We present the detailed analysis of the spontaneous emission coupling factor of the micro cavity based on a 2D photonic crystal in an optically thin dielectric slab. We investigate the maximum (beta) value that can be achieved with this micro cavity and discuss its dependence on the quantum well position, as well as on the pumping area diameter. The analysis is performed using the general method for the (beta) factor calculation that we developed. The method is based on the classical model for atomic transitions in a semiconductor active medium. Finite difference time domain method is used to solve the electromagnetic fields of the system and calculate the total radiated energy, as well as the energy radiated into the mode of interest.

3D photonic crystal structures can be fabricated into photopolymerizable resins by using laser beams interference with high precision. Three laser beams interfere into a glass cell filled with a liquid photopolymerizable resin to form a hexagonal periodic structure. Rods are formed in hexagonal arrangement after being photopolymerzed according to the 3D periodic light distribution which resulted from the lasers interference. Two beams of another laser interfere also to form layers which cross perpendicularly the rods array. After photo-fabrication, the non-solidified resin is removed by ethanol. The lattice constant can be selected by tuning the angles of the incident beams and the laser wavelength. We have fabricated a 500 m X 500 m X 500 m photonic crystal structure, the lattice constant of which is 1 m, and which contains 150 lateral layers.

We review the status of 3D anisotropic crystals based on opal-semiconductor and opal-polymer nanocomposites with respect to controlling the spontaneous emission in space and frequency. An approach to grow photonic crystal structures form PMMA balls containing a laser dye is also presented. We show that depending mainly on the refractive index contrast and the choice of light emitter, photonic crystal effects manifest themselves in several forms. These are illustrated by choosing a suitable dopant for the polymer, such as laser dyes or rare-earth ions, under condition that their fluorescence should fall within the stop-band of the photonic crystals. The refractive index contrasts obtained are far from ideal and yet the impact of the anisotropic PBG is manifested unambiguously in, for example, the change of the density of states of photons and the directionality of the emission.

We describe a novel method of fabricating macroporous ceramics employing colloidal dispersion of ultrafine ceramic particles with latex particles as the templates. The colloidal particles form a particulate gel on drying and fill the voids of the ordered latex templates. Subsequent removal of the template by calcination results in the formation of an ordered macroporous ceramic. The process has significant advantages over the traditional sol-gel process employing alkoxide precursors. Most importantly, the much lower shrinkage compared to the sol-gel process enabled us to produce larger pieces of the sample. The larger shrinkage involved in the sol-gel process often results in small and fragile pieces of the macroporous material which has to be subsequently heat treated to induce crystallization. The ability to choose crystalline colloidal particles in our method obviates the need for heat treatment to achieve crystallinity. We have synthesized a variety of materials such as macroporous silica, titania, alumina and recently have also extended the approach to macroporous silicon which is not amenable to the sol-gel process.

This paper describes a convenient method for self-assembling monodisperse colloidal spheres into 3D ordered arrays with domain sizes as large as several square-centimeters. These arrays have a cubic-close-packed structure or a face-center- cubic lattice similar to that of a natural opal. Each array exhibits a stop band whose position is mainly determined by the diameter of the colloidal particles. This type of structure can serve as a 3D photonic band-gap crystal, which is potentially useful in controlling the emission and propagation of light. The versatility of the present technique has allowed us to tailor the photonic properties of these arrays of colloidal particles. For example, the maximum attenuation of the photonic band-gap can be modulated by controlling the number of layers along the propagation direction of the light. The position of the mid- gap can be roughly changed by controlling the diameter of the particles and subsequently fine-tuned by sintering the sample at elevated temperatures.

We discuss a method for fabricating photonic crystals of closely packed air spheres with diameters on the order of 300 nm in a rutile titania matrix. These differ from the air sphere/titania materials reported elsewhere in that the matrix is the high-index rutile phase of titania as opposed to the low-index anatase phase. We make these material by a sol-gel process with oil-in-formamide emulsions as templates. The emulsion droplets are stable and have a polydispersity of 15 percent or less, allowing them to form small colloidal crystallites when concentrated in a titania sol. The oil template can be removed after gelation of the sol and prior to drying, allowing us to produce monolithic samples with few cracks. Calcination at 1000 degrees C converts the structure to the rutile phase with an average crystallite size of 60 nm. Optical transmission spectra show the presence of a broad minimum at a wavelength of 500 nm for a sample with ordered 200 nm pores.

