bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiplex H2 CARS thermometry and C2 LIF absolute concentration measurements in a microwave diamond CVD plasma
Authors: Kaminski C.F. , Ewart P.
Published: February 2023

Temperature and radical concentration measurements are important for validation of theoretical models of the complex interplay between flow dynamics, gas phase and surface chemistry in chemical vapour deposition plasmas. Furthermore it is useful to have rapid measurements of temperature and other parameters to aid in monitoring and control of the growth environment for deposition of such materials as diamond and diamond-like carbon. Multiplex CARS of N2 is the well established technique for remote, nonintrusive thermometry of flames and hostile environments [1]. Unfortunately, in several industrially important plasma systems used for synthesis of diamond, N2 is absent, and required to be so to avoid corruption of the growing diamond. An alternative to N2 is molecular hydrogen which is present in large quantities and is a suitable Raman active medium for CARS thermometry. However, owing to the open structure of the H2 molecular spectrum, only a very few rotational lines may usually be sampled by multiplex CARS in single shot spectra. When conventional lasers are used to provide the broadband Stokes beam mode noise can render the CARS spectrum difficult to interpret quantitatively. For this reason H2 CARS is usually done by using a narrow linewidth Stokes laser, scanned across the spectrum leading to only a time averaged temperature measurement. For turbulent flames, unstable plasmas or for rapid temperature monitoring for process control, multiplex H2 CARS would be very useful. We report here the use of a modeless laser [2] as the Stokes source for H2 CARS thermometry of a low pressure microwave excited diamond CVD plasma.
Laser-Induced Fluorescence Measurements for Hydroxyl Radicals and Temperature in Nanopowder-producing Flames
Authors: Glumac N.G. , Chen Y.J.
Published: February 2023

Laser-induced fluorescence measurements are performed in silica nanopowder-producing low pressure flat flames in a stagnation-point flowfield. Spatial hydroxl concentrations and two-line rotational temperature measurements are obtained for several conditions to asses the effect on the flame of the addition of the silica precursor hexamethyldisilazane (HMDS) and to evaluate the validity of the one-dimensional stagnation-point flow model for these flames. It is observed that, while the HMDS has little effect on the flame temperature profile, the OH concentration is substantially reduced throughout the flames. In addition, significant non-uniformities at the burner face appear to be present which limit the applicability of the 1-D model for this flow geometry.
CARS Temperature Measurements in a Driven Jet Diffusion Flame
Authors: Hancock R. D. , Schauer F. R. , Lucht R. P. , Katta V. R. , Hsu K. Y.
Published: February 2023

This paper discusses the use of a broadband coherent anti-Stokes Raman scattering (CARS) system to investigate local gas temperatures during a vortex/flame interaction. The CARS system is first used to obtain flame temperature measurements in a series of near adiabatic hydrogen/air flames produced with a Hencken burner (Hencken, 1994; Hancock, et al., 1996). These temperatures are compared to adiabatic flame temperatures found using the NASA-Lewis equilibrium code (Gordon and McBride, 1976) and a computational fluid dynamics code developed by Katta, et al. (1994). These results help to validate the CARS system. Next, the CARS system is used to obtain local gas temperature measurements in an undriven hydrogen/nitrogen jet diffusion flame and during a vortex-flame interaction in the same flame, but under driven conditions. Experimental results (Hsu, et al., 1993; Carter, et al., 1995) and direct numerical simulations (Katta and Roquemore, 1995) indicate that preferential diffusion (manifest as Lewis number), acting together with flame curvature, influence the local flame temperature along the flame surface. Under certain conditions the local temperature will rise even though the flame is positively stretched-a condition which is typically thought to cause a reduction in local flame temperature. In this paper such a condition is investigated for a hydrogen/nitrogen diffusion flame using CARS and direct numerical simulations.
NO Laser-Induced Fluorescence as a Flame Thermometer
Authors: Luque Jorge , Tamura Masayuki , Harrington Joel E. , Smith Gregory P. , Crosley David R. , Jeffries Jay B.
Published: February 2023

Measurement of the temperature field is crucial to understanding combustion in practical devices. Imaging of laser-induced fluorescence (LIF) from NO molecules seeded into the flow is an attractive method to determine the temperature field.1 If the seeded NO does not react or become diluted in the flow, accurate temperature measurements can be made from single line excitation with careful consideration of energy transfer and quenching collisions, overlap of laser and transition bandwidth, and detector bandwidth.2 However, NO reacts in the flame front of hydrocarbon flames via reburning phenomena. We investigate the accuracy of LIF measurements of gas temperature using NO seeded into a premixed, laminar, low-pressure methane/air flame. The NO LIF temperature measurements are compared with temperatures determined from rotational distributions measured with LIF using OH as a function of height above the burner. Using the OH temperature profile, the chemical composition of the flame is predicted from a model of the combustion chemistry. This model predicts the amount of NO as a function of reaction time (height above the burner) including reburning in the flame front, the dilution from the combustion products, and the axial transport. The predicted major species concentrations are used to calculate the rate for NO(A) collisional quenching which are compared to measured quenching rates. In the flame front CH temperature measurements using LIF from A-X and B-X electronic transitions are compared to the OH results.
Resonant Laser Ablation Ion Trap Mass Spectrometry - Recent Applications for Chemical Analysis
Authors: Gill Chris G. , Garrett A. W. , Hemberger P. H. , Nogar N. S.
Published: February 2023

