bluuebunny/crossref_metadata_2025 huggingface dataset:
Γ-X Mixing in GaAs/AlAs Superlattices
Authors: Meynadier M.-H.
Published: February 2023

There is a growing interest towards understanding the effect of two-dimensional confinement on the symmetry properties of the Bloch wavefunctions of carriers in superlattices (SLs) and quantum wells (QWs). In particular, recent theoretical studies have evaluated the possibilities of obtaining direct or "pseudo-direct" Si/Ge superlattices although both constituents are indirect, through the combined effects of strain and superperiodicity [1]. Useful insights in this still scarsely documented field can be obtained from the more conventional GaAs/AlAs system, in which one of the constituents is direct and the other one is not. It has been reported recently [2,3] that such superlattices could be indirect provided that the GaAs layer was thin enough. We will show here that they can further be continuously tuned from indirect to direct by means of an externally applied electric field. This experiment and others have allowed us to demonstrate that in such superlattices the conduction minimum is a combination of X and Γ states, with a degree of admixture related to the superperiodicity. Possible mechanisms responsible for this mixing will be discussed.
Temperature-Dependent Characteristics of GaAs/AlGaAs Multiple Quantum Well Optical Modulators
Authors: Bailey R.B. , Sahai R. , Lastufka C. , Vural K.
Published: February 2023

Optical modulators using the quantum confined stark effect1 in GaAs/AlxGa1−x As multiple quantum wells (MQWs) have been studied extensively for their potential applications in integrated optoelectronic devices and optical computing systems. This paper investigates the increased performance that can be achieved by operating the device at low temperatures and by improving the quality of the MQW layers.
Excitons in Double Quantum Wells-beyond the single-subband limit
Authors: Galbraith Ian , Duggan Geoffrey
Published: February 2023

Calculations of the exciton binding energy in quantum well systems carried out in the single sub-band limit where only the lowest electron and hole states contribute to the exciton have been widely reported.(1,2) This limit is valid when the confined electron and hole energy levels in the well are widely separated in energy compared to the exciton binding energy. At the other extreme would be the case of a superlattice in which the electron and hole subband bandwidths are much larger than the exciton binding energy and the exciton would be made from a linear combination of a number of subband states.(3) In this paper we wish to treat an intermediate case, namely a double quantum well system consisting of two identical wells of width Lw separated by a barrier of width Lb. When Lb is large the two lowest lying states ( i.e. the first symmetric and anti-symmetric electron and hole states ) arc almost degenerate. This near-degeneracy is progressively lifted as the barrier thickness, decreases. This means that for thick barriers in order to correctly calculate the exciton binding energy one must account for the mixing caused by the Coulomb potential between the two pairs of states.
Energy Transport of Strongly Localized Excitons in 2D Limit: Monolayers of Te Isoelectronic Traps in ZnSe
Authors: Fu Q. , Lee D. , Fritze M. , Nurmikko A. , Gunshor R. , Kolodziejski L.
Published: February 2023

It is now well established that Te is a strong isoelectronic center for excitons in II-VI compound semiconductors such as ZnSe [1],[2], and ZnS [3], Deeply bound states (>100 meV) exist due to the attractive short range potential by Te for holes. Furthermore, it has been argued [2] that the process involves strong local lattice relaxation in a dynamical sense, i.e. that photoexcited holes are subject to self-trapping while the electron component of the exciton simply Coulomb orbits the ’Frenkel-like’ hole [4]. The use of such isoelectronic centers may be especially useful in developing light emitters in the blue-green region of the spectrum. Fundamentally, introducing the centers by ’delta-doping’ can provide an unusual opportunity to study 2-dimensional energy transport of carriers under conditions of strong localization and coupling to the lattice; i.e. a lower dimensional ’polaron’ problem. We have performed optical experiments, including direct imaging of trapped exciton population gratings, to obtain first results in ZnSe-based superlattices and quantum wells where incorporation of one or two monolayers of ZnTe by atomic layer epitaxy provides a planar distribution of Te isoelectronic centers.
Quantum Well Intersubband Infrared Detectors
Authors: Levine B. F.
Published: February 2023

Transport physics, device performance (high responsivity, high detectivity, high speed, broad bandwidth) and potential advantages (over HgCdTe) of 10 μm GaAs/AlxGa1−xAs superlattice infrared detectors will be discussed.
Tri-State Optical Switch for Local Area Fiber Optics Network
Authors: Simms Garfield , Hodari Apriel K.
Published: February 2023

In fiber optics communications systems, emission and detection are usually handled by separate devices. Additionally, lenses, mirrors, couplers and amplifiers are used to focus the beam and amplify the corresponding signal. Devices such as this novel structure, which will reduce the number of components required and produce an inherently less expensive and more reliable system, incorporate emission and detection into a monolithic structure. The tri-state optical switch is a heterojunction phototransistor which can be used as an emitter-detector as well as a passive transmitter. By varying the voltage bias, this device will switch between all three modes of operation. Such a device has broad application in network environments with operation speeds of less than 50 MHz and distances of less than 1km, e.g. automobiles, airplanes and intra-instrumentation. This display will show the recent studies of emission mode operation of this device and the resulting mathematical model.
Survey of Lidar Systems
Authors: Russell Edgar D.
Published: February 2023

