We have developed a near-field optical probe by introducing the metallized pyramidal structure of a Si probe with a slit-shaped tip for high-density optical storage. Numerical analysis using the finite-difference time-domain method showed that the optical spot generated at the aperture measured 13×30 nm. We fabricated a slit-type Si probe and evaluated the spot size using fluorescence imaging of a single dye molecule. The full-width at half maximum of the signal profiles was 16 nm×26 nm, which corresponds to a data density of 1.5 Tbit/in2. Furthermore, a large extinction coefficient depending on the polarization was confirmed.

We fabricated a 50-nm-wide slit on a glass substrate using the lift-off process with a bilayer resist including Cr. The nanometric slit is designed for detecting a small number of neutral atoms in the ground state with high spatial accuracy by way of two-step photoionization with two-color near-field lights. Conducting the finite difference time domain simulations, we drew the spatial profiles of near-field lights generated in the vicinity of the slit for both cases of normal illumination and total-internal reflection (TIR) illumination with a linearly polarized light beam. In the slit-parallel-incident TIR configuration with s-polarization, we obtained a good throughput of 1.1 x 10-2 and the highest extinction ratio of 2.2 x 10-7 for a wavelength of 780 nm. In this case, the ionization efficiency of low-energy 87Rb atoms in the 5S1/2 hyperfine state is estimated to exceed 1%.

Using illumination-collection mode optical near-field spectroscopy, a a spectral shift of photoluminescence of silicon (Si) nanocrystals compared with the far-field measurement was observed, due to the near-field coupling of the Si nanocrystals and the probe.

By combining dedicated near-field generation and detection techniques with Raman spectroscopy, optically inactive phonon activity is predicted. Observation of these phonons opens a new era as a novel analytical technique beyond near-field microscopy/spectroscopy which has previously only been concentrated on obtaining higher spatial resolution. As a possible example of optically inactive phonon observation, measurement of a Raman spectrum of polydiacetylene was demonstrated.

Progress in nanophotonics in Japan emphasizes that the true nature of nanoophotonics is to realize "qualitative innovation" in photonic devices, fabrication techniques, and system design by utilizing novel functions and phenomena caused by optical near-field interactions. Such innovation and the evolution into related sciences are exemplified. Nanophotonics research is being undertaken in Japan through several academic initiatives as well as national projects.

Exciton energy transfer between quantum dots via an optical near-field and subsequent dissipation was observed. Two sizes of CdSe/ZnS quantum dots with resonant energy levels were mixed to confirm the energy transfer and dissipation using time-resolved photoluminescence spectroscopy. It was estimated that the energy transfer time was 135 ps, which is shorter than the exciton lifetime of 2.10 ns. This indicates that CdSe quantum dots are promising material for nanophotonic devices.

The nonuniform distribution of nitrogen in dilute GaInNAs alloys was investigated by low-temperature near-field photoluminescence (PL) imaging spectroscopy of localized states driven by giant band-gap reduction due to nitrogen incorporation. The depths and spatial profiles of exciton confinement potential were visualized through the measurement of power-dependent PL spectra and high-resolution PL images. For two GaInNAs quantum wells with different nitrogen contents, we observed strongly localized excitons confined in nitrogen clusters and rather delocalized excitons, which indicate the onset of alloy formation.

Photons and electrons are the key quantum media for the quantum information processing based on solid state devices. The essential ingredients to accomplish the quantum repeater were investigated and their underlying physics were revealed. The relevant elementary processes of the quantum state transfer between a single photon and a single electron were analyzed, to clarify the conditions to be satisfied to achieve the high fidelity of the quantum state transfer. An optical method based on the Faraday rotation was proposed to carry out the Bell measurement of two electrons which is a key operation in the entanglement swapping for the quantum repeater and its feasibility was confirmed. Also investigated was the quantum dynamics in the electron-nuclei coupled spin system in quantum dots and a couple of new phenomena were predicted related to the correlations induced by the hyperfine interaction, namely, bunching and revival in the electron spin measurements. These findings will pave the way to accomplish the efficient and robust quantum repeater and nuclear spin quantum memory.

