bluuebunny/crossref_metadata_2025 huggingface dataset:
First Lidar Measurements of Water Vapor and Aerosols from a High-Altitude Aircraft
Authors: Browell Edward V. , Ismail Syed
Published: February 2023

Water vapor plays an important role in many atmospheric processes related to radiation, climate change, atmospheric dynamics, meteorology, the global hydrologic cycle, and atmospheric chemistry, and yet our knowledge of the global distribution of water vapor is very limited. The Differential Absorption Lidar (DIAL) technique has the potential of providing needed high resolution water vapor measurements from aircraft and from space, and the Lidar Atmospheric Sensing Experiment (LASE) is a key step in the development of this capability. The LASE instrument is the first fully engineered, autonomous DIAL system, and it is designed to operate from a high-altitude aircraft (ER-2) and to make water vapor and aerosol profile measurements across the troposphere. The LASE system was flown from the NASA Wallops Flight Facility in a series of engineering flights during September 1994. This paper discusses the characteristics of the LASE system and presents the first LASE measurements of water vapor and aerosol profiles.
Measurements of Daytime and Upper Tropospheric Water Vapor Profiles by Raman Lidar
Authors: Bisson Scott E. , Goldsmith J. E. M.
Published: February 2023

One of the most important atmospheric constituents needed for climate and meteorological studies is water vapor. It plays an important role in driving atmospheric circulations through latent heat release and in determining the earth’s radiation budget, both through its radiative effects (water vapor is the major greenhouse gas) and through cloud formation. The vertical distribution of water vapor is particularly important because in addition to determining convective stability, radiative effects are also strongly altitude dependent. In fact, several one-dimensional radiative convective models1have shown that although upper tropospheric (8-12 km) water vapor concentrations are 2-3 orders of magnitude less than those near the surface, upper tropospheric water vapor exerts an important influence on climate. What these models show is that for a givenabsoluteincrease in water vapor in the upper troposphere, the response or change in surface temperature is extremely disproportionate to the amount of water vapor. At present, considerable controversy exists over the nature of the vertical redistribution of water vapor in a changing climate, and particularly the distribution of water vapor in the upper troposphere. Understanding upper tropospheric moistening processes such as deep convection are therefore of prime importance in addressing the water vapor feedback question. Accurate measurements of the vertical and temporal variations of water vapor are essential for understanding atmospheric processes and hence model refinement.
DIAL Measurements of CO2 Using a Tunable, Narrow-Linewidth 2.066 μm Ho,Tm:YLF Laser
Authors: Taczak Thomas M. , Killinger Dennis K.
Published: February 2023

We have developed a Ti:S laser pumped, narrow-linewidth, 2.066 μm Ho, Tm:YLF laser as a tunable laser source for Differential Absorption LIDAR (DIAL) remote sensing of atmospheric CO2. The laser has been tuned across several absorption lines of CO2 in a laboratory absorption cell, and atmospheric long-path measurements of CO2 are planned.
The Retrieval of Vertical Profiles of Chlorine Source Gases and N2O5 from MIPAS-B-92 Limb Emission Spectra
Authors: Clarmann T.v. , Linden A. , Wetzel G. , Oelhaf H.
Published: February 2023

During the European Arctic Stratospheric Ozone Experiment (EASOE) the balloon-borne cryogenic Fourier transform spectrometer MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) recorded several sequences of mid infrared limb emission spectra, which were used for the retrieval of vertical profiles of CFC-11, CFC-12, HCFC-22, CF4, and N2O5. These gases are characterized by very dense emission bands of unresolved lines. Results are consistent with the current theories of stratospheric dynamics and chemistry.
Observations of Polar Ice Using Enhanced Resolution Microwave Scatterometer Data
Authors: Long David G.
Published: February 2023

Increasing interest in the role of ice sheets in regulating global climate has created a need for synoptic interannual recording and monitoring of the earth’s major ice sheets. Based on their ability to “see” into ice, microwave remote sensing instruments are well-suited for monitoring the polar regions.
High Spatial Resolution Atmospheric Wind Measurements with the Edge Technique
Authors: Korb C. Laurence , Gentry Bruce M. , Li S. Xingfu
Published: February 2023

The edge technique1,2 is a new and powerful method for measuring small frequency shifts such as the Doppler shift of an atmospheric backscattered signal from a pulsed laser. The edge technique can be used for high spatial resolution, high accuracy ground and airborne wind measurements as well as high accuracy spaceborne wind measurements. We have recently made our first ground based wind measurements. These have a spatial resolution of 15 m and an accuracy of 25 cm/s and these measurements are presented in this paper. This is a unique capability and provides valuable information for studies of turbulent processes in the lower atmosphere. It could also be used for high sensitivity detection of wind shear and microbursts in the vicinity of airports. In addition, global wind measurements can be made with the edge technique from space with an accuracy of 1 m/s and a vertical resolution as high as 150 m in the boundary layer and 1 km through the troposphere. Such a system could make eyesafe wind measurements using well developed diode pumped solid state laser technology at 1.06 μm. Multi-pulse averaging would provide a spatially representative wind measurement.
Accelerated Line-by-Line Calculation of Spectral Absorption Coefficients with High Numerical Accuracy
Authors: Sparks L.
Published: February 2023

