Search

We propose an optimization-based theoretical approach to tailor the optical response of silver/silica multilayer nanospheres over the visible spectrum. We show that the structure that provides the largest cross-section per volume/mass, averaged over a wide frequency range, is the silver coated silica sphere. We also show how properly chosen mixture of several species of different nanospheres can have an even larger minimal cross-section per volume/mass over the entire visible spectrum., Sponsored in part by the Edgewood Chemical Biological Center and the Department of the Army Basic Research Program. Published in Optics Express, v20 n16 p18494-18503, 30 Jul 2012; published online 27 Jul 2012. Article contains color.

An experiment was designed to study the effects of material type and configuration on Optical Cross Section (OCS) and spectrum. The experiment was conducted at an Air Force Research Laboratory (AFRL) far-field imaging facility, using different diffuse and specular materials and various configurations and/or combinations of each. It was hypothesized that the OCS of certain combinations of materials is dependent on the diffuseness or specularity of the materials used, but the spectrum is independent of these factors and does not change. The objective of the experiment is to capture both OCS and spectra of different material configurations using different combinations of diffuse and specular materials in the bistatic illumination condition. OCS was calculated relative to the scattering of a Spectralon material that was in the scene during all data collects. Results show the accuracy of the above hypothesis and other effects that material type and configuration have on OCS and spectra., In Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS), 11-14 Sep 2012, Maui, HI.

The Air Force Research Laboratory (AFRL) Time-domain Analysis Simulation for Advanced Tracking (TASAT) was used to explore the variation of Optical Cross Section (OCS) with glint angle for a solar panel with different solar cell distribution statistics. Simulations were conducted using a 3D model of a solar panel with various solar cell tip and tilt distribution statistics. Modeling a solar panel as a single sheet of solar cell material is not appropriate for OCS glint studies. However, modeling each individual solar cell on the panel, the tips and tilts of which come from a distribution of specified statistics (distribution type, mean, and standard deviation), accurately captures the solar panel OCS with glint angle. The objective of the simulations was to vary the glint measurement angle about the maximum glint position of the solar panel and observe the variations in OCS with angle for a bi-static illumination condition. OCS was calculated relative to the simulated scattering of a Spectralon material in the glint orientation. Results show the importance of solar cell distribution statistics in modeling the OCS observed for a solar panel., In Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS), 11-14 Sep 2012, Maui, HI.

A broadband spectral-polarimetric Bidirectional Reflectance Distribution Function (BRDF) measurement system from 350nm to 2500nm with 1nm wavelength resolution is providing data for satellite radiance modeling and specifically for Michigan Tech's OCULUS-ASR space mission. The satellite has four deployable panels, which are covered with solar cells on one side, and are brightly colored on the other. BRDF data for the colored panels show interesting spectral features, including wavelength variability of first surface scatter, volumetric scatter and second surface scatter. Additional surface scatter data for other spacecraft materials including anodized aluminum, multilayer insulation (MLI) and solar cells is presented. The continuum nature of the data indicates that either dedicated BRDF models or a method for incorporating complex wavelength data into simulations will be needed for passive spectral radiance modeling and accurate spectral correlations., Presented at Advanced Maui Optical and Space Surveillance Technologies Conference, AMOS, 12-16 Sep 2011, Maui, HI.

Several parameters are proposed for describing the statistical thermodynamic component of the exchange of photons between a pump and a laser beam. They are based on the occupation probability of absorbing and emitting, pump and laser levels, and are complementary to the optical cross sections. The "occupation factor," f0, is appropriate for describing an optical amplifier in the small signal regime. f1 is appropriate for describing an amplifier in the large signal regime, e.g., a laser. They serve to facilitate a quantitative comparison of laser gain media, operating temperatures, and choice of pump and laser wavelengths. After a simple scaling, both occupation factors have a numerical value that coincides well, in most cases, with conventional usage of the terms two-, three-, and four-level laser. They can thus serve as an unambiguous, quantitative alternative to the quasi-two-, quasi-three-, and quasi-four-level terminology. The proposed definitions are general enough to apply to many types of gain media, but are particularly useful for comparing systems with discrete levels, pumped with a narrowband source, in near-resonance with the laser wavelength. Several low-quantum-defect combinations of pump and laser wavelengths are analyzed for Er3+, Nd3+, Yb3+, and Ho3+ in YAG, as a function of temperature., The original document contains color images. Published in IEEE Journal of Quantum Electronics, v45 n10 p1213-1220, October 2009.

