bluuebunny/crossref_metadata_2025 huggingface dataset:
Remote Sensing of Cirrus Cloud Optical and Microphysical Properties Using AVHRR Data
Authors: Liou K.N. , Ou S.C. , Rao N. , Takano Y.
Published: February 2023

The importance of understanding the radiative and microphysical properties of cirrus clouds in weather and climate research has been articulated by Liou (1986). This importance has also been recognized in view of the intensive field observations that have been conducted as a major component of the First ISCCP Regional Experiment (FIRE) in October-November 1986 (Starr 1987) and more recently in November-December 1991 (FIRE-II) as well as the European experiments on cirrus (ICE/EUCREX) that has been carried out in 1989. One of the fundamental objectives of the FIRE program has been and is to apply the field campaign and theoretical results to develop and verify improved techniques for the inference of cloud radiative and microphysical properties from satellite and surface-based data.
Analysis of the MOPITT CO Profile Retrieval Algorithm
Authors: Pan Liwen , Gille John C. , Edwards David P. , Bailey Paul L. , Rokke Laurie A. , Wang Jinxue , Rodgers Clive D.
Published: February 2023

Scheduled for Launch in 1998 on board the EOS/AM satellite, the MOPITT (Measurements of Pollution In The Troposphere) instrument will measure global tropospheric CO and CH4 distributions. The instrument and its scientific objectives have been described by Drummond [1992] and forward model studies have been discussed by Pan et al. [1995]. This paper presents some results of linear error analysis for retrieving CO profiles and the comparisons with the results of retrieval simulations.
Raman-DIAL Measurements in the Upper Troposphere and Stratosphere: The Effect of High-Altitude Ice Clouds on Ozone
Authors: Reichardt J. , Weitkamp C.
Published: February 2023

For many years lidar systems have proved to be valuable tools for the measurement of atmospheric data with high spatial and temporal resolution. The lidar variant used so far for ozone height profiling has been known as the differential absorption and scattering, or DIAL, technique.1 In DIAL two light pulses of different wavelengths are transmitted into the atmosphere, the elastically backscattered return signals are registered, and the ozone concentration is calculated from the difference of optical absorption by ozone at the two wavelengths. However, due to elastic particle scattering DIAL measurements are hardly possible in altitudes with enhanced particle content. The influence of particle scattering on the retrieval of ozone concentrations from measured lidar profiles can be reduced substantially if inelastic molecular return signals of a gas such as nitrogen are used instead of the elastic lidar returns. This so-called Raman-DIAL technique2 has been implemented in the GKSS Raman lidar in spring 1994.3 A XeCl excimer laser and a frequency-tripled Nd:YAG laser serve as light sources, and the return signals at the nitrogen Raman wavelengths are used for the calculation of ozone concentration profiles. In addition, tropospheric water vapor and backscatter and extinction properties of atmospheric particles are obtained with the Raman-lidar technique. Elastic depolarization ratios are measured as well. Whereas the conventional DIAL and the Raman lidar techniques have undergone an extensive error analysis,4,5 an error treatment of the Raman-DIAL technique has not been published so far. In the present contribution an outline of a Raman-DIAL error analysis is given. As space is limited, only ozone measurements in the free troposphere in the presence of cirrus clouds are considered.
Polarized radiance distribution measurements of skylight for passive remote sensing of aerosol optical properties
Authors: Voss Kenneth , Liu Yi
Published: February 2023

The intensity and polarization of skylight, measured at the surface, can be used as a passive remote sensing tool to provide information on the optical properties of aerosols in the atmosphere. Wang and Gordon1 have discussed techniques to use measurements of the intensity of skylight to obtain much of the aerosol phase function. Zhang and Gordon (this meeting) show that elements of the aerosol polarized scattering matrix (Mueller matrix) can be obtained if the Stokes vector of the downwelling skylight is known.2
Meteorological Dependence on Ground - Based Interferometer Temperature and Water Vapor Retrieval Accuracy
Authors: Feltz W. , Smith W. , Knuteson R. , Howell B. , Revercomb H.
Published: February 2023

