This PDF file contains the front matter associated with SPIE Proceedings Volume 7712, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We propose the development of optically rectifying antennas (rectennas) as a technology to develop ultra-high efficiency solar cells that are compatible with large scale fabrication (self assembling) and low-cost (plastic) technologies. We size the field enhancement factor that is needed to reach high efficiencies and we propose solutions for its implementation.

We study both, theoretically and experimentally the light-to-surface plasmon polariton (SPP) and SPP-to-SPP scattering using the Green's function method and leakage radiation microscopy. The scattering structures are fabricated by nonlinear lithography and laser induced transfer (LIT). SPPs are exited on dot- and ridge-like surface structures. We demonstrate symmetric or asymmetric excitation of SPP beams and show that the SPP excitation efficiency strongly depends on the component of the excitation field perpendicular to the metal surface. By adjusting the angle of the incident beam to the maximum of the total electric field component perpendicular to the metal surface, the scattering efficiency of light on a single nanoparticle into SPPs can be increased by a factor of 200. The SPP beams allow studying scattering properties of perfectly spherical gold particles with diameters between 200 nm and 1600 nm fabricated by LIT of liquid gold droplets. For these diameters, the description of scattering of electromagnetic waves with optical frequencies has to take into account higher-order terms. Leakage radiation microscopy provides the unique possibility to observe scattering features attributed to magnetic dipole and electric quadrupole contributions in the 2D scattering patterns of SPPs. The results are supported by numerical modelling using the Green's tensor approach.

Using rigorous magneto-optical waveguide modelling, we have calculated the dichroic transmission of the fundamental TM waveguide mode through a magnetoplasmonic waveguide grating. The ferromagnetic metallic grating material is a CoFe alloy that is magnetized parallel to the grating. When deposited on top of a standard III-V waveguide with a thin top cladding layer and thus placed in the evanescent tail of the guided TM ground mode, it induces both plasmonic and magneto-optic effects in the transmission of this waveguide grating. Due to the direction of the magnetization - perpendicular to the light propagation and parallel to the waveguide layer interfaces - the integrated transverse magnetooptic Kerr effect induces non-reciprocal dichroic transmission for the guided TM light. We have numerically studied the TM ground mode dichroism (for a telecom wavelength of 1300nm) as a function of the cladding layer thickness and the grating parameters, namely its duty cycle, period and thickness. This study has revealed that there exist clear grating designs where the dichroic transmission is resonantly enhanced as compared to the case where the ferromagnetic metal is a continuous film. A detailed study of the field maps associated to these points reveals that the guided TM ground mode resonantly couples to a vertical cavity plasmonic resonance in the air slots of the CoFe grating. This behaviour is reminiscent of extraordinary optical transmission but here in an integrated non-reciprocal version. We have previously reported experimentally strong integrated and forward transparent optical isolation based on this TM dichroism but using a continuous film [1,2]. The present design study indicates that the extraordinary magnetoplasmonic effects taking place in a properly designed CoFe grating improves the performance of this device by at least a factor 4.

The interactions of silver nanorings with polarized optical wave are numerically studied. If the resonant conditions are tuned, the polarization of incident field, inside the nanoring hole, will be reversed by the single silver nanoring due to the surface plasmon resonance, thus, the nanoring hole becomes a region of which permittivity is negative. Put two identical silver nanorings closely, there are two nodes happened between nanorings. It indicates that there is a very steep gradient of electric field and quasi-standing waves exist between nanorings. If many silver nanorings are lined up, the holes of the nanorings will form a negative permittivity chamber. The more close to the center of the chamber, the more ideal the polarization is reversed.

We report on the resonant coupling between localized surface plasmon resonances (LSPRs) in nanostructured Ag films, and an adsorbed monolayer of Rhodamine 6G dye. Hybridization of the plasmons and molecular excitons creates new coupled polaritonic modes, which have been tuned by varying the LSPR wavelength. The resulting polariton dispersion curve shows an anticrossing behavior which is very well fit by a simple coupled-oscillator Hamiltonian, giving a giant Rabi-splitting energy of ~400 meV. The strength of this coupling is shown to be proportional to the square root of the molecular density. The Raman spectra of R6G on these films show an enhancement of many orders of magnitude due to surface enhanced scattering mechanisms; we find a maximum signal when a polariton mode lies in the middle of the Stokes shifted emission band.

We report on design, simulation and fabrication of ultimate and compact 3D close-geometries optical microcavities. These are based on the extension of the so-called 2.5D nanophotonic approach where a quasi 3D control of the photons has been soon demonstrated by our group. A tight control of photons, spectrally and spatially, in a small air region inside a circular regular pattern of high index material-based nanopillars is demonstrated when adjusting the number of pillars, their diameters and the diameter of the pillar-circle. Bottom-up approach based on InP nanowires grown by molecular beam epitaxy and top-down approach based on high aspect ratio anisotropic etching have been developed for fabricating these optical microcavities.