Highly homogeneous arrays of Ag, Au and Cu nanorods were fabricated on glass substrates using electron-beam lithography and lift-off techniques. Optical properties of the fabricated structures related to localized surface plasmons (LSP), and their dependencies on the nanorod size were studied experimentally by optical extinction spectroscopy. Spectral tuning of LSP resonant scattering bands in a wide spectral range, from visible to near-infrared wavelengths, can be accomplished by tailoring of the nanorod dimensions, aspect ratios, and heights. The observed results qualitatively agree with Gans theory and numerical modeling by finite-difference time-domain technique.

We have developed new type of photolithography based on a nonadiabatic photochemical process that exposes an ultraviolet-photoresist using a visible optical near field. Investigating the exposure dependence of the developed depth using nonadiabatic photolithography, we found that the depth increased with the exposure threshold. To explain this result, the optical field intensity was simulated by using the finite-difference time-domain method. The evolution of the developed depth was proportional to the optical field intensity and its spatial gradient, agreeing closely with the simulated result that took into account the nonadiabatic processes. Another experimental result is to support our explanation, that in nonadiabatic photolithography, a component of the exposure progresses inside the photoresist.

A high signal-to-noise ratio in a surface plasmon resonance (SPR) sensor was achieved using a monolithic prism sensor chip. To achieve this, a multi-differential detection technique that uses a wavelength-stabilized laser diode with optical feedback was developed. To achieve easy exchange of the sensor chip and high accuracy of measurement, the monolithic prism sensor chip was fabricated from plastic with low photo-elasticity by the injection molding method. The resolution of our sensor system was estimated to be ‹10-7 refractive index unit. The potential of the developed sensor is very high for biosensing.

We have demonstrated hybrid recording on magnetic bit-patterned media by a near-field optical head with plasmon probe. The near-field plasmon probe "nanobeak" that uses a triangular metallic plate with a three-dimensionally tapered apex can provide a highly efficient optical spot as small as 16 nm x 20 nm. The bit-patterned media consist of a Co (0.3 nm)/Pd (0.7 nm) multilayer of 20-nm-thick magnetic nanodots each with a diameter of 20 nm and a period of 30 nm. We confirmed magnetic single-dot recording on the Co/Pd bit-patterned media. Hybrid recording simulation results suggest that hybrid recording on bit-patterned media can achieve significant data-density recording, even when the magnetic dot size is less than 5 nm. For practical use, we made a prototype of nanodot circularly aligned Co/Pd bit-patterned media, and also demonstrated light delivery method using either solid immersion optics or an optical fiber.

Glycerol/water microdroplets take almost spherical shapes when standing on a superhydrophobic surface. Hence they are suitable to function as optical microcavities. Using Rhodamine B doped water microdroplets, large spectral tunability of the whispering gallery modes (WGMs) (>5 nm) was observed. Tunability was achieved by evaporation/condensation in a current controlled mini humidity chamber. Experiments revealed a mechanism stabilizing the volume of these microdroplets with femtoliter resolution. The mechanism relied on the interplay between the condensation rate that was kept constant and the size dependent laser induced heating. The radii of individual water microdroplets (>5 µm) stayed within a few nanometers during long time periods (several minutes). By blocking the laser excitation for 500 msec, the stable volume of individual microdroplets were changed stepwise. Laser emission was also observed from Rhodamine B doped glycerol/water microdroplets using a pulsed, frequency-doubled Nd:YAG laser (=532 nm) as the excitation source. The observed largely tunable WGMs and laser emission can pave way for novel applications in optical communication systems. Besides due to the sensitivity of the WGMs to the size and shape of the microdroplets, the results can find applications in characterizing superhydrophobic surfaces and investigating liquid-solid surfaces.

A new approach allows the realization of an electro-optical modulator or a transistor that is integrated on a silicon chip. The operation principle includes the realization of optical multimode interference (MMI) as the operation core of an electro-optical metal-oxide-semiconductor (MOS) field effect transistor (FET). Externally applied voltage generates a depletion region as well as layer of inversion which is full with free carriers. The free carriers vary the relative phase shift as well as the attenuation of one arm of the interferometer due to the plasma dispersion effect in silicon. This variation allows breaking the balance of the mode conversion and results with amplitude modulation in the output of the MMI region. The device does not have high finesse resonance and yet its overall length is only about 18 µm.