The Atmospheric Emitted Radiance Interferometer (AERI) is used to produce temperature and water vapor profiles every ten minutes in the Planetary Boundary Layer (PBL), the lowest 3 km of the earth's atmosphere. AERI measures infrared (IR) radiation (3 to 18 um) passively, yielding high resolution radiance spectra (Figure 1). The spectra contains valuable meteorological information. These radiance spectra are transformed to vertical temperature and water vapor profiles by inverting the IR Radiative Transfer (RTE). Good temperature and water vapor retrieval skill for the PBL have been shown in several field experiments using AERI.
Holographic Detection System for use with Fabry-Perot Interferometers and Particular Applications for Lidar Work
Authors: McGill Matthew J. , Marzouk Marzouk , Scott V. Stan , Spinhirne James D.
Published: February 2023

Many applications employ Fabry-Perot interferometers as spectral-resolving elements. In the past, the spectral distribution had to be measured using multi-channel circular detectors1. In the absence of circular detectors the output light must to be transformed into a linear pattern, which usually means the Fabry-Perot is not being optimally utilized or that a large fraction of the light is lost.
OPTICAL INTERCONNECTS: Single Mode Etched Active Channel Polyimide Waveguides
Authors: Fujimoto Harry H. , Valley John F. , Stiller Marc , Dries Larry , Binkley Ed S. , Nurse Jim C. , Kenney John T.
Published: February 2023

Broad band services such as high speed, wide band data transmission or video communication are expected to used widely in future computing applications. As data transmission capacity increases, throughput requirements of the module will need to increase. Many parallel lines transmitting many gigabytes of data or lines that are multiplexed and transmitting at very high data rates will be required in the future.
Low Loss, Buried Channel Waveguides Fabricated From New, Fluorinated Polyimide Copolymers
Authors: Binkley E. S. , Nara S.
Published: February 2023

The introduction of optical interconnects for electronic packaging promises to make a major contribution to high speed systems from the standpoint of increased bandwidth, lower capacitance, and lower power requirements. Low optical loss polymer systems show considerable promise for the fabrication of low cost waveguide structures. In order to be implemented in commercial products, the waveguide system must be capable of withstanding the assembly operations that are used in current production processes, where temperatures up to 350 °C may be experienced fro short periods of time. Polyimide resins are an accepted class of polymers in the microelectronics industry due to their high thermal stability (>400 °C) and outstanding dielectric and mechanical properties. Recently, a new type of fluorinated polyimide[1,2] copolymers has been introduced by Hitachi Chemical that feature low optical attenuation, a broad range of refractive index control, and high temperature stability. These resins are designated OPI and have been used to fabricate low loss single mode channel waveguides that have been characterized optically at 830 and 1300 nm. We wish to report on these results.
Passive polymer waveguide technology for low cost device fabrication
Authors: Cush R. , Goodwin M.J. , Stewart W. J. , Allen S. , Bone D.J. , Bone E.L. , Carter N. , Cinderey M.B. , Harvey T.G. , Laidler D.E. , Quinn S. , Ryan T.G. , Shearman J.E. , Summersgill P. , Thorne A.J.
Published: February 2023

As the use of fibre optic networks increases in telecoms, datacoms, avionic and automotive areas, there will be increased demand for passive optical components, such as splitters, combiners, multiplexers and demultiplexers. However, for widespread application, fibre networks must be economically attractive in comparison with alternative solutions and so these passive components must be available at low cost. Polymer device fabrication techniques offer the potential to achieve these low cost targets and so are receiving increasing interest.
Pyroelectrical Thermal Analysis, Pyroelectrical Microscopy, and Pyroelectrical Depth Profiling of Poled Polymer Films
Authors: Bauer S. , Ren W. , Yilmaz S. , Wirges W. , Gerhard-Multhaupt R.
Published: February 2023