Sub-wavelength structures in metal films have interesting optical properties that can be implemented for sensing applications: gratings act as wire grid polarizer, hole arrays with enhanced transmission can be used as spectral filters. This paper demonstrates the feasibility of these nanostructures using 180 nm and 90 nm complementary metal-oxide semiconductor (CMOS) processes. The metal layers of the process can be used for optical nanostructures with feature sizes down to 100 nm. We describe the design and simulation of these metal structures using the finite-difference timedomain (FDTD) method. The spectral response of the test structures was measured for different polarizations, where the gratings showed typical features of wire grid polarizers. Using a 180 nm CMOS image sensor process, an image sensor with 6 μm pixel size was designed and fabricated with different polarization selective structures allowing for polarization imaging. A polarization camera using this image sensor is demonstrated, visualizing stress birefringence as an application example. Finally, first results on the fabrication of hole arrays with a period of 320 nm are presented, showing color filters with enhanced transmission.

We report a practical and novel concept based on reproducible fluidic mechanisms coupled with silica nano-particles for the development of nano-optical-connections directly on organic integrated photonic chips. Silica nano-rib waveguides have been shaped with various widths ranging between 50 nm and 300 nm and about a hundred μm in length respectively. An effective nano-photonic coupling mechanism has been demonstrated and a sub-wavelength propagation regime obtained between two organic rib tapers and waveguides with a perpendicular and a parallel configuration respectively. The specific silica nano-rib-waveguides structures show off optical losses propagation ranging around [37- 68] dB/mm at visible and infra-red (IR) wavelengths. Such flexible devices offer a versatile fabrication control by changing respectively nano-particles and surfactant concentrations. Thus, they present great potential regarding future applications for shaping nano-connections and high-density network integrations between original optical segmented circuits such as plots, lines or any pre-formed photonics structures.

Surface enhanced Raman scattering (SERS) has been extensively investigated for rough metal surfaces fabricated by chemical etching and particles fabricated by different methods of nanolithography. Surface roughness is assumed to be necessary for SERS. Sharp edges of nanoparticles are desired for near-field enhancements and, consequently, contribute to the enhanced Raman effect. However, high porosity and roughness decreases the optical near-field strength due to losses by radiation. Arrays of nanoparticles fabricated by nanosphere lithography, are able to generate strong near-fields and do not have reduced roughness. Despite its advantages this fabrication method has an undesired effect: contaminant carbonaceous species attached to the nanoparticles generate strong Raman spectra and prevent their use for other molecules. We have investigated the effect of the particle roughness and preparation method on the characteristics of SERS spectra and how the contamination can be avoided. Samples were prepared by nanosphere lithography and using silver and gold nanoparticles in solution. Dye molecules and alkanethiols were used to decorate the nanoparticles in order to obtain enhanced Raman scattering. SERS spectra were acquired using a scanning confocal Raman microscope. Concentrated solution of alkanethiols reduce or remove completely the SERS spectra typical of the contaminants.

In this work a fully three-dimensional parameterization model for the investigations of gold nanostars by the ultraspherical Spectral Boundary Integral Equation method has been developed. The set of the numerical results provide guidelines for a choice of the system parameters for tuning. These can be exploited for new approaches to medical diagnoses or testing for environmental contaminants.

Optical microresonators are structures which confine light to a small region in the range of one wavelength. The radiation of a quantum emitter is coupled to cavity resonances which leads to an optical confinement of the broadband fluorescence. A practical design for this single-mode microresonator is formed by two silver mirrors enclosing a transparent dielectric medium with single quantum emitters. In our tunable microresonator, the resonator length can be changed reversibly with piezoelectric elements to a distinct position corresponding to a specific emission wavelength. The local mode structure of the electromagnetic field is changed at this position which results in a redistribution of the fluorescence and a modification of the lifetime for the same single molecule. The radiative coupling of the emitter to the electromagnetic field is also determined by the orientation of its transition dipole moment with respect to the cavity normal. The doughnut laser modes used for illumination of the single molecule allow us by analyzing the excitation patterns to determine its three-dimensional orientation in the microresonator. In addition, these modes provide an excitation pattern which can be used to detect the longitudinal position of a fluorescent bead in the microresonator with an accuracy of a few nanometers.