For this work, we have gathered information concerning the physical layout and some uses of Lidar systems. Uses for Lidar systems include atmospheric science, for the purpose of weather prediction, to laser altimeter systems that may be used in mapping the Moon and Mars in future space missions. The collected information was obtained from the Laboratory for Terrestrial Physics' (LTP) atmospheric science branch, code 920, at the NASA Goddard Space Flight Center in Greenbelt, Maryland.
Proposal to Utilize 3-Dimensional Lidar Data to Model Aerosol and Cloud Evolution and Dispersal
Authors: Farrukh Usamah O. , Kuhl Frank P.
Published: February 2023

The University of Wisconsin volume imaging Lidar system is designed to produce a continuous sequence of three-dimensional data of aerosol backscattering. Presently, the image of the cloud structure is produced by vertically stacking a series of horizontal aerosol contours. Mathematical tracking and prediction methods for objects moving in space were developed by A. P. Reeves, D. Andrisani II, and F. P. Kuhl. These methods could be modified to track dynamic aerosol structures as a function of time. In addition, properties such as growth, transport, roll, and dispersion could then be obtained and analyzed.
Numerical Calculation of Cloud Optical Extinction from Lidar
Authors: Alvarez J. M. , Vaughn M. A.
Published: February 2023

A simple numerical algorithm to calculate optical extinction from cloud lidar data is presented. A two-component atmosphere consisting of "clear air" and cloud particulates is assumed. "Clear air" consists of either molecules only or a mix of molecules and the atmospheric aerosol. If the lidar data can be used to determine the cloud optical thickness then the method provides an estimate of an assumed cloud-atmospheric constant. The optical thickness is used as a constraint on the numerical solution and provides the additional information necessary to calculate the cloud-atmospheric constant. Conversely, the method may also be applied to obtain cloud extinction and optical thickness from lidar cloud soundings provided the cloud-atmospheric constant is known.
Luminescent Properties of Yb-Sensitized AlF3-Based Glasses
Authors: Copeland L. R. , Reed W. A. , Shahriari M. R. , Iqbal T. , Hajcak P. , Sigel G. H.
Published: February 2023

Rare earth ions can easily be incorporated into fluoride glasses in moderate to large concentrations, and, due to their low phonon energy, these glasses appear to have many advantages over oxide glasses as hosts for rare earth ions used in optical amplifiers and lasers. We have therefore investigated the luminescence and radiative lifetimes of Pr3+, Pr3+/Yb3+ and Pr3+/Yb3+/Lu3+ doped bulk AlF3-based glass samples as a function of rare earth ion concentration. Initial results show a lifetime of about 150 µs for the 1G4 → 3H4 state and a 20% decrease with the addition of Yb3+. In addition we find that the addition of 2 wt% of Yb increases the fluorescence of Pr3+ at 1.32 microns by a factor of 7 when excited with 488 nm radiation. The effect of Yb3+ and Lu3+ on the 1G4 → 3H5, 1D2 → 3F4 and 1D2 → 1G4 transitions of praseodymium would be presented.
Welcome Address
Authors: Harvey William R.
Published: February 2023

Since 1978, Hampton University has devoted considerable resources to the development and enhancement of its research programs. The University has established an excellent track record in faculty research and in the acquisition of funded grants to support research activities. The Department of Physics faculty members have been major contributors to this growth in research activities at Hampton.
Performance of the NASA/Marshall Airborne Doppler Lidar System
Authors: Lee R. W.
Published: February 2023

Extensive measurements of two-dimensional horizontal flow fields were made with the NASA/Marshall coherent CO2 Doppler lidar system during the summer of 1981. Data was obtained at altitudes from near the surface to above 10 km, in a variety of weather conditions, and over terrain ranging from smooth to very complex. Preliminary analysis of data obtained over this wide range of situations indicates that the system is capable of vector flow measurements at ranges to 5-15 km with accuracies on the order of 1 m/s.
Multichannel Radiometer for Tropospheric Flux Measurements
Authors: Valero Francisco P. J. , Gore Warren J. Y.
Published: February 2023

Aerosols directly affect climate through their alteration of the radiation budget. In the case of tropospheric aerosols, the main impact is on the solar energy deposition profile since they are generally at a temperature similar to that of the surface and hence do not greatly influence the infrared radiation fields. Thus, one fundamental measurement for assessing the climatic effects of aerosols is to directly measure the radiative flux divergence in the layers of the atmosphere within which they are located.
Moisture Retrievals form the DMSP-SSH/2 Sounder: A Simulation Study
Authors: Hogan D. B. , Bowman C. K. , Rosenberg A. , KIeespies T. J. , Chahine M. T. , Haskins R. D.
Published: February 2023

A nonlinear iterative relaxation moisture retrieval technique employing a first guess profile (FGP) derived by a statistical method has been developed for the DMSP-SSH/2 sounder. Simulation studies indicate that the relaxation technique can significantly improve the accuracy of the FGP's in the 300-700 mb region. Levels near the ground showed little or no improvement over the statistical technique. This behavior is not unexpected, since none of the eight water vapor sounding channels are sensitive to changes near the surface while there is a high degree of overlap in their sensitivity in the middle atmosphere.
The Use of Backscattered Ultraviolet Spectral Scans to Infer the Global Nitric Oxide Distribution
Authors: McPeters R. D.
Published: February 2023

