bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations of Glistening in the Environment and It’s Relationship to Stereo Vision
Authors: Bates Harry E.
Published: February 2023

One very interesting phenomenon observed with keen interest by the author over the years has been the effect of glistening snow. At first glance, this seems to be a simple optical effect caused by specular reflection from the flat surfaces of large ice crystals, similar to the sparkle created by sparklers. It would seem that a painter painting a landscape could render such an effect by painting a tiny white dot at the point of each sparkle. This is not the case for all glistening points. The light from each point that glistens is directed from the crystal surface in a beam who’s angular size is limited by a combination of diffraction and the apparent source size. If this beam size is large enough to more than fill both pupils of the eyes of an observer, then the visual impression is the same as a simple sparkle. On the other hand, if the beam width is small enough so that the observers two pupils receive significantly differing amounts of light, the visual impression is unlike that of a simple sparkle. Each eye sees points of light of differing intensities from a point. In fact, in many cases the sparkling point is seen by only one eye.
Multifunctional Thin Films in Butterflies
Authors: Wong Peter Y. , Miaoulis Ioarnis N.
Published: February 2023

Summary not available.
The Opposition Effect as Seen on the Earth and Other Worlds
Authors: Hapke Bruce
Published: February 2023

The opposition effect is an ubiquitous phenomenon in the bidirectional reflectances of particulate materials. Naked-eye telescopic examples are presented and causes discussed.
A Cirrus Cloud Glory
Authors: Sassen Kenneth
Published: February 2023

On 20 January 1995, an apparent cirrus cloud glory was photographed over central Utah from an airline passing through the 10.7 km MSL level as it began its descent into Salt Lake City International Airport. The cirrus cloud layer was geographically widespread and optically thin enough to view the snow-covered Wasatch Mountain Plateau beneath the cloud. The glory was easily visible surrounding the shadow of the aircraft, ahead of a short contrail. Photographic analysis shows a single reddish-brown ring of ~2.1° radius surrounding a central bright spot, although a vague second ring appeared visually to have been present over the brief (~3-min) observation period. The presence of a glory can only be accounted for through the interference effects of the backscattered light rays for particles that are spherical in shape. Coincident Salt Lake City radiosonde data show a cirrus cloud top temperature in the -50° to -55°C range. We are unable to evoke the presence of other, more exotic cloud forming substances at the indicated cloud temperature to explain this phenomenon. Hence, employing Mie theory scattering simulations, we conclude that this apparently unique atmospheric optical observation provides evidence for the occurrence of a population of ~20 μm diameter spherical ice particles. This size is consistent with those derived from cirrus cloud top corona displays, although in such cases unusually high linear depolarization ratios suggest the presence of complicated particle shapes. The lack of vivid colorization in the glory implies that the particle size distribution may have been broader than those of typical cloud droplet populations producing glories, or that the ice spheres were somewhat irregular in surface complexity. The brief appearance of this cirrus cloud glory, and its location over mountainous terrain, suggests that the cloud generating mechanism was a mountain wave cloud at about the cirrus cloud top position.
Lidar observes the aureole: a robust way to measure particle sizes
Authors: Eloranta E. W.
Published: February 2023

A circular region of increased brightness is often observed surrounding the sun and the moon. The outer edge of the pattern is often slightly reddish in color and on occassion one or more faint rings can be seen surrounding the inner pattern. This phenomena is caused by the diffraction of light around cloud or aerosol particles and is called the aureole. Practiced observers of atmospheric optical phennomena realize that the solar or lunar aureole can be used to estimate the diameter of the particles. The angular diameter of the aureole generated by small particles is larger than that generated by large particles. For optically thin clouds, theory, based on the wave nature of light, shows that the angular diameter of the inner lobe of the aureole,Θ, can be related to the particle diameter, D, and the wavelength of the light,λ, by the following approximation: The wavelength dependence of Θ explains why the outer edge of the aureole often appears reddish.
Spectroscopic Techniques for Diagnosis and Evaluation of Therapeutic Response
Authors: Svaasand L.O. , Fiskerstrand E.J. , Norvang L.T. , Nelson J.S. , Berns M.W.
Published: February 2023

Several optical methods have proved useful as a diagnostic tool for characterizing various skin disorders. The techniques vary from non-coherent methods such as, e.g., time independent reflectance spectroscopy and phase resolved photon migration based on evaluating the phase of the envelope of a high frequency amplitude modulated optical beam. A typical example a coherent or interferometric technique is optical coherence tomography where the spatial resolution is determined by the small coherence length a superluminescent diode source. Various infrared or thermal techniques are also important, ranging from imaging of the normal black body emission to time resolved measurements of the surface temperature initiated by transient selective heating of subcutaneous structures, such as, e.g., blood vessels.1-3)
Developing an Optical Fiber Reflectance Spectrometer for Home-Care Monitoring of Neonatal Jaundice
Authors: Jacques Steven L.
Published: February 2023

An optical fiber-based reflectance spectrometer for hospital and home-care monitoring of hyperbilirubinemia in neonates illustrates many aspects of dermal optics.
Determination of the Optical Properties of Turbid Media using Pulsed Infrared Tomography
Authors: Milner Thomas E. , Telenkov Sergey , Goodman Dennis M. , Smithies Derek , Tanenbaum B. Samuel
Published: February 2023