Second-order nonlinear optical polymers must be poled in order to achieve the required non-centrosymmetry. Periodically poled materials are required for phase-matched operation of polarization converters1 and parametric devices2. For second-harmonic generation with modes of different order1, three-dimensionally (3-D) poled patterns are needed to optimize the overlap integral, as suggested by Akhmediev and Novak3. As the poled polymer is in a metastable state, the partially aligned dipoles relax, thus limiting the lifetime of the poled polymer. Easy-to-use experimental methods, which allow for the investigation of dipole relaxation as well as periodical and 3-D dipole patterns, are highly desirable. It will be shown that the recently developed techniques of Pyroelectrical Thermal Analysis (PTA), Scanning Pyroelectrical Microscopy (SPM), and Pyroelectrical Depth Profiling (PDP), respectively, are almost ideal solutions for these tasks.
Applications of Electro-Optic Polymer Integrated Optic Devices
Authors: Lipscomb G. F. , Lytel R. , Ticknor A.J.
Published: February 2023

A decade of research in organic and polymeric nonlinear optical (NLO) materials and devices has now begun to reach fruition. In this paper we will concentrate on the progress that has been made in the application of organic materials, both passive and active, to integrated optic waveguide devices. Similar organic polymers can be used to fabricate passive waveguide devices, such as splitters or filters, and active devices based on the thermo-optic (TO) or the electro-optic (EO) effects. Proof-of-principle experiments have demonstrated that polymer materials offer potential advantages for integrated optics applications in the areas of process, fabrication, and performance. Work has now begun to utilize these advantages in specific applications in a wide variety of industries, including telecom, datacom and CATV. We will first give an introduction to polymeric waveguides, followed by an overview of the current performance achievable with Akzo electro-optic polymers, and then briefly describe how components derived from these materials can be used in specific applications.
Dependence of the Performance of Vacuum Deposited Organic Light Emitting Diodes on Layer Thickness and Composition
Authors: Burrows P.E. , Forrest S.R. , So F.F.
Published: February 2023

Efficient green electroluminescence from an organic double-layer device between two electrodes was first reported by Tang and Van Slyke [1,2]. Subsequently, there has been considerable interest in using various fluorescent organic molecules in similar structures to produce electroluminescence in different spectral regions. Also, more complex, triple layer "double heterostructure" devices have been reported[3]. However, although devices emitting throughout the visible spectrum have been successfully fabricated [1,4,5], there is a lack of quantitative information relating the organic layer thickness and heterojunction properties to device performance.
Optimization of the First and Second Hyperpolarizabilities of Organic Dyes
Authors: Bourhill Grant , Brédas Jean-Luc , Cheng Lap-Tak , Friedli Andrienne C. , Gorman Christopher B. , Marder Seth R. , Meyers Fabienne , Perry Joseph W. , Pierce Brian M. , Skindhøj Jørgen , Tiemann Bruce G.
Published: February 2023

We have been attempting to correlate hyperpolarizabilities with bond-length alternation (BLA), which is defined as the difference in the average length between adjacent carbon-carbon bonds in a polymethine ((CH)n) chain.(1, 2) Polyenes have alternating double and single bonds (bond length equal to 1.34 Å and 1.45 Å, respectively), and thus show a high degree of bond-length alternation (BLA=-0.11Á). In donor-acceptor polyenes, this parameter is related to the degree of ground-state polarization in the molecule. To better understand this correlation, it is illustrative to discuss the wave function of the ground state in terms of a linear combination of the two limiting charge-transfer resonance structures. For substituted polyenes with weak donors and acceptors, the neutral resonance form dominates the ground-state wavefunction, and the molecule has a high degree of (conventionally negative) bond-length alternation. With stronger donors and acceptors, the contribution to the ground state, of the charge-separated resonance form increases and simultaneously, BLA decreases in absolute value. When the two resonance structures contribute equally, as in a symmetrical cyanine, the molecule exhibits essentially no bond-length alternation. Finally, if the charge-separated form dominates the ground-state wave function, the molecule acquires a positive bond-length alternation. Neutral molecules with aromatic rings have a diminished contribution of the charge-separated form to the ground-state wave function, due to the energetic price associated with the loss of aromaticity in that form.(3) As a result, push-pull molecules with aromatic ground states tend to be more bond-length alternated for a given donor and acceptor pair than for a polyene of comparable length.
Design and Fabrication of Electro-Optic Polymer Waveguides
Authors: Liang J. , Levenson R. , Zyss J.
Published: February 2023

