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No Abstract available.

This PDF contains the commentary "Multichannel ellipsometry for monitoring processes."

Electromagnetic surface waves have been a subject of investigation since the beginning of the 20th century when Zenneck proposed that radio waves might propagate as surface waves bound to the air/Earth interface. Although that possibility is still being debated, the midtwentieth century saw the resurfacing of this idea with application to waves at optical frequencies bound to metal/insulator interfaces. In this regime, the surface wave is known as a surface-plasmon-polariton (SPP) wave. Within the past few decades, SPP waves have proved to be extremely valuable as a means of creating sensitive chemical sensors, especially for the detection of biochemicals [1,2]. As the ability to manipulate materials at the microscopic scale has developed, improved implementation of SPP waves with various structures and geometries continue to be proposed and realized. It is well known that the advent of nanotechnology has brought about composite materials with properties that can be quite different than those of the constituent materials in the bulk. Recent investigations [3–8] have shown that interfaces of nanostructured periodic dielectrics and metals can support SPP waves in a very novel way.

The last two decades have been witness to two exciting and independent developments that have forever changed our conventional view of how light interacts with matter. One relates to coherent control via quantum interference, wherein the possibility of making an otherwise opaque medium transparent [1], now known as electromagnetically induced transparency (EIT), set off intense research activity. EIT essentially requires careful creation of atomic coherence, that results in diverse effects varying from almost freezing light in its tracks (slow light) to freezing atoms to nanoKelvin temperatures via velocity-selective coherent population trapping. The second development relates to metamaterials whose origins are very classical in nature. In electromagnetics, these designer materials were originally proposed for realizing a super-lens wherein the evanescent field becomes the work horse that accords sub-wavelength resolution in imaging [2]. Since then a variety of metamaterials have been proposed, where even the propagating fields can be dramatically controlled, as in electromagnetic cloaks wherein the fields are maneuvered around an obstacle so as to make it invisible. The biggest technological contraints in realizing large-scale device applications of metamaterials have been two. The first is the large dissipation associated with an inherently resonant phenomenon. The second arises due to the very design of metamaterial; once the metamaterial structures (inclusions) are fabricated, they offer little maneuverability in terms of the operating frequency.

Investigating interactions of intense soft X-rays with solid surfaces and resulting phenomena is still challenging. One could expect material removal from the surfaces (ablation) caused by soft X-ray irradiation at a precision as high as the diffraction limit of the soft X-rays. The X-ray ablation technique could enable us to fabricate nano- and micro-structures on surfaces of even transparent materials such as silica glass, polymethylmethacrylate (PMMA) and polydimethylsiloxane (PDMS), which are highly valued for their use in the fields of nanometric chemical analysis and chemical reactions in medicine and biotechnology.

A short technical commentary on a specific topic.

In recent years, silicon nanophotonic devices have attracted more and more attention due to their compactness, low power consumption, and easy integration with other functions. In addition to the higher index of silicon material providing stronger light confinement, the optical resonance associated with the novel structure design also enhances the performance of nanophotonic devices and offers stronger light-matter interaction. Silicon nanophotonic devices such as polarization beamsplitters, mirrors and reflectors, slow light waveguides, and microring sensors are studied, and all of them demonstrate much better performances due to the incorporated optical resonance enhancement.

A full understanding of Doppler, either acoustic or electromagnetic, depends on representing the effect in the time domain as well as in the frequency domain. In the time domain, the Doppler perturbation (f - f₀)/f₀ for a signal becomes its time-delay time derivative. A surprising physical consequence (deduced here for an acoustic reflection problem) is that the Doppler perturbation depends on ratios of distances (source-to-echoer and echoer-to-receiver) as well as on various velocities and angles. Another surprise from the time domain concerns the reverse Doppler effect observed both for electromagnetic and acoustic signals. In certain artificial environments (metamaterials with negative refractive index), radiation can be received with a lower frequency when the source approaches a receiver and with a higher frequency when receding from it. The time-delay time derivative picture represents this effect as a paradox: The time delay (hence source-to-receiver distance) increases when its time-delay time derivative is negative. The restriction of reverse Doppler to a dissipative domain may ameliorate the paradox but does not solve it.

In terms of the effective medium theory, we propose a general solution to such a fundamental problem as designing nanostructured materials with the very low permittivity (epsilon-near-zero metamaterials) over a frequency range. We show, in particular, that this can be accomplished for a columnar metal-dielectric composite consisting of parallel cylinders with varied thickness that resembles a forest of identical stems. The applicability of our method and some limitations are also discussed. Whilst the corresponding production procedure does not appear to be very simple, it nevertheless is realizable.

A dielectric columnar thin film (CTF), characterized macroscopically by a relative permittivity dyadic, was investigated theoretically. The CTF was assumed, on the nanoscale, to be an assembly of parallel, identical, elongated ellipsoidal inclusions made of an isotropic dielectric material that has a different refractive index from the bulk material that was evaporated to fabricate the CTF. The inverse Bruggeman homogenization formalism was developed in order to estimate the refractive index of the deposited material, one of the two shape factors of the ellipsoidal inclusions, and the volume fraction occupied by the deposited material, from a knowledge of relative permittivity dyadic of the CTF. A modified Newton-Raphson technique was implemented to solve the inverse Bruggeman equations. Numerical studies revealed how the three nanoscale parameters of CTFs vary as functions of the vapor incidence angle.

Oxide nanocrystallite aggregates are candidates for use in dye-sensitized solar cells. The aggregates are of submicron size, formed by nano-sized crystallites and, therefore, able to offer both a large specific surface area and desirable size comparable to the wavelength of light. While used for a photoelectrode in a dye-sensitized solar cell, the aggregates can be designed to generate effective light scattering and thus extend the traveling distance of light within the photoelectrode film. This would result in an enhancement in the light harvesting efficiency of the photoelectrode and thus an improvement in the power conversion efficiency of the cell. When this notion was applied to dye-sensitized ZnO solar cells, a more than 120% increase in the conversion efficiency was observed with photoelectrode film consisting of ZnO aggregates compared with that comprised of nanocrystallites only. In the case of TiO₂, the photoelectrode film that was formed by TiO₂ aggregates presented conversion efficiency much lower than that obtained for nanocrystalline film. This may be attributed to the non-ideal porosity of the TiO₂ aggregates and the unsuitable facets of the nanocrystallites that form to the aggregates. However, a 21% improvement in the conversion efficiency was still observed for the TiO2 films including nanocrystallites mixed with 50% aggregates, indicating the effectiveness of the TiO₂ aggregates as light scatterers in dye-sensitized solar cells. Optimization of the structure and the surface chemistry of TiO₂ aggregates, aiming to yield more significant improvement in the conversion efficiency of dye-sensitized solar cells, is necessary.

