bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors Affecting Detection Sensitivities of Sputtered Neutrals Using Ultra-High Intensity Laser Post-Ionization
Authors: Wise Michael L. , Downey Stephen W.
Published: February 2023

Ultra high intensity post ionization mass spectrometry combines many positive features of secondary ionization mass spectrometry (SIMS) and sputtered neutral mass spectrometry (SNMS). All of these techniques use ion beam sputtering to sample the material or structure in question, affording both depth profiling and surface analysis with excellent depth resolution. Post-ionization is one form of SNMS, using a laser to photoionize sputtered atoms and is relatively free from SIMS-type matrix effects. The main question of ultra high intensity post ionization is can most or all elements be detected with nearly equal efficiency? If so, then no standards are required for quantitative analysis. The ratio of signals would be equal to the ratio of elemental concentrations. By contrast, SIMS requires a standard for each analyte determined in each matrix present in the sample because ionization yields vary by many orders of magnitude. Ideally, ultra high intensity post-ionization(1) detects all species similarly with one set of laser conditions, including electronically excited atoms or molecules. Other forms of SNMS detect neutrals with varying efficiency (electron impact) or require different laser parameters (like resonant post-ionization) for multi element detection. This paper will address the sputtering of the sample, which determines the species to be ionized. The partitioning into atoms, molecules or ions strongly affects the uniformity of detection efficiency.
Extending Wavelength Coverage and Spectroscopic Applications of Diode Lasers
Authors: Fox R. W. , Hollberg L. , Waltman S. , Petrov K. P. , Tittel F. K.
Published: February 2023

Atomic spectroscopy of an electronic transition from the ground state often requires a tunable blue or UV source. Traditionally one approach in the laboratory has been to double or sum-frequency mix pulsed or CW-dye lasers to obtain the necessary wavelength. These lasers and nonlinear crystals such as LiNbO3, and LiIO3, have also been used in difference frequency experiments to reach the molecular vibrational bands in the infrared. However, these laboratory lasers suffer the well known litany of size, cost and complexity when compared to solid-state diode lasers. To reach these wavelength regions starting with less expensive diode lasers would allow for the possibility of decreased size, cost and power.
Rayleigh and Raman Diagnostic of Laser Generated Plasmas
Authors: Pugsley Deborah Nassif , Hüwel Lutz
Published: February 2023

Laser-produced plasmas have long attracted the attention of researchers because of their unusual properties coupled with ease of generation. With laser power densities above approximately 1013 W/cm2 high electron densities and temperatures can be achieved and here x-ray lasers and laser fusion are important applications. At lower intensities, among other applications plasma etching and spectrochemical analysis make use of laser plasmas. We have found1 that for laser power densities of about 1010 W/cm2 the temperatures in the aftermath of Q-switched laser sparks in air (or other gases) can be several thousand degree Kelvin, even at times as late as 100 μs after ignition. Obviously, the plasma must eventually decay and approach ambient temperature. At least in principle, this opens the possibility to access conditions relevant for combustion and other high temperature chemical processes-even if only on a small spatial scale and during short time intervals. To study the feasibility of such high rep rate generation of temperatures in the range from say 300 to 3000 K we have investigated the spatial and temporal structure of Nd:YAG laser generated sparks in air and other gases during their final stages of decay, i.e. when their temperature and pressure approaches that of the surrounding gas.
Hydroxyl Measurements in Air-Breakdown Microplasmas
Authors: Parigger Christian , Lewis J. W. L. , Plemmons D. H. , Guan G. , Hornkohl J. O.
Published: February 2023

The hydroxyl radical has been extensively investigated for the thermal- and chemical characterization of combustion processes.1–4 High temperature OH spectra are also of interest for the characterization of laser-induced air plasmas and laser-ignited gaseous combustible mixtures. Spectral studies of laser-induced breakdown microplasmas in laboratory air were performed and time-resolved OH recombination emission spectra were measured and compared with theoretical predictions. Particularly in view of laser ignition of, for example, gaseous combustible mixtures, analysis of such recombination spectra is required prior to the use of OH as a combustion indicator in laser-ignited media.
All-solid-state Miniaturized Fluorescence Sensor Instrument for the Determination of Critical Gases and Electrolytes in Blood
Authors: Bruno Alfredo E. , Barnard Steven , Rouilly Marisel , Ehrat Markus
Published: February 2023

Care of patients in hospitals require often the routine determination of various critical blood analytes in untreated blood. The partial pressure of CO2 and O2 are the most important within the so-called blood gases, H+ (i.e. pH), Na+, K+, Ca2+ and Cl- are the significant blood electrolytes, and lactate, glucose, hemoglobin and creatinine are the crucial blood metabolites. We are developing a rugged miniaturized opto-electronic device to measure these analytes. In this work we will report the results obtained with a six channel, all-solid state, miniaturized fluorescence instrument, featuring super-blue LEDs as excitation sources, μ-optics to input/output light, and photodiodes as light detectors assembled according to pigtailing1 procedures. The six fluorescence channels can be used to determine the concentration of various blood analytes by selecting the appropriate combination of excitation light (i.e. LED and excitation filter), emission filter and sensing membrane. The performance of this instrument has been evaluated in terms of response, reproducibility, reversibility, photo-bleaching of indicator, selectivity etc..
Tunable Polymer Dye Lasers: A Review and Recent Achievements
Authors: Nechitailo Vladimir S.
Published: February 2023