We use the technique of ironically self-assembled monolayers (ISAMs) to produce photovoltaic devices of well-controlled thickness and composition. The ISAM nanostructure fabrication method simply involves the alternate dipping of a charged substrate into aqueous cationic and anionic solutions at room temperature. We have employed several approaches to combine the tetrahydrothiophenium precursor of PPV with fullerenes and other organic materials .We apply modulation spectroscopy for the electro-optical characterization of the ISAM-devices. Analyzing the thickness dependence of the recorded photocurrent action spectra allows us to identify the photoactive region within the devices. The modulation frequency dependence of the photocurrent can be assigned to the influence of trapped charges taking part in the photovoltaic process. By utilizing the ability to control both thickness and composition of the organic layer at a nanometer level of precision, the composition and concentration of these defects has ben systematically varied.

Chiropticenes are a novel class of single-molecule chiroptical dipole switches. The fundamental mechanism of the Chiropticene switch is that the combination of light and electric field cause both the chirality and the dipole direction to be simultaneously reversed. The information stored in the Chiropticenes can be read nondestructively with circularly polarized light, which ensures erase-read- write capability. These molecular switches are exceptional in that they have the potential to be exploited on both the molecular and macroscopic scale. The Chiropticene switch has been designed for incorporation into an optical data storage device that will be faster and have a higher capacity than the currently available technology. The organic Chiropticene is molecularly engineered to fulfill all the requirements of a switching device in electronic applications. Its modular structure is able to provide an extraordinary capacity to chemically tune the properties of the switch molecule. The synthesis of the Chiropticenes and characterization of their optical properties will be presented. The design of nanodevice architectures based on Langmuir-Blodgett films and/or self-assembled monolayer swill also be presented.

We have observed visible photoluminescence from hydrogenated amorphous silicon nitride (a-SiNx:H) as well as the enhancement and inhibition of this photoluminescence in a microcavity formed with metallic mirrors. The a-SiNx:H was grown both with and without ammonia. The photoluminescence of the a-SiNx:H microcavity. The distributed Bragg reflector mirrors were fabricated using alternating pairs of quarter wavelength thick silicon oxide and silicon nitride. The photoluminescence is enhanced by at least an order of magnitude at the dielectric a-SiNx:H microcavity resonance at 710 nm. The minimum resonance linewidth is 6 nm, which corresponds to a quality factor of 118. The maximum rejection bandwidth is 150 nm. The enhancement and inhibition of the photoluminescence is understood by the modified photon density of states of the dielectric microcavity. The linewidth of the photoluminescence is also narrowed with respect to the linewidth of the bulk a-SiNx:H, again due to the presence of the electromagnetic modes of the dielectric microcavity. The resonance enhancement and inhibition of the photoluminescence in a-SiNx:H opens up a variety of possibilities for optoelectronic applications such as color flat panel displays or active resonant cavity enhanced devices for wavelength division multiplexing.

Thermal emission from heated materials follows the blackbody curve, multiplied by emissivity. Emissivity may be, but is not usually a strong function of wavelength. Ion Optics has developed a variety of surface texturing processes that create specific nano-structures which alter the emissivity in predictable fashion. Random structures produced by ion beam etching create long and/or short wavelength cutoffs. Repeated patterns produced by fine-line lithography, resembling photonic bandgap materials, have large peaks in the emitted spectrum. The central wavelength and bandwidth for lithographic structures can be varied with geometry. FWHM values for ((Delta) (lambda) /(lambda) ) are less than 0.1. These light sources reduce power requirements for applications now using broadband sources with filters, and in some cases entirely eliminate the need for filters.

We have presented a method to fabricate and image 3D microstructure by using two-photon absorption and imaging with sub-micron resolution capability. This method is based on two-photon-induced absorption and fluorescence into a photopolymerizable resin which is stained with a fluorescent dye, and is able to produce complex microstructuring such as boxes, gear, tubes and icosahedron.