A new microscopy method for multi diffraction-limited spot illumination is based on extraordinary light transmission through a periodic metal grid (typical period of 600 nm) of sub-wavelength holes (150 nm). Multiple spots illuminate a fluorescently labeled sample and the emission is collected by far-field optics. Theoretical comparison with a confocal microscope reveals equivalent spot sizes and a scanning method with the advantage of multiple illumination spots. The system is used to measure the actual transmitted field with a fluorescent sample in far-field. The obtained results are consistent with the theoretical prediction and provide a proof of concept of the midfield microscope.

Whispering gallery modes of a microdisk resonator are useful for the optical detection of single rubidium and cesium atoms near the surface of a substrate. Light is coupled into two high-Q whispering-gallery modes of the disk which can provide attractive and/or repulsive potentials, respectively, via their evanescent fields. The sum potential, including van der Waals/Casimir-Polder surface forces, may be tuned to exhibit a minimum at distances on the order of 100 nm from the disk surface. Simultaneously optically trapping and detecting is possible, with the back-action of an atom held in this trap on the light fields being suffciently strong to provide a measurable effect. Atom trapping and detection depend on a variety of system parameters and experimental realizations differ for different atoms.

Circular resonators are key elements, essential for research involving highly confined fields and strong photon-atom interactions such as cavity QED, as well as for practical applications in optical communication systems, biochemical sensing and more. The main characteristics of such resonators are the Q-factor, the free spectral range (FSR) and the modal volume, where the last two are primarily determined by the resonator radius. The Total-Internal-Reflection (TIR) mechanism employed in"conventional" resonators couples between these characteristics and limits the ability to realize compact devices exhibiting large FSR, small modal volume and high Q. Recently, a new class of annular resonator, based on a single defect surrounded by radial Bragg reflectors, has been proposed and analyzed. The radial Bragg confinement decouples the modal volume and the Q and paves a new way for the realization of compact and low loss resonators. Such properties as well as the unique mode profile of the annular Bragg resonators (ABRs) make this class of devices an excellent tool for ultra-sensitive biochemical detection as well as for studies in nonlinear optics.

Resonant and non-resonant phenomena in grating based photonic structures were investigated as biological and biochemical sensors particularly for water contaminants. Detectivity on the order of 10-6 RIU was found to be possible. Spectroscopic scatterometry in conical mounting at normal incidence was found to offer high sensitivity and it allows specificity in addition to refractive-index-variation measurement.

Nanocomposites that incorporate TiO2 and ZnO nanoparticles separately in three-dimensional solgel matrices through full chemical integration are prepared to perform highly efficient photocatalytic activities for applications of environmental decontamination. Spectral responses of photocatalytic TiO2 and ZnO nanoparticles exposed to UV activation for self-cleaning process were obtained as also their optical relative spectral efficiency curves from 270 to 370 nm in the UV regime. Our investigations of the optimal conditions to increase their spectral photocatalytic efficiencies resulted in remarkably high levels of optical recovery and efficiency.

We developed a technique for the fabrication of 1D and 2D periodic structures in thin gold and silver films by irradiation with two and four intersecting beams of a nanosecond pulsed laser. The periodically alternating intensity distribution caused by interference induces mass transfer in thin metal films. The mechanisms and kinetics of mass transfer depend on the film thickness, morphology, and laser intensity. In the films thinner than some transitional value, h*, redistribution of material between "hot" and "cold" regions on the substrate occurs as a result of melting and beading of the film in "hot" regions and subsequent motion of liquid drops towards "cold" regions in the optically induced temperature gradient. In the films thicker h* redistribution of the film material occurs by hydrodynamic flow of the molten film in the temperature gradient, with subsequent crystallization in the "cold" regions and formation of tall and narrow ridges or rims. Theoretical models were developed that allowed us to calculate the time dependent temperature distributions around irradiated regions of the film. From the temperature distributions we calculated the expected speed of liquid beads, as well the distances between the ridges, the rim diameters and found good agreement with the measured values.

Two dimensional (2D) left-handed metamaterials (LHM) exhibiting negative refraction and subwavelength imaging are studied experimentally. A left-handed transmission band is observed at the frequencies where both dielectric permittivity and magnetic permeability are simultaneously negative. 2D LHM structure is verified to have a negative refractive index by measuring the refraction through a prism-shaped sample. Subwavelength focusing is observed by using a flat LHM superlens.