Gold/silver core/shell nanorods with precisely tunable resonance peaks covering the visible and near-infrared wavelength range were obtained using a simple wet-chemical synthesis approach. These nanoparticles surfaces can be further modified to improve their biocompatibility and stability in biological media. After conjugating with some biomolecules, these functionalized nanoparticles were used as multicolored optical probes for targeted dark field imaging of live human cancer cells. These experiments suggest that the gold/silver core/shell nanoparticles can serve as a potential platform for multichanneled and ultrasensitive bioimaging.

Continuing our ongoing investigations of random lasing, we used the Monte Carlo method to simulate random walks of photons within a multiply scattering medium. By initially applying this technique to calculate pulse-stretching in a passive disordered medium, we elucidated its agreement with analytical diffusion theory. Thereafter, we introduced conditions of optical amplification, and reproduced the experimentally observed spectral features like spectral narrowing, intensity enhancement, bichromaticity, mode competition, etc., in a random laser. After investigating diffusive and sub-diffusive regimes of scattering, we formulated our results in terms of a gain subvolume, the functioning of which depends upon local gain conditions. We then used a modified approach of this technique to study ultranarrow random lasing modes, and successfully reproduced these modes observed in a random laser. Based on our simulations, we were able to explain the origins of ultra-narrow lasing modes as excessively amplified extended modes.

A spectral approach to the Lorenz-Mie problem was adopted to obtain a pole expansion of the Lorenz-Mie coefficients in the complex variable z = 4π=(n² - 1), where n² is the dielectric permittivity of the scatterer. In the absence of magnetic properties (which is assumed), n is the refractive index of the scatterer. It is shown that the Lorenz-Mie coefficients are meromorphic functions of z with simple poles. The poles and the residues are functions of the size parameter x = ka = 2πa/λ and of the order of the Lorenz-Mie coefficient, l, but are independent of the material properties. This leads to a numerically efficient representation of the Lorenz-Mie coefficients.

Van der Waals (VDW) forces arise from quantum mechanical fluctuations of local charge densities. Whereas computing VDW interactions between two atoms requires only 2-body interactions, by definition, computing interactions between macroscopic bodies required multi-body interactions, where the presence of a third atom affects how any two atoms interact, and a fourth atom affects the first three, and so on. Often, 3-body interactions have been found to be small, and 4-body and higher interactions are almost always neglected in calculating interactions between atoms. But is it possible that 4-body and higher order interactions can actually be more important than 3-body interactions, and indeed comparable to 2-body interactions? We explored the following question: how important is the sum of 4-body and higher order interactions? A set of problems involving finite and infinite chains was explored numerically and analytically, including a single chain, a pair of parallel, long chains and a two-dimensional array of long, parallel chains. The "coupled dipole method" was used, providing a type of "nanoscale Lifshitz theory" for calculations of nanoscale VDW interactions. Calculations were made for the static polarizability, as well as the VDW interaction between chains. This latter energy was compared with that found by summing 2-body interactions for the chains. It was found that when a "coupling constant" ν, which is the polarizability per unit volume of the material, is large, then the sum of 4-body and higher order interactions dominates both the 2-body and the 3-body interactions. In addition, it was found that for all geometries examined, a divergence of the polarizability and a dynamical energy instability occur simultaneously when ν reaches a limiting value ν_max, giving a well-known polarization catastrophe.

When off-resonant light travels through a transparent medium, light scattering is the primary optical process to occur. Multiple-particle events are relatively rare in optically dilute systems: scattering generally takes place at individual atomic or molecular centers. Several well-known phenomena result from such single-center interactions, including Rayleigh and Raman scattering, and the optomechanical forces responsible for optical tweezers. Other, less familiar effects may arise in circumstances where throughput radiation is able to simultaneously engage with two or more scattering sites in close, nanoscale, proximity. Exhibiting the distinctive near-field electromagnetic character, inter-particle interactions such as optical binding and a variety of inelastic bimolecular processes can then occur. Although the theory for each two-center process is well established, the connectivity of their mechanisms has not received sufficient attention. To address this deficiency, and to consider the issues that ensue, it is expedient to represent the various forms of multi-particle light scattering in terms of transitions between different radiation states. The corresponding quantum amplitudes, registering the evolution of photon trajectories through the material system, can be calculated using the tools of quantum electrodynamics. Each of the potential outcomes for multi-particle scattering generates a set of amplitudes corresponding to different orderings of the constituent photon-matter interactions. Performing the necessary sums over quantum pathways between radiation states is expedited by a state-sequence development, this formalism also enabling the identification of intermediate states held in common by different paths. The results reveal the origin and consequences of linear momentum conservation, and they also offer new insights into the behavior of light between closely neighboring scattering events.

The Maxwell stress tensor method is used to calculate the optical forces acting upon a glass nanosphere in the proximity of optically excited gold nanoantenna structures. The dependence of optical forces over a full range of excitation angles is explored: the total internal reflection excitation does not bring any particular advantage to trapping efficiency when compared to the normal incidence excitation. Our calculations show multiple trapping sites with similar trapping properties for the normal and the total internal reflection cases, respectively; furthermore, the convective heating probably dominates over any optical forces in such systems.

Resonances of symmetric and antisymmetric polarization states in tightly coupled nanoshell particles made of either a metallic core and a dielectric shell or, vice versa, a dielectric core and a metallic shell were analyzed at optical frequencies. The investigation was performed by using the single dipole approximation (SDA) with all the dynamical retarded field terms included. Furthermore, analytic formulas for the four possible resonances were derived for the first time by retaining only the static (non-retarded) term in the dipolar field expression. The image principle was used to distinguish a priori between symmetric and antisymmetric modes and for full-wave simulations performed to confirm the identification of resonances achieved by the SDA. It was observed that the resonance frequencies of a pair of nanoshells can be tuned over a wide range of wavelength/frequencies by varying the relative dimensions of the core and shell. This makes this kind of particle pairs suited very well to be adopted either as constituents of metamaterials or to enhance local fields when operating frequencies range from the visible to the infrared spectral regions.