Poled functionalized electro-optic polymers provide an interesting alternative to bulk materials such as lithium niobate for a range of application encompassing electro-optic modulators, switches, or directional couplers. Their ability to be spin-coated on semiconductor substrates and their compatibility with such processing techniques as photolithography or reactive ion etching, now classically used in III-V semiconductor-based optoelectronics, provide a great potential towards their integration in optronic circuits.
Measurement of the Nonlinear Refractive Index and Two Photon Absorption Coefficient of Pts at 1064 NM
Authors: Lawrence Brian , Torruellas William , Stegeman George , Etemad Shahab , Baker Gregory
Published: February 2023

PTS has been reported to have a very large non-resonant nonlinearity by a number of groups, making it a prime candidate for applications in nonlinear optics.[1-6] At 1064 nm there have been a number of measurements published for both the nonlinear refractive index coefficient n2 and the two photon absorption coefficient β2.[2-6] Although the published two photon coefficients agree with each other to within a factor of two, the values for n2 vary over more than one order of magnitude. As a result the two photon figure of merit, T, which is used to assess the effectiveness of a material for nonlinear optics varies from 0.3 to 22. This parameter needs to be less than unity and hence it is not clear whether this material will be useful or not. In this paper we report on detailed z-scan measurements of the nonlinearity in single crystal PTS at 1064 nm.
Polymorphs of oxotitanium phthalocyanine exhibiting large third-order nonlinear optical susceptibility
Authors: Nalwa Hari Singh , Saito Toshiro , Kakuta Atsushi , Iwayanagi Takao
Published: February 2023

Metallophthalocyanines have been considered valuable materials for the development of nonlinear optical devices because of their versatility, architectural flexibility, exceptionally high environmental stability, and ease of processing and fabrication. Furthermore physical properties of metallophthalocyanines can be tailored over a wide range either by inclusion of a variety of central metal atoms or by substituting peripheral functionalities at the ring. Phthalocyanine ring has a two-dimensional conjugated π-electron system and the magnitude of third-order nonlinear optical susceptibility χ(3) varies by several orders depending on the metal atom substitution.1-7 Recently polymorphs of oxotitanium phthalocyanine (TiOPc) have been utilized in developing photoreceptor devices8-10 and their photoconductivities were found to vary remarkably depending on the crystal structures. With same view, we selected to investigate the third-order nonlinear optical properties of different polymorphs of TiOPc. This report discusses a systematic study of the third-order nonlinear optical properties of amorphous, α, β, and Y polymorphs of oxotitanium phthalocyanine.
A Simple Quasi-free Electron Model for the Description of Linear and Nonlinear Optical Properties of Conjugated Oligomers : A Focus on Length Dependence, Monomer Anharmonicity and Delocalisation.
Authors: Verbandt Y. , Thienpont H. , Veretennicoff I. , Rikken G. L. J. A.
Published: February 2023

Conjugated molecules are very promising organic materials for nonlinear optics applications. It has been established that the linear and nonlinear properties of this class of molecules scale in a nonlinear way with respect to the π-electron delocalisation length along the conjugated backbone. Some systematic experimental investigations on the length dependence of the molecular optical response of thiophene and phenyl oligomers have been published [1,2]. Thienpont et al. [1] found a saturation of the polarizability α and the second hyperpolarizability γ at about 7 repeat units. We use the term saturation point to denote the transition point where the scaling of the optical properties with the molecular length becomes linear.
Fabrication of Computer Generated Holograms on Metal Ion Doped Polymer Systems by Contact Copying
Authors: Lemelin Guylain , Manivannan Gurusamy , Lessard Roger A.
Published: February 2023