Plasmons are collective oscillations of electrons that have been exploited in many applications by manipulating and guiding light at resonant frequencies. The transition from understanding the origin and fundamentals of surface plasmon resonance to its many revolutionary applications has been intriguing. Advances in nanofabrication techniques over the last few years have led to variety of applications such as high-resolution plasmon printing, nanoscale waveguides, biodetection at the single-molecule level and enhanced transmission through sub-wavelength apertures, which are all examples of plasmon-assisted nanophotonics. Fundamental aspects of the surface plasmon resonance underlie enticing applications in nanophotonics.

In recent years the concept of "colloidal devices" has emerged. These include colloidal crystals with photonics properties, as well as displays, machines, and other assemblies having a particular purpose. The assembly of colloidal devices, or even simpler assemblies, can proceed with top-down approaches, applied fields, bottom-up approaches, or combinations of these. Bottom-up assembly, in which the particles have "colloidal force information" encoded chemically on their surfaces and interiors, appears to be especially suited for larger-scale production. The encoded information directs how the particles assemble and function, and a simple example is a colloidal crystal that has purely repulsive forces between all the particles. A richer assembly process can occur with site-specific chemistry, which sometimes occurs naturally on particles, such as when a particle has two different crystal faces. And in recent years, researchers have developed techniques for intentionally placing site-specific chemistry on particles, enabling assembly to proceed through localized electrostatic, van der Waals, depletion, hydrophobic, and receptor-ligand forces. Site-specific colloidal forces are useful in effecting colloidal and nanocolloidal assembly for state-of-the-art and future structures and devices.

The recent development of new types of light-activated, conformation-changing polymers has stimulated much interest. These 'smart' materials offer new functionalities and may enable diverse novel devices. One possible application of these substances may be in optically-driven nanoscale actuators, especially in the case of devices in which a plasmon resonance in a precious-metal nanostructure is actively modulated. A one-way or two-way shape memory effect is possible, however, application at the nanoscale will necessitate certain design changes. Nanoscale devices based on these materials could conceivably be used for drug-release or to switch the spectral selectivity of a coating.

The attempt to integrate photonic dynamic devices with microelectronic circuits is becoming a major scientific as well as industrial trend. Such integration is important since currently processing is mainly done with microelectronic chips but transmission, especially for long distances, is done over optical links. We review the common physical effects that support various photonic dynamic devices and then overview the large variety of existing integrated micro- and nanophotonic dynamic circuits. We provide a general overview of existing devices and technologies and then cover the topic of silicon photonics where various micro- and nanophotonic dynamic modules are integrated on a silicon chip together with nonphotonic microelectronic components. Although the scope of this review paper deals with a large variety of components, we focus mainly on modulators. The different types of modulators that we introduce include electro-optical as well as all-optical devices. These modulators perform a role that is similar to the role of microelectronic transistors, while acting as the first evolution phase towards fully integrated lightwave processing circuits.

Surface-wave propagation at the planar interface of a columnar thin film (CTF) -- a biaxial dielectric medium -- and an isotropic dielectric substrate may occur over a narrow range of propagation directions, range being dependent on (i) the bulk matgerial that is evaporated to deposit the CTF, (ii) the vapor incidence angle used for the deposition, and (iii) the refractive index of the substrate material.

We propose a new strategy for ultrafast magnetization reversal of nanomagnets. Due to the Inverse Faraday Effect, circularly polarized optical pulses induce a pulsed magnetic flux in materials with large magneto-optical susceptibility. Alternatively, intense optical pulses can induce a pulsed magnetic flux by means of ultrafast demagnetization of a metallic thin film or multilayer with a perpendicular magnetic anisotropy. The time varying magnetic flux induces a transient electro-motive force and electric current in a conducting loop on the surface of the illuminated material, and hence a transient magnetic field. The magnetic field pulses due to the transient current appear to be too short for use in the magnetic field or spin-current induced precessional switching of magnetization. However, our calculations suggest that the magnetic field could lead to ultrafast switching of a nanomagnet overlaid on the surface of the conductor and demagnetized by the same optical pulse. In the case of magnetic pulses due to the Inverse Faraday Effect, the switching direction could be controlled by the helicity of the optical pulse.