Nanometer- and micrometer-sized solid particles play an important role in the evolutionary cycle of stars and interstellar matter. The optical properties of cosmic grains determine the interaction of the radiation field with the solids, thereby regulating the temperature structure and spectral appearance of dusty regions. Radiation pressure on dust grains and their collisions with the gas atoms and molecules can drive powerful winds. The analysis of observed spectral features, especially in the infrared wavelength range, provides important information on grain size, composition and structure as well as temperature and spatial distribution of the material. The relevant optical data for interstellar, circumstellar, and protoplanetary grains can be obtained by measurements on cosmic dust analogs in the laboratory or can be calculated from grain models based on optical constants. Both approaches have made progress in the last years, triggered by the need to interpret increasingly detailed high-quality astronomical observations. The statistical theoretical approach, spectroscopic experiments at variable temperature and absorption spectroscopy of aerosol particulates play an important role for the successful application of the data in dust astrophysics.

An ensemble of spherical particles with arbitrary dielectric permittivity and magnetic permeability was considered in the dipole approximation. Each particle was described by complex electric and magnetic polarizabilities. A computational approach based on the coupled dipole method, also called the discrete dipole approximation, was used to derive the optical force experienced by each particle due to an incident electromagnetic field and the fields scattered by all other particles. This approach is general and can handle material dispersion and losses. In order to illustrate this approach, we studied the case of two spherical particles separated by a distance d, and illuminated by an incident plane wave whose wave vector is normal to the axis of the particles. We computed the optical force experienced by each particle in the direction of the beam (radiation pressure), and perpendicular to the beam (optical binding) for particles with positive and negative refractive indices. We also considered the effect of material losses.

We studied the accuracy of the discrete dipole approximation (DDA) for simulations of absorption and scattering spectra by gold nanoparticles (spheres, cubes, and rods ranging in size from 10 to 100 nm). We varied the dipole resolution and applied two DDA formulations, employing the standard lattice dispersion relation (LDR) and the relatively new filtered coupled dipoles (FCD) approach. The DDA with moderate dipole resolutions is sufficiently accurate for scattering efficiencies or positions of spectral peaks, but very inaccurate for e.g. values of absorption efficiencies in the near-IR. To keep relative errors of the latter within 10% about 10⁷ dipoles per sphere are required. Surprisingly, errors for cubes are about 10 times smaller than that for spheres or rods, which we explain in terms of shape errors. The FCD is generally more accurate and leads to up to 2 times faster computations than the LDR. Therefore, we recommend FCD as the DDA formulation of choice for gold and other metallic nanoparticles.

The properties of gold and silver nanorods and nanodisks with geometric parameters typical of wet chemical fabrication protocols were investigated. With an extended-precision T-matrix code, a representative set of simulations for extinction, light scattering, and depolarization ratio spectra of randomly oriented particles and for dichroism and birefringence spectra of particles with an arbitrary predominant orientation with respect to incident linearly polarized light were obtained. The appearance of ultra-depolarized light scattering from random ensembles was elucidated by several 3D maps illustrating the dependence of the depolarization ratio on particular orientations of rods and disks. A simple dipole model sufficed to explain the orientation dependence of dichroism and birefringence and the unusual invariant spectral localization of the depolarization ratio maxima. Reasonable agreement was obtained with experimental data on depolarized light scattering from gold nanorods.

A few decades ago, Kerker et al. [J. Opt. Soc. Am. 73, 765-767 (1983)] theoretically pointed out the interesting possibility of conceiving small magnetodielectric spheres that may provide zero scattering in the forward direction, despite significantly larger scattering in any other direction. Recent experimental and theoretical papers on the topic have further discussed this possibility in more realistic scenarios. Inspecting some of their analyses, it seems indeed possible to conceive nanoparticles characterized by a scattering pattern with a sharp minimum, although not zero, in the forward direction. From a theoretical standpoint, however, it is well known that the total scattered power from any object has to be proportional to a portion of the scattered field in the forward direction, implying that very small or zero forward scattering should be synonymous to even smaller or zero total scattering, regardless of the nature of the object and of its design. Using analytical theory and an accurate scattering formulation, we clarify the nature of this apparent paradox and the limitations of this anomalous phenomenon in terms of particle size. In this way, we shed some new light on theoretical and experimental papers on the topic, identifying relevant missteps in some of their physical interpretation, and considering the general possibility of verifying these effects. This discussion may also be relevant to some cloaking applications using exotic artificial materials.

Craig Bohren has offered a million-dollar prize to anyone who can devise a detector that accepts scattered light but rejects diffracted light. This challenge was examined from a theoretical perspective by considering the scattering of red light by a spherical droplet of water with diameter 20 μm. Illumination of the droplet by short pulses (e.g. a duration of 5 fs) could allow a detector to distinguish between light scattered by various mechanisms, such as diffraction, transmission, reflections and surface waves. Although such techniques would not satisfy the precise terms of the challenge, the time domain approach can deliver remarkable insights into the details of the scattering processes.

Craig Bohren has enhanced science education in many ways, including email mentoring of non-scientists and scientists, informal science books, and science textbooks. I had numerous interactions with Bohren over a ten year period, and he influenced my own informal-science-education efforts, which include educational modules, science education posters, and curriculum reviews.

"The race is not to the swift, nor the battle to the strong, neither yet bread to the wise nor yet riches to men of understanding, nor yet favor to men of skill; but time and chance happeneth to them all." This in a nutshell describes the life and scientific career of Craig Bohren.

This PDF file contains the editorial “Special Section Editorial: Felicitations to Craig Frederick Bohren on his 70th Birthday” for JNP Vol. 4 Issue 01

Angular dependence of X-ray emission and absorption spectra was measured for both graphite and films of carbon nanotubes (CNTs) oriented perpendicular to the substrate surface. The ratio of intensities of Π and σ peaks in the X-ray spectra of CNT films was found to depend not only on the orientation of nanotubes but also on the orientation of graphite-like layers inside multi-walled nanotubes. Fluorescence measurement for the samples also showed the dependence on the degree of CNT alignment as well as on the texture of CNT layers. A possibility of X-ray photon propagation in CNTs in the conditions of anomalous dispersion near the C K-edge is discussed.

