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High-transparency polymers, called optical polymers (OPs), are used in many thin-film devices, for which the knowledge of film thickness (h) and refractive index (n) is generally required. Spectrophotometry is a cost-effective, simple and fast non-destructive method often used to determine these parameters simultaneously, but its application is limited to films where h > 500 nm. Here, a simple spectrophotometric method is reported to obtain simultaneously the n and h of a sub-micron OP film (down to values of a few tenths of a nm) from its transmission spectrum. The method is valid for any OP where the n dispersion curve follows a two-coefficient Cauchy function and complies with a certain equation involving n at two different wavelengths. Remarkably, such an equation is determined through the analysis of n data for a wide set of commercial OPs, and its general validity is demonstrated. Films of various OPs (pristine or doped with fluorescent compounds), typically used in applications such as thin-film organic lasers, are prepared, and n and h are simultaneously determined with the proposed procedure. The success of the method is confirmed with variable-angle spectroscopic ellipsometry.

High-transparency polymers, called optical polymers (OPs), are used in many thin-film devices, for which the knowledge of film thickness (h) and refractive index (n) is generally required. Spectrophotometry is a cost-effective, simple and fast non-destructive method often used to determine these parameters simultaneously, but its application is limited to films where h > 500 nm. Here, a simple spectrophotometric method is reported to obtain simultaneously the n and h of a sub-micron OP film (down to values of a few tenths of a nm) from its transmission spectrum. The method is valid for any OP where the n dispersion curve follows a two-coefficient Cauchy function and complies with a certain equation involving n at two different wavelengths. Remarkably, such an equation is determined through the analysis of n data for a wide set of commercial OPs, and its general validity is demonstrated. Films of various OPs (pristine or doped with fluorescent compounds), typically used in applications such as thin-film organic lasers, are prepared, and n and h are simultaneously determined with the proposed procedure. The success of the method is confirmed with variable-angle spectroscopic ellipsometry.

The design and fabrication of thin-film based organic optoelectronic devices require knowledge of the film optical properties. A low-cost and non-destructive method often used for optical characterization of films is the well-established spectrophotometric envelope method. However, this method is typically limited to thickness above 400 nm, a value often higher than that of the films involved in these devices. This paper studies a procedure to obtain the thickness of sub-400 nm active films from their spectrophotometric trace when the refractive index is previously known. The proposed procedure is based on comparing the experimental transmission spectrum in the transparent spectral window with that obtained by simulation. The capabilities of the proposed method are demonstrated here by its application in the fabrication of organic distributed feedback lasers, for which a fine control of film thickness is important to obtain an optimized and reproducible response. Results are verified with other techniques, such as ellipsometry and profilometry. Thus, with the proposed method, film thickness can be easily determined down to 40 nm maintaining an accuracy of about 5 nm even for films with low refractive index (1.5–1.7). Different methods to determine refractive index of these films are also discussed.

The design and fabrication of thin-film based organic optoelectronic devices require knowledge of the film optical properties. A low-cost and non-destructive method often used for optical characterization of films is the well-established spectrophotometric envelope method. However, this method is typically limited to thickness above 400 nm, a value often higher than that of the films involved in these devices. This paper studies a procedure to obtain the thickness of sub-400 nm active films from their spectrophotometric trace when the refractive index is previously known. The proposed procedure is based on comparing the experimental transmission spectrum in the transparent spectral window with that obtained by simulation. The capabilities of the proposed method are demonstrated here by its application in the fabrication of organic distributed feedback lasers, for which a fine control of film thickness is important to obtain an optimized and reproducible response. Results are verified with other techniques, such as ellipsometry and profilometry. Thus, with the proposed method, film thickness can be easily determined down to 40 nm maintaining an accuracy of about 5 nm even for films with low refractive index (1.5–1.7). Different methods to determine refractive index of these films are also discussed.

The structural and electronic properties of buckled antimonene have been analysed using density functional theory based ab-initio approach. Geometrical parameters in terms of bond length and bond angle are found close to the single ruffle mono-layer of rhombohedral antimony. Inter-frontier orbital analyses suggest localization of lone pair electrons at each atomic centre. Phonon dispersion along with high symmetry point of Brillouin zone does not signify any soft mode. With an electronic band gap of 1.8eV, the quasi-2D nano-surface has been further explored for NH3/NO2 molecules sensing and qualities of interaction between NH3/NO2 gas and antimonene scrutinized in terms of electronic charges transfer. A current-voltage characteristic has also been analysed, using Non Equilibrium Green's function (NEGF), for antimonene, in presence of incoming NH3/NO2 molecules.