Resonant Laser Ablation (RLA) is a useful ionization process for selectively producing gas phase ions from a solid sample. Recent use of RLA for mass spectrometry by this group1 and by others2 has produced a wealth of knowledge and useful analytical techniques. The method relies upon the focusing of modest intensity laser pulses (≤ 107 W·cm-2) upon a sample surface. A small quantity of material is vaporized, and atoms of desired analyte are subsequently ionized by (n+m) photon processes in the gas phase (where n = # of photons to a resonant transition and m = # of photons to exceed the ionization limit). We have been using (2+1) resonant ionization schemes for this work; a comprehensive list of (2+1) transitions used by this and other research groups has been published elsewhere3.
New Trends in Analytical Atomic Laser Spectroscopy
Authors: Winefordner James
Published: February 2023

Recent advances in laser excited atomic fluorescence spectrometry (LEAFS) and laser excited ionization spectrometry (LEIS) will be discussed. In LEAFS, analytical studies using electrothermal atomization (ETA), inductively couple plasma (ICP) and glow discharge (GD) atom (ion) reservoirs will be stressed. The possibility of achieving very low detection limits will be discussed with respect to the noise sources. The theoretical efficiencies of detection and measurement will be given and will be discussed with respect to measurements near the single atom level. Similarly, in LEIS, analytical studies using flames and furnaces with optogalvanic detection will be stressed, although mass spectrometric detection will also be mentioned. The probabilities of very low detection limits will also be stressed and the theoretical efficiencies of detection and measurement will be given.
Influence of Ambient Conditions on the Laser Air Spark
Authors: Yalçin Serife , Crosley David R. , Smith Gregory P. , Faris Gregory W.
Published: February 2023

When a powerful laser pulse is focused in air, a bright, free-standing
plasma is formed. By measuring the intensities of characteristic
emission lines, elemental analysis can be performed in a manner
similar to other emission-based techniques. Like other optical
emission-based analysis techniques, laser spark spectroscopy can
provide rapid and simultaneous measurements of many elements at once.
However, the laser spark has the additional ability to perform remote,
insitu, measurements. Also, the laser spark vaporizes molecules and
small aerosols, allowing measurement of both gaseous and particulate
phases. These abilities make the laser air spark an attractive
technique for applications such as monitoring toxic metal emissions
from incinerator or power plant stacks.
Laser-Based Sensors for Environmental Analysis
Authors: Vo-Dinh T.
Published: February 2023

Summary not available.
Laser Induced Breakdown Spectroscopy (LIBS) for Real-Time Detection of Halon Alternative Agents
Authors: Williamson Cindy , Daniel Robert G. , McNesby Kevin L. , Forch Brad E. , Miziolek Andrzej W.
Published: February 2023

Laser induced breakdown spectroscopy (LIBS) is a variation on the
method of spark spectroscopy in which the light from a pulsed laser is
focused to produce the spark rather than an electric discharge. This
technique (LIBS) has been largely developed at Los Alamos National
Laboratory and shown to be useful for elemental analysis,
concentration determination, or molecular species differentiation
depending upon the experimental configuration. The capability of
determining concentration of analytes at high sensitivity gives LIBS
an advantage over some other measurement techniques.
Dynamics of single Molecules at Room Temperature
Authors: Lu H. Peter , Xie X. Sunney
Published: February 2023

Recent advances in fluorescence microscopy have made room temperature single molecule spectroscopy an active area of research. In this work, we investigate the room temperature spectral evolution of single sulforhodamine 101 molecules adsorbed on a silicate glass surface and covered by a PMMA polymer film. Single molecule emission spectra are taken and analyzed with a time resolution of 250 millisecond. Time correlation functions of single molecule spectral trajectories are obtained, with decay time constants inversely proportional to excitation intensities, demonstrating the spectral fluctuation is photo-induced in nature. A stochastic model is developed in order to account for the experimental observations. Understanding the origin of the spectral jumps encountered in the room temperature single molecule experiments is important for conducting further experiments to study chemical dynamics of single molecules in a variety of systems. The latest results of the further experiments will also be presented.
Frequency-Converted Diode Lasers for Analytical Applications
Authors: Bamford Douglas J.
Published: February 2023

For many analytical applications, a compact, inexpensive laser source is desired. Compactness is needed to move analytical techniques off the laboratory bench and into the real world, while low costs will place laser-based instrumentation within the reach of a larger community of users. Although room temperature diode lasers are small, cheap, and readily available today, they are limited to wavelengths between 0.6 microns and 1.8 microns. Intense efforts to develop new semiconductor lasers at wavelengths outside this range are underway, but these efforts are unlikely to pay off before the end of the century. In the meantime, light at wavelengths needed for analytical applications can be produced using the nonlinear frequency conversion of existing diode lasers.
Optical emission spectrometry of laser produced plasma with microwave re-excitation for micro-analysis of solid samples
Authors: Ciocan A. , Uebbing J. , Niemax K.
Published: February 2023

