nanoscale.

Porous silicon is a potentially useful substrate for fluorescence and scattering enhancement, with a large surface to volume ratio and thermal stability providing a potentially regenerable host matrix for sensor development. A simple process using XeF₂ gas phase etching for creating porous silicon is explained. Moreover, how pores diameter can be controlled reproducibly with commensurate effects upon the silicon reflection and pore distribution is discussed. In previous work with this new system, it was clear that control on pore size and morphology was required and a systematic optimization of process conditions was performed to produce greater consistency of the result. The influence of the duration of the pre-etching processing in HF, concentration of the HF in the pre-etching process, and the XeF₂ exposure time during the dry etching on surface morphology, pore size, and optical reflectance is explored.

The effect of thermal annealing on the performance of bulk heterojunction poly (3-hexylthiphone) (P3HT): [6,6]-phenyl-C_61-butyric acid methyl ester (PCBM) solar cells has been examined. We found that the efficiency of the solar cell increases from 0.08% to 3.81% as the annealing temperature is varied from room temperature to 120°C. This improvement in the efficiency is due to the rearrangement of polymer molecules and nanoparticles. Annealing reorders the P3HT polymer chain structure (which was ruined by the PCBM nanoparticles) by segregating out PCBM molecules from polymer. Due to annealing, movement in the P3HT and PCBM particles is induced, which reorganize and form a phase segregated 3D structure of donor and acceptor molecules enhancing the charge transfer efficiency. It also improves the surface morphology and polymer chain interconnections resulting in enhancement of hole mobility through the polymer network.

Infiltrated liquid sensors based on a 2D photonic crystal waveguide were devised. This waveguide is designed by taking into account lowering of the radius of the central air holes in a single row and the optical resonance shifts due to refractive index change of these holes by selectively filling with different liquids. The transmission spectrum of the infiltrated liquid sensor was obtained with the use of a finite difference time domain method. At the working wavelength of 1550 nm, the waveguide mode gap edge shifts with sensitivity of 200 nm per refractive index unit. The mode gap shifts are consistent with dispersion diagrams.

A simple and straightforward approach was devised to fabricate microspherical aggregates of alumina nanoparticles by self-assembly. Two different organosilanes were used as surfactant agents. Spherical aggregates were spin-coated on a silicon substrate. Spheres with diameters ranging from 100 nm to a few micrometers were thus assembled within an hour. The spatial distribution and the size distribution of the spheres are adjustable by changing the concentration of used organosilane. Effects of different organosilane agents, mixture molarity, and temperature on the size distribution of the spheres were also investigated.

A dual-beam method for the near-axial rotation of dielectric nanorods was devised. The method uses two laser beams, where a focused Gaussian beam holds the object in the beam axis while a focused Laguerre-Gaussian beam rotates the object. The near-axial rotation of ZnO nanorods using this method was then experimentally demonstrated, and the radial offset distance of the rotating nanorod from the beam axis was quantified via a video tracking method.

The phonon frequency distribution function (FDF) of aligned multiwalled carbon nanotubes (MWNTs) was obtained by unfolding its observed temperature variation of specific heat in the temperature range 1.8 to 250 K. An anisotropic dynamical model which incorporates the presence of two-dimensional modes on the surface of the tube and the intertube coupling was used as a trial function to carry out the unfolding process numerically. Temperature variation of Rayleigh Mössbauer scattering fraction of Sn-119 gamma-photons was computed using the trial and final FDF of MWNT. The temperature variation of Rayleigh Mössbauer scattering fraction in each case is quite marked and can be observed experimentally.