In order to meet the goals of the Department of Defense (DoD) for smaller and more accurate weapons, the Munitions Directorate of the Air Force Research Laboratory (AFRL/RW) has numerous projects investigating the miniaturization of weapons and munition fuze components. One of these efforts is to characterize the performance of small detonators. The velocity of the flyer, the key component needed to initiate a detonation sequence, can be measured using a photonic Doppler velocimeter (PDV). The purpose of this research was to develop a microelectromechanical system (MEMS) device that would act as an optimal retroreflective surface for the PDV. Two MEMS solutions were explored: one using the PolyMUMPsTM fabrication process and one in-house fabrication design using silicon on insulator (SOI) wafers. The in-house design consisted of an array of corner reflectors created using an SOI wafer. Each corner reflector consisted of three separate mirror plates which were self-assembled by photoresist pad hinges. When heated to a critical temperature (typically 140-160C), the photoresist pads melted and the resulting surface tension caused each mirror to rotate into place. The resulting array of corner reflectors was then coated with a thin layer of gold to increase reflectivity. Despite the successful assembly a PolyMUMPsTM corner reflector, assembling an array of these reflectors was found to be unfeasible. Although the SOI corner reflector design was completed, these devices were not fabricated in time for testing during this research. However, the bidirectional reflectance distribution function (BRDF) and optical cross section (OCS) of commercially available retroreflective tapes were measured. These results can be used as a baseline comparison for future testing of a fabricated SOI corner reflector array., The original document contains color images.

We present newly measured results of an ongoing experimental program established to measure optical cross sections in the mid and long wave infrared for a variety of chemical and biologically based aerosols. For the present study we consider only chemically derived aerosols, and in particular, a group of chemical compounds often used as simulants for the detection of extremely toxic organophosphorus nerve agents. These materials include; diethyl methylphosphonate (DEMP), dimethyl methylphosphonate (DMMP), diisopropyl methylphosphonate (DIMP), and diethyl phthalate (DEP). As reported in a prior study, we combine two optical techniques well suited for aerosol spectroscopy (i.e., flow-through photoacoustics and FTIR emission spectroscopy), to measure in situ the absolute extinction and absorption cross sections over a variety of wavelengths spanning the IR spectral region from 3 to 13 um. Aerosol size distribution(s), particle number density, and dosimetric measurements are recorded simultaneously in order to present optical cross sections that are aerosol mass normalized, i.e., m2/gram. Photoacoustic results conducted at a series of CO2 laser lines, compare well with measured broadband FTIR spectral extinction. Both FTIR and photoacoustic data also compare well with Mie theory calculations based on measured size distributions and previously published complex indices of refraction., The original document contains color images.

This paper presents a set of xenon apparent emission excitation cross sections for emission lines that have diagnostic value in the analysis of Xe-propelled Hall thruster plasmas. Emission cross sections are presented for three excitation processes involving ground-state xenon atoms: e^- + Xe, Xe^+ + Xe, and Xe^2+ + Xe. The cross sections are derived from luminescence spectra produced at single-collision conditions. Apparent emission excitation cross sections are tabulated for 12 visible and 8 near-infrared lines for electron energies ranging from 10 to 70 eV. In case of the near-infrared lines, radiation trapping effects are accounted for by measuring the detailed pressure dependence of the apparent emission cross sections and extrapolating to zero pressure. A semiempirical expression for the pressure dependence is derived that allows zero-pressure extrapolation from threshold to 70 eV. Ion-induced cross sections are reported for the same emission lines at an energy per unit charge E/q of 300 eV, chosen for typical Hall thruster operating voltages. Radiation trapping effects are negligible for the ion emission excitation cross sections between 0.1 and 2.0 mTorr in the present luminescence experiment., Prepared in cooperation with the Central Research Institute for Machine Building (TSNIIMASH), Korolev, Russia. Published in the Journal of Applied Physics, v99, paper 113304. The original document contains color images. Partially funded by AFOSR.

In an effort to establish a more reliable set of optical cross sections for a variety of chemical and biological aerosol simulants, we have developed a flow-through photo-acoustic system capable of measuring the absolute, mass-normalized, extinction and absorption cross sections. By employing a flow-through design, we avoid issues associated with closed aerosol photo-acoustic systems and improve sensitivity. Although the results shown here were conducted over the tunable carbon dioxide laser waveband region (i.e., 9.20 to 10.80 m), application to other wavelengths is easily achievable. Aerosols considered are categorized as biological, chemical, and inorganic in origin, i.e., bacillus subtilis endospores, dimethicone silicone oil (SF-96 grade 50), and Kaolin clay powder (alumina and silicate), respectively. Results compare well with previously measured spectral extinction using Fourier transform infrared spectroscopy. Comparison with Mie theory calculations based on previously published complex indices of refraction and measured size distributions is also presented., The original document contains color images.