Computer Generated Holograms (CGHs) are attractive devices because of their capabilities to reconstruct a wavefront defined by mathematical relations. They are promising display, interconnects, multiplexing, fan-in and fan-out but the cost of producing one efficient element is again prohibitive. We are developing simple techniques of fabrication of CGHs on real-time recording materials. Cr(VI) and Fe(III) doped poly(vinyl alcohol) and poly(acrylic acid) systems have been used as real-time recording media for volume transmission and reflection holograms in our laboratory. For some years, we have worked on improving the performance of these materials by studying the reaction scheme of photo-crosslinking that is evolved in the formation of the grating and by systematically evaluating the holographic characteristics of each material under different experimental conditions such as different dyes, pH and concentrations[1,2,3]. These studies can show the way to change the chemical components of the layer to speed up the reaction in solid matrix.
Hybrid Waves Guided by Ultrathin Organic Films Bounded by Birefringent Media
Authors: Santos C. , Torner L. , Torres J.P.
Published: February 2023

The existence conditions and waveguiding properties of new hybrid, TE and TM dominant waves guided by ultrathin organic films cladded by birefringent crystals are reported.
Polarization Insensitive Crystalline Organic Waveguides
Authors: Taylor R.B. , Shen Z. , Forrest S.R.
Published: February 2023

Interest in crystalline organic semiconductors has increased recently due to their diverse optical and electronic properties which have numerous device applications. Considerable effort has been focused on utilizing the large optical nonlinearities found in many of these materials.1 One crystalline organic semiconductor: 3,4,9,10 perylenetetracarboxylic dianhydride (PTCDA), has been of particular interest due to its excellent electronic properties, giant dielectric anisotropies2 and potential uses in optoelectronic devices. Recent research with PTCDA has yielded considerable success with waveguide structures.3,4 Special properties of PTCDA such as low optical absorption loss at near-infrared wavelengths, environmental stability, and capability of patterning make waveguide integrated devices and organic - semiconductor hybrid devices very attractive.
Nonlinear Absorption in the Liquid Crystal 5CB
Authors: Kosa T. , Dogariu A. , Palffy-Muhoray P. , Van Stryland E.W.
Published: February 2023

Nematic liquid crystals exhibit large optical nonlinearities in response to laser fields. Since these materials are highly transparent in the visible, they are attractive candidate materials for device applications. A variety of mechanisms are responsible for the observed nonlinearities, operating on different time scales. In earlier studies, the response on the nanosecond timescale was investigated in a geometry where director reorientation is not expected to occur. In the present work, nonlinear absorption on the picosecond timescale is studied in detail.
Photocarrier Generation Efficiency of Pyrromethene-Doped Polymers
Authors: Kang Kwang-Sun , Sisk Wade N. , Farahi Faramarz , Raja M. Yasin Akhtar
Published: February 2023

Solid-state dye lasers based on polymethylmethacrylate (PMMA) polymers and pyrromethene laser dyes are currently being evaluated for lasing yield, damage threshold, and device lifetime.1 The fluorescence pathway in these solid-state dyes competes with the carrier production path. Popovic2 has demonstrated the connection between fluorescence yield and carrier generation for the phthalocyanines, namely higher fluorescence yield correlates with lower carrier yield. An improved understanding of the mechanism of organic photoconductors may enable selective optimization of conditions for lasing (fluorescence) or photocarrier production. Since pyrromethene dyes are known to exhibit strong fluorescence under zero field conditions3, low photocarrier yield and thus a high activation barrier for carrier production is predicted. The objective of this study is to determine the activation energy of photocarrier production in laser excited pyrromethene/PMMA samples by measuring the temperature dependence of the photoresponse. The dependence of charge generation on electron donor dopants, dye concentration, and laser intensity are also investigated; consequently information on charge traps and thermal decomposition rates is obtained.
Surface Functionalized Nanostructured Gold/Polymer Composites
Authors: Gonsalves K. E. , Carlson G. , Chen X. , Kumar J. , Perez R. , Yacaman M. Jose-
Published: February 2023

Nanometric gold particles were synthesized by a liquid/liquid phase-transfer reaction. Composites of these particles were prepared by free-radical polymerization of solutions of the particles in methyl methacrylate monomer. Concentrations of 1.0, 0.7, and 0.3 mg/mlwere prepared, with no noticeable agglomeration of particles during processing. PMMA/gold films showed a linear absorption peak at 530 nm, which is characteristic of nanosized gold. High-resolution electron microscopy measurement showed that the particle diameters varied from 5 to 11 nm. Degenerate four-wave mixing experiments on 10- micron films yielded a maximum value of 1.4 × 10‒11 e.s.u. for the third-order nonlinear optical susceptibility at 532 nm.
Studies of Photopolymerization at Metal Surfaces
Authors: Subrahmanyan Suchitra , Chen Fang , Lackritz Hilary S.
Published: February 2023