Knowledge of the optical properties of turbid media such as human skin is important for selection of the optimal dosimetry in many laser dermatological therapies. For example, knowledge of the relevant light fluence distribution in skin is especially important for therapies involving the combined application of laser heating and surface cooling.1,2,3 We present a technique using pulsed infrared tomography4,5 to estimate the optical properties of homogenous absorbing and scattering media; the more difficult problem corresponding to inhomogeneous media is not analyzed.
Analysis of Surface Cooling Techniques During Dermatological Application of Lasers
Authors: Anvari B. , Tanenbaum B.S. , Milner T.E. , Nelson J.S.
Published: February 2023

A comparative study of human skin thermal response to (1) contact cooling with a sapphire window and (2) spray cooling with various cryogens is presented.
High Energy/Intensity Polymer Dye Lasers with Variable Wavelengths for Medical Applications
Authors: Anderson Robert S. , Nechitailo Vladimir S. , Picarello Stephen C. , Matyushin Gennady A.
Published: February 2023

The Q-switched Nd: YAG laser is one of the most popular in a series of pulsed solid-state laser systems for dermatology and plastic surgery applications. The 532nm wavelength has been shown to be absorbed by a variety of chromophores. These include oxy-hemoglobin, melanin-containing epidermal cells and red tattoo pigments to name a few. However, for some medical treatments the physician may need additional wavelengths in the yellow-red spectral range.
Scanning Technologies in Laser Dermatology
Authors: Assa Shlomo
Published: February 2023

Summary not available.
Use of Variable Pulsewidth, Variable Pulse Duration Dye Laser in Treatment of Vascular Lesions
Authors: Narurkar Vic A.
Published: February 2023

We examined variable pulse duration and wavelength lasers at 532 nm and pulse durations between 2 ms and 10 ms and lasers with adjustable wavelengths at 585 nm, 590 nm, 595 nm and 600 nm with pulse durations of 450 μsec and 1500 μsec. Treatment of recalcitrant vascular lesions such as unresponsive port wine stains and lesions such as lower extremity telangiectasias have shown a favorable clinical response to these lasers. Long-term studies are underway to determine optimal pulse duration, wavelength and number of treatments with these lasers.
Use of Long Pulse Alexandrite and Ruby Lasers for Pigmented Lesions
Authors: Kilmer Suzanne
Published: February 2023

Use of the longer pulsed ruby and alexandrite lasers for pigmented lesions shows promise. Clinical and histological data are presented.
Increased Smooth Muscle Actin, Factor XIIIa, and Vimentin positive cells in the papillary dermis of CO2 laser debrided porcine skin
Authors: Smith Kathleen J. , Skelton Henry G. , Hurst Charles , Hackley Brennie E.
Published: February 2023

Skin is a major target for the chemical warface agent sulfur mustard (bis-2-chloroethyl sulfide; HD). Delayed wound healing is seen with HD-induced cutaneous lesions, and was the initial stimulus for our study using a pulsed CO2 laser to potentiate wound healing. Another factor we wanted to determine was what factors present within dermis and/or stromal cell populations therein could account for the tightening of skin seen after pulsed CO2 laser debridement.2-7
The Comparison of Erbium: YAG and CO2 Lasers in Facial Resurfacing
Authors: Khatri Khalil A. , Ross Victor , Grevelink Joop , Anderson R Rox
Published: February 2023

The use of lasers in Dermatology has increased significantly in past few years. The use of Carbon Dioxide laser (10,600 nm) allows to remove wrinkles and other effects of sun damage. The laser-tissue interaction time is limited to < thermal relaxation time of epidermis (1 ms) so that thermal diffusion does not occur during the laser pulse. The resulting band of thermally altered collagen usually measures less than 150 um. One of the limitations of CO2 laser resurfacing is the incidence of side effects, specifically prolonged redness, swelling, and changes in skin pigmentation. In addition, the thermal damage creates a “culture medium” in which bacteria can proliferate, so that the risk for infection is higher. Many otherwise ideal candidates are unwilling or unable to take the time off to recover before interacting with the public. This has led to a search for alternative laser resurfacing techniques.
Coating Thermal Transport Properties Measurement Using Thermal Diffusion Wave Interferometry
Authors: Swimm Randall T.
Published: February 2023

Recently there has been an upsurge of interest in measuring the thermal transport properties of optical coating materials in thin-film format in order to determine by what amount, if any, the coating properties differ from the bulk properties. The motivation for this interest is the possibility that thermal properties may be as important as optical properties in influencing the laser-induced damage threshold.
Picosecond Time Resolved Emission of Mercury Cadmium Telluride and Related II - VI Semiconductor Crystals
Authors: Hutchinson J. Andrew , Dutton T.E. , Rentzepis P.M. , Cooper Donald E. , Bajaj J. , Newman P.R.
Published: February 2023

Picosecond resolved emission of HgCdTe and CdTe crystals by IR-VIS streak camera shows temperature dependent multiexponential decay kinetics and elucidates the mechanisms of exciton trapping and anihilation.
Raman Analysis of Inorganic Thin Films*
Authors: Tallant D.R. , Higgins K.L. , Hargis P.J. , Stewart A.F.
Published: February 2023