To model radiative transfer through the atmosphere with high accuracy, one must resort to the calculation of spectral absorption coefficients on a line by-line basis. The calculation of these coefficients is computationally expensive for three reasons: (1) thousands of spectral lines can contribute to absorption at a single frequency: (2) the tails of spectral line profiles are long (i.e., a given line can contribute to absorption over a wide range of frequencies), and (3) the sampling frequencies at which monochromatic radiances are to be calculated must be spaced sufficiently close together to resolve the thinnest lines of interest (e.g., those that arise in the stratosphere). We have developed a new algorithm to accelerate the calculation of spectral absorption coefficients while retaining high numerical accuracy.
Intercomparison of Radiance Algorithms for the Microwave
Authors: Clough Shepard A. , Brown Patrick D.
Published: February 2023

The retrieval of atmospheric state parameters from remotely sensed radiance observations using physical retrieval methods is highly sensitive to the accuracy of the forward model. This is a direct consequence of the generally poorly posed nature of the inverse problem. To address the question of the accuracy of forward model calculations, an initiative has been undertaken under the auspices of the International Radiation Commission to intercompare transmittance and radiance models with observed radiance observations, ITRA (Intercomparison of Transmittance and Radiance Algorithms; Chedin et al., 1988). For the present model intercomparison the participants and their affiliation are presented in the lower part of this summary.
The Determination of Spectral Components of Multispectral Images
Authors: Gruninger John , Sundberg Robert
Published: February 2023

Imaging spectrometers can collect data in a large number of narrow bands providing a low spectral resolution spectrum for each pixel. Pixel to pixel spectral variations can be attributed to varying concentrations of constituents and to environmental variations. Identification of the material constituents provides for both interpretation and compression of the data. Identifying constituents by directly comparing data to laboratory spectra is hindered by pixel foot print size, typically more than one constituent contributes to each pixel, and by environment effects. Environmental effects, such as variations in illumination, atmospheric scattering and transport effects, are generally not included in the reference spectra. Analysis approaches which remove or reduce the effects of the environment and produce apparent reflectances are desired.1 It is also desirable to determine constituents directly from the data and to rely on reference libraries for later confirmation or analysis. This effort focuses on the constituent analysis problem. The estimation of spectral components from the data has been based on finding convex hulls of data base spectra.2,3 The approach reported on here finds bounds on the possible component spectra and abundances. These bounds can be narrowed by using additional information or constraints on spatial characteristics or knowledge of one or more of the constituents. In this summary, the method is outlined and preliminary results are discussed.
New Generation of Tunable Diode Laser based Instruments for Atmosphere Monitoring
Authors: Nadezhdinskii Alexander
Published: February 2023

During the last decade various Tunable Diode Laser (TDL) applications were demonstrated in different areas of high resolution molecular spectroscopy, chemistry, plasma physics, atmosphere monitoring, medicine, high technologies, and other ones. More than 800 papers were published dealing with TDL applications(1). However, the method was not widely used in routine operations due to several reasons. One of them is a necessity of laser cooling systems. Complicity of TDL systems and their inevitable high costs are the other one. Moreover, lasers' properties, their irreproducibility and necessity of highly qualified operators to run the instrument may be considered as the main reason restricting dramatically the broad implementation of TDL systems. In the present paper we will discuss briefly the last subject and possible improvement of TDL system characteristics.
Remote Sensing of the Atmosphere by Resonance Raman LIDAR
Authors: Sedlacek Arthur J. , Harder David , Leung King P. , Zuhoski Peter B , Burr D. , Chen Carl L.
Published: February 2023

With our increased environmental awareness has come the need for technologies that can detect, identify and monitor pollutants and, where necessary, verify their destruction. This need is evidenced by the recent creation of the Clean Air Act Amendments (CAAA), of which the Title III-Hazardous Air Pollutants (HAP) amendments mandate the complete revision and expansion of the earlier Clean Air Act (CAA), section 112.1 As was pointed out by Grant, Kagann and McClenny,2 optical remote sensing technologies are expected to play a very important role in insuring that various facilities are in compliance with the Maximum Achievable Control Technology (MACT) standards for the reduction of HAP emissions that are called for in section 301 of Title III. Unfortunately, however, many of these technologies have varying detection and applicability characteristics which often dictate the conditions under which one can use the sensor to detect, identify or monitor a chemical species. Some of the advantages3-8 that a Raman-based pollution sensor possess are: (1) very high selectivity (chemical specific fingerprints), (2) independence from the excitation wavelength (ability to monitor in the solar blind region), (3) chemical mixture fingerprints are the sum of its individual components (no spectral cross-talk), (4) near independence of the Raman fingerprint to its physical state (very similar spectra for gas, liquid, solid and solutions), and (5) insensitivity of the Raman signature to environmental conditions (no quenching, or interference from water). The detection of atmospheric components using Raman backscattering of laser radiation dates back to the pioneering work of Leonard9 in 1967. In that study, he used a pulsed N2 gas laser at 337.1 nm to generate Raman return signals from N2 and O2.
Summed-Frequency Nd:YAG-Based Sodium Temperature Lidar
Authors: Burka Michael
Published: February 2023