The solar backscattered ultraviolet (SBUV) instrument on the Nimbus 7 satellite, when operated in the continuous spectral scan mode, measures the radiance emerging from the atmosphere between 200 nm and 400 nm. In these spectral scans we observe emission features resulting from fluorescent scattering of sunlight in the nitric oxide gamma bands, superimposed on a background of Rayleigh scattered sunlight. We have developed a technique for subtracting this background to allow estimation of the nitric oxide band intensities. We then can calculate total nitric oxide above 45 km on a global and seasonal basis.
Differential Inversion
Authors: King Jean I. F.
Published: February 2023

The externally-viewed thermal emission spectrum of the atmosphere may be expressed as an integral transform of the Planck intensity and a kernel weight function which depends on the line character of the sampled frequency interval. The radiances Ri = R(pi) of the N sensing channels can be considered as functions of pi, the pressure at the weighting function peak. A continuous R vs z = −ln p curve can be constructed using a suitable interpolation scheme. The forward problem consists of a mapping of the Planck intensity into the radiance profile, while the inverse problem infers the Planck intensity (temperature) as a function of pressure from the radiance profile.
Application of New Technological Developments to the Remote Detection of Atmospheric Hydroxyl Radicals Using 308 nm Excitation
Authors: McDermid I. Stuart , Laudenslager James B. , Pacala T. J.
Published: February 2023

Attempts made to date to detect OH radicals in the atmosphere using LIF have all used excitation near 282 nm. The primary reason for using 282 nm is that the fluorescence detection is centered at 309 nm and thus the filtering requirements are simplified. However, these experiments have identified a number of interfering effects which severely limit the accuracy with which OH can be measured. Perhaps the two most serious effects for LIDAR are the artificial generation of OH, through photolysis of ozone and subsequent reaction with water vapor giving the overall reaction O3 + H2O + hv → OH + OH + O2, the observation of high levels of non-resonant ("white") fluorescence especially in the dirty troposphere, and solar scatter.
Measurements of Sulfur Dioxide in the Volcanic Cloud from the El Chichon Eruption by Ultraviolet Differential Absorption Spectrometry
Authors: Evans W.F.J. , McElroy C.T. , Kerr J.B.
Published: February 2023

Ground based and aircraft measurements of the amount of sulfur dioxide in the global volcanic cloud resulting from the El Chichon eruptions on March 29th and April 4th, 1982 are presented. These measurements were made by remote sensing differential spectrometry (the Brewer spectrophotometer also measures ozone and aerosol amount). Typical column amounts of sulfur dioxide of 5 to 15 matmcm have been measured from ground based locations at Toronto, Jamaica, Mauna Loa, Laramie and Houston. Aircraft measurements on the NASA AMES CV-990 taken from San Francisco down to 20° and up to 70° are presented. Further measurements on the WB57 Project Airstream Flights from Houston down to the Equator and up to the Pole in July are presented. These measurements all indicate the presence of very large amounts of sulfur dioxide in the stratosphere. The total amount of sulfur dioxide injected from the El Chichon eruption into the stratosphere will be estimated.
Molecular Oxygen Singlet Delta State and Ozone Concentration Profiles from SPIRE Data
Authors: Winick J.R. , Sharma R.D. , Picard R.H. , Nadile R.M.
Published: February 2023

The rocketborne SPIRE (SPectral InfraRed Experiment) probe was launched from Poker Flat Research Range, Alaska, on Sept 28, 1977 to measure infrared atmospheric emission from the earth’s limb.1 The payload included two coaligned, telescoped, circular-variable-filter (CVF) spectrometers. The short-wavelength spectrometer, cooled to 77° K, covered the spectral region between 1.4μm and 7.0μm while the long-wavelength instrument, cooled to 4° K, made measurements between 9.0μm and 16.5μm. The payload reached an altitude of 285 km. The earthlimb was continuously spatially scanned from hard earth to local horizontal at 0.5 deg/sec while taking a spectrum at 2 scans/sec. The spectrometers measured the earthlimb emission during 12 vertical spatial scans at different azimuths. In doing so the emission was measured from the night (scan 8), terminator (scans 1 through 7), and daylit (scans 9 through 12) sectors of the earthlimb. For a given tangent height day scans correspond to different solar elevation angles. The emission from the a 1Δg (v′=0) --> x3Σg (v″=1) transition of O2 at 1.58μm is observed during the day scans only and increases in radiance with solar elevation angle (Figure 1). This shows that the only important process lending to the production of O2(1Δg) is the photodissociation of ozone. The emissions from ozone at 9.8μm (ν3 band), as well as the 4.8μm v1 + v3 combination band, are measured during both day and night (Figure 2). Around 80 km tangent height, the daytime 9.6μm emission is smaller than the nighttime value by a factor of about 5, because of the decreased daytime ozone density due to photodissociation. Below 50 km tangent height the daytime and nighttime emissions do not show a significant variation, in spite of the fact that some daytime ozone is photodissociated to O2(1Δg) which is observed at 1.58μm. The observed emissions from ozone and O2(1Δg) state are discussed in terms of modelled time-dependent ozone concentrations along the line-of-sight.
The Modeling of Atmospheric Aerosol Backscatter Cross-section At CO2 Wavelengths
Authors: Murty Rom
Published: February 2023