We discuss the concept of resolution in the context of our recent work [Opt. Express 17, 19969-19980 (2009)] in which the realization of a point-like scanning single photon near-field source (based on a single color center in a nano-diamond) was reported. We compare this new near-field optical microscope (NSOM) probe with usual aperture-NSOM probes. We conclude that the nanodiamond-based NSOM microscope has a resolving power which is only limited by the scan height over the imaged system. This contrasts with the aperture-NSOM resolution which also critically depends on the aperture diameter.

GaAs micro-nanodisks (typical disk size 5 μm × 200 nm in our work) are good candidates for boosting optomechanical phenomena thanks to their ability to confine both optical and mechanical energy in a sub-micron interaction volume. We present results of optomechanical characterization of GaAs disks by near-field optical coupling from a tapered silica nano-waveguide. Whispering gallery modes with optical Q factor up to a few 10⁵ are observed. Critical coupling, optical resonance doublet splitting and mode identification are discussed. We eventually show an optomechanical phenomenon of optical force attraction of the silica taper to the disk. This phenomenon shows that mechanical and optical degrees of freedom naturally couple at the micro-nanoscale.

It is well established that the presence of interfaces separating regions of real space that are occupied by different materials, has given rise to a wealth of new phenomena and a number of significant applications. It is therefore evident that surfaces must feature prominently in the physics of structures at the small scale and the influence of such structures on the properties of quantum systems in their vicinity. This article is concerned with a structure created using two surfaces forming an open cavity, and we concentrate on the right-angle geometry. Although apparently simple, this structure adequately serves to illustrate the essential physics, which turns out to be surprisingly complex when one considers correlations. We discuss how excited quantum emitters localized within this open cavity, and which can be manipulated optically, would discharge the excitation, both when the emitters are in isolation from other similar emitters and when taken in pairs. Quantum correlations of this kind are essential in the context of implementing scalable architectures for quantum information processing and quantum computing. Optical manipulation near surfaces is one possible scenario that has been highlighted in that context.

The use of structured metal films where electromagnetic waves are confined and manipulated as surface plasmon polaritons (SPPs) has potential use in applications ranging from biosensing, chip-to-chip optical interconnects and in data storage. In general, the SPPs are excited using a separate light source which compromises the compactness of any system. As a solution the SPPs can be directly excited on a layer of gold which is deposited on the top surface of a Vertical Cavity Surface Emitting Laser. Here, we have designed the surface of the VCSEL to include a customised planar gold layer upon which we can excite, propagate and manipulate SPPs over distances of up to 100 microns. We launch the SPPs using a low threshold 850 nm emitting VCSEL under continuous wave operation using a diffraction grating etched through the gold surface. Shallow etched gratings are used to manipulate the SPPs through, for example, a 90° bend using a Bragg mirror and to out-couple the SPPs into air where the polarization dependent relative intensity of the extracted light is measured using a CCD camera. We measure a SPP propagation length of about 50 microns. The result paves the way to compact integrated plasmonic devices.

In this paper we propose new optical waveguides, made of glasses and noble metals. Such waveguides are like coaxial cables where inner metal rods are replaced by thin metal annuluses filled with a glass inside. Numerical simulations demonstrate that the proposed waveguide, having nanosize cross-section, supports propagation of modes, which phase velocity is close to the speed of light and which field is localized outside the metal. These modes are dipole-like modes and are characterized by comparatively low losses.

Extensive work has been reported on making nanometre sized phosphors to keep up with continuing trends of high resolution displays and nanotechnology. However most of these nanophosphors suffer from surface agglomeration. Thus, a novel method has been developed to prepare discrete phosphor nanoparticles. The precursor phosphor powders obtained from solution by the urea precipitation method were coated with silica. Coating with silica before firing the precursor avoids sintering the particles which occurs when the precursors are fired to convert them into phosphors. The coated precursors were fired with ethanol at desired temperatures to get core-shell particles consisting of nanophosphor cores in silica shells. The silica coating was removed by washing with NaOH solution to liberate discrete phosphor nanoparticles. The particle size analysis results of these discrete phosphors show a narrow particle size distribution in the sub-micrometre range. The emission and excitation spectra have been obtained, and compared with those of commercial phosphors. These nanophosphors can be incorporated into printable ink formulations and might find applications in high resolution display devices.

Herein we present the characterization of the photomechanical effect of thin films of azobenzene based polymers PDR1A, PDR13A and PMMA-co-PDR1A using an AFM based sensor. The polymers were coated on silicon and mica cantilevers, and the cantilever bending and surface stress changes were characterized. We have shown that the photoisomerization results in fast and significant cantilever bending ranging from 50-313 μm and changes in surface stresses ranging from 96 to 568 N/m for PDR1A coated mica cantilevers. The photomechanical effect was shown to be robust and repeatable. Of all the polymers studied, PDR1A exerted the largest forces with variations in solvent presence, main chain modification and chromophore modification, all reducing the change in surface stress in order of increasing impact. The utility of this new sensor in the understanding and characterization of the photomechanical effect of azobenzene based polymers is demonstrated.