The seminal discovery that an ideal negative-index lens may overcome Abbe's diffraction limit has raised enormous interest in the field of metamaterials and of subwavelength focusing. This finding is based on the anomalous wave propagation in ideally isotropic and homogeneous metamaterials with negative index of refraction and low loss, provided they are available. We have designed a metamaterial lens based on one of the simplest metamaterial geometries, a cubic array of spheres, with the aim of verifying its imaging properties in a practical configuration. After a rigorous homogenization, we have shown that, for suitable designs, the effective bulk parameters may indeed provide a quasi-isotropic negative-index response, ideal for imaging applications. We have then tested the imaging properties for finite-size lenses, analyzing challenges and potentials of going beyond the diffraction limit in a practical setup. We have also explored an alternative venue to exploit the negative-index property of the designed metamaterial in a concave lens, in order to resolve subwavelength features in the far-field. Our results indicate that, although subwavelength resolution and evanescent-wave amplification are possible in metamaterial arrays, practical imaging beyond the diffraction limit is challenging and a careful design should consider the granularity, degree of isotropy, and transverse size of the metamaterial lens.

Nonperturbative theoretical analysis of the temporal evolution of a spontaneous photon with atomic frequency &ohgr;_a, emitted by a motionless two-level atom in a one-dimensional high-finesse nanocavity into a single resonance decaying mode, is presented. The explicit solution of the Schrödinger equation was found in an interaction picture with use of the Green functions technique. It has been assumed that emission leaks out of the empty cavity by exponential law at rate &Ggr;, which is a function of coupling constant g, distance between the mirrors, penetrability coefficient of the left mirror, and the velocity of light. The stationary superpositional co-phased structure of two photons with the same profiles and average frequencies 1/2(&ohgr;_a ± g), quenched with continuum of final photonics states, has been revealed. The profile of this structure has been found to have the form &Ggr;t exp(-&Ggr;t/4) with maximum attained for &Ggr;/4g = 0.05 and average photon cavity lifetime equal to 4ln&Ggr;/&Ggr;.

Multiple trapping and clustering of gold nanoparticles (Au-NPs) of 254- and 150-nm diameter was affected using optical tweezers near the plasmon excitation wavelength. To ensure that the gradient force exceeded the sum of multiply-enhanced destabilizing absorption and scattering forces originating from plasmon excitation, embedded intensity gradient regions of a spatially featured asymmetric (SFA) laser beam were exploited. Thus, an intra-cavity generated SFA beam, also referred as hybrid TEM₁₁* mode, is an intermediate between pure TEM₀₀ and TEM₁₁ beams and was directly obtained from a diode-pumped solid state (Nd:YAG) laser resonator without introducing any external beam modulation devices. The parabolic Gaussian-ray model of a tightly focused laser beam was adopted to evaluate the radiation forces including the volume-correction factor raised from fractional polarization of such large diameter Au-NPs under laser illumination. Temperature rise of Au-NPs and its dissipation profile in surrounding medium has also been presented. This multiple trapping and clustering of Au-NPs at plasmon excitation wavelength using sufficiently low power could be realized due to embedded intensity gradients of the SFA beam. The study might be useful for understanding the light-matter interaction, improving the sensitivity of diagnostics, and safety and efficacy of therapeutic nanotechnologies in medicine, photothermolysis, and surface-enhanced Raman spectroscopy, etc.

The coherent combination of electric and magnetic responses is the basis of the electromagnetic behavior of new engineered metamaterials. The basic constituents of their meta-atoms usually have metallic character and consequently high absorption losses. Based on standard "Mie" scattering theory, we found that there is a wide window in the near-infrared (wavelengths 1 to 3 μm), where light scattering by lossless submicrometer Ge spherical particles is fully described by their induced electric and magnetic dipoles. The interference between electric and magnetic dipolar fields is shown to lead to anisotropic angular distributions of scattered intensity, including zero backward and almost zero forward scattered intensities at specific wavelengths, which until recently was theoretically established only for hypothetically postulated magnetodielectric spheres. Although the scattering cross section at zero backward or forward scattering is exactly the same, radiation pressure forces are a factor of 3 higher in the zero forward condition.

A comparative study of the adsorption behavior of 4, 3, and 2 aminothiophenol on gold nanorod (AuNRs) solution and film substrates is carried out using surface-enhanced Raman spectroscopy (SERS) to provide information about the adsorption mechanisms of aminothiophenols on AuNRs. SERS from gold nanorods in solution form could reveal the distribution of aminothiophenol molecules adsorbed on different facets of gold nanorods. Significant and sudden changes in the relative intensities of some of the vibrational bands are observed above a particular concentration of aminothiophenol, which could be related to adsorption of molecules on different facets of nanorods. The enhancement factor is found to be maximum for the excitation wavelength close to the absorption maximum of gold nanorods. Our results are not only useful for the application of nanorods as sensors and in molecular electronics, but also depict the potential of gold nanorods as the effective SERS substrate.