Aerosol backscatter measurements give information directly on the backscatter coefficient and not on the size distribution of the aerosols. This being the practical situation, is it possible to work with a backscatter cross-section (bcs) distribution model instead of a size distribution model?
Recovery of Water Vapor Profiles in the 0.94 μm Band Using the SAGE II Instrument System
Authors: Buglia James J.
Published: February 2023

A limited study of the possibility of using the 0.94 μm water vapor band for the recovery of water vapor atmospheric profiles is presented. This band is virtually free from other contaminant species, and thus the vexing problem of how to handle the effects of interfering gases is avoided.
The Upcoming Test Flight of a Laser Heterodyne Spectrometer
Authors: Alvarez J. M. , Larsen Jack C. , Chu W. P.
Published: February 2023

The perception that some of man's activities in the Earth's atmosphere might be inimical to his well being (1, 2) has led to the need to thoroughly understand the chemical and physical processes controlling the Earth's stratosphere. At present, there is a considerable effort being made to do this by a combination of theoretical modeling efforts (3, 4) and accompanying experimental work to obtain stratospheric data using devices on the ground (2, 5), aboard aircraft (6), on rocketsondes (7), on parachutesondes released from balloons (8), on high altitude balloons (9), and aboard spacecraft (10). The remote­sensing devices aboard spacecraft are capable of monitoring the stratosphere almost globally and for long periods of time. These attributes are not economically feasible for devices on any other platform. It is therefore to be expected that in the future, spacecraft-borne instruments will become increasingly important in monitoring the stratosphere. Spacecraft-borne instruments, for the most part, detect atmospheric emission or atmospheric solar absorption (during solar occultation) at infrared wavelengths where many of the important species in the stratosphere exhibit vibrational-rotational spectra. The Laser Heterodyne Spectrometer (LHS) is one of the instruments under development by the NASA for possible spacecraft use in monitoring the stratosphere. This instrument owes its uniqueness to its ultrahigh spectral resolution and its shot-noise limited sensitivity.
A Continuously-Tunable Rf-Excited High-Pressure CO2 Waveguide Laser for Remote Probing of the Atmosphere
Authors: Lovold Stian , Wang Gunnar
Published: February 2023

Infrared differential absorption LIDAR (DIAL) systems using line-tunable CO2 lasers have been demonstrated1,2. The lack of continuous tunability in these systems limits their performance. In this paper we report the demonstration of a continuously-tunable, pulsed, high PRF, rf-excited CO2 waveguide laser which should be useful for infrared laser remote sensing of atmospheric species.
Selection of Carbon Dioxide Laser Wavelengths for Satellite-Based Remote Measurement of Ozone in the Lower Troposphere
Authors: Shumate Michael S. , Margolis Jack S. , Menzies Robert T.
Published: February 2023

Remote measurement of stratospheric ozone in the atmosphere from an earth-orbiting satellite is a relatively straight-forward procedure (Ref. 1). However, in order to measure ozone in the atmosphere near the earth's surface, a satellite-borne instrument must be able to "see through" the stratospheric ozone layer and all the way to the ground. This paper de scribes an active laser system which uses carbon dioxide lasers and is capable of measuring tropospheric ozone distributions. The procedure for selection of the appropriate laser wavelengths is discussed. Previous work has described a method for measurement of ozone using carbon dioxide lasers (Ref. 2, 3, 4) and for calculating altitude distributions from these measurements (Ref. 5). The method discussed here takes advantage of the fact that atmospheric pressure broadens the ozone absorption lines in the lower troposphere much more than the same feature in the stratospheric ozone layer. Thus, a carbon dioxide laser wavelength that is located about three Lorentz half-widths (0.25 cm-1 or 10 GHz) away from an ozone line center will be absorbed mostly by the tropospheric ozone.
Introductory Remarks
Authors: Toth Robert
Published: February 2023

Summary not available.
Troposphere: Trace Gas Photochemistry and the Impact of Pollution
Authors: Chameides W. L.
Published: February 2023

Over the past decade great strides have been made in our understanding of the trace gas composition of the troposphere and the physical, chemical, and biological processes that control this composition. It is now recognized that the production of free radical species in the presence of solar radiation leads to a complicated series of reactions. These reactions tend to oxidize reduced species released at the earth's surface, transforming them into soluble forms which can be removed in rain and other precipitation. Thus, tropospheric photochemistry represents the atmospheric link in the biogeochemical cycling of the elements and in so doing may influence important environmental parameters such as surface temperature, the acidity of rainfall, the column abundance of stratospheric ozone, and the concentration of potentially toxic gases.
Spectrometers and Passive Interferometers
Authors: Murcray David G.
Published: February 2023

Spectroscopic instrumentation for atmospheric research has improved dramatically in the last two decades, closely following the development of similar laboratory instrumentation. In some cases the constraints imposed by the field environment have delayed the use of the instrumentation for atmospheric measurements while in other cases the need for the atmospheric data has resulted in the field use of the instrumentation prior to its laboratory use.
Active Techniques
Authors: Chanin M. L.
Published: February 2023

Different processes of interaction of a laser beam with the atmosphere and requirements from spectroscopy data to increase the possibilities of the Lidar technique.
A Cooled Optics Spectrometer for High Resolution Measurements in Support of Atmospheric Research
Authors: Strow L. L. , Korb C. Laurence , Gentry Bruce M.
Published: February 2023