Optical binding is a phenomenon that is exhibited by micro-and nano-particulate systems, suitably irradiated with offresonance laser light. Recent quantum electrodynamical studies have shown that the optomechanical effect owes its origin to a radiative intervention with the Casimir-Polder dispersion force. The potential energy surfaces for optically induced inter-particle coupling reveal unexpected features of considerable intricacy, and when several particles are present, the effect can result in the formation of geometrically varied non-contact assemblies. In general, previous studies have been restricted to considering only the dynamic electromagnetic coupling between particles, where the latter are considered to be non-polar and centrosymmetric. However, when optical binding between non-polar particles takes place, other forms of interaction need to be entertained - more especially so, since any presence of a permanent dipole moment necessarily also admits a non-zero hyperpolarizability. Consequently, amongst the static contributions to the interaction between any pair of particles, a coupling between the electric dipole of one and the hyperpolarizability of the other must also be considered. In this paper we study these static contributions to the overall optical binding, comparing their effect with other inter-particle interactions, particularly the prominent electric dipole-dipole coupling. The results suggest that static coupling between polar particles can significantly modify the observed optical binding.

The nonlinear optical response of gold films of different thicknesses is investigated by two-beam second-harmonic generation to address the role of surface and bulk effects in their second-order nonlinear optical response. Preliminary results suggest that both types of effects contribute to the measured second-harmonic signals. Furthermore, both effects are found to be enhanced for the thin film with a higher level of nanoscale surface roughness.

We consider the problem of surface plasmon (SP) oscillations in a pair of coupled spherical metallic nanoparticles (MNP) analytically and compare the results with those obtained experimentally as well as by numerical methods: discrete dipole approximation (DDA), boundary integral method and T-matrix. The calculation of SP frequencies of the pairs of spherical MNPs with size less than SP wavelength is reduced to the electrostatic boundary problem and is solved analytically. Such reduction becomes impossible when the system size is comparable with SP wavelength and the retardation effects in this case must be accounted for. Since this problem does not allow exact solution we develop an approximate analytical approach in which we account for retardation effects within each of the spheres, neglecting it in the electromagnetic interaction between the spheres. We prove that this approximation is accurate for interparticle gaps down to 0.1 of sphere diameter. To check the validity of the approximation we performed also numerical calculations based on DDA method for the system of two dielectrically coated small spheres, and the pair of larger spheres for which the retardation effects are essential. Good agreement demonstrated in both cases indicates the applicability of presented analytical approach allowing quick calculation of SP frequencies of coupled spheres. The theoretical results are compared with known experimental data for the pairs of 42 nm and 87 nm particles. In the valuable for biological applications gap range 5÷50 nm there is a good agreement between experimental data and the results of our calculations.

Second-order nonlinear optical effects are electric-dipole-forbidden in centrosymmetric materials, but become allowed through magnetic-dipole and electric-quadrupole effects. Furthermore, such higher multipole effects can play a role also in the response of non-centrosymmetric materials, as demonstrated for second-harmonic generation (SHG) from chiral thin films of organic molecules and from metal nanostructures. For nanostructured materials, higher multipole effects can occur due to elementary light-matter interactions or due to field retardation across nanoparticles. For SHG from metal nanostructures, the latter mechanism was operative and associated with nanoscale defects, which attract strong local fields. The evidence of multipolar SHG emission was obtained from the different radiative properties of the various multipolar sources. The goal of the present work is to perform a more comprehensive multipolar analysis of SHG from arrays of L-shaped metal nanoparticles. In particular, we seek evidence of the presence of multipole interactions also at the fundamental frequency by performing detailed polarization measurements of the SHG response and relying on the different transformation properties of the various multipolar interactions for SHG emitted in the transmitted and reflected directions and for the fundamental beam incident on the metal or substrate side of the sample.

In the optical excitation of many nanoscale systems, the primary result of photon absorption is an electronic excitation that is typically followed by ultrafast relaxation processes. The losses associated with such relaxation generally produce a partial degradation of the optical energy acquired, before any ensuing photon emission occurs. Recent work has shown that the intensity and directional character of such emission may be significantly influenced through engagement with a completely off-resonant probe laser beam of sufficient intensity: the mechanism for this optical coupling is a secondorder nonlinearity. It is anticipated that the facility to actively control fluorescent emission in this way may lead to new opportunities in a variety of applications where molecular chromophores or quantum dots are used. In the latter connection it should prove possible to exploit the particle size dependence of the nonlinear optical dispersion, as well as that of the emission wavelength. Specific characteristics of the effect are calculated, and suitable experimental implementations of the mechanism are proposed. We anticipate that this all-optical control device may introduce significant new perspectives to fluorescence imaging techniques and other analytical applications.