A simple dynamically tunable metasurface (two-dimensional metamaterial) operating at microwave frequencies is developed and experimentally investigated. Conceptually, the simplicity of the approach is granted by reconfigurable properties of unit cells partially filled with distilled water. The transmission spectra of the metasurface for linear and circular polarizations of the incident wave were experimentally measured under the metasurface rotation around a horizontal axis. The changes in the transmission coefficient magnitude up to 8 dB at 1.25 GHz are reported while rotating the metasurface by the 90 degrees angle. The proposed approach manifests the cheap and accessible route for the electromagnetic wave control in the microwave region with the help of metasurfaces. Published by AIP Publishing.

Two types of liquid crystal phase modulators: dual frequency liquid crystal (DFLC) and polymer network liquid crystal (PNLC) with 2-pi phase change and submillisecond response time were demonstrated. For DFLC, a record-high birefringence DFLC, an ultra-low crossover frequency DFLC (UCF-01), and a high figure-of-merit DFLC (UCF-02) intended for elevated temperature operation were developed. The figure-of-merit of UCF-02 is 5X higher than that of Merck MLC-2048. For PNLC, a PNLC phase modulator with low scattering (3%) at =1.06 m was demonstrated. The operating voltage for 2-pi phase change is 70V at room temperature, and the relaxation time is 220 s at 25 C and 30 s at 70 C. Finally, a partially fluorinated terphenyl liquid crystal with low absorption in both mid-wave infrared (MWIR) and near IR regions was synthesized. This compound exhibits a nematic phase (although only 2 C), reasonably high birefringence (0.2), low visco-elastic coefficient, and modest dielectric anisotropy. This compound serves as an important first example for future development of low-loss MWIR liquid crystals., The original document contains color images.

Design and simulation results are presented for an ultralow switching energy, resonator based silicon-on-insulator (SOI) electro-optical modulator. The nanowire waveguide and resonator are seamlessly integrated via a high-transmission tapered 1D photonic crystal cavity waveguide structure., Prepared in collaboration with the Univ of Massachusetts and Argonne National Lab. Journal article to be published in Optics Express. Sponsored in part by AFOSR.

A new method to determine semiconductor bandgap energy directly from the easily measured transmission spectra was developed. The method was verified using many binary semiconductors with known properties and utilized to determine the unknown ternary semiconductors were determined at various wavelengths and temperatures. Photoluminescence and Hall-effect measurement were performed to identify various electronic transitions, as well as sample quality. The determination of electrical and optical properties of the material will provide important addition to the database of material properties for future optoelectronic device applications. In the near future, newer materials and their applications need to be developed, and often binary and ternary III-V compounds (GaSb, GaP, GaSbP etc.) can be studied using the method developed in this work., The original document contains color images.

Silica opal structures and photonic crystal heterostructures are fabricated by vertical deposition technique. The structures of samples are characterized by scanning electron microscopy and optical transmission spectra. The long-range order of the silica opals is confirmed by fast Fourier transform analysis of scanning electron microscopy image at different region of the same sample. The smooth decline of background in the transmission spectra of different silica opals is attributed to the contribution of scattering from the structural defects. The photonic stop band of photonic crystal heterostructures exhibits obvious broadening and flattening in contrast to the corresponding silica opals, where the effect of film thickness is considered. The positions of photonic stop band show consistency between photonic crystal heterostructures and corresponding silica opal structures. The overlap of photonic stop band in heterostructures is discussed in detail.

Silica opal structures and photonic crystal heterostructures are fabricated by vertical deposition technique. The structures of samples are characterized by scanning electron microscopy and optical transmission spectra. The long-range order of the silica opals is confirmed by fast Fourier transform analysis of scanning electron microscopy image at different region of the same sample. The smooth decline of background in the transmission spectra of different silica opals is attributed to the contribution of scattering from the structural defects. The photonic stop band of photonic crystal heterostructures exhibits obvious broadening and flattening in contrast to the corresponding silica opals, where the effect of film thickness is considered. The positions of photonic stop band show consistency between photonic crystal heterostructures and corresponding silica opal structures. The overlap of photonic stop band in heterostructures is discussed in detail.

Silica opal structures and photonic crystal heterostructures are fabricated by vertical deposition technique. The structures of samples are characterized by scanning electron microscopy and optical transmission spectra. The long-range order of the silica opals is confirmed by fast Fourier transform analysis of scanning electron microscopy image at different region of the same sample. The smooth decline of background in the transmission spectra of different silica opals is attributed to the contribution of scattering from the structural defects. The photonic stop band of photonic crystal heterostructures exhibits obvious broadening and flattening in contrast to the corresponding silica opals, where the effect of film thickness is considered. The positions of photonic stop band show consistency between photonic crystal heterostructures and corresponding silica opal structures. The overlap of photonic stop band in heterostructures is discussed in detail.