Lidar sounding of the mesospheric sodium layer for density and temperature profiling has been conducted primarily with dye lasers.1 This work has been very successful, and dye laser systems based on CW dye laser oscillators are precise enough to measure wind-induced Doppler shifts of the sodium fluorescence line shape.2 However, there is a need for sodium fluorescence lidar transmitters based on solid state laser technology for use on mobile platforms and other locations for which dye lasers are not optimal. The first successful solid state sodium fluorescence lidar is based on a tunable Alexandrite transmitter.3 In this technique, an Alexandrite laser produces light that is Stokesshifted to 1178 nm, then frequency doubled to the 589 nm sodium line. Alternatively, tests have shown that the Alexandrite primary beam can be directly frequency shifted to 589 nm using the anti-Stokes shift. In both cases, the laser is injection seeded to ensure single mode operation and the narrow linewidth required to measure the Doppler-broadened width of the sodium fluorescence line shape.
Cirrus Physical and Radiative Parameters from Simultaneous Lidar, Radar, and Infrared Radiometer Measurements
Authors: Eberhard Wynn L. , Intrieri Janet M.
Published: February 2023

Cirrus clouds are important modulators of radiative transfer in the atmosphere. The processes that form cirrus and the resulting radiative properties must be properly understood to model climate correctly. Bulk properties (such as optical depth, fractional cover, and cloud temperature) as well as microphysical properties (such as particle effective radius and ice water content) are important to radiative transfer. Knowledge about many of these parameters and the relationships between them are still inadequate for satisfactory parameterizations in general circulation models.
Off-Beam Cloud Lidar: First Detection of Diffusing Photons
Authors: Davis Anthony , Spinhirne James D. , McGill Matthew , Cahalan Robert F.
Published: February 2023

Current atmospheric lidar systems are designed, in the true spirit of radar, to detect optical “echoes” (back-scattering events); in addition to radar, two-way beam attenuation must be accounted for.
On the Optical and Radiative Properties of Phytoplankton
Authors: Mengüç M. P. , Alstedt S. , Manickavasagam S.
Published: February 2023

More than 70 percent of the surface of the earth is covered with water, which serves as habitat for a vast number of living creatures. The suspended particulate matter in the sea is divided into living organisms, known as plankton, and dead (decaying) matter called detrius. Plankton includes all passive creatures drifting in the sea; actually, the Greek term plankton means migratory, wandering. Plankton are varying greatly in size and growth rate, and is divided in subgroups, most importantly the nutritionally dependent zooplankton and phytoplankton, which represent a large group of planktonic plants residing in the surface waters. The phytoplankton group encompasses hundreds, maybe thousands of species, ranging in size from less than 2 μm to more than 2 mm, with most falling within 5 – 50 μm.
Lidar Measurements Of Particle Concentrations Near Roadways
Authors: Hofeldt David L. , Olson Bernard A
Published: February 2023

Traffic engineers and city planners need either a large empirical database or improved models to assess and predict the impacts of new traffic management strategies or business developments on air quality. The spatial and temporal resolution of lidar technology coupled with its relatively wide-area remote sensing capability make it ideally suited for studying traffic-related air quality problems, which are by nature distributed, mobile, and transient. With proper eye-safety precautions, lidar systems can be used to monitor ambient particle concentrations near ground level in urban environments.
Trace Gas Remote Sounding with the High Resolution Dynamics Limb Sounder (HERDLS)
Authors: Gille John C.
Published: February 2023

HIRDLS is a 21-channel infrared limb scanning radiometer for determining the distributions of 10 trace species from the upper troposphere to the mesosphere.
Observations of Atmospheric Water Vapor and Spectral Line Shapes with HIS
Authors: McMillan W. Wallace , Strow L. Larrabee , Hannon Scott E. , Tobin David C. , Smith William L. , Revercomb Henry E. , Knuteson Robert O.
Published: February 2023

The global measurements of temperature and water vapor required by increasingly sophisticated forecast models can only be supplied by satellite observations. Upcoming satellite atmospheric sounders such as the Atmospheric Infrared Sounder (AIRS) (Aumann and Pagano, 1994) will have sufficient spectral resolution to see in between spectral lines where the radiances are most sensitive to spectral line shapes and associated continua. Because these spectral regions have the narrowest weighting functions they are especially useful for retrieving atmospheric parameters.
Wavelength Tunable LIDAR and DIAL Computer Simulations
Authors: Wilcox William E. , Killinger Dennis K.
Published: February 2023

A Lidar simulation computer program and associated atmospheric spectral databases have been developed which simulate the laser remote sensing of the atmosphere and the system performance of a direct-detection Lidar or tunable Differential Absorption Lidar (DIAL) system. This simulation program allows the use of several large atmospheric spectral databases (HITRAN, BACKSCAT) to be coupled with Lidar parameters to provide a real-time and interactive design tool for atmospheric Lidar simulation and modeling. The overall program, LIDAR-PC, can be used for a range of different Lidar simulations and these results compared to experimental Lidar data to determine the range-resolved attenuation coefficient of the atmosphere and the effect of the telescope overlap factor. The software and databases operate on an IBM-PC or compatible computer platform (Windows or Windows 95 Operating System).
Retrieval of Effective Cloud Radiative Properties from Ground Based Spectral Measurements
Authors: Moncet J.-L. , Clough S. A.
Published: February 2023