The first plastic-host dye laser was built by Soffer and McFarland in 1967. A lot of efforts have been made to develop tunable solid state lasers in the visible spectrum afterwards.
CW Diode-Pumped Tunable Nd3+:KY3F10 Laser for Environmental Sensing
Authors: Dubinskii M. A. , Schepler K. L. , Naumov A. K. , Semashko V.V. , Abdulsabirov R. Yu. , Korableva S. L.
Published: February 2023

Laser environmental remote sensing is a powerful modem pollution control (atmosphere monitoring) technique. Hydrogen bromide (HBr) is a dangerous pollutant present in the atmosphere as a byproduct of commercial chemical reactions (chemical waste). HBr has quite high intensity molecular absorption lines in the near- and mid-IR (with respect to other species of atmospheric importance). In particular, HBr has a group of absorption lines between 9,300 and 9,800 cm−1 (1.020 and 1.075 μm) with typical intensities on the order of 10−24 cm−1/(molecule × cm−2), some of them going up to 10−23 cm−1/(molecule × cm−2). A simple Nd-activated laser with diode pumping and reasonably wide tunability in this region would be an appropriate source of radiation for HBr monitoring. Wide tunability particularly for wavelengths near 1055 nm not available from commercial Nd lasers will be the key issue for such a device.
Dual-wavelength temperature measurements in an IC engine using 3-pentanone laser-induced fluorescence
Authors: Einecke S. , Schulz C. , Sick V.
Published: February 2023

Exact knowledge of the local temperature during the compression of air/fuel-mixtures in engines is crucial for evaluating modeling results of the ignition conditions and the flame development after ignition. Especially in ultra-lean burning modern engines using stratified load and exhaust gas recirculation inhomogeneous mixing takes place and causes inhomogeneous temperature distributions. Thus two-dimensional temperature imaging techniques have to be applied to provide the necessary information for model calculations. Temperature measurements in the compression stroke both before and after ignition have been performed in specially designed optically accessible engines using Rayleigh scattering 1. In more production-like engines, however, due to background scattering the use of Rayleigh scattering for temperature measurements is very limited.
High sensitivity detection of molecular oxygen using cavity-enhanced frequency modulation spectroscopy
Authors: Gianfrani L. , Fox R. W. , Hollberg L.
Published: February 2023

In recent years, high finesse optical cavities have been used for high
sensitivity spectroscopy by exploiting the very long absorption path
lengths, 10 to 100 times greater than in traditional multipass cells.
Cavity Ring Down Spectroscopy applications have been widely performed
with both pulsed [1] and CW laser sources
[2]. Direct absorption spectroscopy with an optical
cavity has also been demonstrated by recording the peak transmitted
power around an absorption line [3]. Another relevant
application is represented by saturated absorption spectroscopy of
overtone molecular transitions. In this case, high finesse and high
build-up provide enough intracavity power for saturation of the
absorbing gas [4]. More recently, the
“NICE-OHMS” method, using frequency modulation
techniques, has been used to detect extremely weak saturated signals
in a high finesse cavity [5]. In this novel method,
the laser beam is frequency modulated at exactly the cavity
free-spectral-range (FSR) frequency. Using heterodyne detection of the
transmitted power, the phase shift of the central carrier produced by
optical dispersion gives rise to the signal. The NICE-OHMS method has
reported detection sensitivities for absorption of
10−12 cm−1 [5].
In this work, we demonstrate how the cavity enhanced frequency
modulation technique can be used to perform high sensitivity
measurements of small absorption signals, corresponding to weak
absorption lines in molecular oxygen.
A Phase-Based Metrology System for Measuring Trace-Gas Concentration
Authors: Rentz J.H. , Gargas J.A. , Schwarze C.R.
Published: February 2023

Recent advances in tunable laser diodes and their availability at multiple wavelengths in the near-IR has opened a new era of spectroscopic gas concentration measurement techniques. By adjusting temperature and injection current, the laser diode can be tuned to the wavelength of a molecular resonance of interest, and the absorption can be measured and used to obtain concentration. The injection current can also be modulated, allowing for synchronous detection schemes such as wavelength and frequency modulated spectroscopy (WMS and FMS) which effectively bypass the large 1/f noise component of the laser diode.1-4 In this paper, a new WMS technique is presented which measures phase due to the anomalous dispersion around a resonance for trace gas detection.
Laser Probe of Surfaces of Bacteriorhodopsin Langmuir-Blodgett Films by the Method of Second Harmonic Generation
Authors: Kir'yanov A. V. , Maslyanitsyn I. A. , Savranskii V. V. , Shigorin V. D.
Published: February 2023

Among the numerous methods of laser probing surfaces of Langmuir-Blodgett films (LBF), the method of Second Harmonic Generation (SHG) seems to be one of the most powerful ones. This method followed the discovery of SHG phenomenon in LBF [1]. So far, SHG was observed in LBF of various organic compounds. Recently, a few papers appeared dealing with studies of LBF surfaces by the SHG method (see, for example, [2]). It is characteristic that one can use this method to conclude about such properties of the films as degree of their homogeneity, orientation of the component molecules, etc. A strong dispersion-induced increase in the nonlinearities in combination with weak absorption in thin LBF can result in the generation of quite strong SH even if the molecules do not have the specific structural criteria [3] of high hiperpolarisability. Among such molecules, bacteriorhodopsin (bR, pygment of purple membranes of bacterium Halobacterium Halobium) is selected in this paper to demonstrate possibilities of the method.
Optical Pulse Propagation via Whispering Gallery Modes in Glass Spheres
Authors: Whitten W. B. , Shaw R. W. , Barnes M. D. , Ramsey J. M.
Published: February 2023