The results of research of optical properties (width of the energy gap, refractive index and spectrums of transmission in visible and infra-red areas) of the chalcogenides glassy semiconductors As2 S3 , synthesized by different methods., Наведені результати дослідження оптичних властивостей (ширина забороненої зони, показник заломлення та спектри пропускання у видимій та інфрачервоній ділянках) халькогенідних скловидних напівпровідників As2 S3, синтезованих різними методами., Приведены результаты исследований оптических свойств (ширина запрещенной зоны, показатель преломления и спектры пропускания видимой и инфракрасной областей) халькогенидных стеклообразных полупроводников As2 S3, синтезированных разными методами.

The effect of oblique deposition on the optical and electrical properties of As(2)S(3) and As(2)Se(3) thin films has been investigated. Amorphous films of As(2)S(3) and As(2)Se(3) were deposited on glass substrate by vacuum evaporation of source materials. The indirect optical bandgap energy was obtained to be 2.40eV for As(2)S(3) and 1.81 eV for As(2)Se(3). The band gap was found to be independent of angle of deposition. DC conductivity of the films was very low. The refractive index and extinction coefficient have been calculated using the transmission spectra, Published in Jnl. of Optoelectronics and Advanced Materials, v3 n2, Jun 2001. p319-322 This article is from ADA398590 International Workshop on Amorphous and Nanostructured Chalcogenides 1st, Fundamentals and Applications held in Bucharest, Romania, 25-28 Jun 2001. Part 1

Analytical equipment for spatially resolved composition mapping in the electron microscope has been purchased in accordance with the originally proposed intent of the grant. A scanning beam attachment for scanning transmission electron microscopy (STEM) has been acquired as well as attachments for composition mapping utilizing characteristic X-ray signals (EDS) and electron energy loss signals (Gatan Imaging Filter).

An atom interferometer is constructed in which the atom waves are physically separated prior to being recombined. Fabricated transmission gratings are used as optical elements for the matter waves. Atom interferometers should be useful in studies of atomic properties, tests of basic quantum physics, for metrology, as rotation sensors, and perhaps ultimately as devices to make ultra- small structures using atom holograms. During the last year our atom interferometer has evolved from a rough plan to an essentially complete device. At present all the major components of the interferometer have been built, and tested at least once. The system will be given its first real try in the next year. Our interferometer consists of three 0.2 microns - period diffraction gratings equally spaced approx. 0.65 m apart in our atomic beam machine. The maximum separation of the beams will be approx. 60 microns. The first two gratings separate and redirect the atomic beam forming a standing wave interference pattern in the atomic flux at the third grating, which acts like a mask to sample this pattern. A principle technical obstacle is the mechanical vibrations of our machine which will blur the interference pattern.

The infrared spectral transmittance of cryofilms formed by H2O, NH3, CO2, and mixtures of these constituents in an N2 matrix were measured. These 0. 25- to 14-micronmeters-thick films were cryopumped onto 20 and 77 degrees K germanium substrates; the deposition pressure for the films deposited at 20 degrees K and that for the 77 degrees K films was approximately 2 time 10 to the minus 6 torr. Transmission spectra were obtained for the 500- to 1/3,700 cm wave number range with a Fourier transform spectrometer. Values of the complex index of refraction for the H2O, NH3, and CO2 cryodeposits were derived from the experimental data using an analytical model and the nonlinear least-squares method. The analytical model treats the germanium as a thick noninterfering film and the deposit as a thin film. Results from the least-squares method are compared with a Kramers-Kronig determination of the real part of the index of refraction. The optical properties (n, k) of such cryofilms are essential for predicting the degradation of contaminated cryocooled optical surfaces., Prepared in cooperation with ARO, Inc., Tullahoma, TN.

This report deals with the theory, development and validation of molecular transmission band models for the uniformly mixed nitric oxide methane, carbon monoxide, oxygen, and carbon dioxide, and for the trace nitrogen oxide, nitrogen dioxide, ammonia, and sulfur dioxide gases. The models were specifically designed for direct incorporation into the LOWTRAN atmospheric transmission code. The transmission function adopted for each gas, acting individually consists of a double exponential function defined by three gas dependent parameters and a single spectrally-dependent parameter. All of these parameters were determined optimally through a numerical procedure that generally incorporates line-by-line and measured transmittance spectra. The resulting nine models were defined at 5/cm intervals throughout their absorber bands, for transmittance calculations of 20/cm spectral resolution at typical atmospheric conditions. Averaged vertical mixing ration profiles for these gases were obtained for direct use with the 33-level standard atmospheric models in the calculation of slantpath transmittance. Comparisons are presented between line-by-line and measured transmittance spectra, and between these spectra, and model calculations using LOWTRAN 6.