Parameterization of optical Case 2 waters, especially near-shore waters, continues to challenge our modeling and predictive capabilities because of the significant effect of suspended mineral matter on the optical properties of these waters. It has been pointed out that there is a paucity of optical information for the suspended mineral matter of coastal waters2'3. Supplying this gap our knowledge will create a new field, geo-optics, which is absolutely necessary for construction of adequate coastal optical model and will even be of importance for Case 1 waters when the open ocean receives mineral matter from dust storms and gets a significant admixture of iron for plankton blooms. The majority of activity in the study of ocean optical properties has been the creation of chlorophyll-based models4, the quantification of absorption cross sections, and the partitioning of the absorption coefficient into its various organic components. In this report we are making a contribution to the new field of geo-optics by investigating the optical scattering cross section of suspended mineral matter in Mobile Bay, Alabama. Combining these data with bio-optically based optical data on suspended organic matter gives us the biogeo-optical model of coastal ocean optical properties.

Predictions of chlorophyll concentration from satellite ocean color are an indicator of primary productivity, with implications for foodwebs, fisheries, and the global carbon cycle. Models describing the relationship between optical properties and chlorophyll do not account for much of the optical variability observed in natural waters, because of the presence of seawater constituents that do not covary with phytoplankton pigments. in order to understand variability in these models, the optical contributions of seawater constituents were investigated. A combination of Mie theory and flow cytometry was used to determine the diameter, complex refractive index, and optical cross-sections of individual particles. In New England continental shelf waters, eukaryotic phytoplankton were the main particle contributors to absorption and scaftering. Minerals were the main contributor to backscattering (bb) in the spring, whereas in the summer both minerals and detritus contributed to bb. Synechococcus and heterotrophic bacteria were relatively unimportant optically. Seasonal differences in the spectral shape of remote sensing reflectance, Rrs, were contributed to approximately equally by eukaryotic phytoplankton absorption, dissolved absorption, and non-phytoplankton bb. Differences between measurements of bb and Prs and modeled values based on chlorophyll concentration were caused by higher dissolved absorption and non-phytoplankton bb than were assumed by the model., Original contains color plates: All DTIC reproductions will be in black and white. Prepared in cooperation with Woods Hole Oceanographic Institution, MA.

The wind forcing and transport response in the synoptic frequency band (2-20 days) is examined through the Korea/Tsushima Strait. The lagged correlation of transport to wind stress indicates southerly wind stress across the both the Yellow Sea and Japan/East Sea is related increased transport. A linear barotropic adjoint model indicates more directly where and at what time lag the wind stress is most important in determining the strait transport. Results indicate that the southerly wind stress across the Japan/East Sea off the Korea coast is most important in forcing the transport through the strait. The wind stress across the Yellow Sea is not dynamically linked to the strait transport. The wind stress information is carried through Kelvin waves that propagate to the strait from the Japan/East Sea, but away from the strait in the Yellow Sea., Presented at Meeting (2nd) on the Physical Oceanography of Sea Straits, held in Villefranche, France, on 15-19 Apr 2001.

Two photon confocal microscopy is an emerging technique in the field of laser scanning microscopy which has an inherent capability for optical sectioning in 3D. We have used this two photon confocal scanning microscopy as a nondestructive tool to study onset of corrosion of meatallic substrates beneath the paint layer in-situ without removing or peeling off the paint layer. The result shows that the onset of corrosion can be studied by a combination of reflection and two-photon fluorescence modes of detection in confocal microscopy. We have used the newly developed localized spectrometer (multi-photon or confocal) to study the microenvironmental changes inside the polymeric paint coatings. We have also explored a new technique called "Optical Coherence Tomography" (OCT) for imaging through the paint coatings. In the process, we have developed a Confocal enhanced OCT (CEOCT) for imaging through highly scattering media. CEOCT was found to have a better S/N ratio while imaging through highly scattering coatings compared to two photoniconfocal or normal OCT.