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.

A facile single step strategy for the synthesis and large area patterning of silver nanoparticles via photodecomposition of a photoactive silver nitrite aliphatic amine complex was developed. Decomposition of the silver complex was facilitated using either a UV or an Argon ion laser (514.5 nm) irradiation. The synthesis was performed both in solution and thin films. The silver nanoparticles displayed characteristic localized surface plasmon resonance in the absorption spectrum. Utilizing laser beam interference, silver nanoparticles were synthesized and, as well, patterned in a single step.

We analyzed capabilities and functionalities of a multisegment superlens recently suggested for long-distance transport of color images with subwavelength resolution. We studied the performance of three- and six-segment nanolens structures by analyzing numerically both transmission and reflection coefficients and by employing the full-wave simulations for a particular source arrangement. Our results suggest that such multisegment structures offer limited subwavelength imaging performance with a relatively narrow frequency band.

We optically excited the eigenmodes of an elliptic resonator in a semiconductor microcavity. Using a pulsed excitation, we created a superposition of eigenmodes, and imaged the temporal evolution of the coherent emission pattern. A semiconductor quantum well was embedded in the microcavity structure. The system was operated in the strong light matter coupling regime, where the eigenmodes are hybrid half-photonic half-excitonic quasiparticles called exciton polaritons. Oscillations between orbital angular momentum states (or vortex states) were observed, and turned out to be remarkably well described within the Poincaré sphere representation.

A polymer light emitting diode (PLED) based on poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene]:CdSe/ZnS core shell uncapped quantum dots (QDs) was fabricated. It was observed that the presence of QDs in the polymer tunes the emission spectrum of the PLED as their QDs concentration increases to 10% w/w and above. It was also found that the QDs present in the polymer improved the PLED luminance by ∼20 times at a typical current density of 75 mA/cm². This was attributed to the suppression of nonradiative electrostatic energy transfer from excitons to the metallic cathode due to the insertion of a high dielectric constant QD layer. Also, the presence of QDs layer between the active layer and the cathode shifts the recombination zone away from the cathode. This reduces the diffusion of radiative excitons into the metal electrode.

We devised a new configuration of optical logic gates based on a single hexagonal-lattice photonic crystal ring resonator (PCRR) composed of two-dimensional (2D) cylindrical silicon rods in air. The modal behavior of the proposed logic gates was comprehensively analyzed with a topology optimization technique based on the principle of beam interference and perturbation theory. It was then numerically verified by using a 2D finite-difference time-domain technique. The predictions have a very good agreement with the numerical results. This new single PCRR can really function as NOT and NOR gates. And the logic "0" and "1" of the hexagonal ring can be defined as less than 8% and greater than 86%, respectively, much better than earlier reported square-lattice results.

We investigate the effect on transmission of p-polarized light of the excitation of plasmons of metallic nanocylinders, placed at the exit of subwavelength slits. Morphology-dependent resonaces of the aperture may then be excited, thus leading to supertransmission. The possible enhancement of transmittance is investigated by working out appropriate choices of the geometrical parameters and illumination. Additionally, we study conditions in which supertransmitted light may propagate through sets of metallic cylinders with excited plasmons, in front of either one slit or placed in front of a periodic array of slits. We find that the concentration and intensity of the transmitted field is mainly governed by both the material and geometrical configurations of the particle sets.

A two-dimensional (2-D) photonic crystal ring resonator-based bandstop filter is conceived, its stopband efficiency is investigated using the 2-D finite difference time domain method, and its band diagram is calculated by plane wave expansion method. The stop-band efficiency of the filter, ∼98%, is observed over the wavelength range 1562-1573 nm. Furthermore, the effects of the relative permittivity and geometrical parameters are considered for determining stop-band efficiency and stop-band width. The overall dimension of the device is 11.4 × 11.4 μm, which is highly suitable for photonic integrated circuits.