We studied the Raman intensities of the radial breathing mode(RBM) in carbon nanotubes excited resonantly into the first and second optical transitions of semiconducting nanotubes and the first transition of metallic nanotubes. Several variations in the maximum Raman intensities of different (n₁, n₂) nanotubes are observed from which we discuss the dependence on the nanotube family ν, the chiral angle θ and the optical transition E_ii. By comparison to theory we attribute variations with ν and θ to variations in the exciton-phonon coupling. Differences between different E_ii are dominated by variations in the linewidth of the optical transitions.

We investigated several proposals utilizing the unique electronic properties of carbon nanotubes (CNTs) for a broad range of applications to THz optoelectronics, including THz generation by Cerenkov-type emitters based on carbon nanotubes and by hot electrons in quasimetallic nanotubes, frequency multiplication in chiral-nanotube-based superlattices controlled by a transverse electric field, and THz radiation detection and emission by armchair nanotubes in a strong magnetic field. Dispersion equations of the electron beam instability and the threshold conditions of the stimulated emission have been derived and analyzed, demonstrating realizability of the nanotube-based nanoFEL at realistic parameters of nanotubes and electronic beams.

The problem of the electron tunneling through the interface carbon nanotube/ graphene in the presence of a strong oscillating electric field was considered. An approach was developed to overcome the standard restrictions of the Kubo theory. A system of equations for mean values of number of particles describing the tunneling process was obtained. The current-voltage characteristics for a weak external field were constructed. The case of strong exposing field was analyzed and compared with the weak external field approximation. Modulation of current in the presence of external oscillating field was found.

Structural and energy characteristics of the smallest magnetic endofullerene Fe@C₂₀ have been calculated using the density functional theory approach. The ground state of Fe@C₂₀ is found to be a septet state, and the magnetic moment of Fe@C₂₀ is estimated to be 8 Bohr magnetons. Characteristics of an (8,8) carbon nanotube with a single Fe@C₂₀ inside are studied in the framework of the semiempirical approach. The scheme of a magnetic nanorelay based on cantilevered nanotubes filled with magnetic endofullerenes is elaborated. The proposed nanorelay is turned on as a result of bending of nanotubes by a magnetic force. Operational characteristics of such a nanorelay based on (8,8) and (21,21) nanotubes fully filled with Fe@C₂₀ are estimated and compared to the ones of a nanorelay made of a (21,21) nanotube fully filled with experimentally observed (Ho3N)@C₈₀ with the magnetic moment of 21 Bohr magnetons. Room temperature operation of (21,21) nanotube based nanorelays is shown.

A linear augmented cylindrical wave method for calculating an electronic structure of the single-wall, double-wall, and embedded nanotubes is developed. The approximations are made in the sense of muffin-tin potentials and local-density-functional theory only. The method is implemented as a program package and applied to determine the total band structures and densities of states of the chiral and achiral, semiconducting and metallic both pure and copper intercalated tubules. The effect of As impurities on the electronic structure of the BN nanotubes demonstrates application of method to the non-carbon nanotubes.

The use of carbon nanotubes as optical probes for scanning near-field optical microscopy requires an understanding of their near-field response. As a first step in this direction, we investigated the lateral resolution of a carbon nanotube tip with respect to an ideal electric dipole representing an elementary detected object. A Fredholm integral equation of the first kind was formulated for the surface electric current density induced on a single-wall carbon nanotube (SWNT) by the electromagnetic field due to an arbitrarily oriented electric dipole located outside the SWNT. The response of the SWNT to the near field of a source electric dipole can be classified into two types, because surface-wave propagation occurs with (i) low damping at frequencies less than ~ 200-250 THz and (ii) high damping at higher frequencies. The interaction between the source electric dipole and the SWNT depends critically on their relative location and relative orientation, and shows evidence of the geometrical resonances of the SWNT in the low-frequency regime. These resonances disappear when the relaxation time of the SWNT is sufficiently low. The far-field radiation intensity is much higher when the source electric dipole is placed near an edge of SWNT than at the centroid of the SWNT. The use of an SWNT tip in scattering-type scanning near-field optical microscopy can deliver a resolution less than ~ 20 nm. Moreover, our study shows that the relative orientation and distance between the SWNT and the nanoscale dipole source can be detected.

We investigated the application of one-dimensional fluid model in modeling of electron transport in carbon nanotubes and equivalent circuits for interconnections and compared the performances with the currently used copper interconnects in very-large-scale integration (VLSI) circuits. In this model, electron transport in carbon nanotubes is regarded as quasi one-dimensional fluid with strong electron-electron interaction. Verilog-AMS in Cadence/Spectre was used in simulation studies. Carbon nanotubes of the types single-walled, multiwalled and bundles were considered for ballistic transport region, local and global interconnections. Study of the S-parameters showed higher transmission efficiency and lower reflection losses. Theoretical modeling and computer-aided simulation studies through a complimentary CNT-FET inverter pair, interconnected through a wire, exhibited reduced delays and power dissipations for carbon nanotube interconnects in comparison to copper interconnects in 22 nm and lower technology nodes. The performance of CNT interconnects was shown to be further improved with increase in number of metallic carbon nanotubes. Our study suggests the replacement of copper interconnect with the multiwalled and bundles of single-walled carbon nanotubes for the sub-nanometer CMOS technologies.

We formulated a hydrodynamic model in order to describe the dynamical behavior of the π- electrons in single carbon nanotube shells of arbitrary chirality, either metallic or semiconducting, below terahertz frequencies, as long as only intraband transitions of the π- electrons are allowed. The hydrodynamic equations were derived in a self-consistent way from the semiclassical Boltzmann equation. The electron fluid was taken to comprise many electron species, each characterized by a different effective mass, which takes into account the interaction with the nanotube ion lattice. A linear transport model for the π- electrons was derived from the hydrodynamic equations. A transmission line model was eventually formulated to describe the propagation of an electric signal along a single-wall carbon nanotube of arbitrary chirality. The transport model formulated can be also used for analyzing electromagnetic propagation in complex structures composed of single carbon-nanotube shells with different chirality, such as bundles of single wall carbon nanotubes and multi-wall carbon nanotubes, provided that the tunneling between adjacent shells may be disregarded.

This PDF file contains the editorial “Special Section Editorial: Carbon Nanotubes” for JNP Vol. 4 Issue 01

We investigated the morphology of polyethylene films by the Differential Evanescent Light Intensity (DELI) imaging method developed by us previously. The films were prepared by the Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. Rough or smooth organic layers were fabricated with thickness depending on the deposition conditions. We used the DELI imaging method here as a fast, low cost method for surface morphology diagnostics of large areas (i.e., hundreds of mm2) of nano layer polyethylene films.