This paper describes the design and deployment of a transportable test bed for a short pulse optical augmentation (OA) system to detect optical directors of potential threats in amphibious operations. The use of a short pulse duration allows discrimination of retroreflections from natural sources such as rock formations and vegetation. The test bed has been fielded in experiments on ground ranges and aboard ships in the Chesapeake Bay and Cardigan Bay. The data collected in these trials show that an optical cross section of 300 sq m/sr can easily be detected at a range of 9 kilometers, proving the feasibility of using such a system aboard vessels in amphibious operations. The test bed was built in a 15' long trailer that incorporated an optical bench with the probe laser, steering gimbals, detector assembly, visible tracking camera and data acquisition subsystem. Data collection and storage as well as beam control and tracking were performed by a computer system located in the front of the trailer. With a water chiller for the laser attached to the tongue, the trailer became a self contained unit which could then be towed for ground testing, shipped inside a standard ISO container, and lifted onto the decks of ships for testing. In this way the test bed was loaded onto an LCM-8 landing craft and was also deployed aboard the R/V Colonel Templer in the UK to participate in sea trials off the coast of Wales. The probe beam used was a 532 nm Nd:Yag with pulse energy of up to 500 mJ and a repetition rate of 10 pulses per second. The detector was a photomultiplier tube which was connected to a data acquisition system sampling at 1 gigasamples per second. A range gate was set up to collect 1500 samples around a selectable range of interest. A global positioning system (GPS) receiver was used to calculate ranges to known targets. The system incorporated visible image-based beam steering and stabilization., Prepared in collaboration with Maryland Advanced Development Laboratory, Greenbelt, MD.

The Ballistic Missile Defense Organization's (BMDO) Innovative Science and Technology Experimentation Facility (ISTEF(1)) is located on the Kennedy Space Center at Cape Canaveral Florida. The ISTEF conducts research and development in the area of passive and active electro-optical science and technology for missile defense and its location provides a unique opportunity to observe a large number of rocket launches. Atlas II first stage engines use LOX-kerosene as the propellant and are representative of a number of tactical and theater ballistic missiles. Incomplete (non-stoichiometric) combustion of LOX-kerosene leads to soot formation, the presence of which could be a useful threat discriminant or identifier. The concentration and size of the soot particles is extremely important when modeling the signature from LOX-kerosene plumes. Previously, ISTEF measured the laser radar cross sections of LOX-kerosene plumes in the visible and NIR. This paper reports the results of follow-on measurements, which greatly improve the accuracy and sensitivity of the previous measurements. To our knowledge these are the only multi-wavelength, in-situ measurements of laser-radar cross sections of LOX-kerosene plumes. Absolute (calibrated) laser radar cross sections of both the plume and hardbody were measured at wavelengths of 532nm and 1064nm simultaneously at altitudes ranging from 1km to 20km. Significant variation between the visible and NIR laser radar cross sections as a function of altitude was measured which implies that the particle size distribution has a strong dependence on altitude. The laser illuminator was a frequency doubled pulsed Nd:YAG transmitting at both 532nm and 1064nm with a pulse width of 10ns and repetition rate of 10Hz, and the laser backscatter receiver was a 0.5 meter telescope with APD detectors.

The long-term goal of this research is to develop the base of knowledge necessary to: (i) understand the magnitudes and variability of the inherent and apparent optical properties of the ocean; (ii) predict the inherent absorption and scattering properties of sea water and the apparent properties such as remotely sensed reflectance, given the types and concentration of suspended particles; (iii) retrieve the concentration of optically significant constituents of sea water from reflectance measurements. Although mineral particles are a major optical component of coastal ocean, very little work has been done on characterizing the absorption and scattering properties of the various mineral particle assemblages occurring in marine environments. My goal for this past fiscal year was to begin a study of the optical properties of mineral particles. Specific objectives were to: (i) expand single-particle optical property database by determining optical cross-sections and scattering phase functions for generic mineral particles, organic detrital particles, and air bubbles; (ii) conduct a field experiment for the purpose of measuring the inherent and apparent optical properties within a marine environment that exhibits dramatic variations in the optical water type, from the mineral-dominated to phytoplankton-dominated type., See also ADM002252.