A fast and numerically accurate model for monochromatic radiative transfer in scattering atmospheres has been developed to extend the capabilities of the existing LBLRTM line-by-line model [Clough et al., 1992] to the treatment of clouds and aerosols. The algorithm is based on the adding-doubling method and is specifically designed to perform radiance calculations in both the thermal and solar regimes using any specified number of computational streams. The efficient implementation of the adding-doubling scheme makes it possible to use the multiple-scattering algorithm in retrieval applications, an essential requirement for the intended use of the algorithm in atmospheric validation studies. The algorithm is applied to daytime observations of water clouds from the ground-based high spectral resolution Atmospheric Emitted Radiance Interferometer (AERI) [Smith et al., 1995]. Cloud particle size and density, and cloud fraction are retrieved from the spectral measurements in the 520-1500 cm-1 and 1800-3020 cm-1 bands. An initial assessment is made of the spectral information content of the AERI measurements for water cloud properties, and of the quality of the spectral fits obtainable with those three free parameters in the two bands.
All Solid State Diode Pumped Water Vapor DIAL and Wind Lidar for Latent Heat Flux Measurements
Authors: Lehmann Stefan , Bösenberg Jens
Published: February 2023

Only active remote sensing systems can provide water vapor data with high temporal and vertical resolution. The DIAL technique is most promising for accuracy, resolution, and day and night operation [1]. Heterodyne detection can provide information about vertical wind speeds. Measurements of both parameters with a single system provides all necessary data to evaluate latent heat flux (eddy correlation technique), a very important energy transport mechanism in the atmosphere.
Preliminary results from a mini-MOPA CO2 Doppler lidar
Authors: Brewer W. Alan , Rye Barry J. , Hardesty R. Michael , Eberhard Wynn L.
Published: February 2023

We recently deployed the new version of a high-prf, low-power, CO2 Doppler lidar at the cloud and radiation testbed (CART) southern great plains site near Ponca City, Oklahoma. This lidar was developed to study cloud microphysics and boundary layer structure. In its final configuration the instrument will have dual wavelength capability enabling it to make Doppler wind observations and differential absorption lidar (DIAL) species concentration measurements in the lower 3-5 km of the atmosphere. Combining these measurement will allow one instrument to provide concentration and vertical flux profiles of water vapor and ozone to support climate and global-change related research in the lower troposphere.
Retrieval of Microphysical Particle Properties from Backscatter and Extinction Data by Inversion via Regularization
Authors: Müller Detlef , Ansmann Albert , Wandinger Ulla , Althausen Dietrich
Published: February 2023

Atmospheric aerosols, although only a minor constituent of the earth’s atmosphere, play an important role in many atmospheric processes. They have appreciable influence on the earth’s radiation budget, air quality, clouds and precipitation as well as the chemistry of the troposphere and stratosphere. One of the key aspects in a further understanding of the importance of aerosols is the investigation of the spatial and temporal variability of the particles’ microphysical properties, such as parameters describing their mean size, mass and surface-area concentrations. A data-evaluation algorithm that uses the method of inversion via regularization is currently being developed to retrieve microphysical parameters from optical data. Hereby, the main focus will be the information on mean values of the particle size distribution. The optical information will be provided by two lidar systems, a multiple wavelength lidar and a Raman lidar. Altogether, these systems will give six backscatter coefficients and two extinction coefficients in the wavelength range from 0.355 to 1.064 μm. Additional information will come from depolarization and water vapor measurements at 0.532 μm.
Atmospheric Cooling Rate Calculations for the Airborne Southern Hemisphere Ozone Experiment (ASHOE) using MODTRAN3
Authors: Lee S.C. , Knuteson R.O. , Revercomb H.E. , Smith W.L.
Published: February 2023

One of the objectives of the Airborne Southern Hemisphere Ozone Experiment (ASHOE) was to examine the causes of ozone loss in the Southern Hemisphere lower stratosphere, and to investigate how the loss is related to polar, mid-latitude, and tropical processes, including radiative transfer. Cooling rates were calculated for ASHOE in order to: (1) understand how the ozone depleted air is transported to populated regions outside the polar vortex, (2) relate vertical motions and transport of air around the South Pole to atmospheric cooling rates, and (3) validate cooling rates in dynamical models for the polar vortex using observed data and more accurate radiative transfer models.
Comparison of Atmospheric Radiances Measured by Two FTIR Spectro-radiometers in the Tropical Pacific
Authors: Shaw Joseph A. , Han Yong , Churnside James H. , Knuteson Robert O. , Revercomb Henry E. , Best Fred A.
Published: February 2023

In early 1996, our two organizations measured infrared atmospheric radiances with two independent Fourier Transform InfraRed (FTIR) spectro-radiometers on the NOAA R/V Discoverer in the tropical Pacific. Our objective was to make highly accurate measurements that would be useful for improving radiative transfer models and for establishing FTIR technology as a practical tool for measuring atmospheric radiation in the tropics. However, the usual problem with such an approach is that there is no easy way to assess the accuracy of the resulting data. Therefore, comparing measurements from the two FTIR systems is useful.
Assimilation of constituent observations in the stratosphere
Authors: Ménard Richard , Lyster Peter M. , Chang Lang-Ping , Cohn Stephen E.
Published: February 2023