Techniques for the Raman analysis of plasma-deposited submicrometer silicon films on metallic substrates and dielectric films on Raman-active substrates will be described and typical results will be presented.
A Differential Absorption Lidar System for Measurements of Tropospheric NO, NO2, SO2 and O3
Authors: Jolliffe Barrie W , Michelson Elizabeth , Swann Nigel R , Woods Peter T
Published: February 2023

A differential-absorption lidar facility has been developed by the National Physical Laboratory and mounted in a custom-built vehicle. It is now being deployed in a range of field measurement exercises. The facility operates in either a mobile or a stationary scanning mode. It is presently capable of range-resolved measurements of the atmospheric concentrations of NO, NO2, SO2 and O3 in the troposphere in the visible and ultraviolet regions of the spectrum. The system can be configured to monitor up to three species near-simultaneously and is currently being extended so that it can be operated in the infrared.
Analysis of Information Content of Multifrequency Laser Sounding of Aerosol and Molecular Atmosphere
Authors: Zuev V.E. , Kavkyanov S.I. , Krekov G.M.
Published: February 2023

The use of a single-frequency lidar for investigating the space-time structure of atmospheric aerosol has a limited field of application due to a possible ambiguity of interpreting the experimental data [1-3]. This paper considers the potentialities of spectral measurements for obtaining more complete data on the aerosol profiles.
FLIDAR-2 a Compact Lidar Fluorosensor and Spectrometer
Authors: Castagnoli F. , Cecchi G. , Pantani L. , Radicati B.
Published: February 2023

The FLIDAR-2 is the result of the researches carried out at IROE-CNR on the remote sensing of the environment by lidar fluorosensors and passive optical sensors.
Simulation of Lidar Pressure and Temperature Profile Measurements from the Earth Observing System (EOS) Satellite
Authors: Korb C. Laurence , Weng Chi Y.
Published: February 2023

The atmospheric pressure and temperature fields are two of the basic variables of fundamental importance in meteorology, climate studies, and for all scales of weather forecasting. The pressure field is used to describe the state of the atmosphere, frontal characteristics and to determine mass movement. The temperature field is needed for determining tropopause height, the depth and structure of the planetary boundary layer, and frontal and air mass characteristics. This paper presents an analysis of the sensitivity and instrumental parameters needed for lidar differential absorption (DIAL) measurements of pressure and temperature from the Earth Observing System (EOS) satellite. The proposed Lidar Atmospheric Sounder and Altimeter (LASA) facility on the EOS platform will allow global measurements of pressure and temperature profiles from a 700 km polar orbit.
Nonlinear Optical Interaction of Laser Radiation with Water Droplets
Authors: Chang Richard K.
Published: February 2023

In considering high-intensity laser propagation through the atmosphere, nonlinear optical effects such as stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), superbroadening, self-focusing, and dielectric breakdown of the optically transparent air become even more important when the air contains water droplets. For transparent water droplets with large size parameter (defined as droplet circumference 2πa divided by wavelength of interest λ), the droplet can be envisioned as a lens to concentrate the incident intensity (10) at three main locations:1 (1) outside the shadow face with ≅ 103 × 10; (2) inside the shadow face with ≅ 102 × 10; and (3) inside the illuminated face with less than 102 × 10. The nonuniform internal-field distribution and internal intensity enhancement significantly affect the nonlinear optical effects. Furthermore, a large transparent droplet can be envisioned as an optical cavity for specific internal wavelengths which satisfy the droplet cavity resonance condition [commonly referred to as morphology-dependent resonances (MDR’s)] associated with a sphere or spheroid.2-4 An analogy to a Fabry-Perot interferometer can be made by associating the liquid-air interface with the reflector (via total internal reflection) and the droplet circumference with the round-trip distance. For spheres5,6 and spheroids,7 the Q-factor of the droplet and the precise wavelengths which satisfy the MDR’s can be predicted by Lorenz-Mie and T-matrix formalism.
Lidar Measurements of the Troposphere
Authors: Carswell A.I. , Pal S.R. , Cunningham A.G.
Published: February 2023

This paper reports on an extended program of measurements of tropospheric properties using lidar remote sensing techniques. Two lidar systems have been employed. One is a dual frequency ruby lidar operating at low pulse repetition frequency (~0.2 Hz) and high energy output (~ 3 J @ 694 nm and ~450 mJ @ 347 nm) and the other is a Xe Cl excimer lidar operating at a single ultraviolet wavelength (308 nm) with prfs of up to 50 Hz at energy levels of the order of 50 mJ. Both systems are equipped with high speed digitizers (100 MHz) and are coupled to IBM PC's for data capture and analysis. The excimer lidar data system also includes a high speed signal averaging system. The ruby system has a multichannel receiver so that several return signals (at different wavelengths or polarizations) can be recorded simultaneously but the Xe Cl lidar has only a single receiving channel.
Accuracy of Temperature Measurements Using High Spectral Resolution Lidar
Authors: Krueger David A. , She C. Y.
Published: February 2023