Early in this century, Rayleigh 1 showed that waves could propagate close to the wall of a spherical cavity with very little loss as long as the wavelength was small compared to the cavity circumference. The treatment was primarily for acoustic waves, modeling the whispering gallery effect, but he pointed out that electromagnetic waves should behave similarly. Study of the optical properties of dielectric spheres has received new interest with improvements in optical instrumentation and the emergence of new applications for high-Q resonators. It has recently been shown that optical pulses propagating in whispering gallery modes can be treated analogously to pulses in a fiber optic waveguide. Since the optical fields extend beyond the surface of the sphere, the sphere's environment could alter propagation properties such as cavity ringdown time. We describe here some time and frequency-domain measurements of picosecond pulses in glass spheres of millimeter dimension and discuss potential analytical applications.
Mid-Infrared Interband Cascade Lasers with External and Internal Quantum Efficiencies > 200%
Authors: Yang B. H. , Zhang D. , Yang Rui Q. , Lin C.-H. , Pei S. S.
Published: February 2023

Recently, we have proposed[1-3] and demonstrated[4] a new type of mid-IR quantum cascade (QC) lasers based on interband transitions in type-I quantum wells. This interband cascade (IC) laser takes advantage of the broken-gap band alignment in the InAs/Ga(In)Sb heterostructure to recycle electrons from the valence band back to the conduction band, thus enabling sequential photon emission from active regions stacked in series. However, by sticking to the interband transitions, it circumvented the fast phonon scattering which limits the performance of devices based on intersubband transitions such as the QC lasers based on InGaAs/InAlAs quantum wells (QWs). In addition to realizing stimulated emission at wavelengths around 3 and 4 μm,[4-6] room temperature electroluminescence has also been observed at wavelengths up to 15 μm.[7] In comparison, the QC lasers based on intersubband transitions have been successfully demonstrated to operate at wavelengths from 4.3 to 11 μm.
Mid-IR Vertical-Cavity Surface-Emitting Lasers for Chemical Sensing
Authors: Bewley W. W. , Felix C. L. , Vurgaftman I. , Aifer E. H. , Meyer J. R. , Goldberg L. , Chow D. H. , Selvig E.
Published: February 2023

Vertical-cavity surface-emitting lasers (VCSELs) are in many ways ideal for chemical sensing. A spectrally-narrow single-mode output beam with relatively low divergence may be obtained by confining the lateral dimensions to the order of a few wavelengths, whereas edge-emitting semiconductor lasers must either undergo extensive processing or employ an external cavity. However, until now the only published report of a short-cavity VCSEL emitting at a wavelength beyond 1.7 μm was a HgCdTe device which operated only to T = 30 K and required a threshold pump intensity of 45 kW/cm2 at 10 K.1
Continuously Tunable, Single Mode, External Cavity Diode Lasers at 2 μm
Authors: Feller G. S. , Wu I-Fan , Day T. , Menna R. J. , Martinelli R. U. , Connollv J. C. , Mihalcea R. M. , Baer D. S. , Hanson R. K.
Published: February 2023

Compact, inexpensive laser sources in the 2-4 μm wavelength region are of growing interest for applications in environmental detection of trace gases as well as medical diagnostics, process control and combustion analysis. Many organic compounds, including hazardous pollutants, have characteristic absorption spectra in this region. Although external cavity diode lasers (ECDLs) are commercially available from 0.6 μm to 1.6 μm 1, 2, they have not yet made it into the 2 μm wavelength range. Others have recently demonstrated tunability in an external cavity at 3.3 μm3 which was not continuous or single mode. We present room temperature operation of single longitudinal and single spatial mode, external cavity tunable diode lasers operating around 2 μm. We also present high-resolution absorption measurements of CO2 over the 250 cm−1 laser tuning range.
Laser Based Absorption Sensor for Trace Gas Monitoring in a Spacecraft Environment
Authors: Lancaster D. G. , Richter D. , Graf J. C. , Curl R. F. , Tittel F. K.
Published: February 2023

Formaldehyde is a chemical widely used in many industrial manufacturing processes due to its high chemical reactivity and good thermal stability. Commonly used building materials like foams, paint and polymer products can contain formaldehyde. Studies indicate that H2CO can cause a variety of health effects ranging from irritation of eyes, nose, and throat to nausea and headaches at concentrations above 100 ppb. For extended habitation, NASA has set a more stringent spacecraft maximum allowable concentration of 40 ppb for crew exposure from 7 to 180 days. To reduce formaldehyde levels below this concentration, outgassing materials and equipment need to be identified. In order to monitor the concentration and to locate emission sources, the development of an in-situ, real-time, portable gas sensor capable of detecting formaldehyde of sub-ppm levels in air was developed.
Molecular Photoionization and Chemical Imaging
Authors: Willey K. F. , Vorsa V. , Winograd N.
Published: February 2023