Optical properties of the marine diatom thalassiosira pseudonana were examined in nitrate-limited semicontinuous cultures at four rates of growth. Two experiments were conducted at each growth rate in which sampling of the culture was done at either the dark-to-light (D-L) or light-to-dark (L-D) transition of a 12 h photoperiod. Optical cross-sections and efficiency factors for absorption, scattering, and attenuation were calculated from measurements of the spectral absorption and beam attenuation coefficients, cell concentration, and the size distribution of cells in suspension. The refractive index of cells was calculated from this data using an inverse method. Nitrogen limitation strongly influences the optical properties of this species. Absorption cross-sections increased more than twofold with increasing growth rate, predominantly caused by increases in the imaginary part of the refractive index, n'. Variability in n(1) was strongly correlated with intracellular chlorophyll alpha concentration. In contrast; to absorption, scattering cross-sections were not a strong function of growth rate but exhibited significant differences between D-L and L-D experiments at any given growth rate. Variability in the real part of the refractive index was correlated with intracellular carbon concentration. The chlorophyll alpha-specific absorption coefficient decreased with increasing growth rate in response to decreases in the carotenoid to chlorophyll alpha ratio and increased pigment packaging. The chlorophyll alpha-specific scattering coefficient also decreased with increasing growth rate, and was correlated with the cellular carbon to chlorophyll alpha ratio. Our results suggest that the optical properties of phytoplankton populations in nitrogen-limited surface waters may be significantly altered from those in deeper portions of the water column.

The absolute electron-impact optical emission cross sections of numerous vibrational bands of the second positive band system of the nitrogen molecule have been measured for electron impact energy from threshold up to 600 eV. From the optical data the apparent electron-impact excitation cross sections for five vibrational levels of the C3Pi sub u electronic state of the nitrogen molecule have been determined. We have constructed a new apparatus for measuring the electron-impact optical cross sections for infrared emissions using a Fourier Transform spectrometer for optical detection. This apparatus allows us to study many important infrared emissions which could not be detected previously by our photomultiplier optical detection systems.

To appreciate laser safety, we introduce a beam spot method of measuring long-distance laser irradiation. Based on laboratory eye injury data, we calculated the laser beam divergence, energy distribution over the laser cross section, and laser beam hazard probability. With the ever-wider applications of laser technology and with advances in designing related equipment, such as laser ranging, laser communications, lidar, laser target indicators, etc., laser safety has become one of the critical issues faced by researchers. In particular, since the human eye focuses on the laser beam, low irradiation exposure may cause serious eye injuries., Trans. of Laser Technology (China) p308-313 n.d.

The theory for the scattering of magnetic spheres is developed by means of scaling functions. This theory leads in a natural way to the development of scattering algorithms which use exponential scaling to overcome computational overflow problems. The design and testing of the algorithm is described. Fortran codes which implement the algorithmic design are presented and examples of code use are given. Listings of the code are included. (AN)

Axicon optical systems can transform a gaussian beam into a diffraction-free Bessel beam. In addition mutual, transformation between solid beam and annular beam can also be realized. The paper details theoretical analyses and experimental studies on the axicon and its composite optical system; both results are in agreement. Axicon optical systems are shown to have wide applications in laser techniques. (AN), Trans. of Zhongguo Jiguang (China) vA21 n1 p21-25 Jan 94.

A new procedure is developed for calculating light scattering from a spherical particle on a conducting plane. The discussion is limited to problems in which the incident light beam is perpendicular to the plane. A general proof is given for the method of images, which is used to convert the problem of a particle on a conducting plane to an equivalent two-particle problem is then obtained by the multipole expansion method. Mirror symmetry is exploited to simplify the calculation. Formulas are developed for the extinction and absorption cross sections. Several example problems are calculated, and the exact solutions are compared to the results from two commonly used approximation procedures

Our objective is to conduct a comprehensive study of the optical properties of marine microorganisms and other biogenic particles in order to determine their optical cross-sections and contribution to absorption and scattering by sea water. Our major effort during the last year was aimed at quantifying diel changes in scattering and absorption cross-sections of phytoplankton cells. This study is related to our hypothesis that the relatively large diel cycle in the beam attenuation coefficient that has been observed in the ocean is in part caused by diel change in the size and refractive index of cells comprising the phytoplankton community. Another effort was focused on testing the applicability of the dynamic light scattering (DLS) technique for characterizing the size distribution of small marine particles (< 5 microns) including the submicron range. While we previously used this technique for studying the cultures of heterotrophic marine bacteria, this time we focus our attention on natural assemblages of marine particles. This effort is related to the hypothesis that submicron particles make major contribution to particulate backscattering in the ocean. Another major effort was aimed at examining marine cyanobacteria which represent small autotrophic organisms from the picoplankton size range. We also assessed the effect of gas microbubbles on light scattering in the upper ocean. (AN)