The High Spectral Resolution LIDAR (HSRL) technique has been proposed (1,2) to measure the temperature profile in the atmosphere with a resolution of 1°K in real time with a spatial resolution of 15 to 30 m. A 10-nanosecond pulse centered on frequency, vL, is sent into the atmosphere. The returning light is split and each beam is passed through one of two very narrow atomic vapor filters centered on vF, but with slightly different band widths corresponding to different vapor temperatures. Tuning the laser frequency to coincide with the center of the filter will remove the strong central aerosol scattering peak. The transmitted light is that scattered by the air molecules at a range determined by the time delay. The ratio of these two signals is then compared to that calculated from kinetic theory (3,4) for different temperatures. The signal through the two filters will be given by where R is the calculated intensity of the scattered light, F is the transmission profile of the atomic vapor filter, A is the amplification factor of the electronics, and v is the frequency of the returning light. F will be a function of the temperature of the atomic vapor.
Applications of Laser Remote Sensing to Cell Biology and Medicine
Authors: Inaba Humio
Published: February 2023

Experimental studies are reported on laser sensing of cytotoxic T-cells, which play an essential role in rejection episode in clinical organ transplantation, and of microscopic fluorescence-intensity distribution in various single cells.
Remote Temperature Distribution Sensing Along Optical Fibers
Authors: Hartog A.H.
Published: February 2023

The use of optical fibres as transducers is currently the subject of active research justified by the promise of sensors able to offer high accuracy and measurement bandwidth, small size and immunity from interference even over long transmission paths. However, single point sensors only seldom utilise the very high intrinsic bandwidth of the optical fibre transmission medium. The need has therefore emerged to multiplex a number of sensing elements onto a single fibre or fibre pair and thus to form a sensor network distributed in space. This paper reviews recent progress in a particular class of distributed fibre optic sensors, based on the principle of optical reflectometry, which has considerable similarity to some of the LIDAR measurements reported in the literature.
Simultaneous Measurements of Ocean Surface Roughness and Atmospheric Pressure with a cm Resolution Two-Color Laser Altimeter
Authors: Abshire James B. , McGarry Jan F.
Published: February 2023

Gardner has proposed a technique for measuring both atmospheric pressure [1] and ocean surface roughness [2] by using a short pulse two-color laser altimeter. Two sets of airborne altimeter measurements have been performed using this technique, both of which utilized < 100 psec wide modelocked laser pulses. The impulse response of the initial PMT-based altimeter receiver was 800 psec [3], while that of the later streak camera-based receiver was 85 psec [4]. In the first airborne tests, the atmospheric pressure accuracies of the high resolution altimeter were 3-7 mbar [4].
Signal Requirements for Remote IR Limb Sounding of Atomic Oxygen and Temperature in the Thermosphere
Authors: Sharma R. D. , Zachor A. S.
Published: February 2023

Atomic oxygen plays an important role in chemical and collisional processes in the earth's mesosphere and thermosphere. Current techniques, both in situ and remote, for measuring oxygen atom densities in this altitude regime have produced results with unexplained large disparities. We are investigating the feasibility of an approach wherein vertical profiles of translational temperature and oxygen atom density are recovered from measurements of the earth’s limb radiance profile near 147 micrometers and/or 63 micrometers wavelength, corresponding to the OI (3P0-3P1 and 3P1-3P2) transitions of the ground electronic state of atomic oxygen. The assumption that the 3P fine structure levels are in thermodynamic equilibrium (LTE) with the local translational temperature is crucial to the proposed technique, but seems a reasonable one based on the very long radiative lifetimes of the level transitions.
Experimental Observations of Line-Mixing In A Infrared CO2 Q-Branch
Authors: Gentry Bruce , Strow L. Larrabee
Published: February 2023

The successful remote sensing of atmospheric temperature, humidity, pressure, and trace gas profiles depends upon a detailed knowledge of the radiative characteristics of atmospheric gases. For example, existing passive remote temperature and humidity sounders utilize infrared spectral channels that sense atmospheric CO2, N2O, O3, and H2O.
Tunable Waveguide CO2 Laser Local Oscillators for Spaceborne Infrared Heterodyne Spectrometers
Authors: Degnan J. J. , Rossey C. E. , Rowe H. E. , McGarry J. F. , Hochuli U. E. , Haldemann P. R.
Published: February 2023

For over a decade, the technique of infrared heterodyne spectroscopy has provided sub-Doppler resolution spectra of planetary atmospheres from Earth-based telescope facilities. The goals of our current local oscillator development program are twofold: (1) to design, build, and demonstrate a totally automated, compact, space-qualifiable engineering model of an RF–excited CO2 laser local oscillator; and (2) to extend the lifetimes of such lasers to a degree where they can be seriously proposed for longterm near earth or planetary flight missions. The current status of these two research areas is discussed.
Inversion Techniques for Backscatter Data from Remote Sensing Systems
Authors: Hummel John. R. , Kebchull Kurt A. , Bedo Donald E. , Swirbalus Robert A.
Published: February 2023

An examination of inversion techniques applicable to bakscatter data from remote sensing systems has been made. The purpose of the study was to develop an inversion technique that could be used with remote sensing systems under development at the Air Force Geophysics Laboratory (AFGL).
A Free Flying Experiment to Measure the Schawlow-Townes Linewidth Limit of a 300 THz Laser Oscillator
Authors: Byvik C. E. , Newcomb A. L. , Byer R. L.
Published: February 2023