In recent years considerable research efforts have been made in data assimilation methods, developed originally for numerical weather prediction, directed now towards more general classes of Earth science problems. Towards these kinds of goals, and in particular to assimilate EOS data, the Data Assimilation Office (DAO) of NASA/Goddard Space Flight Center was founded about five years ago. Data assimilation can be thought of as a generalized inversion problem that uses a dynamical model (e.g. a GCM) and measurements to form a global, time-evolving analysis, or state estimate of the Earth system. Many of these algorithms proceed sequentially in time by continuously updating the state of an Earth system model with new measurements. The resulting analyses are supposed to be not only temporally and spatially consistent, but dynamically, radiatively and chemically balanced as well.
Automated Remote Operations of Bruker FTIR Instruments
Authors: Stephen T. M. , Murcray F.J. , Kosters J.J. , Nasiri S.L.
Published: February 2023

The need for consistent long term monitoring of the composition of the atmosphere is recognized as a priority in the scientific community. This is certainly demonstrated by the wide support of the Network for the Detection of Stratospheric Change (NDSC) and the Department of Energy's support of the Atmospheric Radiation Measurement program (ARM). This paper describes automated Fourier transform infrared (FTIR) spectrometers that were developed for these programs and deployed in the field to fulfill mission requirements. These systems are typically in the care of site technicians with little or no training in FTIR spectroscopy. The technicians are primarily responsible for filling detector dewars with liquid nitrogen and performing visual inspections of the instrument on a daily basis.
Shipborne measurements with a new mobile aerosol lidar system
Authors: Schäfer J. , Schrems O. , Beyerle G. , Mildner W. , Theopold F.
Published: February 2023

In this paper a new mobile aerosol Raman lidar system with a modular design will be introduced and measurements performed aboard the research vessel Polarstern during the ALBATROSS campaign in October/November 1996 will be presented (ALBATROSS = Atmospheric chemistry and lidar studies above the Atlantic Ocean related to ozone and other trace gases in the tropo- and stratosphere). Results obtained for the distribution of stratospheric aerosols during the ship cruise from 35°N to 45°S and water vapor measurements will be shown and discussed in detail.
New Side-Chain Polymers for Second-Order Nonlinear Optics
Authors: Robello Douglas R. , Schildkraut Jay S. , Willand Craig S.
Published: February 2023

Because of advances in optical communications and information storage, researchers have sought materials for devices operating at the boundaries between the electronic and optical realms. Second-order nonlinear optical (NLO) materials, particularly organic polymers, have received attention because of their facility for constructing waveguiding thin films that are capable of frequency doubling or electrooptic modulation in integrated optical circuitry.
Thermally Stable Poled Polymers: Highly Efficient Heteroaromatic Chromophores in High Temperature Polymers
Authors: Jen Alex K-Y. , Wong K. Y. , Drost K. , Rao V. Pushkara , Caldwell B. , Mininni R. M.
Published: February 2023

There has been considerable interest in developing processible, thermally stable second order nonlinear optical thin films using the poled polymer method. Thermoplastic guest-host polymers or copolymers have demonstrated the feasibility of getting higher electro-optic coefficients than that of lithium niobate. However, these polymers generally have low glass transition temperatures so that the poled polymers suffer from the thermal re-orientation of chromophores within the polymer host. This strongly limited the use of these polymers for practical applications. Polyimides have been reported in recent years as the promising host for the nonlinear optical chromophores due to their high glass transition temperatures and compatibility with semiconductor processing technologies. However, to use polyimides as the host, the guest chromophores must be able to sustain the stringent chemical environment during the high temperature processing of polyimides. The conventionally used nonlinear optical chromophores generally decomposed during the process. Furthermore, since the loading density of chromophores in a guest-host form is lower than that of a side-chain copolymer system, the resultant bulk nonlinear optical properties are generally smaller. Thus, for guest-host polyimides, chromophores with higher βμ values are reguired to maintain or exceed the demonstrated bulk nonlinear optical properties in copolymer systems.
Second Harmonic Generation from Langmuir-Blodgett Films: Interleaved and Z-type Multilayers
Authors: Ashwell G.J. , Jackson P.D. , Lochun D. , Bahra G.S. , Brown C.R.
Published: February 2023

Langmuir-Blodgett (LB) film-forming materials which comprise a hydrophilic head and a hydrophobic tail tend to form centrosymmetric Y-type structures in which the layers pack head-to-head and tail-to-tail, whereas materials with hydrophobic tails at opposite ends of the chromophore form non-centrosymmetric Z-type films in which interlayer packing is head-to-tail. Here, we report the second harmonic generation (SHG) from both the interleaved and the homomolecular LB films.
Excited State Dynamics of the Third Order Nonlinear Optical Susceptibility in Conjugated Linear Chains
Authors: Chen W.D. , Rodenberger D.C. , Shi R.F. , Zhou Q.L. , Garito A.F.
Published: February 2023