A high resolution, 3 meter focal length grating spectrometer utilizing liquid nitrogen cooled order sorting optics has been developed for laboratory spectroscopy of atmospheric constituents in the 2 μm to 30 μm spectral region, the spectrometer uses a Littrow optical design modified to allow either two or four diffractions off the 25 cm echelle grating. The theoretical resolution is 0.011 cm−1 for double pass and 0.006 cm−1 for four pass operation. The fundamental limitation in achieving high resolution in infrared grating spectroscopy has been the problem of high noise associated with high room temperature background. In order to perform measurements with sufficient signal to noise, grating spectrometers must generally be operated with slit widths substantially greater than the diffraction limit. This results in an increase in signal but with a loss in resolution. In the near infrared, where relatively low blackbody background photon fluxes occur, spectrometers with resolutions as high as 0.015 cm−1 have been used. In the thermal infrared, however, the resolution of grating spectrometers has been limited to about 0.05 to 0.10 cm−1 by the high blackbody backgrounds occurring in this region.
A Xe Laser Source for Atmospheric Transmission Measurements in the Atmospheric Windows from 2 to 12 Microns
Authors: Horton R. F. , Damon E. K.
Published: February 2023

From 1971 to the present, NRL has been involved in making absolute atmospheric transmission measurements at laser wavelengths over long natural paths, typically five kilometers. These measurements have been reported directly, along with relevant meterological parameters, or have been used to calibrate high resolution spectra obtained concurrently.1
Tunable Diode Laser Sulfuric Acid Stack Monitoring System
Authors: Pearson E. F. , Mantz A. W.
Published: February 2023

A two frequency tunable diode laser system has been constructed for the purpose of monitoring sulfuric acid emissions in stacks of electric power plants where high sulfur content or oil are consumed.

The system is digitally controlled and self-calibrating in units of parts per million meter of sulfuric acid concentration.

The system will be described and laboratory stability test results will be presented.
Millimetre-Wave Spectroscopy OF Atmospheric Gases Using Untuned Cavity Resonators
Authors: Llewellyn-Jones D T , Knight R J , Johnston W B , Moffat P H
Published: February 2023

This technique has very important advantages when applied to spectroscopy of gases in a frequency region which extends from 10 GHz to 1000 GHz.

These advantages will be described and discussed. Data on absorption by atmospheric water vapour and oxygen, with emphasis on temperature dependence, will be presented, including some obtained in a large cavity giving close to 500 metres absorption path length.
Methane Profiles at 32°N from Infrared Absorption Measurements on Project Stratoprobe
Authors: Fast H. , Evans W. F. J. , Buijs H. L. , Vail G. L.
Published: February 2023

The results presented here were obtained from interferograms recorded at an altitude of 40 km during the sunset period of the Stratoprobe VI balloon flight from Palestine, Texas (32°N latitude) on Nov. 8, 1978. The interferometer, built by Bomem Inc., has a resolution of 0.05 cm-1 un-apodized, and has been described by Buijs et al.(1980). For the Stratoprobe balloon flights series several modifications were made. A sun tracker was added to the instrument to improve the tracking provided by the solar table on the gondola. The installation of an electronic numerical filter reduced the data rate by a factor of 31, providing 5100 samples from each one-sided interferogram. The time required for one interferometer scan was 83 seconds. Interferograms were recorded in the 1840-1990 cm-1 and 2860-3000 cm-1 regions simultaneously.
Satellite IR Radiance Deficits and Transmittances
Authors: Neuendorffer A.C.
Published: February 2023

The TIROS High Resolution Sounder1 (HIRS), like previous atmospheric sounders, relys heavily upon CO2 v2 15 micron R branch (675–715 cm−1) absorption and adjacent CO2 (v1 – v2) "hot" band absorption (at 721 cm−1 and 742 cm−1) for tire purpose of obtaining atmospheric temperature retrievals.2 Although this region is somewhat complicated by a weak 710 cm−1 ozone band, it is near the Planck function peak and (unlike the P branch) is relatively unaffected by water and CO2 heavy isotope absorption.
"Complete" Spectral Maps in the Millimeter and Submillimeter Spectral, Region†
Authors: Helminger Paul , De Lucia Frank C.
Published: February 2023

We define a "complete" spectral map as one that contains all transitions within a given spectral region above some threshold intensity. The spectral intensity depends both upon molecular parameters (e.g., transition matrix elements) and environmental parameters (e.g., temperature and pressure).
Quantitative Fluorescence Spectroscopy of NO2: Is NO2 Fluorescence Lidar a Viable Stratospheric Measurement Technique?
Authors: McGee T. J. , McIlrath T. J. , Dulcey C. S.
Published: February 2023

A stratospheric measurement of the NO2/NO ratio is important to our understanding of the photochemistry of the upper atmosphere. Lidar as a technique for making such measurements is particularly attractive for a number of reasons. In the case of balloon-borne experiments, data are taken some distance away from the contamination cloud of the balloon itself; altitude and horizontal profiles can be obtained; and since it is an active measurement and therefore not dependent on solar flux, nighttime measurements are also possible. Our laboratory has studied the quantitative fluorescence properties of NO2 at several wavelengths and these data as well as the lidar simulations arising out of them will be presented.
Diode Laser Heterodyne Spectroscopy of Sulfur Dioxide
Authors: Sattler J. P. , Worchesky T. L. , Lafferty W. J.
Published: February 2023