Progress at Stanford University in the development of a LIDAR operating at one micron in a master oscillator power amplifier configuration required a reasonably stable, narrow linewidth laser oscillator. The required stability was achieved by the development of a non-planar Nd:YAG ring oscillator pumped by a ten-stripe diode laser array. Ten kilohertz linewidths are typical for this 300 THz oscillator. The Schawlow-Townes linewidth limit for this laser oscillator is predicted to be 1Hz per milliwatt output. A first time measurement of this linewidth limit for a laser oscillator operating at 300 THz is the objective of a proposed free-flying space experiment.
An Experimental Measurement of the Susceptibility of Spatial Filter Profiling Techniques to Saturation
Authors: Ochs G. R. , Hill R. J.
Published: February 2023

The current interest in the use of spatial filtering techniques to profile wind and refractive-index turbulence raises the question of how saturation of scintillation may affect these systems. Some experimental observations of saturation effects have now been made with a wind profiling system that is under development at the Wave Propagation Laboratory. The wind profiling technique, which is a modification of a method originally proposed by Lee,1 employes zero-mean spatial filters at both the transmitter and receiver to restrict the observation of refractive-index irregularities moving across a light path to those of a particular spatial wavelength and at a particular location along the path. The wind profiling system employs a number of sets of spatial filters of different spatial wavelengths to measure winds simultaneously at various path positions.
Simultaneous Measurements of Turbulence Level and Inner Scale Using Laser Scintillation
Authors: Frehlich R.G.
Published: February 2023

Laser propagation through the atmosphere produces random scintillation patterns. The statistics of these intensity fluctuations is determined by the refractive index spectrum of the atmosphere

Φ
n

(

q
→

)

where

q
→

denotes spatial wavenumber. Tatarskii proposed the following model for the turbulence spectrum1 where

C
n

2

is a measure of the level of turbulence and l0 is proportional to the inner scale λ0(λ0=2.95l0). The inner scale is defined as the intercept of the two power law regions of the three dimensional structure function of refractive index fluctuations.
Sum Frequency Mixing of two Tunable Nd:YAG Lasers for Sodium Fluorescence Lidar Measurements*
Authors: Jeys T.H.
Published: February 2023

An interesting coincidence of nature is that by sum frequency mixing the output of two appropriately tuned Nd:YAG lasers, the sum radiation may be made resonant with the sodium D2 transition wavelength. By exploiting this coincidence we have generated high power pulsed sodium resonance radiation. We plan to use this new source of sodium resonance radiation for characterizing the sodium layer in the earth's atmosphere. Figure 1 shows the cw wavelength tuning curves of the two Nd:YAG laser transitions. The 1.064 pm laser has a tuning range of about 6Å while the 1.319 μm laser has a tuning range of about 4Å. By operating the lasers at the wavelengths indicated by the arrows in Fig. 1 it is possible to generate sodium resonance radiation. In addition, it is possible to easily tune the sum radiation over the complete sodium Doppler absorption profile.
Detector Response Characterization for DIAL Application
Authors: Lee H. S. , Schwemmer G. K. , Korb C. L.
Published: February 2023

For accurate DIAL measurements, the detector output should have a linear response to the input light signal. In addition to good linearity, the detector should also have good gain stability and negligible signal-induced noise.

The requirement for gain stability is less stringent compared to the other requirements as long as the gain stability pattern is preserved between the pair of on-line and off-line pulses. The linearity of the detector response is critical in the sense that the nonlinear behavior of the PMT responsivity is normally dependent upon the signal amplitude itself. Therefore, for off line and on-line signals which are not identical, the effect of the non-linearity is not cancelled in the DIAL signal processing. The same argument applies for the signal-induced noise term. The cause and characteristics of the signal-induced noise which appears as a bias is not well understood.
Speckle Effects on Laser Wavelength Measurements with a Fizeau Wavemeter
Authors: Prasad Coorg R. , Korb C. Laurence , Schwemmer Geary K.
Published: February 2023

In this paper, we present results of an investigation of laser wavelength measurement with a wavemeter incorporating a coated Fizeau high resolution wedge. The effect of speckle on the measurement has been studied and several approaches have been taken to reduce the effect of speckle.
Effective Source of Coherent Radiation Based on CO2 Lasers and ZnGeP2 Frequency Converters
Authors: Andreev Yu. M. , Voevodin V.G. , Geiko P.P. , Gribenyukov A.I. , Zuev V.V. , Zuev V.E.
Published: February 2023

The ZnGeP2 monocrystals have high nonlinear figure of merit, third after Te and CdGeAs2. ZnGeP2 is sufficiently birefringent (B = + 0.04) for three-frequency matching mixing practically all over the transmission range. However, mainly due to low optical transmission of the monocrystals available, the experimental studies of frequency converters (FC) have been limited until recently to approbation of the CO2 laser radiation up-[1] and downconverters [2].
Implementing a New High-Spectral-Resolution Lidar Technique for Backscatter Ratio and Atmospheric Temperature Profiling
Authors: She C. Y. , Alvarez R. J. , Moosmüller H. , Krueger D. A.
Published: February 2023