Laser ablation of solid samples by pulsed lasers is a convenient and fast sampling technique for element analysis of solid samples. Furthermore, if the laser beam is focused, microbulk analysis with a spatial resolution limited by diffraction is possible. This paper presents experimental results and instrumentation for matrix-independent simultaneous multi-element analysis by a method which got the acronym LA-MIP-OES (Laser Ablation-Microwave Induced Plasma-Optical Emission Spectrometry).
Dual-molecule fluorescence spectroscopy: kinetic observation of single molecule reactions
Authors: Weiss Shimon
Published: February 2023

Traditional structural biology ensemble techniques such as x-ray crystallography, electron cryomicroscopy with angular reconstruction, electron microscopy, nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) provide detailed information on the structure of biological macromolecules. In cases where the crystal form of the macromolecule is available, the structure is known with the ultimate atomic resolution. The knowledge of the static structure can provide some insight to the macromolecule function, especially if it is coupled with other biochemical measurements, but in general the structure-function relationship is to a large extent unknown. With the aid of recently developed techniques such as patch clamp, atomic force microscopy (AFM) and optical tweezers, ionic current fluctuations in individual ion channels and forces and/or displacements generated during single molecular motor reaction were measured. Such measurements furnish information about function, but do not provide local, dynamical structural information.
Lab-on-a-Chip Devices: Thinking Small About Chemical and Biochemical Measurements
Authors: Ramsey J. Michael
Published: February 2023

Demonstrations of microfabricated chemical instrumentation initially
focused on chemical separations, first in the gas phase and later in
condensed phase using capillary electrophoresis. It soon became clear
that microfabrication could be extended to include a much larger
portion of the chemical measurement problem and the concept of the
Lab-on-a-Chip resulted[1,2,3]. The realization of the
Lab-on-a-Chip requires the development of a number of functional
elements or unit processes that can eventually be integrated to solve
chemical and biochemical measurement problems. As the field of
micromachined chemical instrumentation continues to grow, more
sophisticated devices with increased functionality are being
fabricated and tested. Functional elements that have been demonstrated
for chemical and biochemical analysis include free solution
electrophoresis [4,5,6,7,8,9], electrophoretic sizing
of DNA fragments [11,12], and methods for isolation of
neutral species [13,14,15]. In addition, initial
levels of monolithic integration have been demonstrated by coupling
chemical separations with chemical and enzymatic reactions
[16,17,18,19,20]. Quantification tools used for
detection of materials on or from microchips have primarily included
fluorescence which is particularly applicable due to its extreme
sensitivity[21] and electrospray ionization for
off-chip analysis using mass spectrometry [22]. In
addition to these more conventional chemical analysis methods,
electrokinetically driven fluidics have been used to perform
electrokinetically focused flow cytometry [23] and
homogeneous enzyme reaction kinetics [24]. These
latter two capabilities are described in greater detail below.
Raman measurements of supersonic hydrogen/air mixing
Authors: Kasal Peter , Boltz Joachim , Gerlinger Peter , Brüggemann Dieter
Published: February 2023

The investigation of fuel/air mixing in high velocity compressible flow is important for a complete understanding of fluid dynamic and for engine development of a future space transportation vehicle with subsonic (ramjet) or supersonic (scramjet) combustion. Numerous configurations with parallel, transverse and oblique fuel injection through walls, ramps or struts have already been investigated[1-5].
Spectroscopic Characterization of Semiconductor Surface Impurities by Near-Field Scanning Optical Microscopy
Authors: Schade Wolfgang , Osborn David L. , Preusser Jan , Leone Stephen R.
Published: February 2023

Near-field scanning optical microscopy (NSOM) is a very promising tool for the characterization of optical and optoelectronic properties of semiconductors and other devices at the nanometer scale [1]. Defect and impurity characterization of surfaces and interfaces is an important field in semiconductor physics. Since these materials are opaque in the visible spectral range, transmission contrast mechanisms which are most common for NSOM can not be applied in these investigations. However, near-field photocurrent (NPC) is a very attractive method for studying surface characteristics of optoelectronic devices [2,3]. The near-field laser light illumination excites electron-hole pairs directly under the fiber tip in the semiconductor material. These photoexcited carriers are collected by p-n junctions and result in a photocurrent that can be measured accurately by lock-in techniques, while moving the sample or the fiber tip to measure images.
Single-Shot Laser-Induced Breakdown Spectroscopy (LIBS) of Energetic Materials
Authors: Lancaster Edwin D. , McNesby Kevin L. , Daniel Robert G. , Miziolek Andrzej W.
Published: February 2023

The application of Laser-Induced Breakdown Spectroscopy (LIBS) is being investigated as a tool for the determination of energetic/explosive materials for a variety of applications.
In situ Sensing of Atmospheric Trace Gases Using Airborne Near-IR Diode Laser Sensors
Authors: Sonnenfroh David M. , Kessler William J. , Allen Mark G. , Barrick John
Published: February 2023