Photochemical reactions which can be activated by the simultaneous absorption of two photons provide a means for single-step fabrication of complex 3D microstructures. These types of structures are needed for a wide range of applications, including microfluidics, electrooptics, and micro-electromechanical systems. We have shown that chromophores can be engineered to have both large two-photon absorptivities as well as an efficient means for activating chemical processes, such as radical polymerization, subsequent to the photoexcitation. Chromophores designed following this strategy two-photon-activate the radical polymerization of acrylates at lower incident laser powers than conventional UV initiators. Efficient two-photon photopolymer resins based on these chromophores were used in the fabrication of complex microarchitectures, such as photonic bandgap structures and tapered waveguides. We have devised a strategy which allows this approach to be extended to other chemical systems.

We report the latest 3D fabrication system based on two- photon-initiated polymerization. In two-photon 3D microfabrication, 3D microstructures can be made by scanning an ultrashort-pulsed near-IR laser beam inside liquid photopolymer without layer-by-layer process. Our current system has achieved lateral and depth resolutions of 0.2 micrometers and 0.28 micrometers , respectively. Movable micromechanisms, i.e., microgears, can be also fabricated without any use of supporting parts. For instance, a microgear with an attached shaft was successfully fabricated. Rotation of a microgear was verified during washing out unsolidified photopolymer.

We present a systematic study of the influence of probing laser power-density on the band-edge of CdS_xSe_1-x nanoparticles embedded in a glass matrix. Both the position and the strength of the band-edge luminescence are found to be very sensitive to the laser power. It is observed that the band-edge luminescence shifts initially towards low energy and then towards high energy with increasing laser power. The result are analyzed in terms of laser induced local heating and band-filling mechanism, both of which are found to be very effective processes for nanoparticle systems. Laser induced local heating of the nanoparticles are determined by analyzing temperature- dependent Raman spectra from the sample.

Large third-order susceptibilities, (chi) ⁽³) or (gamma) , have been observed for II-VI semiconductor nanoparticles. However, there are only few studies on the second-order susceptibilities because it is usually believed that the centrosymmetry or near-centrosymmetry of the particles eliminate the (beta) to zero or very small vale, Here the Hyper-Rayleigh scattering (HRS) technique is used to measure the second-order NLO response of nanoscale CdS Colloids with different surfaces in solution, which are denoted by CdS/Cd²⁺, CdS/S^2-, CdS/SC(NH₂)₂ CdS/AOT^- and CdS/Py. The result shows that the 'per particle' (beta) values for CdS nanoparticles are very large. And the (beta) values are different for CdS nanoparticles with different surfaces. Time dependent experiment show that the HRS signal deceases remarkably as time goes by. Further studies reveal that it has mutli-photon fluorescence (MPF) emission under the radiation of 1064 nm for newly made samples, but for aged stable sample the MPF is rather weak. All these experiments show that the HRS and MPF signals are very sensitive to the changes of the nanoparticle surface or the nanoparticle/solution interface. They also give the evidences proving that the surface termination of the crystalline lattice that creates a condition of non- centrosymmetry is contributing to the large (beta) values for CdS nanoparticles.

Polymerization of acetylene on metallocomplex catalysts was studied. It was shown that morphology, stability and optical properties of polyacetylene (PA) compositions depend on the conditions of the PA solid phase formation. Using catalysts base don Re in highly viscous polyvinylbutiral solutions allows to obtain high stable compositions of trans- nanopolyacetylene (NPA) with unique optical properties. Compositions of NPA could be prepared in the form of solutions, films and plates. They are characterized by: (1) Vibrational structure of cis- and trans- bands in optical absorption spectra; (2) Absence of the low-energy peak in photoinduced optical absorption spectra; (3) Extremely low intensity of fluorescence; (4) Passband in the near-IR region; (5) High intensity of Stokes and anti-Stokes lines of the fundamentals of polyene chain in resonance and off- resonance Raman spectra. Compositions of NPA could be used as material for: (1) Different types of switches and sensors: (2) Raman lasers; (3) Micro label for security of objects and documents against forgery. Raman scattering recording instruments for NPA compositions could be designed based on standard digital camera, laser pointer, longpass filter and two or three lenses.