We have earlier presented theoretical and experimental results demonstrating that the nonresonant third order optical susceptibility χ(3)(−ω;ω,ω,−ω) can be enhanced for nonlinear optical processes originating from real population of electronic excited states in conjugated linear chains[1,2]. Compared with the ground state, χ(3)(−ω;ω,ω,−ω) of π-conjugated linear chains can be enhanced by orders of magnitude when the first S1 or second S2 π-electron excited state is optically pumped and then populated for times long enough to perform nonresonant measurements of χ(3)(−ω;ω,ω,−ω) at frequencies different from the resonant pump frequency. In this paper, a dynamical model is developed for the time evolution of the nonresonant microscoopic degenerate four wave mixing (DFWM) susceptibility γ(-ω;ω,ω,-ω) for the excited state enhancement mechanism. The model is applied to the case of the six site chain, diphenylhexatriene (DPH).
The Sign and Magnitudes of the Off-Resonant Nonlinearities of Polydiacetylene Crystal Measured By Z-Scan
Authors: Thakur M. , Quintero-Torres R.
Published: February 2023

We have used the z-scan technique to determine the sign and magnitude of the off-resonant n2 and two photon absorption coefficient of PTS-polydiacetylene. The sign of n2 is negative and the magnitudes of nonlinearities are consistent with our previous reports on waveguide measurements.
Advances in Photorefractive Polymers: High Efficiency, Improved Speed, and Net Two-Beam Coupling Gain
Authors: Moerner W. E. , Bjorklund G. C. , Burland D. M. , Miller R. D. , Jenkner P. K. , Scott J. C. , Silence S. M. , Twieg R. J. , Walsh C. A.
Published: February 2023

Polymers exhibiting the photorefractive (PR) effect have attracted attention lately because this new class of photorefractive materials1 has the potential for improvements in photorefractive figures of merit due to the low dielectric constant of these materials. PR polymers also possess other advantages over inorganic materials, such as compositional flexibility and ease of sample preparation and processability. As usual, in addition to photoconductivity, optical nonlinearity, and four-wavc-mixing (FWM) measurements of holographic diffraction efficiency, we routinely perform two-beam coupling (TBC) measurements to observe the non-zero phase-shift characteristic of the photorefractive effect in order to obtain unequivocal proof of photorefractivity as the source for the observed gratings.
High Two-beam Coupling Gain in a Photorefractive Polymer
Authors: Ducharme Stephen , Goonesekera Arosha , Jones Brian , Takacs James M. , Zhang Lei
Published: February 2023

In the last three years, a number of researchers have succeeded in making polymers which exhibit the photorefractive effect.1-4 These polymers have numerous potential applications in integrated optics, optical processing, optical data storage, optical computing, communications, image processing, optical switching, thresholding, laser resonators, simulation of neural networks, and studies of nonlinear dynamics. Elements of these applications have been implemented in the laboratory using high-performance photorefractive crystals. However, the cost of crystal growth and preparation has been a primary impediment to commercial application of crystal photorefractive devices. Photorefractive polymers, on the other hand, have very low production cost and will be particularly suitable for formation of waveguide devices for use in, e.g., integrated optics. The photorefractive performance of the polymers must be greatly improved, to meet or exceed the performance of available crystals.
Optically Induced Birefringence in Copolymers and Blends Containing Azobenzene Groups
Authors: Brown D. , Natansohn A. , Rochon P. , Xie S.
Published: February 2023

Azoaromatic (azo) polymers have been shown to exhibit stable, reversible optically induced birefringence and dichroism.1
Nitrophenylhydrazone Based Phenoxy Thermoplastic Electro-Optic Polymers
Authors: Gulotty R. J. , Brennan D. J. , Chartier M. A. , Gillie J. K. , Haag A. P. , Hazard K. A. , Inbasekaran M. N. , Ashley P. R. , Tumolillo T. A.
Published: February 2023

The first demonstration of a registered multilevel Mach-Zehnder intensity modulator array has recently been reported by Tumolillo et al. [1]. The nonlinear optical (NLO) polymer in these structures is a 4-nitrophenylhydrazone (NPH) based phenoxy thermoplastic developed at The Dow Chemical Co.[2] The properties of this and related NPH phenoxy NLO polymers and monomers are described below. In addition, a study of NLO activity versus chromophore loading is presented.
Optical Storage in Polymers Containing Azo Groups without Electron-Donor - Electron Acceptor Substituents: Poly[4-(2-methacryloyloxy)ethyl-azobenzene]
Authors: Natansohn A. , Rochon P. , Mao J. , Xie S.
Published: February 2023

Some degree of supramolecular organization can be induced in amorphous polymers containing azobenzene groups by means of polarized light. This phenomenon has been known for about a decade and the relevant literature has been reviewed in one of our recent publications1. This induced preferred orientation of the azobenzene groups can be monitored by a significant change in the refractive index of the polymer film and can thus be usea as an information storage mechanism. Circularly polarized light restores the natural disorder of the azobenzene orientations, enabling erasure of the stored information1-5. This phenomenon was first noticed on polymers doped with substituted azobenzenes and was intensively studied on liquid crystalline polymers containing substituted azobenzenes as the mesogenic group. Probably by chance - due to the availability of various azo dyes and to the ease of synthesis - almost all examples previously studied in the literature had electron-donor and electron-acceptor substituents on the azobenzene groups. Their presence conferred another important dimension to this type of supramolecular organization: starting with a polarizable group one could induce second order nonlinear susceptibility in the material, thus opening the possibility of applications in photonics.
Thermal Cis-Trans Isomerization Rates Of Azobenzenes Bound In Acrylate Polymers
Authors: Barrett C. , Natansohn A. , Rochon P. , Xie S.
Published: February 2023