Surface second harmonic generation is used to study surface reactions during photopolymerization of vinyl monomers on metal surfaces. Photopolymerization shows promise in making defect-free insulating and abrasion resistant coatings, and in the fabrication of microelectronic devices1. Although researchers have studied the gas phase reaction in some detail, little is known about the surface reactions2. Also, the effects of various physical parameters such as monomer pressure, light intensity, and the nature of metal and the monomer on the physical properties of polymer films are not known.
Physical aging after photo-induced or thermally assisted poling for enhancing the stability of polymeric dipole glasses
Authors: Bauer-Gogonea S. , Bauer S. , Wirges W. , Gerhard-Multhaupt R. , Wintle H. J.
Published: February 2023

The thermal stability of the dipole orientation is a critical issue for poled polymers. Particularly for the newly developed photo-induced-poling (PIP) technique [1], it was shown that the dipole orientation is less stable than for thermally assisted poling (TAP) [2]. Physical methods to improve the thermal stability are thus highly de­sirable. Physical aging under applied field is known to significantly enhance the long-term stability of the dipole orientation [3]. Here, we study the improvement in the thermal stability of the dipole orientation achieved with physical aging under field after photo-induced and thermally assisted poling, using the recently introduced pyroelectric techniques (pyroelectric relaxation spectroscopy (PRS) and pyroelectric thermal analysis (PTA) [4]). In particular it is shown that two routes are possible to improve the thermal stability following PIP. One route is the use of high glass- transition polymers and PIP at a higher temperature, the other is physical aging under field after removing the pump light. The experimental results are discussed within the framework of a modified Narayanaswamy-Moynihan model. All the ex­periments were performed on P(S-MA)-DR1 side-chain polymers from Sandoz [5] (TG of 140°C or 165°C).
Donor-Acceptor Systems Derived from Tetraethynylethene
Authors: Tykwinski Rik R. , Schreiber Martin , Spreiter Rolf , Bosshard Christian , Boudon Corinne , Gisselbrecht Jean-Paul , Diederich François , Günter Peter , Gross Maurice
Published: February 2023

An increasing number of conjugated, organic molecules and polymers are finding application as materials for electronics and photonics due to their inherent synthetic flexibility, potential ease of processing and the possibility of tailoring material characteristics to suit a desired property.1 To more efficiently design organic materials to specific tasks, it is necessary to understand how and to what degree alteration of molecular electronic structure affects materials properties. Investigation of a comprehensive series of synthetically related molecules and the relationship between their electronic and physical properties is perhaps the best approach to the rational design of useful organic materials. Hence, we have synthesized a complete series of conjugated, electronically varied molecules based on a tetraethynylethene (TEE, 1) framework. Study of the optical and electrical properties of these electronically diverse building blocks will aid in tuning specific properties for the ultimate formation of functionalized polytriacetylenes (PTAs, 2).
The Efficiency and Time-Dependence of Luminescence in a High Electron Affinity Conjugated Polymer
Authors: Samuel I.D.W. , Rumbles G. , Collison C.J. , Crystall B. , Moratti S.C. , Holmes A.B. , Friend R.H.
Published: February 2023

Measurements of luminescence in conjugated polymers give insight into their photophysics and the operation of electroluminescent devices. The same excited state, the singlet exciton is believed to be responsible for both photoluminescence and electroluminescence. Excitons decay by a combination of radiative and non-radiative processes, and the relative rate of these processes determines the luminescence efficiency. An important feature of conjugated polymers is the possibility of chemical tailoring to realise desired properties. A recent innovation has been the development of high electron affinity polymers made by cyano substitution of members of the poly (arylene vinylene) family [1]. The increased electron affinity improves the performance of light-emitting-diodes by facilitating electron injection.
Enhanced Photo-oxidative Stability and Nonlinear Optical Response of a Dialkoxy-Substituted Poly-Phenylenevinylene through C60 Addition
Authors: Sarkas H. W. , Flom S. R. , Bartoli F. J. , Kafafi Z. H.
Published: February 2023