The use of a HgCdTe photomixer well beyond its 1.2 GHz bandwidth in conjunction with a tunable diode laser has permitted the rapid, precise and accurate frequency measurement of many Doppler-limited infrared. (IR) absorptions lying within ±9 GHz of a CO2 laser emission. With care, IR line centers may be determined to within ±3 MHz. A schematic of the apparatus appears in Fig. 1.
NBS Infrared Laboratory Measurements on Atmospheric Molecules
Authors: Maki A. G. , Olson Wm. B. , Kagann R. H. , Lafferty W. J. , Sams R. L. , Wells J. S. , Petersen F. R.
Published: February 2023

High Resolution infrared measurements and analyses are being made on a number of molecules of significance for understanding the chemistry of the upper atmosphere. Molecules recently studied include N2O, HONO, HNO3, NO2, HOCl, OCS, SO2, and H2O2. Both a tunable diode laser system and a Fourier transform spectrometer are being used to provide frequency, intensity, and line width information.
Fracture Mechanics of Glass
Authors: Lawn Brian R.
Published: February 2023

A survey of the fracture mechanics of glass and brittle ceramics, with special attention to contact configurations, will be presented. The underlying focus is "indentation fracture," where a sharp point is used to generate a deformation-crackpattern in the material surface. This pattern forms the basis for analysis of many wear and polishing phenomena in brittle materials.
Lapping: Polishing and Shear Mode Grinding
Authors: Brown Norman J.
Published: February 2023

It is the thesis of this paper that shear mode grinding (SMG), (ductile grinding, nanogrinding, fractureless grinding) is just a particular form of polishing. It may be unique in that it can involve a hard wheel of very precise dimensions compared to the soft laps usually used in polishing. Such a wheel would permit the fabrication of a precision surface on a brittle material such as glass at a precisely located and oriented position on a part. The technological and economic consequences of such a process seem important but the technical obstacles to implementing the technique are for the moment formidable. It is in production in Japan. This paper provides a bit of understanding of that process obtained by making an end run around the obstacles to view the process from the vantage point of lapping.
Computer Simulations of Precision Ground Surfaces
Authors: Fawcett Steven C. , Dow Thomas A.
Published: February 2023

The majority of precision refractive optical components are fabricated from brittle glasses. The fabrication usually involves grinding the desired contour of the component followed by polishing to remove the undesirable surface features. These surface features are remnants of the brittle fractures that occur in the grinding operation. Previous studies at the Precision Engineering Center have demonstrated the feasibility of achieving ductile material removal (Ductile Mode Grinding) on samples of brittle materials. Experimental measurements and analytical models have demonstrated the relationship between the depth of cut and the damage to the surface. The extrapolation of such one-dimensional critical depth information to three dimensions is being developed through computer simulations of the grinding process and the resulting chip geometry.
Truing and Dressing of Metal Bond Diamond Wheels for Ductile Regime Grinding
Authors: Hashimoto Hiroshi , Blaedel Kenneth L.
Published: February 2023

The traditional theory of brittle-fracture grinding is based on self-sharpening of grains of wheels. Ductile regime grinding requires precision truing and dressing of wheels so that the diamond grains protrude above the bond material surface.
Estimation of Subsurface Damage Depth by Dimpling
Authors: Dettmann Lee
Published: February 2023

Sample Preparation- To test each of the methods of measuring subsurface damage, three fused silica samples were used. Two of the samples were one inch in diameter and one inch thick. These were ground using resin bonded diamond pellets bonded to a metal plate using a conventional Strasbaugh grinding machine. Both 12 and 30 micron diamond pellets were used. These were then diamond generated to approximately 1 mm thickness from the back. The back was then ground and polished using conventional techniques. The other sample began as a 1"X3" fused silica microscope slide that was generated on a swing arm generator with a 320-grit resin bonded diamond cup wheel.
Surface Preparation Technique for Rapid Measurement of Sub-Surface Damage Depth
Authors: Lindquist A. , Jacobs Stephen D. , Feltz A.
Published: February 2023

Most methods for fabrication of optical materials produce, in addition to the desired result (dimensional accuracy, surface figure, and surface roughness, etc.), the undesirable side effect of cracks or fractures in the material known as sub-surface damage. The "sub" prefix denotes the absence of clear evidence on the surface as to the existence of the damage below, particularly if the surface is subsequently polished. As a source of scattered light, figure instability, or in some cases, total failure of an optic, sub-surface damage can be detrimental in high precision optical systems. Detection and measurement of this sub-surface damage has become vital to the improvement of optical fabrication techniques. This paper describes the methods by which we detect and measure sub-surface damage (SSD).
Investigation of Polished Optical Glasses with a MAI—MWL Ellipsometer Arrangement
Authors: Linder Michael
Published: February 2023

Surface layers are investigated by means of MAI–MWL (multiple angle of incidence, multiple wavelength) ellipsometry. The "layers" investigated are modifications of optical glasses in the near-surface region, caused by polishing and cleaning processes. The influence of several treatments on different materials is discussed.