Lidar systems rely on backscattering from air molecules (Rayleigh scattering) and from suspended aerosol particles (Mie scattering) for their return signal. Due to the thermal motion of both molecules and particles the backscattered light is Doppler broadened in frequency. Molecular backscattering has a temperature dependent linewidth of 2 GHz. Aerosol particles, being many orders of magnitude heavier than molecules, show much slower thermal motion and the resulting Doppler broadening can be neglected in most circumstances. The spectrum of backscattered light, consisting of a wide Rayleigh and a narrow Mie scattering component, is shown in Fig. 1(a).
0.53 µm Incoherent Doppler Lidar: Current Status
Authors: Sroga J. , Rosenberg A.
Published: February 2023

Measurements of the atmospheric wind field have been shown by simulations to improve global numerical weather prediction (Atlas, et al., 1985) and several spaceborne lidar systems have been proposed to meet the global wind measurement requirements. Menzies (1986) has given a comparison of the relative performance of four potential spaceborne Doppler lidar systems utilizing either coherent (heterodyne) detection at 1.06 µm and 9-11 µm wavelengths or incoherent (direct) detection at 0.35 µm and 0.53 µm wavelengths. This paper describes a ground based, 0.53 µm incoherent Doppler lidar and presents preliminary results of atmospheric testing to demonstrate this incoherent Doppler lidar technique.
Pulsed Frequency Stable Narrow Linewidth Lasers and Optical Remote Sensing
Authors: Lee K.K.
Published: February 2023

Usually people consider single mode pulsed lasers to be frequency stablized. But in a pulsed laser, mode selection is not equivalent to frequency stablization. This is because with any type of mode selection method or device, a long term frequency drift may occur from pulse to pulse due to thermal or mechanical disturbances of the cavity length. Furthermore, short term frequency drift (chirping) may occur within one pulse due to rapid refractive index variations of the active gain medium.
Theoretical aspects of above-threshold absorption
Authors: Shakeshaft Robin
Published: February 2023

We will review computational and physical aspects of the ionization of an atom by N photons with N>P, where P is the minimum number of photons required to ionize the atom. In perturbation theory the matrix element, M(N), for N-photon absorption can be decomposed as M+(N) + M−(N), which results from the decomposition of the stationary wave of the emergent photoelectron into its outgoing ( + ) and ingoing (−) parts. Each of the M±(N)are N-dimensional integrals over N radial coordinates ri, i=1,…,N. Although these integrals are not formally convergent for N>P, the integrand of M+(N) consists of functions that either decay exponentially or are outgoing waves for ri~∞.
Double Rydberg Spectroscopy of Barium Atom
Authors: Camus P. , Pillet P. , Boulmer J.
Published: February 2023

One of the interesting problem of atomic physics is to understand better the dynamic of highly excited two-electron systems (nℓn‘ℓ’). Recently, the exploration of highly excited two-electron states so called "double-Rydberg" states have been performed using multiphoton laser excitation in barium. From a theoretical point of view two classes of "double-Rydberg” states can be considered. At the so-called Wannier ridge (n~n’), the correlation between the electrons becomes pre-dominant. On the other hand, on both sides of the Wannier ridge (n’>>n), the outermost electron is moving in the field of the ionic core, partly screened by the inner electron. Properties of such "double-Rydberg states called "valley states" or planetary atoms could be described in terms of quantum defect theory.
Doubly Excited States
Authors: Gallagher T. F.
Published: February 2023

Doubly excited atoms, with two excited electrons, occur both above and below the first ionization limit. The interactions between the doubly excited states and the energetically similar singly excited channels are manifested by autoionization and series perturbations in these two cases. Historically these states have been studied by ultraviolet photo-absorption from the ground state. The absorption of the doubly excited state can be thought of as originating in the small excited state admixture of the ground state. This absorption is neccessarily weak with the result that it is comparable to direct photoionization. As both the excitation to the autoionizing state and the excitation to the continuum lead to an ion and an electron these two processes interfere to produce the familiar Beutler Fano profile characteristic of autoionizing states.
Dressing to the Hydrogen Atom in an Extremely Intense Laser Field
Authors: Janjusevic M. , Mittleman M.H.
Published: February 2023

The mutliphoton ionization rate of atoms in intense laser field is profoundly affected by the "dressing” of the states of the atom by the field. For example, the continuum threshold is known to be shifted upward by the ponderomotive potential. However, little has been done on the dressing of the initial (ground) state beyond lowest order perturbation theory. This is insufficient for intense lasers and this dressing is at least as important to the process as the shift mentioned above.
Laser Spectroscopy of Core-Excited Levels of Neutral Rubidium
Authors: Harris S. E. , Spong J. K. , Kmetec J. D. , Pedrotti K. D. , Wallace S. C. , Young J. F.
Published: February 2023

We describe first experimental results on a new technique for obtaining level positions, autoionizing linewidths, and oscillator strengths of core-excited levels.
An Overview of Above Threshold Ionization: There is Only One Physics
Authors: Freeman R.R.
Published: February 2023