The conjugated polymer poly-phenylenevinylene (PPV) and its derivatives have been the subject of numerous nonlinear optical1 and light-emitting diode2 studies. These polymers can photobleach in the presence of oxygen and the photo-oxidation can modify their optical properties.3 For instance, it was recently shown that the nonexponential photoluminescence decay of this polymer is caused by exciton quenching at defects.4 One type of defect has been identified as carbonyl groups formed on the polymer chain as a result of photo-oxidation.3 The present work explores the effect of C60 doping on the photo-oxidative stability and the nonlinear optical (NLO) response of a derivative of PPV called poly-[2-methoxy,5-(2’-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV). Photoinduced electron transfer from the excited state of MEH-PPV to C60 has been reported to occur on a subpicosecond time scale.3 By direct excitation into the tail of the π-π* transition of MEH-PPV, one may be able to access this charge transfer state, stabilize MEH-PPV against photo-oxidation, and enhance the NLO properties of the composite material.
Passive Polymer Directional Couplers: Theory and Experiment
Authors: Bintz Lou , Feng Wei , Ma Jiong , Lin Sihan , Tomic Darja , Mickelson Alan
Published: February 2023

We present a Computer Aided Design model of a polymer directional coupler and show some preliminary comparision of the predicted characteristics with characteristics of directional couplers fabricated in a side-chained PMMA/DR1. This model encompasses many of the physical processes and effects encountered in the manufacture of passive polymer directional couplers, including actual transverse index profile induced by bleaching, longitudinal variations in the effective index of the polymer due random variations in the material, and the coupling between wave guides in the s-bend transition region of the directional coupler.
Preparation of High Quality Thin Films. SHG Properties of Y-Type LB Films Prepared by Using Moving-Wall Type LB Deposition System
Authors: Talukder M. , Fujita S. , Watanabe T. , Lindsay G. , Miyata S.
Published: February 2023

The purpose of the present research program is to prepare high quality thin films using Moving Wall type LB trough, which are expected to exhibit an efficient second harmonic generation.
Optical Alignment of Liquid Crystal Displays and Devices Via Polarized Light
Authors: Gibbons Wayne M. , Shannon Paul J. , Sun Shao-Tang
Published: February 2023

The optical alignment of liquid crystals provides spatial and angular control of the local liquid crystal director.1-3 This is achieved by properly designing photosensitive polymer alignment layers. These photosensitive alignment polymers are illuminated with polarized light which alters the bulk and surface properties of the polymer. The liquid crystal molecules adjacent to the alignment polymer interact with the altered polymer and align accordingly. The long range interaction of the liquid crystal molecules transfers the aligned state at the interface to the bulk of the liquid crystal layer. Since the alignment polymer itself is altered, the liquid crystal remains aligned after the illumination is terminated. With the proper design of the alignment material, the process is reversible allowing for the potential of real-time write/re-write control of the local liquid crystal director.
Experimental and Theoretical Studies of Nonlinear Optical Chromophores
Authors: Ahlheim M. , Brédas J.-L. , Barzoukas M. , Bedworth P. V. , Cai Y. , Dehu C. , Blanchard-Desce M. , Fort A. , Hu Z. , Jen A. K.-Y. , Marder S. R. , Meyers F. , Perry J. W. , Runser C. , Staehelin M. , Zysset B.
Published: February 2023