A comprehensive theoretical model for InGaN core/multishell nanowire (CMS NW) light emitting diodes (LEDs) has been developed that accurately predicts both electrical and optical properties of CMS NW structures. Using the model, the electron and hole injection in a CMS NW device was studied, showing that the InGaN quantum well (QW) serves as a high electron mobility channel for electron injection while the poor hole conductivity in the p-GaN outer layer confines hole injection to an area directly below the p-contact. Light generation in the CMS NW was found to occur only directly below the p-contact in the InGaN QW as a result of the isolated hole injection. The model was found to accurately predict the optical emission of the CMS NWs for both changes in thickness and Indium composition of the InGaN QW when compared to experimental values from the literature. Piezoelectric effects were not found to play a significant role in the CMS NWs, suggesting that alloy broadening and excitonic emission are the dominant role in determining the FWHM of the CMS NW emission.

A new system for entangled photon-pair generation using an all-fiber optic scheme consists of a fiber optic Mach-Zehnder interferometer (MZI) incorporating a fiber optic ring resonator. The Kerr nonlinearity effect in the fiber ring resonator is exploited for the generation of two independent squeezed beams. The advantage of such a system is that it requires a simple arrangement without any optical pumping parts or bulky optical components. Polarized light pulse trains are launched randomly into a MZI, and one part of the light is delayed in the longer path. The output pulses from both arms of the MZI enter a fiber optic ring resonator. A polarization controller controls the polarization states of the light pulses while they circulate in the ring resonator. The superposition of the nonlinear light pulses in a fiber optic ring resonator randomly occur. These forms are seen on an avalanche photodetector. The results are in good agreement with previous work.

Basic equations of electrodynamics of carbon nanotubes (CNTs are formulated in the helical parametrization scheme, where the crystalline structure of non-zigzag (n_1,n_2) CNTs is described as a set of n_2 double helices, and the electron energy spectrum of the CNTs consists of n_2 different helicoidal branches. The parametrization scheme is shown to be natural and more convenient for analyzing the electromagnetic response properties of chiral CNTs. Bloch equations for the density matrix have been obtained and adapted for the helical parametrization that allows studying the interaction between chiral CNTs and electromagnetic fields with arbitrary polarization and spatial structure. Linear transverse conductivity of chiral CNTs has been derived and utilized for the formulation of the effective boundary conditions for electromagnetic field on the surface of a chiral CNT. As an example, the spectra of high-order harmonics in chiral CNTs have been evaluated from the Bloch equations.

An implementation of the strong-permittivity-fluctuation theory (SPFT) is presented in order to estimate the constitutive parameters of a homogenized composite material (HCM) which is both cubically nonlinear and anisotropic. Unlike conventional approaches to homogenization, the particles which comprise the component material phases are herein assumed to be small but not vanishingly small. The influence of particle size on the estimates of the HCM constitutive parameters is illustrated by means of a representative numerical example. It is observed that, by taking the nonzero particle size into consideration, attenuation is predicted and nonlinearity enhancement is somewhat diminished. In these respects, the effect of particle size is similar to that of correlation length within the bilocally-approximated SPFT.

Abstract. Conductor-insulator nanocomposites in which the conductor percolates can have optical responses at longer wavelengths like dense conductors with an effective plasma frequency wp*. This applies at wavelengths where the Bergman spectral function F for permittivity varies sufficiently slowly with wavelength. wp* can be engineered by varying the components, the nanostructure's topology, or the dielectric volume fraction f. The homogenized conductor acts like a dense conductor whose charge carriers have effective mass meff*. Results are presented for wp*(f) and meff*(f) using the Maxwell Garnett (MG) and Bruggemann (BR) models for spheres and aligned ellipsoids. In the BR case meff*(f) at the percolation concentration is singular. Example wp* data for spheres and ellipsoids are given which match predictions. Anisotropy in effective mass is considered, such that effective plasma frequency can depend strongly on polarisation direction of incident light.