The device used is a new, special ellipsometer arrangement using only absolutely nescessary elements but allowing fast and very accurate measurements.
Using Hole-Burning to Measure a Molecular Field
Authors: Gradl Gerhard , Kohler Bryan E. , Westerfield Curtis
Published: February 2023

Octatetraene can be photoisomerized even when it is incorporated in a low temperature n-hexane crystal. When this is done by irradiating the zero-phonon component of the S0→S1 origin band with a single frequency laser, very narrow (less than 10 MHz) persistent holes can be burned. We have determined the effect of an externally applied electric field on these persistent holes and fit the observed data with a simple quantum mechanical model parameterized in the S0→S2 and S1→S2 transition dipoles and the projection of the local electric field on the octatetraene chain axis. The magnitude of the local electric field (ca. 106 V/cm) is only consistent with one of the three possible n-hexane sites that could have accomodated the octatetraene guest.
Hole-Burning in Biological Systems
Authors: Small Gerald J.
Published: February 2023

Understanding the excited state electronic structure, optical excitation (energy) transfer and primary charge separation in photosynthetic protein-chlorophyll complexes represents an important but formidable problem [1]. At the outset it is important to realize that the protein, as a host for the various pigments (cofactors), is glass-like, meaning that the optical absorption bands of pigments such as chlorophylls (Chl) suffer from significant site inhomogeneous broadening (ΓI). For Chl and pheophytin cofactors the absorption band of primary interest is the origin or (0,0) band of the lowest excited singlet state which is commonly referred to as the Qy-state, a ππ* state. Such bands carry widths from ~ 100-500 cm-1, depending on the system. For several reasons it becomes important to unravel the ΓI and homogeneous broadening (ΓH) contributions to the bandwidth. Two important contributors to ΓH are the linear electron-phonon coupling (Γep) and exciton level structure accompanied by ultra-fast inter-exciton level relaxation (Γex). It turns out that Γex is most important for antenna protein complexes because their unit cells (of a 2-dimensional array) often contain several strongly interacting Chls.
Hole Shape and Ultrafast Optical Dephasing
Authors: Osad’ko I.S. , Gladenkova S. N.
Published: February 2023

1. The optical Bloch equations predict the lorentzian shape of a hole burnt in the population of atoms by laser light. This hole is related to the exponential echo-signal by the Fourier-transformation Eq.(1) is also used [1] for ultrafast nonexponential dephasing which is usually related to the existence of the phonon side band in an optical spectra.
Trap Effect in Spctral Hole Burning of Sm2+ Doped Crystals
Authors: Zhang Jiahua , Sun Lingdong , Qin Weiping , Huang Shihua , Yu Jiaqi
Published: February 2023

Since the first observation of persistent photon gated spectral hole burning in BaFCl:Sm2+ at liquid helium temperature[1], the successful improvement on this material has been performed in our laboratory by adding bromine and alkline earth metals in the melt to form MyM'1-yFClxBr1-x:Sm (M,M'=Mg, Ca, Sr, Ba; x,y=0-1) system, in which the inhomogeneous line is broadened significantly[2-5] and room temperature hole burning is realized [6]. The hole burning mechanism is found to be photoionization of Sm2+ followed by electron trapping[1]. A kind of principal electron trap is considered to be Sm3+[1], which brings about hole refilling in the holes burnt formerly as burning the next hole because the generated Sm3+ corresponding to the former holes can trap electrons again released in the next hole burning[7]. That means, writing will erase the stored information. To avoiding this effect, introducing an other kind of trap different from Sm3+ for hole burning is necessary In the present paper, we report the results of hole burning in Sm singly doped and Sm, Yb doubly doped SrFCl crystals at 77K and room temperature. Two different trap effects in hole burning are observed and discussed.
Ultrafast Dephasing of Organic Glasses in Wide Temperature Region Investigated by Incoherent Photon-Echo: Resorufin/D- and D6-Ethanol.
Authors: Gruzdev N.V. , Vainer Yu. G.
Published: February 2023

Until now, in spite of a great number of experimental and theoretical works in study of organic amorphous solids, the basic features of the low temperature dynamics of these mediums are poorly understood. One of the main reason of this is the lack of experimental information about these dynamical processes. In particular, it’s necessary to learn more about optical dephasing in doped organic glasses and polymers for wider temperature interval. It will allow to test the existent theories more correctly and to create new conceptions.
Nuclear spin conversion relaxation processes in dimethyl-s-tetrazine doped n-octane measured by spectral hole burning techniques
Authors: Orth K. , Grad G. , Friedrich J.
Published: February 2023

Rotational tunnel systems provide deep insight into the basic laws of quantum mechanics. For a review, see [1]. Let us take the -CH3 entity as a prototype. A rotation by 2π/3 around the symmetry axis perpendicular to the plane of the protons leaves the relevant Hamiltonian invariant. The spatial wave functions have A- and E-type symmetries. Since such a rotation is equivalent with a double permutation of two protons, the total wave function (space ⊗ spin) has to be totally symmetric because of Pauli’s principle. That is, the Pauli principle puts a strong symmetry restriction onto the wave function of the -CH3-rotor: In the E-type states, the total nuclear spin is 1/2, in the A-type states it is 3/2. As a consequence, a relaxation of the total spin in these kind of quantum rotors is always connected with a change of the rotational or librational wavefunction. The corresponding overall process is called spin conversion relaxation.
High Speed Time-Frequency Domain Holographic Storage
Authors: Shen X. A. , Bai Y. S. , Kachru R.
Published: February 2023