It is now possible to desorb a variety of organic molecules from surfaces using a tightly focused energetic ion beam. The molecules are detected as secondary ions using time-of-flight mass spectrometry, and may be spatially resolved by rastoring the ion beam over a larger area. A chemically resolved image is then acquired by examining the intensity of a particular mass as a function of x,y position. Presently, liquid metal ion sources using 25 KeV Ga+ ion projectiles can be focused to a spot of less than 20 nm in diameter. The limiting factor for molecule-specific imaging is sensitivity. The ion dose must be kept less than 1% of the total number of surface molecules to prevent chemical damage. Moreover, the ionization probability of desorbed molecules is generally less than 1 in 104. Since the molecules desorb from the first layer and since there are at most 4 × 106 molecules per square micron (depending on size of course), the signal rapidly approaches zero as the spatial resolution or beam probe size is reduced below 1 micron.1 Here we investigate the use of high intensity 100 fs laser pulses to photoionize the desorbed neutral molecules in an attempt to increase the measurement efficiency of this type of experiment. Our model system is dopamine, an important neurotransmitter that has aromatic character, but is subject to significant fragmentation using ns laser pulses. The results suggest that this approach can indeed expand the performance of mass-spectrometry based imaging experiments and can open new applications in bioimaging.
Laser Probe Of Surface Reaction Dynamics
Authors: Zhu Xiaoyang
Published: February 2023

Understanding surface chemical kinetics is essential to the advancement
of the frontiers of many vital technologies, such as semiconductor
device fabrication and heterogeneous catalysis. This indisputable
driving force, along with the rapid development of a large repertoire
of atomic, molecular, and structural sensitive surface probes, has
been responsible for the built-up of an immense literature on the
chemical pathways and kinetics of a large number of molecules on an
equally large number of solid surfaces. A typical example of a surface
chemical study may involve the identification of surface chemical
species and gas phase products in a certain parameter phase space, as
well as the measurement of kinetic parameters for key reaction steps.
This practice is widely employed today to tackle a seemingly
inexhaustible number of important surface chemical problems. Such a
pragmatic approach is by no means mundane since the problems we are
tackling are increasingly more complex while the tools at hand are
ever more powerful. However, to some in the field, obtaining chemical
kinetics of another molecule on another surface is not as gratifying
as taking perhaps even a blurred glimpse into the elementary chemical
act responsible for the surface chemical reactivity. It is the purpose
of surface reaction dynamics to probe and understand the elementary
chemical acts responsible for the macroscopic kinetic behavior.
Understanding at such a fundamental level may allow us not only to
explain but also to predict surface reaction rates.
A Diode-Laser Based Resonance Ionization Mass Spectrometer for Selective Ultratrace Analysis
Authors: Wendt K. , Blaum K. , Bushaw B. A. , Geppert C. , Müller P. , Nörtershäuser W. , Schmitt A. , Trautmann N. , Wiche B.
Published: February 2023

Resonance ionization mass spectrometry (RIMS) has become a widely used technique for isotope-selective ultra-trace analysis1-4. It provides complete isobaric suppression, high overall efficiency and strongly increased isotopic selectivity in respect to conventional mass spectrometers. Still a major drawback for the application of this technique is the complexity of the experimental set-up, particularly the laser system, which restricts utilization of the technique to a small number of university and research institutes so far.
Toxic Multi-Metal Continuous Emission Monitoring by Laser-Induced Breakdown Spectroscopy
Authors: Zhang Hansheng , Yueh Fang-Yu , Singh Jagdish P.
Published: February 2023

Laser-induced breakdown spectroscopy (LIBS) is a laser-based, advanced diagnostic technique for measuring the concentration of various elements in the test medium.1-3 In LIBS, a pulsed laser beam is focused at the test point to produce a spark. The spark in the focal region generates a high density plasma which atomizes and electronically excites the various atomic elements in the test volume. Atomic emission from the plasma is collected and analyzed to obtained the concentration of the atomic species in the test medium.
Diagnostics and Sensors for Turbine Engines
Authors: Seitzman J. M. , Wainner R. T. , Tamma R.
Published: February 2023

There is a growing urgency for improved performance of combustion devices, for example higher efficiency and lower pollutant emissions. Because of high power requirements and strict size limitations, turbine engines for aircraft propulsion present a particularly difficult challenge. In order to increase specific thrust, improve efficiency and reduce engine size, recent efforts in turbine engine technology have been directed toward increased operating pressures (>30 atm). Maintenance of optimum conditions, e.g., turbine inlet temperature profiles, becomes more difficult as these engines are obliged to achieve optimal performance closer to materials limits and in off-design conditions. Active control of turbine engines offers great potential for such improvements. However, active control of turbine engine combustors requires sensors that are capable of monitoring high temperature and high pressure combustion gases. In such a hostile environment, optical techniques are a natural solution, as they offer the possibility of non-intrusive measurements. At the same time, measurement of combustion particulates, primarily soot, is of great interest. Soot plays a key role in radiative heat transfer in the combustor, and therefore, represents a significant source of combustor liner heating. Soot emissions from aircraft during takeoff are of interest since small particulates like soot have been determined to pose respiratory health risks. Finally, soot emitted from aircraft engines at higher altitudes may act as water condensation sites and therefore play an important role in global climate through changes in the earth’s albedo.
Cavity Ringdown Calibration of Laser-Induced Incandescence
Authors: Vander Wal Randy L. , Ticich Thomas M.
Published: February 2023