Over the last few years, there has been considerable effort at Physical Sciences Inc. (PSI) and elsewhere to develop ultrasensitive trace gas sensors for in situ monitoring of several important atmospheric species including H2O, CO2 and CH4. At PSI, high performance field sensors have been created by combining near-IR diode laser absorption with balanced ratiometric detection. One such sensor is a laser hygrometer developed for NASA which is capable of monitoring water vapor from ground level to the tropopause. The laser hygrometer monitors water vapor through absorption via a strong, isolated line at 7181.172 cm−1 in the ν1 + ν3 combination band. Through a series of laboratory measurements, we have demonstrated a sensitivity of 2 × 1012 molecules cm−3 which corresponds to ~0.3 ppmv water vapor at typical mid-latitude tropopause conditions (12 km or 40 kft) using a 50 cm absorption pathlength. We have also demonstrated a dynamic range of 4 orders of magnitude and a measurement rate of 10 Hz. The hygrometer uses a unique, compact, external air probe for true in situ sampling, thereby obviating well-known limitations in time-response and sensitivity imposed by extractive air sampling systems.
Simultaneous Laser-Induced Fluorescence and Rayleigh Scattering Measurements for Precise Determination of Flame Structure
Authors: Jeffries Jay B. , Heberle Norbert , Smith Gregory P. , Crosley David R.
Published: February 2023

Nearly one third of all natural gas is consumed in Bunsen-type burners, partially premixed flames which have a fuel-rich premixed flame forming an inner core surrounded by a diffusion flame. Pollutant emissions of nitrogen oxides, NOx, in these flames are an important concern. The NO is produced by two chemical pathways, the thermal (Zeldovich) and the prompt (Fenimore) mechanisms. For temperatures below 2000 K, the thermal pathway is minimized because of the high activation energies of the rate-limiting chemical reactions. Thus, at the flame temperatures found in partially premixed flames, the prompt mechanism produces much of the NO.
Measurement of fluorescence of formaldehyde in atmospheric pressure flame
Authors: YAMAGISHI Susumu
Published: February 2023

Formaldehyde (H2CO) is one of the key intermediate species in the initial state of combustion and is also a harmful exhaust constituent, especially in alcohol combustion. A detailed understanding of the reaction system of H2CO can be obtained by comparison between measured and calculated density profiles. LIF is often used for in-situ measurement of flame but the estimation of quenching effects under atmospheric pressure is difficult (1). The electronic band spectrum of H2CO has been discussed in many papers (1,2), but most spectral experiments were performed under low pressure at room temperature. Also the red shaded branch of 350nm band which is important for the YAG THG has been seldom used for measurement.
Diode-laser sensor system for combustion monitoring
Authors: Mihalcea R. M. , Baer D. S. , Hanson R. K.
Published: February 2023

A diode-laser sensor system, comprised of a tunable external-cavity diode laser (ECDL) operating near 2.0 μm and fiber-optic components, has been developed to measure the gas temperature and the concentrations of CO2 and H2O in the combustion and exhaust regions of a flat-flame burner (C2H4/air) using absorption spectroscopy techniques. The present system extends the techniques developed previously 1-4 for the measurement of H2O and CO2 by probing relatively stronger vibrational bands and thus offers higher measurement sensitivity. Measurements of individual transitions (1-cm−1 scans) were recorded by adjusting the internal grating to particular center wavelengths and by applying a 6-volt sawtooth voltage waveform at a 1.25-Hz repetition rate to the wavelength modulation input. Temperature may be determined either from the ratio of measured H2O (ν1+ ν2, ν2 + ν3 bands) or CO2 (ν1+2ν2+ ν3 band) absorbances. Species (H2O, CO2) concentrations were determined from the measured temperature and absorbances of appropriate transitions recorded by tuning the ECDL wavelength across selected transitions within the 250 cm−1 laser tuning range centered at 2.02 μm.
Diode-Laser-Based Ultraviolet Absorption Sensor for NO
Authors: Hanna Sherif F. , Barron-Jimenez Rodolfo , Anderson Thomas N. , Lucht Robert P. , Walther Thomas , Caton Jerald A.
Published: February 2023

We have developed a new diode-laser-based sensor system for ultraviolet absorption measurements of the NO molecule. The laser system is illustrated schematically in Fig. 1. This system is based on sum-frequency-mixing (SFM) of a tunable, 395-nm external-cavity diode laser (ECDL) from Toptica Lasers with a frequency-doubled, diode-pumped Nd:YAG laser (CrystaLaser) in a beta barium borate (BBO) crystal. Because of the strength of the ultraviolet A2Σ+ - X2∏ electronic transition of NO, the detection limit of the system is approximately 0.1 ppm of NO per meter of path length. In addition, the simplicity, generality, and relatively low cost of the SFM-based sensor strategy discussed in this paper will enable the development of absorption sensors throughout the entire ultraviolet spectrum, opening up a wide range of new possibilities for sensing and control of chemically reacting flow processes.
Light and Color on the Wing: Architecture and Development of Butterfly Interference Mirrors
Authors: Ghiradella Helen
Published: February 2023

Lepidopteran scales, the "dust" that covers the wings of moths and
butterflies, are extremely complex in form. Those scales exhibiting
structural colors are especially so, for in these, certain scale
elements are elaborated into fine-grained architectural arrays that
interact with light to produce the colors. The optics of structural
colors are well understood by the physicists; biologists would like to
know the anatomical bases of biological structural colors and to
understand how living cells can make essentially perfect interference
filters.
Finnish observers-network
Authors: Parviainen Pekka
Published: February 2023