Indium nanowires were synthesized by the oblique angle deposition technique, using an e-beam evaporator. The shape of the deposited nanowires changes with the vapor flux angle, and the x-ray diffraction spectrum shows scattering from tetragonal phase indium. Deposition rates ranging from 0.5 to 5 A°/s were used for 200 and 500 nm thick deposits. Nanowires formed at the highest deposition rate and were up to 4.5 μm in length. Raman scattering shows enhanced intensity and optical absorption occurs in the infrared region.

We investigated the field enhancement properties of optical resonant Archimedean spiral antennas by using a finite difference time domain method. Due to the spiral structure, the antennas show a circular dichroism in the electric field enhancement, especially for a large turning angle. A large magnetic field enhancement is also obtained with a confinement in the nanometer size. When the turning angle equals π for a linearly polarized incident beam, the polarization of the enhanced field in the spiral antenna can be perpendicular to the incident polarization with a similar enhancement factor to the optical resonant dipole antennas.

In a zero-average refractive index metamaterial the light propagation is forbidden and a narrow full photonic bandgap is open in correspondence of the frequency where it vanishes and the refractive index is averaged over the volume. However, it should be underlined that Fabry-Pérot resonances can open a propagation state inside such a particular type of bandgap. Based on a photonic crystal exhibiting a negative refractive index, it was found that such Fabry-Pérot resonant states allow images transmission with subwavelength details.

The Morpho sulkowskyi concentrates on its dorsal wings complementary features contributing to its visual attraction: predominantly translucent, their wings display a blue coloration due to light interference. Fluorescent molecules, producing a violet-blue coloration when irradiated by ultraviolet light, are embedded in the scales which present a two-dimensional photonic structure. We investigate i. the effects of the fluorophores confinement in the structure on the variation of the emission intensity and coloration with the observation direction and ii. the correlation between the reflection and emission processes that control the surface optical response. Three types of measurements have been carried out. The morphology of the butterfly was examined with a scanning electron microscope. Then, the spatial distribution of the reflected light was measured with a viewing angle instrument, providing bidirectional reflectance distribution function data. Finally, an automatic method coupling an ultraviolet source to a gonio-spectrophotometer allowed for an extensive fluorescent emission characterization and provided angular emission maps. We find a spatial variation of the emission intensity and coloration and also an exhaustion behavior of the fluorophores. Moreover, we reveal that the spatial distribution of the emitted and reflected light is mainly governed by the photonic structure.

We demonstrated gold-coated polymer surface enhanced Raman scattering (SERS) substrates with a pair of complementary structures-positive and inverted pyramid array structures fabricated by a multiple-step molding and replication process. The uniform SERS enhancement factors over the entire device surface were measured as 7.2×10⁴ for positive pyramid substrates while 1.6×10⁶ for inverted pyramid substrates with Rhodamine 6G as the target analyte. Based on the optical reflection measurement and finite difference time domain simulation result, the enhancement factor difference is attributable to plasmon resonance matching and to SERS "hot spots" distribution. With this simple, fast, and versatile complementary molding process, we can produce polymer SERS substrates with extremely low cost, high throughput, and high repeatability.

The excitation of multiple surface-plasmon-polariton (SPP) waves by the plane wave illumination of a metallic surface-relief grating coated with a sculptured nematic thin film (SNTF) was studied theoretically. The relevant boundary-value problem was formulated such that the grating plane and the morphologically significant plane of the SNTF can be rotated about a common axis with respect to each other. The rigorous coupled-wave analysis was employed to numerically solve the boundary-value problem. Absorptances were calculated as functions of the angle of incidence of a linearly polarized plane wave with wave vector lying wholly in the grating plane, and the excitation of the SPP waves was inferred from those peaks in the absorptance curves that were independent of the thickness of the SNTF. These peaks were successfully correlated with the solutions of the underlying canonical problem solved in Part IV of this series of papers.