The phenomena of Above Threshold Ionization (ATI) has been under intense investigation for nearly 10 years now. During this time not only have many diverse experimental and theoretical investigations been reported, but several major conferences have been held as well with the professed goal of achieving some consensus in the interpretation of the basic phenomena. Still, the ATI research community remains largely fragmented and confused about the basic physics and is in danger of dividing into separate "camps". In this paper I argue that the fundamental ideas necessary to understand the experimental results in ATI have already been put forward by many authors, often in other fields. For example, theorists interested in non-linear Compton scattering worked out the form of the interaction of high intensity light with electrons, and plasma physicists wrote down the consequences of this interaction for real-life measurements of kinetic energies of electrons produced in focused, high-intensity beams. Many investigators concerned with the non-linear interaction of high-intensity light on bound electron systems had to understand the concept of optical field ionization and have subsequently applied this knowledge to the measurement of spectra obtained in multiphoton ionization of molecules with ir light. I will show that if the relevant conclusions of these and other works are combined with the body of experimental and theoretical work from the ATI community, a rather simple and appealing description of ATI emerges, one which emphasizes the universality of its nature.
22 and 46 Degree Halos; Theory and Observations
Authors: Lynch David K.
Published: February 2023

Calibrated photometric intensity data are reported for the 22 degree halo. The observations are shown to agree well with a one dimensional theory (refraction in the principal plane). Theoretical polarization models are presented for a variety of width/length crystal ratios for both halos.
Performance Characteristics of Teleradiometers
Authors: Allard Douglas W. , Bush David H. , Hansen D. Alan , Collins John F.
Published: February 2023

Teleradiometers used in the EPRI sponsored Western Regional Air Quality Study were intercompared and tested for performance uncertainties including flare effects. Test results were used to assess the accuracy and precision of visual range estimates made concurrently with human observer estimates.
Bifrost: The Rainbow Bridge
Authors: Fraser Alistair B.
Published: February 2023

Bridges will be built which link conceptions of the rainbow that come from myth, religion, art, commerce and science.
Why can supernumerary bows be seen in a rainshower?
Authors: Fraser Alistair B.
Published: February 2023

Although the spectra of drop radii in rainshowers are very broad, the supernumerary bows are caused by only those drops with radii of about one-fourth millimeter.
Optical Spectrum of Breaking Wind Waves
Authors: Kerman Bryan R.
Published: February 2023

The spectral radiance of breaking wind waves on an ocean or lake, commonly referred to as whitecaps, has been measured using a multi-spectral scanner mounted in an aircraft. At least seven optical windows extending from .57 to 1.64 μm were employed. The texture of the scene varies with the interrogating wavelength. Many narrow streaks become apparent in the near visible band at 1.64 μm than in the visible bands. Apart from a factor of at least 10 in radiance between the whitecaps and the background water, the breaking waves demonstrate a different spectral distribution. In addition, a change in sensitivity occurs in the spectral radiance of the whitecaps at a wavelength of about .8 μm in the oceanic cases and .65 μm in the fresh water cases which is not observed in the light from the background water. Areas identified as foam indicate a behaviour intermediate in intensity and spectral distribution between whitecaps and background. Several attempts to automatically categorize pixels according to their spectral, probabilistic and spatial characteristics will be described.
Application of the theory of the tenous particles to the calculation of the optical properties of the atmospheric haze.
Authors: Raskin Vadim
Published: February 2023

In this article based on application of theory of tenous particles developed by K.S. Shifrin to the calculation of the optical properties of atmospheric aerosol, scattering diagrams and total scattering coefficients are obtained in analytic form for a polydisperse aerosol having junge slopes n=−3, n=−4, n=−6 Also it is shown that the polydisperse system of spherical particles with a power law size distribution has a scattering diagram most sensitive to the form of the particle size distribution for small angles of scattering.
Observations of Halo Scattering From Single Ice Crystals
Authors: Pluchino Antonino
Published: February 2023

Ice crystal haloes surrounding the sun and moon are a common sight. The most frequently observed halo occurs at 22°; a less frequent occurrence is the 46° halo. Also, rings of unusual radii have been seen and recorded. Although some are very rare phenomena, a host of other haloes, i.e., parahelia, arcs, pillars, the circumscribed halo, etc, have been observed. A comprehensive theory that encompasses all of these light-ice crystals interactions does not yet exist. Until a practical calculational method is developed, we have to rely totally on empirical evidence.
Lateral mirages and the boundry-layer heating problem for optics
Authors: Livingston W. , Lynds R.
Published: February 2023

Photographs of lateral mirages are analysed by mathematical modelling the temperature profile. Optical degradation at mirrors because of heat-exchange processes is similarly interpreted.
The Influence of Ion Bombardment on Etching Reactions
Authors: Winters Harold F. , Coburn J. W.
Published: February 2023

Etching involves the interaction of gaseous species (e.g., XeF2) with a solid surface (e.g., silicon) to produce volatile products (eg., SiF4(gas)). (For recent review papers on this subject see refs. 1-7.) Moreover this type of reaction is frequently enhanced by bombardment with ions,8,9 electrons,8 and photons.10-12
Ablation of Organic Polymers by Ultraviolet and Visible Radiation: A Theoretical Approach
Authors: Garrison Barbara J. , Srinivasan R.
Published: February 2023