Geographic latitude of Finland (between 60° and 70°N) provides a good oppoturnity to observe visually a number of geophysical and atmospherical phenomena. F.ex. aurora is frequent in northern latitudes, during summer months noctilucent clouds (NLC) in southern latitudes. Winter and spring months usually show some good halodisplays.
Polarimetric Observations of a 22° Halo
Authors: Können G.P. , Tinbergen J.
Published: February 2023

It is known for about 15 years that the inner edge of refraction halos are strongly polarized1). This polarization is caused by the birefringence of ice crystals. This causes the halo to consist of two orthogonally polarized components, which are mutually shifted. In case of the 22° halo, this shift is 0.1°. This is five times larger than the resolving power of the human eye. Therefore, the shift of the halo (or the polarization of its inner edge) can be easily observed in Nature. This holds particularly for parhelia: seen through a polarizer, it shifts to and fro as the polarizer rotates.
Rainbows and Fogbows
Authors: Lynch David K. , Schwartz Ptolemy
Published: February 2023

The optics of rainbows and fogbows is investigated theoretically for single water drops using Mie theory. Included in the calculations are a realistic solar illumination spectrum and the finite size of the Sun. Drop radii range from 3 to 300 µm. Results are presented on the location, width, contrast and color of both primary and secondary rainbows. Particular attention is given to rainbows formed in small drops.
Rainbow-Enhanced Forward and Backward Glory Scattering
Authors: Langley Dean S. , Morrell Michael J.
Published: February 2023

When the refractive index m of a sphere is such that rainbows occur in the forward or backward direction, the glory scattering becomes exceptionally strong. A number of these refractive index values have been determined from the geometry of ray paths. Diffraction theory applied to the scattered wavefront leads to an x4/3 dependence in the scattered irradiance, where x = (sphere circumference/incident wavelength) is the size parameter; normal glory-scattered irradiance increases proportional to x. Mie theory computations illustrate the presence of rainbow-glories at predicted m values, and the x4/3 irradiance factor. As in normal glory scattering, the rainbow-glory light contains a strong cross-polarized component. Experiments using single glass spheres immersed in liquids have shown cross-polarized scattering and a sensitive dependence on m in agreement with predictions.
Space Perception in Open Air
Authors: Mattiello Francisco , Biondini Alejandro R. , de Mattiello Maria L F.
Published: February 2023

A classic problem of perception is that biological systems have available through their senses , only very limited information about the external world.
The Appearance of the Sun and Moon as Seen Through Clouds
Authors: Linskens Jeffery R.
Published: February 2023

Although the sun or moon is frequently obscured by clouds, it is quite commonly visible through clouds.
Laboratory Experiments of Optical Phenomena of the Atmosphere
Authors: Vollner M.
Published: February 2023

Old, new, qualitative, and quantitative laboratory experiments on atmospheric optics are presented. In addition to didactical purposes they can help to understand complex halo phenomena.
Solar Eclipses and Elementary Electronics: A Project Involving Experimental Observations and Mathematical Analysis
Authors: Mallmann A. James
Published: February 2023

For the annular solar eclipse of May 10, 1994, we set up two telescopes to produce projected images of the eclipsing sun at a location adjacent to the main engineering building at the Milwaukee School of Engineering campus. Although we did not promote the event in any way, well over one hundred students, faculty, and staff gathered spontaneously to view the images of the eclipsing sun.
"The Blue, Green, and Otherwise Coloured Appearances of the Sun and Moon in 1883-84"
Authors: Greenler Robert , Brandt R. K.
Published: February 2023

The title of this paper is the title of a long section in a book published in 1888 by the Royal Society in London. The five-hundred-page book, The Eruption of Krakatoa and Subsequent Phenomena, includes reports and personal accounts collected from around the world of observable effects attributed to the great volcanic eruption on the island of Krakatoa, located just west of Java.
Introduction to Tissue Optics: An M.D.’s Perspective
Authors: Anderson R. Rox
Published: February 2023

Summary not available.
Noninvasive Measurements of Optical and Physiological Properties Using Multi-Frequency, Multiwavelength Photon Density Waves
Authors: Tromberg B.J. , Svaasand L.O. , Fishkin J.B. , Venugopalan V. , Pham T. , You J.S.
Published: February 2023

Summary not available.
Subsurface Imaging of the Skin Using a New Z-Scanning Technique in Optical Coherence Tomography
Authors: Ma Xiaonon , Su Chin B. , Wang Lihong
Published: February 2023

Low-coherence interferometry using broadband light sources have achieved high spatial resolution for imaging of highly scattering media [1-4]. For in vivo biological imaging [3,4], it is desirable that the optical path length of the reference arm be scanned at high-speed for achieving a fast frame rate. A standard technique for varying the optical path length of the reference arm is by stretching a long length of fiber coiled around a cylindrical piezoelectric transducer. This technique is used for high-speed data acquisition at an ≈ 1- ms rate, and with a probing depth of a few millimeters [4]. Drawbacks of this technique are the mismatched polarization inherent in the fiber, drifts resulting from temperature change , and dynamic birefringent effects owing to stretching action.
Clinical real-time confocal microscopy of human skin and oral cavity lesions in vivo
Authors: Rajadhyaksha Milind , Langley Richard G.B. , Gonzalez Salvador , White Matthew , Zavislan James M. , Webb Robert H. , Anderson R. Rox
Published: February 2023