Carbon nanotube (CNT)-supported Pt nanoparticles with an average diameter of 3.8 {plus minus} 0.7 nm are synthesized using water-in-hexane microemulsion as a template. The Pt nanoparticles are distributed evenly on the outside surface of every CNT and exhibit high catalytic activities for hydrogenation reactions including conversion of benzene to cyclohexane. The kinetics of the conversion of benzene to cyclohexane catalyzed by the CNT-supported Pt catalyst was studied by proton NMR and by fluorescence, which is a good way of monitoring the decrease of benzene concentration in the system. The catalytic hydrogenation process follows a zero order reaction with a rate constant of 1.16 × 10-3 mole/h for neat benzene and 3.58 x 10-3 mole/h for benzene dissolved in ethanol.

Inclusions embedded in conventional positive refractive index materials are used to fabricate artificial materials, with negative permittivity, permeability and negative refractive index (NRI). We consider electromagnetic wave propagation in NRI materials with chiral properties that are not negligible. To this end we initially derive explicit expressions for reflection and transmission matrices for a chiral slab. The diagonal terms of the linearly polarized reflection coefficient matrix are the familiar Fresnel reflection coefficients, and the off-diagonal, cross-polarized reflection coefficients are proportional to the chiral parameter and the product of the vertically and horizontally polarized transmission coefficients of the non-chiral host medium. The-full wave modal expansion of the fields include evanescent and propagating radiation fields, several types of lateral waves associated with the phenomena of total internal "backward" reflection as well as several different surface waves (plasmons). Using NRI materials with chiral properties it is possible to fabricate rectangular slabs that perform as lenses associated with two focal lines at the opposite side of the source. Furthermore, the backward propagating lateral waves could be used to make the chiral metamaterials perform like reflectors.

Gold nanoshells are positioned to become a scattering-based contrast agent to improve the reflectance signals of nanoshell-targeted tissue. However, our study shows that a greater enhancement of nanoshell-induced reflectance signals can now be achieved when angularly oblique fiber geometries are used in place of the conventional orthogonal fiber geometry. This important finding was confirmed by conducting two experiments. First, diffuse reflectance spectra were collected from nanoshell-infused polystyrene phantoms at 0, 10, 20, 30 and 40 degree collection angles. At the 40 deg. fiber angle, the nanoshell-induced reflectance contrast, with respect to the native polystyrene phantom, is significantly increased. Based on these results, a reflectance study was then conducted for human cervical tissue treated with gold nanoshells at the 0 and 40 degree collection angles. Again, at the 40 deg. fiber angle, the signal level of the nanoshell-induced contrast in tissue is determined as statistically significant. Taken together, these results demonstrate that the use of the angularly oblique fiber geometry does significantly improve reflectance contrast.

An optical probe with a single aperture flanked by depth-tuned grooves is presented. It is employed as an example to investigate propagation properties of the plasmonic nanostructures with a nonparaxial Gaussian beam illumination. The propagation through the subwavelength aperture is the process that a near-field diffraction of the Gaussian beam interferes with the surface plasmon polaritons (SPP) wave induced wavelets on surface of the grooves. An enhanced optical transmission at the exit side of a subwavelength aperture and a degraded reflection at top side of the compound dielectric/metal nanostructure (air/glass/C/Ag/air) of the probe can be generated with this illumination. Characteristics of the Gaussian beam illumination have been studied numerically via analysis of the transmission and reflection issues. In contrast, the results for plane wave illumination were given as well. Two-dimensional (2D) finite-difference time-domain (FDTD) algorithm is employed for the 2D simulation.

We report on the experimental study of the structural, electronic and thermal properties of state-of-art Sb-based quantum-cascade lasers (QCLs) operating in the range 4.3-4.9 µm. This information has been obtained by investigating the active region band-to-band photoluminescence signals, detected by means of an GaInAs-array detector. This technique allowed to probe the spatial distribution of conduction electrons as a function of the applied voltage and to correlate the quantum design of devices with their thermal performance. We demonstrate that electron transport in QCLs based on Sb-ternary barriers may be insufficient, thus affecting the tunneling of electrons and the electronic recycling and cascading scheme. Finally, we present the first measurement of the electronic and lattice temperatures and the electron-lattice coupling in Sb-based QCLs based on a quaternary-alloy. We extracted the thermal resistance (RL = 8.9 K/W) and the electrical power dependence of the electronic temperature (Re = 11.7 K/W) of Ga0.47In0.53As/Al0.62Ga0.38As1-xSbx structures operating at 4.9 µm, in the lattice temperature range 50 K - 80 K. The corresponding electron-lattice coupling constant ( = 10.8 Kcm2/kA) reflects the reduction of the electron-leakage channels associated with the use of a high conduction band-offset.