We report a technique of surface plasmon resonance imaging (SPRi) called SSPM (Scanning Surface Plasmon Microscopy) which pushes down the resolution limit to sub-micronic scales. To confirm the sensitivity and resolution of this non labeling microscopy we show images of gold and dielectric nanoparticules detected in air. The contrast mechanism is discussed versus the defocusing and versus the nature of the particules.

Here we report on the two-photon excited visible luminescence, emitted by small gold spheres dispersed in water. The study was performed at the single particle level in order to determine if two-photon luminescence could be an alternative to fluorescently labeled particles for particle tracking. Unexpectedly, the single molecule approach demonstrates that the luminescence is anisotropic at low excitation powers, allowing for the observation of the Brownian rotation of nearly spherical objects. The combined observations of a multi parameter approach suggest that the anisotropy, as well as the power threshold effect, result from the interaction between the capping ligands and the particle surface. The latter interaction favors new radiative deexcitation channels at some very specific sites, in line with the hot spots observed in Surface Enhanced Raman Scattering. The dynamics of the process depends on the excitation power. If the study demonstrates that an increase of the excitation power results in switching on the luminescence of nearly all particles in the sample, it also suggests that the use of two-photon excited gold particles as biolabels will require preliminary characterization of the emission depending on the real system particle and ligands.

Surface plasmons are confined to the surfaces which interact strongly with the electromagnetic waves. They occur at the interfaces where the relative permittivities of the bounding materials are of opposite sign. It is well know that some metals and highly doped semiconductor shows highly negative relative permittivity and such a structure with a dielectric cladding can support surface plasmon modes. These modes decay exponentially, they can be highly localised and can also be confined inside a sub-wavelength size guided wave structure. A rigorous full vectorial finite element-based approach has been developed to characterize a wide range of plasmonic devices, both at optical and terahertz frequencies. Results for wave confinement in quantum cascaded lasers for terahertz (THz) frequencies and metal coated photonic crystal fibres are presented.

A novel emerging technique for the label-free analysis of nano particles including biomolecules using optical micro cavity resonance is being developed. Various schemes based on a mechanically fixed microspheres as well as microspheres melted by laser on the tip of a standard single mode fiber have been investigated to make further development for microbial application. Water solutions of ethanol, HCl, glucose, vitamin C and biotin have been used to test refractive index changes by monitoring the magnitude of the whispering gallery modes spectral shift. Particular efforts were made for effective fixing of the micro spheres in the water flow, an optimal geometry for micro resonance observation and material of microsphere the most appropriate for microbial application. Optical resonance in free micro spheres from PMMA fixed in micro channels produced by photolithography has been observed under the laser power of less then 1 microwatt. Resonance shifts of C reactive protein water solutions as well as albumin solutions in pure water and with HCl modelling blood have been investigated. Introducing controlled amount of glass gel nano particles into sensor microsphere surrounding were accompanied by both correlative resonance shift (400 nm in diameter) and total reconstruct of resonance spectra (57 nm in diameter). Developed schemes have been demonstrated to be a promising technology platform for sensitive, lab-on-chip type sensor of diagnostic tools for different biological molecules, e.g. proteins, oligonucleotides, oligosaccharides, lipids, small molecules, viral particles, cells as well as in different experimental contexts e.g. proteomics, genomics, drug discovery, and membrane studies.

We report the growth of ultrasharp carbon whiskers onto apertured near-field optical glass fiber probes. The ultrasharp carbon whiskers are produced by the electron-assisted dissociation of residual oil vapors present in the vacuum chamber during the electron beam exposition of the tip. This cost effective manufacturing procedure is reproducible, fast and allows controlling the shape of the carbon whisker. The radius of curvature of the whisker apex is approximately 10 nm while its small total length is around 100 nm thus fulfilling the requirements of aperture Scanning Near-Field Optical Microscope (SNOM) probes, i.e. to keep the distance between the sample and the optical aperture during the scanning at subwavelength scale. Furthermore, due to the intrinsic properties of the amorphous carbon whisker, the probes are durable. The carbon whisker optical fiber probes are mounted on tuning-forks using the earlier discussed double-resonant principle. This process ensures a high quality factor of the sensor in the range 2000-5500, which enables to cope with the large stiffness of the tuning-fork actuator and obtain a characteristic noise-limited sensitivity smaller than 10pN necessary to image soft biological samples without destroying them. To illustrate the sensor's performances, transmission near-field optical images of SNOM calibration grating as well as high-resolution state-of-the-art topographic images of single DNA molecules are presented. Prospects of further improvements of the fabrication method enabling to achieve the lighting rod enhancement of the optical near-field (nano-antenna effect) are briefly discussed.