We studied the propagation of plasmonic modes along planar multilayer metal-dielectric structures with finite number of bi-layer unit cells. The dispersion relations for various investigated waveguide structures with the multilayer core and symmetric or asymmetric cladding have been analyzed. In the case of symmetric metallic cladding we have found both TE and TM modes within the light cone, while TM modes only exist outside the light cone. Both symmetric and asymmetric dielectric claddings support modes outside the light cone and of TM-polarization only. Formation of photonic bands and gaps, the structure of their edge lines, and the behavior of modes that cross the edge lines has been investigated. In the subwavelength regime, we have found ordinary surface plasmon polariton dispersion in the forbidden gap that is created via coalescence of the two modes that cross the neighboring band-gap edges. One of those modes can exhibit negative group velocity.

We developed a device in which one can shift and control the position of a gold nanoparticle by using special type of optical tweezers realized by guiding and confining light in a nanosize void structure in which the nanoparticle is placed. The nanosize void is positioned inside a multimode interference (MMI) region of a silicon waveguide. The coupling of light from two opposite sides of the optical device generates standing interference waves in the MMI region. The relative phase between the two coupled beams is controllable and therefore also the position of the fringes of the standing waves. Evanescent tails coming from the guided standing waves interfere in the void and allow control the position of the trapped nanoparticle. A nanoparticle with diameter of 30 nm was experimentally implanted in the void. The particle was trapped by one of the high intensity evanescent fringes. Changing the relative phase between the two inputs to the chip allowed us experimentally to modify the location of the fringes and the position of the particle (similarly to what happens in optical tweezers). This experimentally demonstrated capability may be useful for all-optical nano modulators, sensors, wavelength converters, logic gates and even a state machine (e.g. a flip flop).

We investigated the cavity structure by the deformation of a unit cell of a Composite Metamaterial (CMM) structure. We considered different cavity structures with different resonance frequencies and Q-factors. We observed the Q-factor of the cavity resonance as 108 for a CMM based single cavity wherein the cavity structure is a closed ring structure. We investigated the reduced photon lifetime and observed that at the cavity resonance, the effective group velocity was reduced by a factor of 20 for a CMM based single cavity compared to the electromagnetic waves propagating in free space. Since the unit cells of metamaterials are much smaller than the operation wavelength, subwavelength localization is possible within these metamaterial cavity structures. We found that the electromagnetic field is localized into a region of /8, where is the cavity resonance wavelength. Subsequently, we brought two cavities together with an intercavity distance of two metamaterial unit cells and then investigated the transmission spectrum of CMM based interacting 2-cavity system. Finally, using the tight-binding picture we observed the normalized group velocity corresponding to the coupled cavity structure.

This PDF file contains the editorial “Guest Editorial: Selected Papers from the 2nd Mediterranean Conference on Nanophotonics” for JNP Vol. 4 Issue 01

Artificial molecular machines represent a growing field of nanoscience and nanotechnology. Stimulated by chemical reagents, electricity, or light, artificial molecular machines exhibit precisely controlled motion at the molecular level; with this ability molecular machines have the potential to make significant impacts in numerous engineering applications. Compared with molecular machines powered by chemical or electrical energy, light-driven molecular machines have several advantages: light can be switched much faster, work without producing chemical waste, and be used for dual purposes-inducing (writing) as well as detecting (reading) molecular motions. The following issues are significant for light-driven artificial molecular machines in the following aspects: their chemical structures, motion mechanisms, assembly and characterization on solid-state surfaces. Applications in different fields of nanotechnology such as molecular electronics, nano-electro-mechanical systems (NEMS), nanophotonics, and nanomedicine are envisaged.

Current fabrication and characterization techniques allow the development of nanostructured systems with controlled size, shape and composition. Additionally, modifications can be made to these nanosystems to better suit their integration with biological systems, leading to such interesting properties as enhanced aqueous solubility, biocompatibility or bio-recognition. The particular morphology and overall properties of nanostructured porous silicon allow the use of this material in the fields of drug delivery, eye diseases, tumor imaging, and tissue engineering.

In the past two decades, nanotechnology has made great progress in generating novel materials with superior properties. Quantum dots (QDs) are an example of such materials. With unique optical properties, they have proven to be useful in a wide range of applications in life sciences, especially as a better alternative to overcome the shortcomings of conventional fluorophores. Current progress in the synthesis of biocompatible QDs allows for the possibility of producing a large variety of semiconductor nanocrystals in terms of size, surface functionality, bioconjugation, and targeting facilities. Strategies to enhance the water-dispersibility and biocompatibility of these nanoparticles have been developed, involving various encapsulation techniques and surface functionalization. The major obstacle in the clinical use of QDs remains their toxicity, and the systematic investigation on harmful effects of QDs both to humans and to the environment has become critical. Many examples of the experimental use of QDs prove their far-reaching potential for the study of intracellular processes at the molecular level, high resolution cellular imaging, and in vivo observation of cell trafficking. Biosensing methods based on QD bioconjugates proved to be successful in rapid detection of pathogens, and significant improvements are expected in early cancer diagnostic, non-conventional therapy of cancer and neurodegenerative diseases.

Carbon nanotubes (CNT) were synthesized using a DC thermal plasma method. Nanotubes from the cathode were analyzed by electron microscopy and were then studied for their field emission properties. The CNTs were deposited on a tungsten wire, which acted as the cathode. The main aim was to push the distance between the electrodes outside those previously attempted. The field emission current was measured using a phosphorous coated ITO (indium tin oxide) glass plate. Images of the field emitted electrons impinging on the phosphorous screen were also recorded and analyzed. The I-V curves for the field emission were recorded at various distances between the electrodes. Similar studies were performed for commercially obtained (from two different sources) single-walled carbon nanotubes and the results compared with the as-produced nanotubes.

Numerical simulation of fluorescence correlation spectroscopy (FCS) based on near-field scanning optical microscopy (NSOM) was performed. A finite-difference time-domain method was employed to calculate the electric field distribution in the vicinity of the NSOM aperture and the Brownian motion of nanoparticles was reproduced by a Monte Carlo simulation. The physical validity of the simulation result was confirmed by comparing it with a theoretical calculation using a Gaussian observation volume, which is applied to FCS based on conventional optical microscopy.