Abstract Epitaxial self-assembled quantum dots (SAQDs) are of interest for nanostructured optoelectronic and electronic devices such as lasers, photodetectors and nanoscale logic. Spatial order and size order of SAQDs are important to the development of usable devices. It is likely that these two types of order are strongly linked; thus, a study of spatial order will also have strong implications for size order. Here a study of spatial order is undertaken using a linear analysis of a commonly used model of SAQD formation based on surface diffusion. Analytic formulas for film-height correlation functions are found that characterize quantum dot spatial order and corresponding correlation lengths that quantify order. Initial atomic-scale random fluctuations result in relatively small correlation lengths (about two dots) when the effect of a wetting potential is negligible; however, the correlation lengths diverge when SAQDs are allowed to form at a near-critical film height. The present work reinforces previous findings about anisotropy and SAQD order and presents as explicit and transparent mechanism for ordering with corresponding analytic equations. In addition, SAQD formation is by its nature a stochastic process, and various mathematical aspects regarding statistical analysis of SAQD formation and order are presented.

We report on the investigation of the electronic and thermal properties of high performance terahertz (THz) quantum cascade lasers (QCLs) based on a bound-to-continuum scheme and grown by molecular beam epitaxy (MBE) by a commercial provider. The local lattice temperatures, the subband electronic temperatures and the electron-lattice coupling constant have been extracted from the analysis of microprobe band-to-band photoluminescence spectra measured on devices operating in continuous wave (cw). We found that the electronic distributions in both the active region and the injector are thermalized and that all the subbands share the same electronic temperatures. The measured device thermal conductance C* = 4.6 W/(K x m) reflects the good thermal management of the investigated devices. The electron-lattice coupling constant = 78.5 Kcm2/kA is a factor 1.65 higher than in mid-IR QCLs thus indicating the inefficient cooling of the electronic ensemble caused by the strong reduction of electron-LO phonons scattering channels.

Significantly enhanced absorption at the defect mode can be obtained at surface-normal direction in a dielectric single-defect photonic-crystal-slab, with an absorption enhancement factor greater than 4,000. Complete absorption suppression within the photonic bandgap region can also be observed in defect-free photonic crystal cavities. High spectral selectivity and tunability is feasible with defect mode engineering, making photonic crystal defect cavities a promising nanophotonic platform for the spectrally selective infrared sensing and hyper-spectral imaging, with the incorporation of quantum well or quantum dot infrared photodetector heterostructures.

Quantum Dots (QDs) have been used in life science study because of their higher emission and photostability. Although physicochemical and biological properties of QDs were varied dramatically by the surface modification of QDs, little is known about the reason why the photoluminescence intensity (PLI) of QDs was changed by surface modification. We report on the millisecond-span change of PLI of QD's collective fluorescence oscillation. QDs covered with carboxylic acid and hydroxyl groups show enhanced PLI by adding NaN3, whereas QDs with amine showed less. Removal of NaN3 from QD solution abrogated the enhanced PLI. In addition, observation on evanescent field revealed that addition of antioxidants induced enhanced oscillation of QDs. Furthermore, the blinking count at one millisecond was also increased by addition of antioxidants. However the oscillation enhancement is observed in both aqueous solution and polar organic solvents but not in nonpolar organic solvents, indicating that PLI of QD was varied by the interaction between QDs and their environmental solvents. These millisecond oscillation mechanism was independent of "on" and "off" events which were conventionally known as "blinking". Taken together, the fluorescent emission of colloidal QDs is affected by both surface-covered colloidal molecules and external solvents around at millisecond span interaction.

The superlensing phenomenon of light in photonic-crystal lens-like structures of finite sizes was studied. The wave field was calculated by using the multiple scattering method. The influences of the shapes and interior structures of the lens-like devices on their imaging characteristics were carefully examined numerically. The numerical results revealed that negative refraction is not directly related to the subwavelength imaging phenomenon. For the photonic crystal slab of square-lattice type, superlensing effect was found to be essentially a near field effect.