We introduce and demonstrate a dual-channel radially-polarized surface plasmon microscopy (SPM) system with capability down to single nanoparticle detection. For nanospheres stained with fluorescent molecules, we are able to simultaneously collect both fluorescence and elastic scattering images. By using a radial polarizer, the entire incident beam is TM-polarized, which enables formation of a dark circular ring in the reflected image, thus providing higher sensitivity to refractive index changes. The fluorescence intensity is clearly enhanced by more than 50% under radial polarization as compared to a linear one. The complementary signals acquired from the two separated channels jointly lead to well-co-localized images in scanning mode. This technique is currently extended to study two photon fluorescence (TPF) signals from nanospheres, as well as second harmonic generation (SHG) signals from noncentrosymmetric nanocrystals. It also provides a way to compensate for the eventual blinking of the fluorescence, which does not affect the elastic scattering channel.

We presented the theoretical and numerical approach to the computation of the optical characteristics of two-dimensional photonic crystal structure with active medium and metallic nano-roads. The results of calculations of the spectral characteristics of these structures are presented. The plane wave expansion method has been used.

Chiral Phospholipids are found self-assembled into fascinating cylindrical tubules of 500 nm in diameter by helical winding of bilayer stripes under cooling in ethanol and water solution. Theoretical prediction and experimental evidence reported so far confirmed the modulated tilt direction in a helical striped pattern of the tubules. This molecular orientation morphology results in optically birefringent tubules. We manipulated birefringent lipid tubules under 532 nm linearly polarized laser tweezers. Spontaneous rotation of lipid tubules induced by radiation torque was observed with only one sense of rotation caused by chirality of lipid tubules. Rotation discontinues once the high index axis of lipid tubule aligned with a polarization axis of the laser. Thus, by controlling the direction of linearly polarized light, angle of tubule rotation can be specified. This observation holds promising applications in nano- and bio-technologies.

We present the linear and nonlinear optical properties of Bi₁₂SiO₂₀ (BSO) nanocrystals of sizes 60-150 nm, synthesized using chemical solution decomposition (CSD) method. BSO nanocrystlas were characterized using XRD, UV-Vis absorption, and TEM imaging techniques. X-ray powder diffraction indicated that BSO nanocrystals have formed at the calcination temperature of 700°C. The UV-Visible absorption spectrum showed a distinct peak at 270 nm, due to the nanocrystals. The nonlinear optical properties of BSO nanocrystals dispersed in PMMA were studied using a standard open aperture Z-scan technique in the ns and ps regime using 6 ns and 30 ps laser pulses respectively. Second harmonic of Nd: YAG laser (532 nm) was used as the excitation source with incident laser intensity in the range of 0.1 - 10 GWcm^-2. The BSO nanocrystals showed reverse saturable absorption (RSA) behavior in both temporal regimes. In addition to the nonlinear absorption mechanism, nonlinear scattering is also observed to contribute to the RSA behavior in both the time regimes. Of both the pulse durations, nonlinear scattering was observed higher with the 6 ns excitation compared to the 30 ps excitation.

Analytical definitions are proposed for the width of both the transverse and the longitudinal component of a nonparaxial radially-polarized light field at the focal plane of a highly focusing system. By means of an illustrative example, it is also shown that the irradiance is significant within a circle whose radius is given by the proposed beam width. Moreover, the power contained within such circular region around the focal point is shown to concentrate the main part of the total power.

We have experimentally and theoretically demonstrated plasmonic couplers based on metal nanoparticles film (metal islands) deposited upon the optical dielectric waveguide. These nanoparticles forward scatter radiation into the optical waveguide that would otherwise be reflected and transmitted. Design, fabrication and optimisation of the plasmonic silver islands and tantalum pentoxide waveguide are reported. Broadband characteristics of light transmission showing plasmons excitation have been measured and in good agreement with simulated results from 400 nm to 800 nm. Coupling spectrum up to 15% is measured for the plasmonic coupler and in good agreement with the simulated results.

The authors presented an experimental observation of the dynamically optical response of silver nanoparticle film. A 7nm-thicked sliver film was thermally deposited on an indium tin oxide glass substrate and that be annealed from room temperature to 300°C. The absorbance spectra and the dark-field micrograph of the silver nanoparticle film exhibited novel optical response, strongly dependent on the particle geometry, from the excitation of the localized surface plasmon. In particular, the peak wavelength and the maximum value of the absorbance and the exhibited color of the sample changed dramatically during the heating. A convenient and non-destructive technique to directly explore the substance in nanoscale has been achieved based on the optical analyses.