The confocal scanning microscope (CSM) is becoming a powerful imaging modality in dermatology and otolaryngology, because of its optical sectioning capability which allows us to noninvasively image thin sections of in vivo tissue with high resolution and contrast. The CSM provides a window into living tissue for basic and clinical research; it potentially offers doctors an imaging diagnostic which operates in real-time and is entirely noninvasive compared to conventional biopsy-based histopathology [Pierard, 1993]. High-resolution imaging of skin in vivo has been achieved with a white light tandem scanning confocal microscope [New et al., 1991; Corcuff and Leveque, 1993; Corcuff et al., 1993; Bertrand and Corcuff, 1994] and our confocal scanning laser microscope (CSLM) [Rajadhyaksha et al., 1995]. We recently optimized our CSLM for improved resolution and contrast. Our clinical imaging-and-analyses studies of the past year include (i) fifty pathologic human skin lesions, (ii) effects of ultraviolet-B irradiation on the skin, and (iii) normal and pathologic oral cavity tissue. In this paper, we present optimum CSLM parameters for imaging living skin and oral tissue, and the results of our clinical imaging work.
Treatment of Vascular Lesions with a Long-Pulse Green Laser.
Authors: Dierickx Christine C. , Anderson R. Rox
Published: February 2023

Following the theory of “selective photothermolysis” [1], pulsed lasers were specifically designed during the 1980’s for treatment of pediatric portwine stains (PWS) [2]. 585 nm (yellow) pulsed dye lasers, with a pulse duration of 0.45 msec, cause selective microvascular damage and are at present the standard for treatment of pediatric PWS [3-7]. However, pulsed dye laser treatment usually requires a series of treatments, and is often only partially effective. Gross purpura occurs after each treatment, posing a further cosmetic problem for patients. Adult PWS tend to respond less better presumably because of the change in vessel size and depth with aging.
Ruby laser irradiation results in decreased hair diameter in regrowing hair
Authors: Liew SH , Linge C , Grobbelaar AO , Gault D , Green C
Published: February 2023

Recently, encouraging results have been obtained using a Ruby laser to depilate unwanted hair. Ruby laser with a wavelength of 694 nm is well absorbed by melanin and is poorly absorbed by haemoglobin (1). It is thought that melanin in hair follicles acts as a chromophore which can be targeted to achieve selective photothermolysis (2) of hair follicles while sparing adjacent tissues. A study using Q-switched Ruby laser on guinea pig skin by Polla et al (3) showed that melanin was the fundamental target of energy absorption and at appropriate radiant exposures, it injured melanosomes without inducing any visible damage to unmelanized organelles. A clinical study performed by Gault et al (4), using a Ruby laser (694 nm, continuous mode with pulse width of 600 microseconds), resulted in a reduction of the overall hair density by 58% in a follow up of up to one year. Grossman et al (5) also demonstrated that Ruby Laser (694 nm, continuous mode with pulse width of 270 microseconds) produced a growth delay in hair follicles, with 4 out of 13 dark haired subjects having less than 50% regrowth of hair at 6 months.
Matched Sample Differential Laser Calorimetry
Authors: Bass M. , Swimm R. T. , Innocenzi M. E.
Published: February 2023

Thermocouple laser calorimetry was developed to allow absolute measurement of very small optical absorptions in materials to be used for high power laser optics. The technique involves sending a beam of light through the sample to be studied and, by means of an attached temperature sensor, measuring its change in temperature due to light energy absorption. The temperature change is measured relative to a reference object which is not exposed to the light. Sensitivities to absorptions as small as 10-5 cm-1 are possible. Photoacoustic detection of the absorbed energy allows relative measurements of absorption and when calibrated against thermocouple measurements yeilds similar absolute sensitivities.
Photodarkening In insitu Textured PbTe Eilms - A Novel Technique for High Contrast Optical Storage in Polycrystalline Thin Eilms
Authors: Rao L. Kameswara , Selvarajan A.
Published: February 2023

Recent studies (1,2) have shown that textured films are ideally suited for optical storage as they exhibit appreciable optical contrast upon laser irradiation. Craighead et al (1) demonstrated that relatively thick films of various materials exhibit good reflectance contrast due to a mechanism of columnar collapse, when the films are prepared by sputter-etch technique. Kameswara Rao et al (2) observed that thin films of Ge, prepared by oblique angle deposition technique, exhibit good transmittance contrast due to chemical modification of the irradiated region to a selective oxide phase. It thus appears that the origin as well as the nature of the optical contrast in textured films critically vary with method of preparation as well as the thickness of the film. In the present study we report the observation of optical contrast of thin polycrystalline films of PbTe, via darkening of irradiated region. The observed darkening is found to be similar to the photodarkening widely known in amorphous materials.
Excimer laser photochemistry of Al-alkyls monitored by dye laser mass spectroscopy
Authors: Zhang Y. , Stuke M. , Larciprete R. , Borsella E.
Published: February 2023

Metal Organic Chemical Vapor Deposition (MOCVD) is a powerful technique for the generation of well-defined layers of metals and semiconductors [1]. Extending MOCVD by the use of lasers to Laser-MOCVD, selective area growth can be obtained ([2] and references therein). Laser induced deposition of structured aluminum films can be achieved using UV lasers and Al-alkyls like triisobutylaluminum (TIBA) as gaseous organometallic precursor [3, 4].
Optical Sensing for Automated Inspection
Authors: Strand T.C.
Published: February 2023