The negative refraction inside two dimensional (2D) photonic crystals (PC) and homogeneous structures was studied numerically by inserting a point source inside the negative index part of these materials. The three-dimensional (3D) counterparts of these structures, the synthetic opal, were examined experimentally by infiltrating them with CdS quantum dots (QDs). Confocal microscopy measurements in which we tracked the infiltration of the QDs inside the opal indicate the focusing of light emitted by QDs, which can be due to negative refraction occurring at the opal/glass interface. The formation of a focus can be an indication of the negative refraction happening in these synthetic opals in the [111] direction in its higher photonic band, above the photonic band gap (PBG). This result is very promising because, until now, negative refraction has not been seen in 3D photonic crystals in the visible region of light. This result was made possible due to the use of infiltrated QDs as internal light sources inside the porous photonic crystal, which appears to be a very useful technique for the study of other negative-index materials (NIM) effects. Finally, the possibility of self-focusing of second harmonic by QD in nonlinear opal was developed.

We study light transmission through individual and arrays of sub-wavelength metallic apertures of conical shape as a function of their taper angle. With a fixed aperture size at the substrate, there is a dramatic increase in light throughput with increasing taper angle. Similar behaviors hold when considering the intensity enhancement inside the aperture near the substrate interface, where more than four-fold increase can be obtained. When arranged in regular arrays, apertures can interact via surface waves, creating distinct minima and maxima in light transmission and intensity enhancement. The effect of aperture taper is also to dramatically increase light transmission and intra-aperture intensity, but with a red shift in the maxima and negligible shift in the minima. The use of conical apertures should improve the efficiency of nonlinear optical processes as well as applications of light harvesting, such as biomolecule detection.

The canonical problem of the propagation of surface-plasmon-polariton (SPP) waves localized to the planar interface of a metal and a sculptured nematic thin film (SNTF) that is periodically nonhomogeneous along the direction normal to the interface was formulated. Solution of the dispersion equation obtained thereby confirmed the possibility of exciting multiple SPP waves of the same frequency or color. However, these SPP waves differ in phase speed, field structure, and the e-folding distance along the direction of propagation.

We recently introduced an all-optical method for grafting onto the apex of an optical tip a single 20 nm nanodiamond with single color-center occupancy and used the resulting single-photon tip in scanning near-field imaging at room temperature, thereby achieving a genuine scanning single-photon microscopy working in ambient conditions. A variant of this method is described that allows for attaching several nanodiamonds onto the tip apex, releasing them all at once and finally recapturing them one by one by the scanning tip. This underlines the flexibility and powerfulness of our method and its variant that could be used in applications where a fixed number of selected optically active nano-objects requires positioning, or repositioning, at well defined locations with nanometer accuracy.

The local perturbation method has been applied to investigate wave propagation in a homogeneous medium with an arbitrary number of local perturbations (LP), which are characterized by a time and spatial dispersion giving rise to the occurrence of several types of waves. The equation for propagating waves has been formulated and solved. The eigen frequencies of a medium with one or two local perturbations, the temporal attenuation of the eigen oscillations and the spectrum of photon crystals with two LPs in cell are obtained.

We considered the confinement of N_e interacting electrons in a two-dimensional disk shaped quantum dot (QD) and a one-dimensional quantum ring (QR) when an external magnetic field B perpendicular to the device plane is applied. The energy spectra of low-lying states of the nanodevices as functions of B and N_e were obtained by using an Hartree Fock approximation. Phase diagrams in the interaction versus magnetic field plane indicate a rich variety of ground states.

We revisited the problem of the existence of plasmonic modes guided by metal-dielectric-metal slot waveguides. For the case of lossless slot waveguides, we classify the guided modes in the structure with the metal dispersion and found that, in a certain parameter range, three different guided modes coexist at a fixed frequency, two (symmetric and antisymmetric) forward propagating modes and the third, backward propagating antisymmetric mode. We study the properties of the forward and backward plasmonic guided modes in the presence of realistic losses, and discuss the importance of evanescent modes in lossy structures.

The Bruggeman formalism provides an estimate ε^Br_hcm of the relative permittivity of a homogenized composite material (HCM), arising from two component materials with relative permittivities ε_a and ε_b. It can be inverted to provide an estimate of ε_a, from a knowledge of ε^Br_hcm and ε_b. Numerical studies show that the inverse Bruggeman estimate ε_a can be physically implausible when (i) Re{ε^Br_hcm}/Re {ε_b} > 0 and the degree of HCM dissipation is moderate or greater; or (ii) Re{ε^Br_hcm}/Re {ε_b} < 0 regardless of the degree of HCM dissipation. Furthermore, even when the inverse Bruggeman estimate is not obviously implausible, huge discrepancies can exist between this estimate and the corresponding estimate provided by the inverse Maxwell Garnett formalism.

Experiments were conducted to demonstrate a material with epsilon near zero (ENZ). Dimensions estimated by effective medium theory guided the fabrication of nanolaminate composites of silver and amorphous polycarbonate. This approach ensures that the ordinary component (not the extraordinary component) of the relative permittivity of a uniaxial material equals zero. The nanolaminates were characterized for optical properties using spectroscopic ellipsometry, reflectance, and transmittance. Simulations using both, a new scattering retrieval method, and an effective-medium approximation (EMA) were compared to the experimental results. These results indicate that nanolaminates should enable further exploration into the new optical phenomena predicted for ENZ materials.

Non-interaction of waves (NIW) in the linear domain is an unappreciated but general principle of nature. Explicit recognition of this NIW-principle will add renewed momentum to the progress of fundamental physics and related technologies like spectrometry, coherence, polarizations, laser mode-locking, etc. This principle helps us appreciate that the mathematical correctness of a theorem and its capability to predict certain groups of measured data, do not necessarily imply that the theorem is always capable of mapping real interaction processes in nature. The time-frequency Fourier theorem (TF-FT) is an example since superposed light beams, by themselves, cannot reorganize or sum their energies. Quantum Mechanics (QM) correctly discovered that photons (light beams) are non-interacting bosons. Yet, to accommodate (i) the classical belief that light beams interfere (interact) by themselves, and (ii) Einstein's heuristic hypothesis that discrete packets of energy emitted by molecules travel as indivisible quanta (contradicting spontaneous diffractive spreading), QM has been forced to hypothesize that a photon interferes only with itself. In reality, it is the quantized detecting material media that make the superposition effects become manifest as their physical transformations, from bound electrons to released photoelectrons, after absorbing energy from all the beams due to induced simultaneous stimulations by the beams.