Laser-induced incandescence (LII), a technique which determines relative soot volume fraction, requires calibration to yield quantitative results. Spatially resolved LII signals from soot within a methane/air diffusion flame are calibrated using cavity ring-down (CRD) which avoids extrapolation required of less sensitive methods in current use. Using CRD, quantification of LII for ppb f
v
levels is demonstrated.
Vapor/liquid mass fraction measurements by linear Raman spectroscopy
Authors: Mewes Bernd , Bauer Gerd , Brüggemann Dieter
Published: February 2023

In almost all combustion systems the liquid fuel is injected into the
combustor as a spray. Spray formation, vaporization, and mixing with
the oxidizer determine the quality of the combustion process and
thereby the amount of unwanted emissions. A laser diagnostic is needed
which can monitor these processes in order to optimize them.
Especially the distributions of vaporized fuel and of oxidizer are of
interest including regions where liquid fuel is coexisting. A
well-known method to discriminate between different phases of the fuel
is the exciplex fluorescence technique developed by Melton and
Verdieck [1]. Quantitative results are difficult to
obtain if oxygen, the oxidizer in almost all combustion systems, is
present. Another technique is based on the fluorescence of acetone
which is practically independent of its phase. Phase discrimination is
done by using the huge difference in molecular density
[2]. The high absorption coefficient for the used UV
light prevented saturation of the CCD camera by liquid droplets.
Evaluation of 2 Line Laser Induced Atomic Fluorescence for Two Dimensional Thermometry in Practical Combustion Applications
Authors: Kaminski C. F. , Engström J.
Published: February 2023

The measurement of temperature field distributions in practical combustion devices is an important task in combustion diagnostics because of the sensitive temperature dependence of rate coefficients of chemical reactions. For example, the production of toxic by-products during combustion may be influenced by local temperature variations. Spatially resolved temperature data is thus highly relevant from a theoretical as well as practical point of view: In the former case it may serve for the refinement and validation of models describing the process under investigation. In view of the latter, visualisation of temperature field distributions may aid engineering intuition and ultimately help in the design of more efficient and environmentally friendly combustion systems.
In-situ Oxygen-Monitoring using Near-Infrared Diode Lasers and Wavelength Modulation Spectroscopy
Authors: Ebert V. , Pleban K.-U. , Wolfrum J.
Published: February 2023

Despite increasing recycling quota the removal or long time storage of the remaining municipal waste remains a difficult task. This is valid especially in densely populated countries like Germany or Japan where there is little space for waste disposal sites. Hence waste combustion is used as a effective way to reduce the waste volume and to utilize the energy stored therein. However due to the large inhomogeneities of the refuse its combustion is a very demanding task. To minimize emission of pollutants and corrosion damage and to optimize energy production simultaneously fast in-situ diagnostics and active combustion control systems, like TACCOS [1], a thermography system based on an mid-infrared scanner camera which directly measures local imbalances in the fuel bed temperature or LISA [2], a CO2-laser based in-situ ammonia sensor used for on-line control of NOx removal systems (SNCR or SCR), are required. A very promising tool for the development of fast in-situ sensors are tunable diode lasers. They are inexpensive, compact, rugged, and relatively simple to operate. Due to their fast tunability, high spectral resolution and spectral power density they offer the opportunity for specific, nonintrusive, chemical sensors with a fast time response making them attractive for active combustion control. Since oxygen is one of the most important molecules for all combustion processes and not accessible by alternative optical detection methods there is a strong need (e.g. to adapt the secondary air flow or distribution in incinerators or other combustors) for a fast in-situ oxygen sensor which can measure at high temperatures and close to the reaction zone. Hence in a first attempt we tried to develop a diode laser based in-situ oxygen sensor which had to be fast enough for active control purposes e.g. in incinerators.
Energy transfer processes in OH and CH revealed by time-resolved LIF and numerical simulations
Authors: Brockhinke A. , Bülter A. , Lenhard U. , Rahmann U. , Kohse-Höinghaus K.
Published: February 2023

A picosecond laser system is used to study energy transfer processes in OH and CH in atmospheric-pressure flames. Using these measurements, a numerical code for the simulation of spectra affected by RET and VET is developed. Different methods to obtain quench-free results are suggested.
Application of Angie-Dependent Light Scattering and Fractal Dimension Analysis for Detection and Characterization of Biopolymers
Authors: Miller J. Houston , Souza Glauco R. , Levin Carly , Barter Emily
Published: February 2023

Over the past year we have performed both theoretical calculations and light scattering measurements utilizing simplified model systems in which we demonstrate the feasibility of combining ADLS/FD and Au-DNA nanopariticles of different sizes for detecting specific sequences of DNA and characterizing Au-DNA fractal aggregates. The ADLS apparatus used in this work was constructed from off-the shelf optical components (Souza and Miller, 2001).
The Mie Theory of the Corona
Authors: Lock James A. , Yang Leiming
Published: February 2023