A combined theoretical and experimental study has been conducted to evaluate the effectiveness of using large, hollow micro-balloons as LDV seed particles. The study has focused on the ability of phase Doppler systems to size hollow micro-balloons, the ability of large micro-balloons to respond to high frequency, spatial and temporal flow field variations, and the overall advantages and disadvantages of using large micro-balloons instead of conventional LDV seed particles, such as very small water droplets or polystyrene latex (PSL) particles. This paper discusses the development of a theoretical phase Doppler response model for stratified spheres, a dynamic response model to describe particle behavior in fluid-flows, the experimental facility, and the theoretical and experiment results. (Author)

Some of the research results are: (1) Computer simulation of synthetic aperture radar polarimetric images or rough sea with swell were obtained for an individual resolution cell. (2) Two separate approaches were developed to account for multiple scatter from rough surfaces. (3) In the high frequency limit shadowing is accounted for by limiting the angles of incidence and scatter to less than 90 deg. This is self-shadow. (4) Non Gaussian probability density functions are considered. These are based on the gamma functions of order K. (5) To determine rough surface cross sections, Gaussian and non Gaussian spectral density functions have been considered. (6) The medium below the rough interface is characterized by complex permittivity and permeability so that conduction currents and displacement currents are accounted for. (7) Random rough surfaces are characterized by 4D Gaussian joint probability density functions. (8) At oblique angles single scatter is the principle contributor to the observed enhanced backscatter. Keywords: Electromagnetic scattering/spectra; Backscattering; Electromagnetic wave propagations; Spectral energy distribution; Polarimetry/optical images; Optical cross sections; Ocean surfaces/roughness; Perturbation theory; Computerized simulation.

Absolute apparent cross sections for electron-impact excitation out of the 2-triplet-S metastable level of He to the 3-triplet-S, 4-triplet-S, 3- triplet-P, 3-triplet-D, 5-triplet-D, and 6-triplet-D levels have been measured by a novel method. A beam of metastable atoms from a hollow-cathode discharge was crossed by an electron beam of energy from 3 to 16 eV, and the emission from the excited states was detected. Absolute calibration was made by measuring the ratio of electron excitation cross section to the known optical absorption cross section and using knowledge of the pertinent branching ratios. Direct electron-impact excitation cross sections for the 3-triplet-P, 3-triplet-S, and 3-triplet-D, levels were obtained.

A series of optical depth calculations were accomplished to assess the effects of various existing dust and soot models on the transmission of incident sunlight. A change in the standard deviation of the particle size distribution from two to four, assuming constant total density, resulted in a decrease in the visible optical depth by a factor of ten. A technique using a method of direct integration was developed for the calculation of the effective optical depth of nuclear induced dust and soot clouds. Contributions from directly transmitted photons, first scattered photons using anisotropic cross-sections, and all subsequently scattered photons were used to calculate the amount of light transmitted through the cloud. Absorption effects were also included. The results of this study were comparable to the results of several recent nuclear winter studies.

The energies and wave functions for several series of Rydberg states of the nitrogen molecule have been calculated. Based on these results a long-wave infrared emission spectrum of the nitrogen molecule is predicted. The optical cross sections for exciting a series of atomic oxygen emission lines in the long-wave infrared region by electron impact on oxygen molecules have been obtained. Keywords: Rydberg states, Quantum defect; Dissociative excitation by electron impact; Optical excitation cross sections; Atomic transition probabilities; Ground state; Convergence; Cations; Electron orbitals; Hamiltonian equations; Eigenvalues; Energy levels.

The trap arrays were designed to sample the particulate fluxes both immediately above and within the nepheloid layer. The data derived from the traps have been used to estimate vertical fluxes of particles including, for the first time, an attempt to distinguish between the flux of material settling from the upper water column (the primary flux) and material which has been resuspended from some region of the sea floor (resuspension flux). From these data and measurements of the net nepheloid standing crop of particles one can also estimate a residence time for particles resuspended in the nepheloid layer. This residence time appears to be on the order of days to weeks in the bottom 15 m of the water column and weeks to months in the bottom 100 m., Prepared in cooperation with Massachusetts Inst. of Tech., Cambridge under Contract N00014-67-A-0204-0048.

Electron impact excitation cross sections of the 1 Sigm a (+) sub u yields a 1 Pi sub g emission band of N2 molecules involving different vibrational quantum numbers has been measured. Excitation of the vibrational levels of the c'sub 4 state is analyzed in terms of the Franck Condon factors and perturbation by the b'1 Sigma (+) sub u state. Nonlinearity in the pressure dependence of the emission signal is studied. Optical cross sections have been measured for emission lines of 04 ions produced by electron impact on 02 molecules.