Mesoporous materials, such as porous silicon and porous polymer gratings (Bragg structures), offer an attractive platform for the encapsulation of chemical and biological recognition elements. These materials include the advantages of high surface to volume ratio, biocompatibility, functionality with various recognition elements, and the ability to modify the material surface/volume properties and porosity. Two porous structures were used for chemical and biological sensing: porous silicon and porous polymer photonic bandgap structures. Specifically, a new dry etching manufacturing technique employing xenon difluoride (XeF2) based etching was used to produce porous silicon Porous silicon continues to be extensively researched for various optical and electronic devices and applications in chemical and biological sensing are abundant. The dry etching technique to manufacture porous silicon offers a simple and efficient alternative to the traditional wet electrochemical etching using hydrofluoric acid. This new porous silicon material was characterized for its pore size and morphology using top and cross-sectional views from scanning electron microscopy. Its optical properties were determined by angular dependence of reflectance measurements. A new class of holographically ordered porous polymer gratings that are an extension of holographic polymer dispersed liquid crystal (H-PDLC) structures. As an alternative structure and fabrication process, porous polymer gratings that include a volatile solvent as the phase separation fluid was fabricated. Porous silicon and porous polymer materials were used as substrates to encapsulate gaseous oxygen (O2) responsive luminophores in their nanostructured pores. These substrate materials behave as optical interference filters that allow efficient and selective detection of the wavelengths of interest in optical sensors.

We examined materials which are homogeneous and which posses a negative index of refraction in (10-100) THz frequency range based on the following two ideas. Firstly, there are materials such as magnetic semiconductors (e.g. In2-xCrxO3,), and 3D transition metals (Fe, Ni), in which the high-frequency spin wave modes coexist with the plasmonic modes. Consequently, the spin wave mode, along with the plasmonic mode, are activated by the electromagnetic field of the light, with simultaneous negative permittivity and permeability responses at the edge of the Brillouin zone of the magnon spectra. This permeability response is weakly space-dispersive and anisotropic in the case of a single crystal, and is fully isotropic in a polycrystal with a small grain size. As a result, the polycrystalline material exhibits the negative refractive index effect within the narrow frequency band close to the ferromagnetic resonance. Secondly, based on methods of quantum optics, we investigated the possibility of achieving the negative index of refraction in a doped semiconductor. The quantum states of a hydrogen-like donor atom and states of an electron in the conduction band constitute a discrete-level atomic medium, and the coupling of an electric dipole transition with a magnetic dipole transition leads to coherent permeability and permittivity responses which results in the negative index effect. This scheme was implemented with tin-zinc-doped indium oxide, In2-xSnxO3 :Zn, and calculations show feasibility of this effect with a figure of merit (FOM) greater than 10.

A major problem of current silicon thin film solar cells lies in low carrier collection efficiency due to short carrier diffusion length. Instead of improving the collection efficiency in a relatively thick solar cell, increasing light absorption while still keeping the active layer thin is an alternative solution. Absorption enhancement in a thin film Si solar cell by incorporating a two-dimensional periodic metallic nanopattern was investigated using three-dimensional finite element analysis. By studying the enhancement effect brought by different materials, dimensions, coverage, and dielectric environments of the metal nanopattern, we found that absorption enhancement occurs at wavelength range outside surface plasmons resonance of the nanostructures. The exploitation of the nanostructures also enhances the Fabry-Perot resonance in the active layer. It plays an important role in optimizing the absorption of the solar cell.

Fluorescence intensity changes were investigated theoretically and experimentally using self-assembled colloidal structures on silver semitransparent mirrors. Using a simplified quasi-static model and finite element method, we demonstrate that near-field interactions of metallic nanostructures with a continuous metallic surface create conditions that produce enormously enhanced surface plasmon resonances. The results were used to explain the observed enhancements and determine the optimal conditions for the experiment. The theoretical parts of the studies are supported with reports on detailed emission intensity changes which provided multiple fluorescence hot spots with 2-3 orders of enhancements. We study two kinds of the fluorophores: dye molecules and fluorescent nanospheres characterized with similar spectral emission regions. Using a lifetime-resolved fluorescence/reflection confocal microscopy technique, we find that the largest rate for enhancement (~1000-fold) comes from localized areas of silver nanostructures.

Low dimensional europium (Eu³+)-doped gadolinium oxide (Gd2O₃) lanthanide nanostructures are synthesized by an effective and simple coprecipitation process followed by subsequent heat treatments. Transmission electron microscope (TEM) images indicate Eu³+-doped Gd2O₃ nanostructures undergo significant morphological changes from nanorods to nanoparticles during thermal treatments. Nanostructures with different morphology, including nanotubes, strongly influence the photoluminescence properties. The dependence of luminescence lifetime on morphological nature of the nanostructures demonstrates that the one dimensional nanostructures such as nanorods and nanotubes have higher emission intensity with shorter lifetime. Our analysis suggests that the morphological transformation of the nanostructures plays the most important role in the behavior of radiative and nonradiative relaxation mechanisms, resulting in the overall photoluminescence properties.

We study the performance of quantum well infrared photodetectors (QWIPs) in the case of infrared irradiation. This type of photodetector is interesting from the point of view that QWIPs have numerous advantages over photodetectors based on HgCdTe in terms of large array size, high uniformity, high yield, radiation hardness and lower cost of the systems. Therefore, it is important to evaluate their characteristics theoretically. We develop a simple modeling for this interesting type of photodetector. This model describes a nontrivial evaluation of the most important characteristics. The potential distribution of the developed model is obtained by self-consistently solving the Poisson equation. On the other hand, it is used to calculate the dark current, responsivity and detectivity as a function of the structural parameters. These parameters are the spacing between the wells, the number of quantum wells and the operating temperature. Also, the optimization of the characteristics of QWIPs is of primary concern. The effect of uniformity of the dopant density in the QWIP is studied theoretically. We find that the uniformity of the dopant distribution in the plane of QW decreases the dark current.

Theoretical analysis of lasing instability in quantum-cascade lasers was carried out. A mid-infrared quantum-cascade laser structure with triple resonance levels was chosen as the prototype of the lasing medium with high Kerr nonlinearity from optical transitions. The self-phase modulation effect induced by Kerr nonlinearity was found to possibly change the unstable frequency domain significantly, i.e., not only broaden the unstable domain but also drive it from single-mode to multi-mode. The instability mechanisms of quantum-cascade lasers include one like the coherent multi-mode Rishen-Nummedal-Graham-Haken instability and the spatial-hole-burning-induced single-mode instability.