The so-called diffraction corona is a series of alternating pink and pale green rings that is occasionally seen around the sun or moon when observed through a thin layer of altocumulus or cirrocumulus clouds.1 In the standard explanation of this phenomenon, incident light waves are diffracted by the cloud water droplets and the different wavelengths of visible light possess strong diffraction maxima at different scattering angles.2 As a result, the diameter of the cloud droplets producing the corona may be estimated from the angular diameters of the corona rings. In addition, the diffraction theory of the corona predicts that the saturation of the colors of the rings produced by monodisperse water droplets is independent of the droplet size.
Scattering of White Light from Oblate Water Drops Near Rainbows and Other Diffraction Catastrophes
Authors: Simpson Harry J. , Marston Philip L.
Published: February 2023

Rainbow, transverse cusp, and hyperbolic umbilic caustic patterns of levitated drops in white light were photographed. Observations suggest what natural generalized rainbows would look like.
Rethinking the Rainbow’s Colors
Authors: Lee Raymond L.
Published: February 2023

For most of us, the phrase "all the colors of the rainbow" conjures an image of the natural rainbow1 as a paragon of color variety and vividness. Indeed, both our language and art often invoke the rainbow as a color palette without peer.2 Yet as a color standard, the rainbow has an oddly contentious history. For example, arguments about the number of rainbow colors date to antiquity, with observers as keen as Aristotle3 (who favored three colors) and Seneca the Younger4 (who favored an indefinite number) among the disputants. That this disagreement still persisted in Georgian England2 (and indeed to the present) hints that the rainbow poses special perceptual problems.
Vision and Light Scattering in the Living Eye
Authors: Beckman Claes , Nilsson Olle
Published: February 2023

Bright stars do not appear to us as perfect points but as small irregularly shaped figures from which a few rays may diverge.
Twilight and Daytime Colors of the Clear Sky
Authors: Lee Raymond L.
Published: February 2023

Several years ago Bohren and Fraser1 asked “How can anyone have the audacity to write about colors of the sky in the year 1985?” Nearly a decade later, writing about sky colors is no less audacious — and no less necessary.
Bishop's Rings and Cirrus Cloud Coronas: The Optics of Frozen Sulfuric Acid Particles
Authors: Sassen Kenneth , Peter Th.
Published: February 2023

The variety of optics displays that occurs in our atmosphere, which include bows, arcs, halos, and coronas, are reasonably well understood on the basis of the refraction, reflection and diffraction effects produced during the scattering of sunlight by various types of liquid or solid phase water particles.
Alternative Explanations of Lowitz Arcs
Authors: Tape Walter
Published: February 2023

Lowitz arcs were first described by Tobias Lowitz [1794] in the St. Petersburg Display of 1790.
Halo Photopolarimetry and Direct Crystal Sizing
Authors: Können G.P.
Published: February 2023

During some nearby displays I recorded the light and polarization distributions of halos with a polarimetric camera and simultaneously I replicated the falling crystals in acrylic spray.
A Search for Halos in Martian Condensation Clouds
Authors: Pearl John C.
Published: February 2023

Martian condensation clouds have long been observed from Earth(1) and from spacecraft(2).
A Comparison of Sun Pillars With Light Pillars From Nearby Light Sources
Authors: Hock Jeffrey L. , Mallmann A. James , Greenler Robert G.
Published: February 2023

Sometimes a vertical column of light can be seen either above or below the sun, usually when the sun is low in the sky.
Observation of the E6 Diffraction Catastrophe Associated with the Primary Rainbow of Oblate Drops
Authors: Kaduchak Gregory , Marston Philip L. , Simpson Harry J.
Published: February 2023

Several studies have been conducted concerning the far field focusing of oblate water droplets.
Light Scattering by a Dense Distribution of Haze Particles on a Windowpane
Authors: Lock James A. , Chiu Chin-Lien
Published: February 2023

When one looks at a distant street light through a window covered with small haze particles produced by condensation, one often sees that the region immediately around the street light is dark, with colored rings of light surrounding it1.
Mie Theory, Airy Theory, and the Natural Rainbow
Authors: Lee Raymond L.
Published: February 2023

A commonplace of optics history is that Newton’s (and Descartes’) geometrical optics dominated 18th-century rainbow theory. Similarly, George Airy’s 1838 interference/diffraction theory built on Thomas Young’s work and held sway for several decades in the 19th century, although not without early detractors. The ascendance of these theories clearly depended on their ability to explain naked-eye features of the natural rainbow (i.e., bows seen in rain, clouds, or spray). However, Airy theory was soon held to a different standard: predicting the angular positions of intensity maxima and minima for spheres and cylinders illuminated by nearly monochromatic light (Boyer 1987, pp. 304-310). Despite early success with such predictions, Airy theory was found wanting by 1888, when one experimenter said that his measurements showed it to be “but a first approximation” (Boyer 1987, p. 313).
On the Solar Spectrum and the Color Sensitivity of the Eye
Authors: Soffer Bernard H. , Lynch David K.
Published: February 2023

The peak brightness in the solar spectrum is in the green only when plotted as a distribution in wavelength units It peaks in the infrared when plotted in frequency units. Therefore the oft-quoted notion that evolution lead to an optimized eye whose sensitivity peaks where there is most available sunlight or daylight is misleading and erroneous. The eye does not appear to be optimized for detection of sunlight, daylight nor for the surprisingly large amount of infra red radiation in the environment. The color sensitivity of the eye is discussed in terms of the spectral properties and the photo and chemical stabilities of the available biological materials as well as the possibility that we are viewing a souvenir of the human evolutionary voyage.
Computer Simulations and Visualisation of Mirages and Observations at the North Sea
Authors: Tränkle Eberhard
Published: February 2023