The purpose of this thesis was to construct an experiment that can accurately determine a target's laser radar cross-section. A laser radar cross-section (LRCS) is a measure of the average amount of optical power scattered by a target, and is analogous to the term radar cross-section, which is defined for scattered power radiating at microwave wavelengths. Cross-sections, whether optical or microwave, are quantities which describe the effective area of a specific target which directly scatters an incident electromagnetic wavefront. The focus of this thesis is to investigate the nature of LRCS measurements, with particular attention paid to the measurements of spherical calibration targets. Keywords: Laser pulse scattering; Optical radar; Infrared detection; Mathematical prediction; LADAR (Laser Detection and Ranging).

The laser radar simulator optical design is described. The profile of the mirror surfaces is described in detail. Two test arrangements for analyzing the optical system were set up. These were termed the parent and system tests. These tests and the resulting test results are discussed in the text. The parent test was simply a test of the optical system before the aspheric sections of the secondary and tertiary mirrors were cored out. The system test was a test of the finished optical components in their mounts. The results of these two tests indicated that no appreciable change occurred in the optics due to the coring and both the parent and system tests show that the optical system is performing within the required tolerances. Finally, a detailed step-by-step alignment procedure for the optics is given.

Optical modeling of hollow glass sphere aerosols was undertaken with a two stage approach. The first stage was to develop a model for homogeneous or solid spheres. This was a logical means of proceeding, since modeling of homogeneous spheres is by far the easier of the two tasks and is the area which has received by far the greatest attention from other investigators, hence providing copious examples with which to check our results. The homogeneous glass sphere model, based on the formulation of Mie (1908), was developed without any serious problems and was successfully tested. The second stage of development of optical models consisted of the much more difficult task of developing a model for composite or hollow spheres. The modeled aerosol consists of two concentric spheres composed of two different materials. Results are very different in appearance from those of the solid glass spheres. Qualitatively, this departure can be understood as a combination of two phenomena, a solid sphere of variable refractive index at large aerosol radii and a thin film interference phenomenon at small aerosol radii.

The general objective of this research project is to study radiative transitions in atoms and molecules especially those relevant to infrared radiation. Major efforts include (i) determination of optical emission cross sections for atomic oxygen transitions produced by electron-impact dissociation of O2, (ii) electron excitation from a metastable level to a higher level, (iii) excitation behaviors of Na atoms, (iv) production of excited N atoms b electron impact on N2.

Thallium-doped silicon crystals were grown by temperature gradient transport from a solution consisting of silicon dissolved in a tin-thallium liquid-metal solvent. Thallium concentrations in excess of 10 to the 17th power/cc were obtained. The highest thallium doping concentration, 1.33 x 10 to the 17th power T1/cc, was obtained in material grown using a solvent of 86% T1 and 14% Sn at a growth temperature of 1370 degrees C. Various amounts of shallow acceptor impurities were observed in all of the material grown during the program. From Hall measurements, boron concentrations as high as 1.9 x 10 to the 16th power/cc were observed. A method for encapsulating thin layers (0.1mm thick) of 50% Sn and 50% Tl metal solvent within a silicon source-substrate assembly was developed. This approach was found to eliminate the boron contamination and produce uniform crystal growth. The samples grown exhibited quantum efficiency values as high as 18% at 3.1 microns. The thallium optical cross section at 3.1 microns was 1.45 x 10 to the 17th power/sq cm. Dislocation density measurements were made on some samples which fell in the 5,000 to 8,000 sq cm range.

Measurements of the differential light scattering cross-section in the ocean show that, while the volumetic differential scattering cross section dBeta/dOmega is highly peaked in the forward direction, the mean-square scattering angle is not small. Consequently, the many previous theoretical treatments based on the smallness of (Theta squared) are not applicable. (Author)

This report is the second part of the report entitled 'Absorption Coefficient of Alkali Halides.' In this second report, data analysis on the absorption coefficient in the multiphonon absorption region is carried out for LiF, NaF, NaCl, KBr, and KI. An equation is formulated to describe absorption coefficient as a function of both frequency and temperature. Constants in the equation were determined based on data fitting calculations and empirical correlations. The Urbach rule has been found to be applicable to the UV absorption edge of the transparent region; the equation derived in this study is considered to be its matching rule in the IR absorption edge. (Author)

This report summarizes the progress made during the first half of the climatology study contract period. It presents preliminary results which are useful in estimating the availability of space-to-earth optical communication systems.