We have investigated a new class of high refractive index, non-yellowing, viscoelastic optical gels. Refractive indices for these materials can be adjusted from that needed to match fused silica to above n_D equals 1.6 to match the higher index engineering glasses, plastics, and semiconductors. These materials are designed for permanent optically clear encapsulation in devices where severe mechanical shock or differential thermal expansion, such as occurs during PCB soldering operations, may render conventional high strength optical epoxies unusable. These low shear stress gels can also be customized to exhibit a wide range of rheological 'stiffness'. We have demonstrated quasi-fluid versions with apparent viscosities of 500,000 cP to hard-rubber-like consistencies registering on the high end of the Shore 00 durometer scale. In this paper, we present measurements of engineering properties on both elastometer-like curing optical gels, and thixotropic non- curing optical gels for: a) optical properties from near UV to near IR: refractive index over temperature, dispersion, and optical absorption; b) rheological properties: viscosity vs. shear rate, Shore hardness and cone penetration. Validation of ultra-low volatility and high temperature thermo oxidative stability required for long-lived photonic devices is discussed. Use of gel technology in fiber splices and photonic devices is described.

We demonstrate a patterned submicrometer-thick optical polarizing film in which non-polarizing areas are formed where the light transmits insensitively to polarization. The polarizing film is fabricated by stretching a silver island multilayer consisting of thin glass layers and silver island layers composed of silver nanoclusters of high density. By stretching the silver island multilayer at a temperature higher than the glass annealing point, the silver islands are elongated along the stretching direction and the large optical anisotropy is induced in the silver island multilayer. In this optical polarizing film, the non- polarizing areas can be easily formed by laser irradiation with high power density as the optical anisotorpy is reduce das the elongated silver islands become spherical ones from the thermal deformation in the irradiated area. We have successfully patterned the optical polarizing films fabricated for the wavelength of 800 nm by laser writing with a 1 W-class carbon dioxide laser. In order to confirm that the optical anisotropy is reduced in the laser written are, the optical characteristics of that area have been measured. In most commercially available optical polarizers including a polarization beam splitter and various polarizing prisms, it is difficult to form the transparent non-polarizing areas. Therefore, the demonstrated patterned optical polarizing films are useful for switchable spatial modulators and filters.

Periodic mesoporous oxides are usually synthesized from water/surfactant system with low surfactant concentrations and 1,3,5-trimethylbenzene has been sued as a swelling agent to increase the spore size under certain conditions. The use of pre-formed liquid crystal phases as template in multicomponent system holds promise for even large pore sizes, large monoliths, and a high level of phase, pore size, and morphology control. Here a generalized method has ben employed to prepare liquid crystal phase that subsequently act as template for the formation of periodic mesoporous silica. Once formed, liquid crystal phases persist throughout the inorganic polymerization and gelation processes and directly template the formation of inorganic mesophases. The method is applicable to a diversity of chemical compositions and offers a simultaneous control over the pore size and morphology. Synthetic variables that can be used to tune the pore size include cosurfactant chain length, cosurfactant/surfactant mass ratios, and the amount of oil. The removal of organic components leads to periodic mesoporous silica with excellent thermal and hydrothermal stability.

Nanometer-scale holes and words were reproducibly create don a typical organic charge transfer compound, Triethylammonium Bis-7,7,8,8-tetracyanoquinodimethanide (TEA(TCNQ(₂) single crystal, using scanning tunneling microscope in ambient conditions by applying a pulse voltage across the tunneling gap. The decomposition products of TEA(TCNQ)₂ single crystal were investigated with mass spectroscopy by applying a pulse to the crystal in a vacuum tube. TEA was the sole product being detected. A micro-Raman Spectroscopy was used to fabricate and characterize the sample using a He-Ne laser. A dots array was written by a focused beam and in situ Raman spectra showed the same was decomposited. The most possible mechanism of holes formation appears to be TEA(TCNQ)₂ decomposition and TEA evaporation by heating effect of STM current. Comparing data storage in TEA(TCNQ)₂ single crystal with a market-sell CD-R disk, the writing threshold value of TEA(TCNQ)₂ is much smaller than that of the CD-R disk. This kind of organic conductor may be a promising material for the STM-based high density storage and popular optical storage techniques.