Inferior mirages above hot roads and in the desert are well known. Less familiar are mirages above wet sand banks and mud-flats(watt). Off North Friesland in Germany there is a unique region of mud-flats with about 10 small flat islands with one or a few houses(warft), called Halligen. The distance between these Halligen is 5-10 km. In summer at low tide good conditions often exsist for the appearance of mirages. Typically the mirages are simple inferior mirages. The mirages of Halligen are striking, they look like airships at the horizon [1]. But sometimes the mirages are more complex and cannot easily be explained.
Expanding the Arago Neutral Point: Digital Imaging of Clear-Sky Polarization
Authors: Lee Raymond L.
Published: February 2023

Observations of the clear sky’s polarization have a venerable history that includes such 19th-century figures as David Brewster, Jacques Babinet, and François Arago. In his pivotal 1871 paper on sky color and polarization, Lord Rayleigh provided a succinct theoretical explanation for skylight’s maximum polarization 90° from the sun. Rayleigh did not mention the neutral points (points of zero polarization) observed in the sun-zenith plane by Arago, Babinet, and Brewster. Although Rayleigh was confident that he had “disposed of the polarization” problem (Strutt 1871, p. 110), others did not view his silence on the neutral points as a proscription.
In Situ and Remote Sensing Analysis of a Corona-Producing Cirrus Cloud
Authors: Sassen Kenneth
Published: February 2023

On the night of 19 April 1994 coordinated University of North Dakota Citation aircraft and University of Utah polarization lidar data were collected from a lunar corona-producing high altitude cirrus cloud from the DOE Cloud and Radiation Testbed (CART) site near Lamont, OK. In agreement with earlier lidar studies (Sassen 1991), relatively strong laser depolarization was noted near the frigid (-70°C) cloud top, which was located slightly above the tropopause. Although the two-ringed corona was not successfully photographed, the radius of the first red ring was estimated to be 2.5 moon diameters (~2.5°). The mean in situ ice crystal sizes derived from the FSSP measurements (the particles were too small to be effectively sampled by the 2D-C ice crystal probe) varied from 20-25 μm in diameter, which is consistent with the estimated size of the corona using simplified diffraction theory. Ice crystal concentrations were atypically high for cirrus, ranging between 400-500 cm-3. The habits of these ice crystals are currently being examined photomicrographically using the plastic replicas of the particles captured by impaction during the aircraft mission.
Basic Science of Laser-Assisted Hair Removal
Authors: Dierickx Christine C. , Anderson R. Rox
Published: February 2023

There are 3 means by which light can destroy hair follicles : thermal (due to local heating), mechanical (due to shockwaves or violent cavitation) and photochemical (due to generation of toxic mediators like singlet oxygen or free radicals). Removal of hair has been attempted by all three means.
Photothermal Probe-Beam Deflection Measurement of Moisture Adsorption on a Silicon Surface Under Atmospheric Conditions
Authors: Schroeder Holger , Tam Andrew C.
Published: February 2023

Although there is much work done on thermal desorption of molecules on a solid surface /1/, most previous work was performed in vacuum or low-pressure conditions and utilized direct particle detectors (e.g. mass spectrometer). The present work examines photo-thermal desorption from a surface in atmospheric conditions utilizing a probe-beam deflection /2/ technique. This is demonstrated for an important case of adsorbed water on a silicon wafer with normal surface oxide.
In-Situ Raman Microprobe Analysis of Direct Laser Writing
Authors: Herman Irving P.
Published: February 2023

Raman scattering is a versatile, non-destructive diagnostic of semiconductors and other materials, which can be used either in-situ after processing has occurred or, in many circumstances, in real-time during processing. By proper selection of lasers and optical design, Raman microprobe methods may be used to investigate sample stoichiometry, doping, crystallinity, stress, and temperature with micron or sub-micron lateral and depth resolution. The use of Raman microprobe techniques to analyze microstructures made by direct laser writing and to analyze microstructures heated by localized laser irradiation is described here.
Laser Diagnostics of Cadmium Telluride: Crystal Quality and Exciton Dynamics
Authors: Cooper Donald E. , Bajaj J. , Newman P.R. , Rentzepis P.M. , Hutchinson J. Andrew
Published: February 2023

Cadmium telluride is a II-VI semiconductor of increasing interest because of the use of its ternary alloy HgCdTe as a tunable-bandgap IR detector material. CdTe is often used as a substrate for the growth of HgCdTe epilayers and the detector performance depends upon the purity and crystal quality of both the epilayer and substrate.[1] Laser diagnostics of CdTe make possible the nondestructive screening of detector materials. In many cases electronic properties such as donor and acceptor concentrations can be determined without contact fabrication. Here we present both CW and time-resolved low-temperature spectra of CdTe. The CW spectra are useful for evaluating the crystal quality and the photoluminescence (PL) decays represent the first time-resolved results on single crystal CdTe.
Picosecond Transient Reflectivity and Raman Gain Spectra of GaAs
Authors: Wessel John , Beck Steven
Published: February 2023