One-dimensional quasi-periodic structures whose period is much smaller than the wavelength of exciting optical radiation have been obtained on a titanium surface under the multi-shot action of linearly polarized femtosecond laser radiation at various surface energy densities. As the radiation energy density increases, the one-dimensional surface nanogratings oriented perpendicularly to the radiation polarization evolve from quasi-periodic ablative nano-grooves to regular lattices with sub-wavelength periods (90-400 nm). In contrast to the preceding works for various metals, the period of lattices for titanium decreases with increasing energy density. The formation of the indicated surface nanostructures is explained by the interference of the electric fields of incident laser radiation and a surface electromagnetic wave excited by this radiation, as shown by our transient reflectivity measurements and modeling, because the length of the surface electromagnetic wave for titanium with significant interband absorption decreases versus increasing electron excitation of the material.

We explore structures composed of two gratings with subwavelength slits in silver films. We study the extraordinary transmission of electromagnetic wave in these structures and the conditions at which the transmittance is equal to zero. Dependences on various geometric parameters are analyzed. We show that the zero of transmittance i.e. the suppression of the extraordinary transmission is observed at wavelength that corresponds to the excitation of surface plasmon polariton in a gap between two gratings with subwavelength slits. We also research structures composed of arrays of slits in thick films set close to continuous thin films. We reveal that an efficiency of the transmission of the slit mode of the grating into the thin film is greater than an efficiency of the transmission of plane wave into the same film. The investigations are performed through numerical simulations with the Fourier modal method.

We study the guiding properties of laser-written dielectric-loaded surface plasmon polariton waveguides (DLSPPWs). The guiding structures such as straight waveguides, S-bends, Y-splitter, resonant filters, and Mach- Zehnder interferometers are realized by two-photon induced polymerization of commercial photolithographic resists. The height of the components can be adjusted by spin-coating of the material. Minimum widths of 400 nm of the DLSPPWs fabricated directly on thin metal films can be achieved. Replica molding of polymer surface structures allows a further reduction of the DLSPPW width down to 200 nm. The DLSPPWs are characterized by leakage radiation microscopy in the visible and near infrared spectral region. We demonstrate the possibility to selectively excite different modes in the waveguides. Fourier-plane imaging allows a direct observation of the excited modes of the DLSPPWs. The simultaneous excitation of fundamental and higherorder modes results in a mode-beating, providing the possibility to control the splitting ratio of guided SPPs in Y-splitters. The experimental results are supported by theoretical modelling using the finite-difference time domain method.

Numerical simulations, based on a FDTD (finite-difference-time-domain) method, of infrared light propagation for add/drop filtering in two-dimensional (2D) Ag-SiO₂-Ag resonators are reported to design 2D Y-bent plasmonic waveguides with possible applications in telecommunication WDM (wavelength demultiplexing). First, we study optical transmission and reflection of a nanoscale SiO₂ waveguide coupled to a nanocavity of the same insulator located either inside or on the side of a linear waveguide sandwiched between Ag. According to the inside or outside positioning of the nanocavity with respect to the waveguide, the transmission spectrum displays peaks or dips, respectively, which occur at the same central frequency. A fundamental study of the possible cavity modes in the near-infrared frequency band is also given. These filtering properties are then exploited to propose a nanoscale demultiplexer based on a Y-shaped plasmonic waveguide for separation of two different wavelengths, in selection or rejection, from an input broadband signal around 1550 nm. We detail coupling of the 2D add/drop Y connector to two cavities inserted on each of its branches.

Nanoscaled Si (Ge) systems continue to be of interest for their potential application as Si (Ge) based light emiting materials and photonic structures. Optical properties of such systems are sensitive to nanocrystallite (NC) size fluctuations as well as to defects effects due to large surface to volume ratio in small NCs. Intensive research of Si (Ge) NCs is focused on the elucidation of the mechanism of radiative recombination with the aim to provide high efficient emission at room temperature in different spectral range. The bright visible photoluminescence (PL) of the Si (Ge)-SiO_X system was investigated during last 15 years and several models were proposed. It was shown that blue (~2.64 eV) and green (~2.25 eV) PL are caused by various emitting centers in silicon oxide [1], while the nature of the more intensive red (1.70-2.00 eV) and infrared (0.80-1.60 eV) PL bands steel is no clear. These include PL model connected whit quantum confinement effects in Si (Ge) nanocrystallites [2-4], surface states on Si (Ge) nanocrystallites, as well as defects at the Si/SiOX (Ge/SiO_X) interface and in the SiO₂ layer [5-11]. It should be noted, that even investigation of PL on single Si quantum dots [12] cannot undoubtedly confirm the quantum confinement nature of red emission.