There has been considerable interest recently in the use of laser radiation to remove material from a solid. Of particular interest is the observation that short pulses far-UV (e.g., 193 nm) radiation ablates organic polymers cleanly, i.e., the remaining sample exhibits a precisely defined pit (1-3). It is possible that the radiation could have melted or damaged the remaining sample. Indeed for longer wavelength radiation, e.g. visible light, damaged samples are generally observed (4). Obviously there are at least two distinct processes that can result in ablation of material when it is irradiated by laser light. In the following discussion we will refer to the phenomenon that cleanly etches the material as the photochemical process and the one that melts the sample as the thermal process. We have developed microscopic models for each of the two processes (5). In the photochemical model we assume one photon is directly responsible for dissociating one bond via a transition to an excited electronic state. In the thermal model we assume that the laser energy is absorbed into vibrational modes of the solid.
Raman Characterization of Catalysts
Authors: Wokaun A. , Baiker A. , Fluhr W. , Meier M. , Miller S.K.
Published: February 2023

The use of surface enhanced Raman scattering as a tool for the elucidation of reaction mechanisms in heterogeneous catalysis is investigated. The following information is desired:

- identification of the molecular species adsorbed at the surface, even if present in low concentrations; this includes reactants, major and side products;

- type and geometry of bonding to the surface;

- detection of intermediates which exist only as surface species.
Infrared Spectral Electrochemistry of Surface Reactions
Authors: Pons B. Stanley
Published: February 2023

In situ infrared vibrational spectroscopy of the electrode/solution interface has established itself as an efficient and informative method for study of the orientation and structure of adsorbed species. The method is growing rapidly in popularity due to is ease in implementation. Very high sensitivities (approximately 10-6 adsorbance) is attained with relatively simple instrumentation and by simple single external specular reflection. A range of related experimental techniques and their application has led to study of problems of wide electrochemical and general interest including: a) The detection and identification in aqueous and non-aqueous solvents of the potential dependent populations of solvent, simple ions, and organic solutes both in the adsorbed state and free in the double layer using a wide range of metallic and non-metallic electrode materials including well-defined single crystal surfaces. b) The investigation of the orientation, surface bonding, and intermolecular interaction of adsorbed species and the effects of electrode potential on these parameters. c) The identification and kinetics of reaction of adsorbed and non-adsorbed reaction intermediates such as radical anions and cations.
Excitation of Interacting Adatoms and Surface-Dressed Bloch Equation
Authors: Lin Jui-teng
Published: February 2023

The influence of a solid surface on the electronic excitation of a group of two-level adatoms and the associated power spectrum is investigated by means of a nonlinear surface-dressed Bloch equation. In the presence of a surface at a distance from the adatom which is comparable to the optical wavelength, the energy transfer dynamics is inflenced by the following factors: (i) nonradiative energy relaxation of the excited adatom via electron-phonon coupling, (ii) radiative spontaneous decay and stimulated emission caused by both the applied field and the reflected field, (iii) the oscillatory behavior of the adatom lifetime due to the interference between the applied and reflected field, (iv) the reflectivity and refrection index of the surface, (v) dipole dephasing caused by the surface phonons and plasmons, and (vi) interaction among the adatoms.
Recent Experiments on Photolysis for Low Temperature Epitaxy
Authors: Irvine S J C , Giess J , Mullin J B , Blackmore G W , Dosser O D
Published: February 2023

The infrared detector material CdxHg1-xTe (CMT) has become the most widely used narrow gap semiconductor for photon detection, despite problems such as high volatility of Hg, high interdiffusion coefficient for Hg and Cd, fast dopant diffusion and large segregation coefficients from the melt. The key to overcoming these difficulties lies with low temperature growth of epitaxial CMT and low temperatures for device processing. Photochemical deposition offers an elegant solution to these problems by removing the need for heat to dissociate metal-organics on the substrate. This review will concentrate on the conditions needed for epitaxial growth of these materials at temperatures below 300°C, more than 100°C below temperatures required for the pyrolytic growth process.
The Mechanisms of III-V Movpe and Routes to a UV-assisted process
Authors: Haigh J.
Published: February 2023

The epitaxial growth of III-V compounds by co-pyrolysis of Group III metal alkyls and Group V hydrides constitutes one application of the well-known technique of MOVPE (metallo-organic vapour phase epitaxy). Recently interest has been aroused in the possibility of photolytic enhancement of the process. Encouraging results have been reported [1,2] with GaAs. Photolysis and pyrolysis, at least in the case of the simpler metallo-organics, lead to rather similar products, and this implies that the initial stages are chemically similar and potentially compatible. The motivation for developing a photolytic/pyrolytic process derives primarily from the high spatial resolution of photon fluxes compared with conductive or radiative heat sources.
Unpinned GaAs Surfaces by Photochemistry
Authors: Woodall J.M. , Kirchner P.D.
Published: February 2023

GaAs surfaces routinely exhibit mid-gap Fermi-level pinning, where regardless of doping level or type, the surface Fermi-level lies about 0.8eV below the conduction-band edge. Until recently, unpinned GaAs has only been observed in certain electrolytes, at high-quality hetero junction interfaces, or in vacuum on cleaved (110) surfaces. Our group reported recently that (100) GaAs could be unpinned photochemically by spraying deionized water on a laser-illuminated sample that was mounted on a spin-coater typically used for photoresist. The response of band-edge photoluminescence to changes in excitation wavelength was used to measure the surface Fermi-level position. Both n- and p-type material responded to this treatment, showing that the Fermi-level was in fact unpinned and not simply repinned close to one band edge. Hg/PMMA/GaAs capacitors on unpinned surfaces showed control of the surface Fermi-level.