Image storage in coherent time-domain optical memory (CTDOM) has been demonstrated successfully by using high-power pulsed lasers.1-2 Like photochemical hole burning3 and photorefractives,4 this time-domain approach to image storage has the potential of offering ultrahigh storage density and fast data access time. Unlike other optical memories, CTDOM is capable of providing ultrahigh image transfer rates and offers features such as in-memory image processing.5 However, difficulties arise in using the conventional time-domain approach to image storage, namely multiple images per frequency channel. For example, existing image composers such as an electronically-addressed spatial light modulators (SLM) do not have switching times fast enough to accommodate the required recording speeds (≳ MHz). High-power pulsed lasers are needed to make retrieved images detectable by electronic cameras. In addition, features such as random frame (or page) access and variable playback speed are not available with the conventional approach.
Looking into Frozen Proteins with Hole Burning
Authors: Friedrich J.
Published: February 2023

The solid state physics of frozen proteins shows highly specific features: At the same time proteins reflect structural order as well as disorder. Structural order is expected for biomolecules with spatially highly correlated building blocks. Spatial correlation is convincingly demonstrated in well resolved X-ray diffraction patterns /1/. Yet numerous experiments, mainly in the optical field, demonstrate that proteins behave glass-like /2, 3/. Glasses are charcterized by a rather low spatial correlation of the respective molecules.
Low Temperature Properties of Glasses: Two Level Systems, Soft Modes, and Spectral Diffusion
Authors: Silbey Robert J. , Heuer Andreas , Dab David
Published: February 2023

A theoretical method that systematically finds tunneling systems in glasses and allows a microscopic justification of the standard tunneling model of Phillips and Anderson, Halperin and Varma is presented. The calculation shows that the major assumptions of the tunneling model are qualitatively correct; however, there are small deviations in the distribution functions of tunneling parameters that give rise to the T1+ε law for specific heat and the T2-α law for the thermal conductivity. The calculation also allows a quantitative estimate of the interaction of the two level systems with phonons (the deformation potential). The calculations confirm the weak coupling picture, in contrast with recent conjectures. The theory is then mapped onto all structural glasses via a Lennard-Jones model for the interaction between sub-units in the glass. These sub-units are molecular systems (e.g monomers in a polymer glass or tetrahedra in silicate glasses). From this mapping, we find that the tunneling parameters, and hence the thermal properties, of most structural glasses can be estimated semi-quantitatively from the microscopic parameters of the Hamiltonian. A further argument allows the connection between the tunneling parameters and the macroscopic experimental properties (sound velocity and density) to be drawn. The calculations also go smoothly into the "soft potential" model that explains the thermal behavior at higher temperatures (~10K), thus providing a universal model. From these calculations, the distribution of tunneling rates that give rise to spectral diffusion can be calculated and compared to recent experiments. These will be presented at the conference, along with calculations of the effect on the two level system distributions of introducing an impurity (i.e. chromophore) into the glass.
New Mechanisms and New Systems of Hole Formation in Spectral Hole Burning
Authors: Horie Kazuyuki
Published: February 2023

A variety of studies on persistent spectral hole burning (PSHB) have been carried out for the last twenty years [1-4], since the discovery of this phenomenon in 1974. The elucidation of electron-phonon interaction, the nature of a zero-phonon line and spectral diffusion in PSHB have been studied intensively together with the research aiming at its possible applicability to ultra-high density optical storage. However, as for the PSHB materials, most of the works have been carried out with porphyrins, phthalocyanines, and quinizarin including their derivatives, several organic dyes, samarium and some other inorganic ions. The number of molecules reported to show hole formation so far is restricted compared to a wide variety of chemical structure of organic molecules. This would be because it is usually thought that for the hole formation the existence of a zero-phonon line in guest molecules for SHB should be accompanied by the occurrence of some photochemical reaction of the guest molecules. A well-known exception on this point is the so-called non-photochemical hole burning (NPHB) [4]. Recently triplet-triplet energy transfer of guest molecule to a host photo-reactive matrix has been reported to be a new family [5] of PSHB systems with new mechanism.
Wavelength Dependence of Persistent Spectral Hole Burning in Sm2+-Doped Fluoride Glasses
Authors: Kurita A. , Tanaka M. , Hiyama T. , Hada A. , Kushida T.
Published: February 2023

We reported the first observation of room-temperature persistent spectral hole burning in Sm2+-doped fluoride glass in the last conference [1]. Room-temperature hole burning had been also observed in Sm2+-doped crystals [2]. We found considerable differences in the hole-burning characteristics between Sm2+-doped glasses and Sm2+-doped crystals: The burning-laser-intensity dependence is approximately linear, and no antihole is observed around the hole burned in Sm2+-doped glasses [3]. More detailed experimental studies are needed to clarify the mechanism of the hole burning in this glass and to explore more efficient hole-burning systems. In this paper, we report several experimental results related to wavelength dependence of the hole burning process.
Fluorescence excitation of impurities doping crystals and polymers using single molecule spectroscopy
Authors: Bernard J. , Orrit M. , Brown R. , Lounis B.
Published: February 2023

Single molecule spectroscopy is now a well known technique and a lot of new fields of research begun recently. In this paper we present results we obtained in p-terphenyl crystals where we conbined our technique with detection of magnetic resonance. In polyethylene matrix we obtained with Rhodamine 640 interesting results which we compare with our results on the same system using hole burning.