We study theoretically and experimentally the variation in localized surface plasmon resonance (LSPR) structure (λ_max=660 nm) as a function of dielectric coating thickness. The influence of the morphology and interparticle distance on the LSPR spectra of a glass/Au NSs interface with a constant thickness of diamond (NCD) overcoating was investigated through the calculation of theoretical transmission spectra. Ajusting the theoretical curve to experimental LSPR spectra allowed fixing the geometry of the plasmonic interface and permitted to evaluate the change in the wavelength at maximum absorption (λ_max) as a function of the thickness of the NCD overlayers. The theoretical data were compared with experimental ones obtained on glass/AuNSs/ NCD surface.

Using the electric field present inside a Scanning Tunnelling Microscope (STM) junction, we demonstrate the possibility to create a very local non-centrosymmetry via molecular orientation under the tip. We show this can be used to get localized light emission through second harmonic generation (SHG). Experiments were performed by coupling a femtosecond laser inside a metallic-substrate / metallic-tip junction immersed in concentrated solutions of highly nonlinear azo-dye molecules. The quadratic dependence of the SHG signal intensity with the tip voltage unambiguously shows that it comes from an electric field induced molecular polarisation under the tip. The potentialities of such effects are evoked as an original concept for scanning probe microscopy. Extrapolating the SH intensities that could be recorded, it is estimated that the minimum volume that can be detected in the present experimental configuration is about 1 μm³. In order to be able to decrease this limit, a new experimental set-up is developed towards better signal collection. The implementation of sharp metallic tips to induce amplifying nanoantenna effects (electrostatic lightning rod effects or localized surface plasmon resonances) is also discussed as a complementary way to increase the system lateral resolution.

Enhanced optical transmission (EOT) through subwavelength apertures is usually obtained for p-polarized light. The present study experimentally investigates EOT for s-polarized light. A subwavelength slit surrounded on each side by periodic grooves has been fabricated in a gold film and covered by a thin dielectric layer. The excitation of s-polarized dielectric waveguide modes inside the dielectric film strongly increases the s-polarized transmission. Transmission measurements are compared with a coupled mode model and show good qualitative agreement. Adding a waveguide can improve light transmission through subwavelength apertures, as both s and p-polarization can be efficiently transmitted.

The miniaturization of photodetectors often comes at the expense of a smaller photosensitive area. This can reduce the signal and thus limit the image quality. One way to overcome this limitation is to reduce the photosensitive area but with no reduction of signal i.e. harvest the light. Here we investigate, theoretically and experimentally, light harvesting with nanostructured metals. Nanostructured metals can also give additional functionality such as polarization filtering which is also investigated. After defining the figure of merits used when characterizing light harvesting and polarization filtering structures, we detail the fabrication and measurement process. Structures were made on glass substrate, as a post process step on CMOS fabricated detectors and directly in the CMOS fabrication of the detectors. The optical characterization results are presented and compared with theory. Finally, we discuss the challenges and advantages of integrating metallic nanostructures within the CMOS process.

We present an experimental investigation of the formation of three-dimensional (3D) nonlinear photonic lattices. They are optically induced inside an externally biased cerium doped strontium barium niobate (SBN) photorefractive crystal by a single step multiple beam interference approach. An easy implementation of this scheme using a spatial light modulator (SLM) is demonstrated making the induced structures effortlessly reconfigurable and allowing for a rich variety of two or three dimensional periodic and quasi-periodic crystallographic structures. We show an analysis of these nonlinear photonic lattices based on plane wave guiding, momentum space spectroscopy, and far field diffraction pattern imaging.

Simultaneous absorption of two photons has gained increasing attention over recent years as it opens the way for improved and novel technological capabilities. In the search for adequate materials that combine large two-photon absorption (TPA) responses and attributes suitable for specific applications, the multibranch strategy has proved to be efficient. Such molecular engineering effort, based on the gathering of several molecular units, has benefited from various theoretical approaches. Among those, the Frenkel exciton model has been shown to often provide a valuable qualitative tool to connect the optical properties of a multibranched chromophore to those of its monomeric counterpart. In addition, recent extensions of time-dependent density functional theory (TD-DFT) based on hybrid functionals have shown excellent performance for the determination of nonlinear optical (NLO) responses of conjugated organic chromophores and various substituted branched structures. In this paper, we use these theoretical approaches to investigate the one- and two-photon properties of triazole-based chromophores. In fact, experimental data were shown to reveal quite different behaviors as compared to related quadrupolar and octupolar compounds. Our theoretical findings allow elucidating these differences and contribute to the general understanding of structure-property relations. This work opens new perspectives towards synergic TPA architectures.