The recent interest in the imaging possibilities of photonic crystals (superlensing, superprism, optical mirages, etc.) call for a detailed analysis of beam propagation inside a finite periodic structure. An answer to the following question was sought: "Where does the beam emerge?" We found that, contrary to common knowledge, it is not always true that the shift of a beam is given by the normal to the dispersion curve. This phenomenon can be explained in terms of evanescent waves and a renormalized diagram yields the correct direction.

For weak luminescence, quenching of insensitive luminophores by proximity to a gold film improves signal to noise by suppression of background luminescence of Ru(4,7-diphenyl-1,10-anthroline)₃Cl₂. Initially it was expected that the effects of gold film quenching and nanoparticle enhanced luminescence could be combined to give a summative improvement, but the increase caused by the nanoparticles generates a larger signal to noise ratio and greater sensitivity of those luminophores to the dynamic quenching by gaseous oxygen. Impressive detection limits were achieved on gold coated glass and plain glass, where detection limit was 0.05% and 0.004% and sensitivity 0.02 and 0.05%, respectively.

Tb³⁺ and Ag co-doped glass nano-composites were synthesized in a glass matrix Li₂O-LaF₃-Al₂O₃-SiO₂ (LLAS) by a melt-quench technique. The growth of Ag nanoparticles (NPs) was controlled by a thermal annealing process. A broad absorption band peaking at about 420 nm was observed due to surface plasmon resonance (SPR) of Ag NPs. The intensity of this band grows with increasing annealing time. The transmission electron microscopic image (TEM) reveals the formation of Ag NPs in glass matrix. Photoluminescence (PL) emission and excitation spectra were measured for glass samples with different Ag concentrations and different annealing times. Plasmon enhanced Tb³⁺ luminescence was observed at certain excitation wavelength regions. Luminescence quenching was also observed for samples with high Ag concentration and longer annealing time. Our luminescence results suggest that there are two competitive effects, enhancement and quenching, acting on Tb³⁺ luminescence in the presence of Ag NPs. The enhancement of Tb³⁺ luminescence is mainly attributed to local field effects due to SPR. The quenching of luminescence suggests an energy transfer from Tb³⁺ ions to Ag NPs.

We examined a concentric Si nanocrystal (Si-nc) and Er doped SiO₂ (Er:SiO₂) microdisk structure supporting high-Q whispering gallery modes (WGMs) at both visible and telecom wavelengths. This structure provides a means to utilize Si-nc luminescence as an optical pump for an Er:SiO₂ cavity without subjecting a telecom-wavelength, Er:SiO₂-based mode to loss mechanisms associated with the Si-nc material. After fabricating a concentric microdisk consisting of an inner Si-nc disk and an outer Er:SiO₂ ring, we characterize visible wavelength WGMs excited by the Si-nc photoluminescence and observed spectrometer limited quality factors as high as 10³. Telecom wavelength photoluminescence from the Er:SiO₂ ring was measured to have a quality factor as high as 10⁴ in the erbium luminescence region using a passive pulled fiber setup.

Physical vapor deposited nickel catalyst layers of 10, 50, 100, 200, 350, and 500 angstroms were granulated using hydrogen plasma for varying times to determine an effective carbon nanotube (CNT) growth process using microwave plasma enhanced CVD (MPECVD). Nickel was deposited via sputtering or evaporation. The catalyst granule size, density, and resulting CNTs were analyzed. Sputtered nickel of 50 angstroms with 5 minutes of hydrogen plasma pretreatment resulted in the most effective CNT growth.

Experimental studies of the absorption spectra of CdBr₂-Ag photochromic crystals revealed several absorption bands positioned close to the intrinsic absorption edge. It is suggested that impurity silver ions, neutral silver atoms and intrinsic lattice defects form nanoclusters which are responsible for the absorption peaks within the transparency range of the crystal. The effect of UV radiation on the absorption profile is also discussed in the framework of the proposed model.

Semi-continuous silver film templates are fabricated by focused ion beams (FIB), and surface-enhanced Raman scattering spectra from C60-fullerene deposited on these templates are recorded. Films of silver deposited by thermal evaporation are dry-etched by the ion beams with various etching times. The films tend to become semi-continuous as the etch-time increases. The Raman spectra of C60 show an increase in intensity upon correction with a silver coverage area for increasing etch-times. Increase in Raman intensity is due to the sharp edges of the FIB-etched semi-continuous templates, and the moderate enhancements are attributed to dissipation induced by gallium incorporation. A maximum enhancement factor of about 4×106 is observed, which is comparable with other experimental values. Controlling gallium incorporation during processing or by post processing treatments is being explored, which can help increase the enhancement factor.

Near-field intensity distributions in inhomogeneous silver nanostructures were investigated using near-field optical microscopy. By varying the metallic concentration and the excitation wavelength, different plasmon scattering regimes were addressed and identified using statistical analysis tools such as the probability density function and intensity auto-correlation function. The intensity correlation length was found to indicate an intermediate regime where both surface scattering and plasmon localization coexist on the same scale.

Three-dimensionally ordered photonic crystals were grown using self-assembly technique from Rhodamine-B dye doped polystyrene micro-spheres resulting in a stop band at 611 nm overlapping the emission spectrum of the dye. When excited at a wavelength away from the stop band, using a frequency-doubled Nd:YAG laser, the crystal showed angle-dependent suppression of spontaneous emission of the dye in the wavelength range of the photonic stop band and enhancement at the band edge, in reflection and transmission geometries. Spectral narrowing, a sharp threshold and a highly directional emission, all indicative of stimulated emission, were observed from the active photonic crystal matrix.

Analytic formulas for spherical nanoshell (Au/silica) resonance wavelength and refractive index sensitivity were derived and compared with a numerical nonlinear theory. A universal scaling law was deduced in terms of a normalized thickness defined by the ratio of the shell thickness and its core diameter. The calculated figure of merit shows a maximum at an optimal value of the resonance wavelength and normalized thickness. The nonlinear theory of nanoshells improves the accuracy of the linear theory in the short wavelength regime (500 to 650 nm).

This PDF file contains the editorial “Editorial: Sustainability research and sustainable research” for JNP Vol. 4 Issue 01

This PDF file contains the editorial “Editorial: Very unique omelet concocted by a head chef is a revolutionary breakthrough” for JNP Vol. 4 Issue 01