Amorphous high glass transition polymer films containing electron-donor electron-acceptor substituted azobenzene groups can be used as materials for reversible optical storage1. A polarized argon laser beam is used for "writing" while a low power HeNe laser can "read" the resulting oriented regions, and irradiation with circularly polarized light destroys the order, effectively "erasing" the signal. As orientation is induced by a series of trans-cis-trans isomerizations of the azo groups, writing speeds and efficiencies depend on the rates of these isomerizations. Films of a series of azo polymers used for reversible optical storage were prepared and irradiated in order to study the thermal cis-trans isomerization rates.
Photoinduced Diffraction in Disperse Red 1-Polymethylmethacrylate Waveguides
Authors: Andrews James H. , Singer Kenneth D.
Published: February 2023

We report on measurements of photoinduced diffraction in prism coupled slab polymer waveguides.1 Optical damage in the form of diffractive mode conversion was observed when light whose wavelength was slightly longer than the absorption edge of disperse red 1 was coupled into photochromic gratings in slab waveguides of disperse red 1 in polymethylmethacrylate. Slowly growing satellite beams in the outcoupled light were attributed to anisotropic scattering between the lowest order TE mode and the lowest order TM mode caused by self-diffraction from a grating produced through the photochromic effect. We have also investigated the effect of mode coupling changes on the determination of diffraction efficiency and sensitivity in waveguide experiments. Diffraction efficiencies predicted by measurements of the modulation depth in the guide are found to overstate the actual diffraction efficiencies which could be observed in this geometry.
Photochromic Methyl Violet Polymer Film for HeNe Recording
Authors: Blair Steven M. , Siahmakoun Azad
Published: February 2023

In this paper we present a holographic film made from methyl violet and polyvinyl alcohol (PVA). The significance of this material is that the thermally stable state is colored,1,2 allowing HeNe lasers to be used for grating formation in the bleaching mode. Only a very few photochromic materials have exhibited response to HeNe, and methyl violet exhibits diffraction efficiencies ≈ 2%.
Observation of χ(2) gratings in polydiacetylenus: bulk monocrystalline PTS and Langmuir-Blodgett films of 11/8-acid
Authors: Chudinov A.N. , Barabash A. M. , Kotegov A.M. , Postnikov A.A. , Zel’dovich B.Ya.
Published: February 2023

Optical field 1/2 (Eω(r)exp(-iωt) + E2ω(r)exp(-i2ωt) + k.c.) posesses polar asymmetry in a point r. In particular, the average value of the cube of this field is nonzero. There are numerous effects of interaction of such a field with matter, eg. writting of a holographic gratings of the 2-nd order polarizability χ(2) in fibers and bulk glasses, phase-sensitive interference effects in multiphoton ionization [1], dynamic χ(2) grating in a solution of 4-BCMU polydiacetylene (PDA) [2]
Maleimide based Crosslinked Matrices: high EO Activity and Stability of Orientation.
Authors: Tapolsky G. , Chan Y. , Dickens M. , Lecomte J.-P. , Meyreuix R.
Published: February 2023

Crosslinked matrices have been proposed to meet the thermal requirements of integrated optic devices. In this presentation, we wish to discuss the properties of different maleimide based networks.
Carbazole Main-Chain Polymers with Di-Acceptor-Substituents for Nonlinear Optics
Authors: Zhang Yadong , Wang Liming , Wada Tatsuo , Sasabe Hiroyuki
Published: February 2023

Polymeric second-order nonlinear optical (NLO) materials have been studied extensively in recent years for applications in electrooptic devices [1,2]. There are three types of polymer materials developed for this purpose: guest-host systems [3], side-chain polymers [4-6], and main-chain polymers [7-9]. The second-order NLO effects of these materials were demonstrated after electric poling above the polymer glass transition temperature (Tg). While many guest-host and side-chain NLO polymers have been developed, relatively few main-chain polymers have been prepared. Most of the main-chain polymers reported are heat-to tail; namely, all the Chromophore dipole moments point in the same direction along the polymer main chain.
Creation of Strong Second Order Nonlinearity in Polymers by Asymmetric Injection of Electrical Charges
Authors: Berkovic Garry , Cohen Rami
Published: February 2023

It is well known that strong second order nonlinearity can be induced in polymer/dye systems (blends or copolymers) by the poling technique. Application of a strong electrostatic field at elevated temperature causes partial orientational alignment of the dipolar dye molecules, leading to asymmetry nonlinearity along the direction of the applied field.
High speed polymer optical fiber and amplifier
Authors: Koike Yasuhiro
Published: February 2023

Growing needs for processing and transmission of information have led to the increasing use of optical fibers for high speed communication. Although most long-haul communication has utilized single-mode glass fibers, inorganic glasses are not a universally ideal material especially for fiber connection and handling problem. The large core polymer optical fibers (POFs) will solve such problems because of great flexibility.
Polyimide Optical Waveguides Fabricated by Direct Electron Beam Writing
Authors: Maruno T. , Sakata T. , Ishii T. , Maruo Y. Y. , Sasaki S. , Tamamura T.
Published: February 2023