This report summarizes research carried out to investigate energy transfer in an activator-activator system; that is a system for which energy transfer is reversible between certain metastable levels and for which stimulated emission from each of these levels can be generated. The specific system investigated is Er-Ho:YLF. Laser operation from two different ions in the same solid state host has been demonstrated. The 750nm (5S(2) - 5I(7):Ho) and 850nm (4S(3/2) - 4I(13/2:Er) transitions were observed simultaneously and separately at 77K. Cross transfer between the S levels was also observed and the cross transfer rates measured in crystals of five different compositions. Cross transfer between the S levels is mitigated by other cross relaxation transfer schemes which quench the S level storage time of each ion. Only about 25% of the initial population of one ion is transferred to the other in the optimum concentration, 2%Ho-2%Er, at room temperature. The cross transfer rate is only weakly temperature and concentration dependent; at low temperatures cross transfer is somewhat more effective as the decay rates of each ion are longer.

The objective of this report is to determine which type of reflective material, paint or tape, would be better to use on C3 and C4 missiles for laser tracking. (Author)

The design and construction of a simple, low cost, high power nitrogen laser is reported. The laser meets the optimum requirements for a dye laser pump source: 10-12 nsec FWHM, 1MW peak power, high peak-to-peak stability, and optimum operation to 50 pps. A novel electrode design and circular output beam cross section are emphasized. (Author)

In recent years, Binford's generalized cylinders have become an important tool for imagine understanding. However, research has been hampered by a lack of analytical results for these shapes. In this paper, a definition is presented for Straight Homogeneous Generalized Cylinders, those generalized cylinders, with a straight axis and with cross-sections which have constant shape but vary in size. This class of shapes, while still quite large, has properties which make considerable analysis possible. The results begin with deriving formulae for points and surface normals for these shapes. Theorems are presented concerning the conditions under which multiple descriptions can exist for a single solid shape. Then projections and contour generators are analyzed for some subclasses of shapes. The strongest results are obtained for solids of revolution (which the authors name Right Circular SHGCs), for which a closed-form method for analyzing image contours is presented. It is seen that a picture of the contours of a solid of revolution is ambiguous, with one degree of freedom related to the angle between the line of sight and the solid's axis. (Author), This article is from 'Image Understanding: Proceedings of a Workshop (14th) Held at Arlington, Virginia on June 23, 1983,' AD-A130 251.

An instrument (reflectometer) for continuously measuring the reflectance properties of materials as a function of the angle of incidence in which a sample and a mirror are mounted on a rotating platform in such a manner that, as the angle of incidence on the sample is varied, the reflected radiation is always incident on a detector which is fixed with respect to the rotating platform. The angle of incidence on the sample is measured and used to drive an axis of an X-Y recorder. The angle of incidence on the mirror is measured and used to correct the detected signal for any errors introduced by the properties of the mirror. This corrected signal is then used to drive the other axis of the X-Y recorder to produce a plot of the reflection coefficients vs angle of incidence for the sample. For fixed angles of incidence on the sample the detector can be moved to produce a plot of the diffused reflections as a function of the angular deviation from the specular angle. For this purpose the position of the detector is measured and used to drive the x-axis of the X-Y recorder. The input radiation is generally obtained from a laser and the instrument is supplied with polarizers or a polarization rotator as desired. (Author), Supersedes PAT-APPL-931 235-78, AD-D006 550.

The objectives of this research program are to develop metalorganic chemical vapor deposition (MOCVD) techniques for Manganese-bearing II-VI ternary compounds epitaxially grown on Gallium Arsenide substrates, and to explore the usefulness of UV laser assist for deposition for superlattice structures of wider bandgap II-VI binary compounds. For the first time, high quality single-crystal (111) Cd1-xMnxTe was grown by conventional MOCVD on (100) GaAs wafers with high resolution cross-selectional transmission electron microscopy was used for structural characterization, showing atomically abrupt interfaces, but different microstructures within the epi-film depending on growth temperature. UV adsorption spectra of a number of metalalkyl sources for Cadmium, Zinc, Selenium, and Tellurium were measured and optical adsorption cross sections calculated. Preliminary depositions of Cadmium Telluride and Zinc telluride films on glass substrates were mase at 200 C with UV excitation provided by an excimer gas laser operating at 193 nm and by using a parallel beam geometry. Some optical and X-ray diffraction data are presented as well as a description of the low pressure laser photochemical deposition system. Keywords: UV Photolysis, Superlattices, Thin films, Epitaxy, II-VI Semiconductors.