Optics has always played a major role in industrial inspection and measurement applications. However in the past a critical component in such systems has often been the human eye. This aspect is changing rapidly now with the introduction of new technologies and new concepts in optical measurement. We will describe a number of new tools that provide new capabilities in inspection and also can eliminate the human from the measurement process.
Surface Second Harmonic Generation Spectroscopy of Oxide Surfaces
Authors: Hetherington W.M. , Bandu G.G. Padma , Mazely T.L. , Ho Z.Z. , Wijekoon W.M.K.P.
Published: February 2023

Second harmonic generation has been established recently as a specific probe of interfacial species. On dielectric surfaces, it has been used to detect the presence, the electronic states and the average orientation of interfacial species.
Progress in Solid-State Lasers for Spaceborne Lidars
Authors: Allario Frank
Published: February 2023

As part of the National Aeronautics and Space Administration's (NASA) Space Station program, a lidar facility is being planned to conduct a series of scientific experiments from a polar orbiting platform. The thrust of these experiments is to improve our understanding of atmospheric chemistry and dynamics, altimetry, and meteorology. A number of scientific experiments were recently developed by a panel of scientists and lidar technologists and included both atmospheric backscatter (Lidar) and Differential Absorption and Lidar (DIAL) experiments. The major investigations to be conducted include measurements of the vertical profiles of atmospheric aerosols, the height of the Planetary Boundary Layer (PBL), the distribution of cirrus clouds, vertical profiles of water vapor in the lower and upper atmosphere, vertical profiles of ozone, and measurements of the vertical profiles of pressure and temperature. These experiments were developed by the Lidar Atmospheric Sounder and Altimetry (LASA) panel, and have been summarized in a NASA document.
Lidar Experiment On Spacelab LEOS
Authors: Endemann M. , Klein V. , Renger W. , Quenzel H.
Published: February 2023

There are plans for a second German spacelab mission (D2-mission) (originally scheduled for late 1988) which will be basically a zero-g mission, but will also include earth observation experiments. Encouraged by our experience with airborne lidar systems and the results from theoretical studies, we have proposed a backscatter lidar for this or later spacelab missions.
Performance Testing of the Shuttle Laser Altimeter
Authors: Bufton Jack L. , Garvin James B.
Published: February 2023

A laser ranging instrument has been developed for altimetry measurements of the Earth's surface along the nadir track of the Space Shuttle. The Shuttle Laser Altimeter is designed for transmission of a short laser pulse and reception of the backscattered laser radiation from the Earth's surface. The source laser is a Q-switched Nd:YAG operating at its fundamental wavelength of 1.064 μm. A reflector telescope and silicon avalanche photodiode are the basis of the altimeter receiver. Laser, telescope, detector, data processing and storage electronics, and dc power supplies are packaged for spaceflight into two adjacent Get-Away-Special canisters. This provides the basis for a very compact and low-cost interface to the Space Shuttle.
Lidar Detection of Sub-Visible Cirrus Clouds
Authors: Dubinsky R. , Hunt W. , Moore J. , Osborn M.
Published: February 2023

Cloud measurements using a ground based NdYAG Lidar operating at a wavelength of 0.53 um showed important backscatter returns from an altitude of approximately 12 km. during visually clear atmospheric conditions. The Lidar return signal is attributed to sub-visible cirrus clouds having backscatter ratios of 6.1 to 7.6 and a backscatter coefficient of 2.64 to 3.43 x 10(E-03) /km/sr. The measurements were taken during the FIRE (First International Satellite Cloud Climatology Project Regional Experiment), IFO (Intensive Field Observations) in Wisconsin during October and November 1986. The results are compared with collaborative measurements (eg. satellite, air sampling, radiometric etc. during the FIRE trials), Lidar data from Langley Research Center (LaRC) and literature results.
Oil Film Detection and Characterization by Lidar Fluorosensors
Authors: Cecchi G. , Pantani L. , Radicati B. , Barbaro A. , Mazzinghi P.
Published: February 2023

The use of lidar fluorosensors in the detection of oil films over the water surface is well known and laboratory and field experiments were done by different authors in the past years. A systematic analysis of fluorosensor performances in detection and characterization of oil films was carried out as a part of the IROE program of environmental remote sensing. The investigation concerned the definition of the best laser wavelengths, the measurement of film thickness, the identification of the minimum detectable film thickness, the identification of the oil which composes the film. The results of this analysis were the base of the development of IROE FLIDAR-2 hardware and software.
Remote Determination of Meteorological and Optical Parameters of the Atmosphere Using a Raman Lidar
Authors: Arshinov Yu. F. , Bobrovnikov S.M. , Volkov S.N. , Zuev V.E. , Shumskii V.K.
Published: February 2023

As known, the boundary atmospheric layer is just the region between the Earth’s surface and the free atmosphere where most dynamic processes take place. The investigation of these processes is very important for obtaining the information on the conditions of temperature inversions formation as well as on the diffusion of various atmospheric components including pollutions. It is also important for studying the heat transfer from the ground to the atmosphere.
Spatial Sampling of the Measuring Volume by the Introduction of Dedicated Apertures in Lidar Systems
Authors: Hanson Steen
Published: February 2023