Polymer optical waveguides are attractive for fabricating economical and practical optoelectronic devices and interconnections in optical communication systems [1,2]. Channel waveguides, therefore, have been produced using several polymers such as poly(methyl methacrylate), polystylene, poly(organosiloxane), and polyimide [3-6]. One of the first priorities for polymer waveguides is high thermal stability so that soldering can be used in conventional device fabrication. Fluorinated polyimides are promising candidates for waveguide materials because they show high thermal stability and low optical loss near the IR wavelength region. We have previously developed novel fluorinated polyimides [7] and manufactured a single-mode optical waveguide for them by using conventional reactive ion etching (RIE) [8]. Moreover, we recently clarified that the refractive index of fluorinated polyimides can be controlled by electron beam irradiation [9], and that optical waveguides can thus be fabricated by direct electron beam writing (DEBW) [10,11]. This method is very useful because the fabrication process becomes simpler than when using RIE. In this paper, we propose a new optical waveguide fabricated by DEBW, which consists of a single material and a simple two-layer structure.
Development Of Plastic Optical Fiber Devices and Multiple-Core Plastic Optical Fibers
Authors: Nagarur Aruna R. , Gopalan S. , Dirk Carl W.
Published: February 2023

A vast amount of research has been done on optical fibers. Most of the work has been done on Glass optical fibers (GOFs). Much less has been done on Plastic optical fibers (POFs), and very little with regards to applications of nonlinear optics.1 Plastic optical fibers are currently under intense investigation and are used for Local Area Networks (LAN), vehicular systems2 and optical sensor applications. Though they have much greater losses than Glass optical fibers they display advantages with regard to easy fabrication, flexibility, porosity and permeability (sensors), optical modification by organic dyes and cost.
Electro-refraction and electro-absorption in poled-polymer films
Authors: O’Brien Ned , Dominic Vince , Caracci Steve
Published: February 2023

Poled-polymer investigations largely concentrate on the electro-optic effect since most proposed devices are phase controlled. Relatively few papers discuss the concurrent electro-absorption effect.1-5 The well-known resonant enhancement of electro-refraction near the chromophore absorption band also leads to increased electro-absorption. One might significantly over- or under-estimate the electro-optic coefficient if electro-absorption is ignored.
Structure and Properties of Fluoro-Aluminum Tetraphenyl-porphyrin (FA1TPP) Thin Films
Authors: Yakura Yuji , Shia Rebecca , Sasaki Tomikazu , Ohuchi Fumio
Published: February 2023

In an attempt to design molecular arrays with adjustable periodicity in two dimension, fluoroaluminum tetraphenylporphyrin (FA1TPP) molecules were synthesized and fabricated into thin film forms. This paper describes our preliminary results on structure and properties of FA1TPP thin films.
Optical Nonlinearity Of Co-Polymers Caused By Charge Injection
Authors: Lavi Barak , Berkovic Garry
Published: February 2023

We have shown [1] that asymmetric injection of electric charge into polymer-dye blends can induce second order nonlinear optical effects which are distinct from the more conventional mechanism of using electric fields to align the dye molecules. Using an “in-plane” geometry [1], charges can be injected into polymer-dye films causing symmetry breakage both parallel and perpendicular to the external field. The symmetry breakage perpendicular to the field results from the setting-up of a macroscopic charge gradient, while nonlinearity parallel to the field results from conventional dipolar alignment. Using high voltages but only moderate fields (2000 V across 2mm) charge injection effects can be stronger than dipolar alignment. It is believed that charged dimers and quadrupolar nonlinearities are responsible for the nonlinearity in a charge gradient [2].
Design and Characterization of Phthalocyanine Thin Film Materials
Authors: Flom Steven R. , Shirk James S. , Pong Richard G.S. , Bartoli F.J. , Snow Arthur W. , Chang Young H. , Ford Warren T.
Published: February 2023

The phthalocyanines are a class of organic NLO materials that are of considerable interest both for their nonlinear optical1 and their electrical properties.2 The high nonlinearities, chemical stability, and the variety of molecular architectures that are possible make them promising materials for nonlinear optical applications. One application of these materials, optical limiters, already shows considerable promise.
Photobleaching in Side Chain NLO Polymers
Authors: Eich Manfred , Beisinghoff Hanno , Feix Hubertus , Görtz W. , Vydra Jan
Published: February 2023

We carried out photobleaching experiments on thin films of azo chromophore functionalized side chain polymers at different wavelengths in the UV and visible sprectral regions. Photobleaching alters the polymer layer due to two different mechanisms: In the first place, bleaching results in lowering of the index of refraction by destruction of the highly polari­zable NLO chromophore electronic π system and thus shifting the absorption band. Secondly, as a result of outgassing of molecular fragments and ablation, the polymer layer thickness is significantly reduced. Both effects strongly depend on the wavelength spectrum of the bleaching source and in addition exhibit remarkably different time responses. Limiting the wavelength spectrum the proper way we were able to either concentrate on chromophor modification alone or on both chromophor modification and thickness modification. This allows us to tailor the resulting geometrical profile of channel waveguides as well as the index difference to the surrounding cladding. Figure 1 (left) shows an AFM-micrograph of the geometrical dimensions of the top surface of a channel waveguide photobleached in a NLO-sidechain polymer as described. A very smooth profile (Figure 1 right side) is realized with a rms-value of the surface roughness of only 0.3 nm. In addition to the modification of the surface topography, the refractive index in the bleached region of the polymer is shifted by up to 10-2.