Recently Woodall and co-workers1 at IBM reported interesting results from a photowashing procedure applied to (100) GaAs. Unpinned behavior was observed immediately after washing. Photoluminescence yields measured from regions near the surface increased dramatically. The results suggested that the strong surface band bending ordinarily present in GaAs can be essentially eliminated by the photowashing procedure.
TV-Holography (ESPI) in Material Diagnostics
Authors: Lokberg Ole J. , Malmo Jan T.
Published: February 2023

Almost a quarter of a century ago hologram interferometry was hailed as the promising tool for material testing and diagnosis. This prophesy has been partly fulfilled, but mainly within the safe enclosure of the laboratory and for carefully designed experiments. The limitation of the technique has been-and still is, even with the new thermoplastic materials- the time delay between recording and display.
Laser Mapping of Al-h+ Impurity Distribution in Vacuum Swept Crystalline Quartz
Authors: Anthes J.P. , Garcia P. , Koehler D.R.
Published: February 2023

We have used HeNe laser light absorption to perform 2-D spatial mapping of hole-compensated aluminum (Al-h+) impurity sites produced during vacuum sweeping of crystalline quartz. Application of an electric field parallel to the optic axis can produce a hole(1) trapped at a non-bonding oxygen ion (AlO4)° site. These hole-compensated Al-h+ sites introduce color center absorption. The electro-diffusion process (sweeping) is performed under elevated temperature and vacuum conditions. The diffusion process produces a time-dependent spatial distribution of the Al-h+ centers and associated A1-band optical absorption which is coincident with the 633-nm-HeNe laser wavelength. Spatial variations in the A1-band absorption for swept quartz and for quartz subjected to ionizing radiation are correlated with the observed(1) coloration. Devices fabricated from crystalline quartz with hole-compensated aluminum impurity sites are resistant to the effects of ionizing radiation. The 2-D mapping of optical absorption is compared to electron spin resonance (ESR) measurements of aluminum impurity concentration in samples of vacuum swept cultured quartz.
Analysis of Uranium Solutions Using Laser-Induced Breakdown Spectroscopy
Authors: Cremers David A. , Wachter Joseph R.
Published: February 2023

Measurement of the uranium content in liquid streams is important for criticality safety, process and quality control, and nuclear material accountability in nuclear fuel cycle facilities. Conventional analytical techniques such as spectrophotometry, passive gamma-ray spectroscopy, x-ray fluorescence, and densitometry are frequently unsuitable because they may be slow, require sample handling, or be subject to interference by high concentrations of fission products or neutron emitters in the solutions to be analyzed.
Laser Spectroscopy of Chemical Vapor Deposition
Authors: Breiland William G. , Ho Pauline , Coltrin Michael E.
Published: February 2023

Chemical vapor deposition (CVD) is an important industrial process used
to deposit solid films for protective coatings and microelectronic
applications. The CVD processes used in the fabrication of
microelectronic devices are becoming more complex, and higher demands
are being made on the resulting films. A fundamental understanding of
the chemistry and physics of CVD may help meet future process control
requirements, and could lead to novel deposition methods.
Analysis of the Chemical Vapor Deposition of silicon by Intracavity Laser Spectroscopy
Authors: O'Brien J.J. , Atkinson G.H.
Published: February 2023

Both the analysis and control of chemical vapor deposition (CVD) processes, are greatly aided by the availability of experimental methods for monitoring the gas phase precursors of the depositing material. The real time, in situ detection of intermediate reaction species is an almost essential element in studies directed at understanding the fundamental chemistry and physics of CVD processes. Such studies also can have a major impact on CVD processing practices.
Characterization of Materials by Visible-Near UV Spectrophotometric and Spectroellipsometric Techniques
Authors: Aspnes D. E.
Published: February 2023

The primary advantages of optical measurements are that they are general, convenient, nondestructive, and can yield information about dynamic systems or processes in real time and in any transparent ambient. No special sample requirements are needed other than a reflecting surface, and measurements can be made with the sample in air or in atmospheric-pressure ambients. Nondestructiveness is obviously important for the analysis of unstable materials systems such as interfaces buried under oxide overlayers, while real-time capabilities suggest useful applications in process control. A final advantage is that optical probes offer unsurpassed energy resolution, important for accurately determining compositions of semiconductor alloys.
The Spatial Resolution and Defect Contrast of Optical Beam Induced Reflectance (OBIR) Scans
Authors: Carver G. E. , Joy D. C.
Published: February 2023

There is substantial current interest in developing non-contact, non-destructive probes of semiconductor surfaces.[1] [2] [3] [4] [5] A major reason for this activity is that micro-stuctural flaws near the surface of silicon wafers generally impair the successful manufacture of integrated circuits.[6] Detrimental defects such as stacking faults, dislocations, and metallic precipitates are often 1 to 2 microns in size. Thus, a probing system would need to exhibit both high spatial resolution and contrast at defective sites.
Development of Lasers and Spectral Equipment for Measurement of Atmospheric Molecular Gases
Authors: Zuev V.E.
Published: February 2023

The paper considers the problems of laser applications and laser equipment developed to investigate the vibration--rotation absorption spectra of atmospheric molecular gases as well as the measurements of their concentration in the field conditions based on researches carried out at the Institute of Atmospheric Optics SB USSR Academy of Sciences.