Electro-optical wavelength switch in Si technology operating around = 1.55 µm and based on a photonic crystal directional coupler configuration was studied using Plane Wave Method and Finite Difference Time Domain simulations. Owing to the exploitation of slow wave supermodes, ultra-compact active devices (~ 20 µm) exploiting free carrier plasma dispersion effect in Si can be designed. Injection of input/output strip access waveguides with the photonic core area is optimized using tapering stages to gradually reduce light group velocity. With carrier injection around 1018 cm-3, the coupler configuration can be used as an optical switch of individual wavelengths or a multiplexer/demultiplexer device with active routing of wavelengths.

The broadband optical absorption properties of silicon nanowire (SiNW) films fabricated on glass substrates by wet etching and chemical vapor deposition (CVD) have been measured and found to be higher than solid thin films of equivalent thickness. The observed behavior is adequately explained by light scattering and light trapping though some of the observed absorption is due to a high density of surface states in the nanowires films, as evidenced by the partial reduction in high residual sub-bandgap absorption after hydrogen passivation. Finite difference time domain simulations show strong resonance within and between the nanowires in a vertically oriented array and describe the experimental absorption data well. These structures may be of interest in optical films and optoelectronic device applications.

Diffraction of a de Broglie matter wave by a system of two pinholes on an optical axis exhibits the multifocal focusing effect of matter waves in the near-field (Fresnel zone). The focusing, defocusing and refocusing phenomenon results from periodic phase changes at singular points, which are observed for the even Fresnel numbers, where the intensity is zero and the phase is undefined. As an on-axis observation point passes through a singular point, the nature of the wave in the neighborhood of the axis changes from that of a diverging wave to that of a converging wave, i.e., the wave refocuses. The amplitudes of the oscillations in the intensity and phase of the de Broglie wave depend on the ratio of the radii of the two apertures in the system. This effect of diffractive multifocal focusing of de Broglie waves can be used for designing a diffractive lens for matter-wave beams.

To investigate the nonlinear optical properties of metallic nanoparticles in dielectric composite materials, germano-silicate glass optical fibers incorporated with gold nanoparticles were made by using modified chemical vapor deposition technique and solution doping process. The incorporation of the gold nanoparticles was confirmed by the sharp absorption peak appeared near 498.4nm, which was due to the surface plasmon resonance absorption of Au nanoparticles. Resonant optical nonlinearities of the fibers were estimated by measuring the peak shift of the fringes obtained from the long-period fiber grating pair upon pumping with Argon laser at 488nm. The resonant nonlinearity was found to be 5.00×10-16m2/W by the incorporation of the gold metal concentration and with the addition of Al3+ ions.

A nanometric bow-tie aperture has a resonant wavelength where its power throughput is maximal. The incident wavelength should coincide with the resonant wavelength in order to improve the power throughput. However, sometimes it is impossible to tune the incident wavelength, so the resonant wavelength should be tuned alternatively. In order to implement this goal, the relative permittivity of the dielectric substrate of the bow-tie aperture was altered. Finite-difference time-domain (FDTD) simulation results demonstrated that the resonant wavelength is tuned from 569.7 nm to 694.1 nm when the relative permittivity is altered from 1.0 to 3.5. The advantage of this method is that the resonant wavelength can be tuned continuously if the relative permittivity can be altered continuously.

The Bruggeman formalism provides an estimate of the effective permittivity of a composite material comprising two constituent materials, with each constituent material being composed of electrically small particles. When one of the constituent materials is silver and the other is an insulating material, the Bruggeman estimate of the effective permittivity of the composite exhibits resonances with respect to volume fraction that are not physically plausible.

A nominal model wherein the nanowires of a chiral sculptured thin film (STF) are considered as strings of slender ellipsoids indicates that the circular Bragg phenomenon evinced by chiral STFs can be exploited to optically sense metal nanoparticles.

Multi-dimensional potential energy surfaces are associated with optical binding. A detailed exploration of the available degrees of geometric freedom reveals unexpected turning points, producing intricate patterns of local force and torque. Although optical pair interactions outweigh Casimir-Polder coupling even over short distances, the forces are not always attractive. Numerous local potential minimum and maximum can be located, and mapped on contour diagrams. Islands of stability appear, and structures conducive to the formation of rings. The results, based on quantum electrodynamics, apply to optically trapped molecules, nanoparticles, microparticles and colloids.