The recently discovered ultralow-threshold nonlinear refraction of low-intensity laser radiation in dielectric nanostructures has an atypical dependence on radiation intensity in the pulsed and continuous modes. We first carry out quantitative measurements of the dependence of the nonlinear response of liquid dielectric nanostructures on the low-intensity radiation and then devise a theoretical explanation. The theory suggests that the nonlinearity is of photoinduced nature instead of a thermal one and depends directly on the nanoparticles electronic structure and the relationship between permittivities of dielectric matrix and nanoparticles.

A photonic-plasmonic integration scheme was devised to displace the defect-mode field of a photonic crystal (PC) slab cavity from the spatial center to the surface of the slab. The device was constructed by placing an isolated metallic structure on the top surface of a missing-hole defect in the PC. Excitation of the metal's surface plasmon resonance mode by the PC cavity's defect mode was investigated using a three-dimensional plane wave transfer matrix method. It was revealed that using the PC cavity could minimize the background field around the metal, significantly enhancing the field intensity contrast between the metal and surrounding dielectric.

On the basis of the analysis of material gain, a comprehensive optimization of quantum wells used in a 1-μm vertical-external-cavity surface-emitting laser was carried out. For a single-well structure, the optimized width lies between 8 and 10 nm, the optimized depth is a quantum well with ∼0.1 Al composition in AlGaAs barrier, and the optimized configurations are graded-index quantum well and quantum well with AlGaAs barrier and a GaAs buffer layer. The optimal width of a double- or triple-well structure lies between 6 and 8 nm. Compared to its single- and triple-well counterparts, double-well structure provides higher gain and has more tolerance to the deviation of laser wavelength.

A compact and low power control of photonic crystal nanocavity resonance was devised, simulated, and experimentally validated utilizing a hybrid integration of a microelectromechanical systems driven nanoprobe. The experimental results demonstrated a reversible resonance tuning up to 5.4 nm with minimal Q-factor degradation.

Surface-enhanced Raman spectroscopy (SERS) substrates formed by nanosphere lithography were investigated for their spatial distribution and magnitude of electric field enhancement. An integrated atomic force microscopy and Raman micro-spectroscopy system was used to establish, with high accuracy, the correlation between the local SERS mappings and substrate topography. Using a monolayer of rhodamine 6G as a probe of the local electric field, the high resolution Raman mappings, showed that the highest electric field enhancement originates from the metallic nanostructures rather than the gaps between them. The enhancement factor of the substrates is calculated from Raman spectra of the substrates covered in a monolayer of p-aminothiophenol and spatial measurements, giving a value on the order of 10⁵. The experimental results were confirmed by theoretical calculations using the finite element method.

Ultraviolet (UV) light-emitting diode using salmon deoxyribonucleic acid (sDNA)-cetyltrimethylammonium complex as an electron blocking layer and zinc oxide (ZnO) nanorods as emissive material was fabricated. UV emission, which was blue shifted up to 335 nm with respect to the band edge emission of 390 nm, was observed. This blue shift was caused due to accumulation of electrons in the conduction band of ZnO because of a high potential barrier existing at the sDNA/ZnO interface.

We investigated and optimized the process of soliton self-compression in few millimeters-long air-silica nanowires. A 100 fs prechirped input pulse was compressed to a 1.4 fs pulse by pumping at very low energy of 2.5 nJ an air-silica nanowire. More than one octave spanning coherent broadband supercontinuum extending from 260 to 1800 nm was generated.

We have devised and fabricated high-speed silicon-on-insulator resonant microring photodiodes. The detectors comprise a p-i-n junction across a silicon rib waveguide microring resonator. Light absorption at 1550 nm is enhanced by implanting the diode intrinsic region with boron ions at 350 keV with a dosage of 1 × 10^13cm−2. We have measured 3-dB bandwidths of 2.4 and 3.5 GHz at 5 and 15 V reverse bias, respectively, and observed an open-eye diagram at 5 gigabit/s with 5 V bias.

This PDF file contains the editorial “Editorial: The longitude of technoscientific progress” for JNP Vol. 5 Issue 01

A massage from the Editor-in-Chief.