In ordinary Laser Doppler Anemometry (IDA) light scattered from single particles from two different beams of laser light is mixed coherently on a photodetector surface. The detector current contains information on the velocity of single particles, and various temporal moments of the velocity distribution can be deducted from the readings. LIDAR systems for velocity determination based on infrared sources are usually depending on parametric amplification and will therefore solely probe the longitudinal flow velocity, whereas systems based on lasers emitting visible light are independent of a local oscillator facilitating the probing of all three velocity components in a small measuring volume.
Advanced Airborne DIAL System Capabilities for Ozone and Multiwavelength Aerosol Measurements
Authors: Carter A. F. , Browell E. V. , Siviter J. H. , Higdon N. S. , Butler C. F. , Mayo N.
Published: February 2023

The NASA Langley airborne DIAL system has been modified to give significantly increased measurement capability for conducting atmospheric science investigations. The major modification to the DIAL system was incorporating the capability to make ozone and aerosol measurements above and below the aircraft simultaneously. This was accomplished by a total redesign of the transmitting and receiving sections of the DIAL system to accommodate eight lidar returns simultaneously. Additional modifications were also made to remotely control transmitted laser beam properties and direction; to incorporate a new filtering system for high UV throughput and complete cutoff; and to increase real-time data availability for real-time mission decisions.
An Adaptive Kalman-Bucy Filter for Differential Absorption Lidar Time Series Data
Authors: Warren Russell E.
Published: February 2023

An earlier work1 described a generalization of two-wavelength differential absorption lidar to the case of multiple wavelength channel returns for estimating the path-integrated concentration (CL) for multiple materials. A maximum likelihood (ML) estimator was constructed for the N-dimensional vector CL = [CL1,…,CLN]T of path-integrated concentration values in terms of lidar returns pi(k) collected simultaneously at i = 1,…1, M ≥ N+1 wavelengths at time step k. Those returns were used to define an observation vector s(k), Eq. (1), which could be expressed approximately as Eq. (2) in terms of the M-1 × N-dimensional matrix of absorptivity differences

R

i
l

=

ρ
1
l

−

ρ

1
+
1

l

of material ℓ at wavelength i. The measurement noise ns(k) was taken to be additive, uncorrelated, and zero-mean with covariance Λs (k,k′) = δkk′. The ML estimator for CL was shown to be given by Eq. (3) in terms of the ML estimate for the CL covariance

Λ

CL

ML

, Eq. (4).
High Spectral Resolution Lidar Measurements of Cirrus Cloud Optical Properties
Authors: Grund C. J. , Eloranta E. W.
Published: February 2023

Lidar backscatter signals are generated by scattering from both molecules and particles. The spectral distribution of light scattered by molecules is Doppler-broadened by rapid, thermally induced, molecular motions. Light scattered by aerosols and cirrus particles is essentially unshifted because of the relatively slow Brownian motion of particles. Using this difference, the High Spectral Resolution Lidar (HSRL)1,2 interferometrically separates particulate from molecular backscatter. By using the distribution of molecular scattering as a known target, the HSRL achieves unambiguous, calibrated measurements of atmospheric extinction, backscatter cross section, and backscatter phase function.
Minilidar for pollution monitoring and multiple scattering studies
Authors: Werner Christian
Published: February 2023

A simple backscatter lidar was developed to measure aerosol and cloud backscatter and extinction values. It can be used as ground based instrument as well as airborne unit. For different research goals different modules are available.
Remote Sensing of Earth and Planetary Atmospheres Using Gas Correlation Spectroradiometry
Authors: McCleese Daniel J.
Published: February 2023

Gas correlation spectroradiometry is one of the most frequently used techniques for remote measurements of atmospheric properties. It is a relatively simple and robust technique which is most useful in applications where very high spectral discrimination (up to the line Doppler width) is required and yet signal levels are low. Such is the case for Earth upper atmospheric temperature and species abundance measurements and for numerous planetary measurement objectives. The first spaceborne gas correlation experiment (Abel et al 1970) was flown on Nimbus 4 by Oxford University to obtain global measurements of stratospheric temperature. Since the launch of that instrument in 1970, eight Earth orbital instruments and one planetary experiment have used this technique for a variety of atmospheric investigations. Gas correlation spectroradiometry continues to offer significant advantages over other instrumental approaches for investigations in which instrument capability and complexity are equally important considerations. For example, the atmospheric sounder now being developed at JPL for the Mars Observer planetary mission (McCleese et al 1986) uses gas correlation spectral channels to achieve a resolution of 0.01 cm–1 in the mid-infrared using hardware of minimum complexity and having substantial flight heritage.
Remote Sensing of N2O5 and C10NO2 in the Lower Stratosphere
Authors: Brasunas J. , Herman J. , Kunde V. , Maguire W. , Herath L. , Shaffer W. , Massie S. , Goldman A.
Published: February 2023

The stratospheric ozone concentration depends on a combination of radiation, chemistry and dynamics. Central to the chemistry are the nitrogen, chlorine, and hydrogen cycles of catalytic ozone destruction. Verification of the photochemical models that attempt to predict ozone trends requires the simultaneous measurement of ozone, temperature, and the trace species which participate in the ozone destruction.1