We have described how the first hyperpolarizability, β, varies as a function of ground-state polarization and bond length alternation, BLA.1 Previously, our predictions of this relationship were derived by examining an prototypical push-pull polyene under the presence of static homogenous electric field.1 In order to develop a more realistic understanding of how real molecules behave in solution, we have now examined both p-nitroaniline and the push-pull polyene 1,1-dicyano-6-dibutylamino-hexatriene at the Hartree Fock ab initio level on the basis of an expanded Self Consistent Reaction-Field approach to simulate solvents with dielectric constants up to 37.5. The calculations were carried out using both spherical and elliptical cavities and taking into account multipole interactions up to 26 poles. Predictions were compared to Hyper-Rayleigh Scattering (HRS) results determined by Persoons et al. As had been shown earlier,2 the second-order NLO response of 1,1-dicyano-6-dibutylamino-hexatriene exhibits a peak as a function of solvent polarity, which was confirmed by the HRS measurements. Interestingly, we found that this peaked behavior of β as a function of solvent dielectric constant was predicted only when an elliptical cavity and the up to l = 6 pole contributions were taken into account, but was not observed when the calculations employed either an elliptical cavity and a dipole (l = 1) approximation, or a spherical cavity with up to l = 6 pole contributions. These results suggest that it is possible to model the geometric and electronic structure of polarizable molecules using a Self Consistent Reaction-Field approach, but it is necessary to build into the calculations mechanisms to account for the subtleties of the molecular charge distributions, not taken into account within a simple dipole approximation.
60 GHz Electro-optic Modulation by Polymer Waveguide Phase Modulators
Authors: Wang Wenshen , Chen Datong , Fetterman Harold R. , Shi Yongqiang , Bechtel James H. , Kalluri Srinath , Steier William H. , Dalton Larry R.
Published: February 2023

Organic nonlinear optical (NLO) materials have the potential to become very important for making photonic devices that are inexpensive to produce, capable of being integrated with other electronics, and suitable for ultrahigh frequency broadband operation [1]. 40 GHz electro-optic (E-O) modulation from a Mach-Zehnder intensity modulator has been demonstrated with thermal plastic polymers [2]. We have reported fabrication of traveling wave E-0 phase modulators using a thermally cross-linked NLO polymer, PURDR 19 [3, 4]. Our devices have exhibited good temporal stability and optical power handling capability, and were tested up to 40 GHz [5]. In this paper, we report our new measurement results up to 60 GHz obtained with an optical heterodyne detection technique. This is the highest modulation frequency reported so far for polymer E-0 modulators.
C60:Electron Donor Nanocomposites and Multilayer Structures for Nonlinear Optics
Authors: Sarkas Harry W. , Kafafi Zakya H.
Published: February 2023

Since the development of preparative scale syntheses of the fullerenes,1 we have examined the nonlinear optical (NLO) properties of C60 in the solid state.2-4 Following the characterization of solid films of pure C60, we have explored means of altering the optical and NLO properties of this molecule via chemical modification including photopolymerization, oxygen doping, and the creation of charge transfer (CT) complexes in both the ground and excited states.5-7 Studies on solutions of C60 with the electron donor, N,N,N′,N′-tetramethyl-1,4-phenylene-diamine (TMPD) revealed the formation of a 1:1 CT complex where C60 acted as the acceptor. NLO studies conducted on solutions of C60/TMPD at 675 nm (near the λmax of the CT absorption) showed a great enhancement in the third-order optical susceptibility,
χ
x
x
x
x
(3), of the complex relative to C60 Direct optical excitation in the CT band accessed higher-lying excited states with larger absorption cross-sections than the ground state, which contributed to the enhanced NLO response observed for the TMPD:C60 complex.5
High Efficiency Photorefractive Polymers
Authors: Kippelen B. , Meerholz K. , Volodin B. L. , Sandalphon  , Peyghambarian N.
Published: February 2023

The processibility and structural flexibility of photorefractive polymers give them an important technological potential and have driven intensive research efforts to improve the performance of this new class of PR materials. Since the first proof of principle of photorefractivity in a polymer [1], numerous PR polymeric materials have been synthesized by using different approaches [2], but significant performance improvement was obtained by using the photoconductive polymer poly(N-vinylcarbazole) (PVK) as the composite host and by doping it with nonlinear optical molecules referred to as chromophores [3,4]. In plasticized PVK-based polymer composites doped with the chromophore 2,5-dimethyl-4-(p-nitrophenylazo)anisole) (DMNPAA) [4], we recently demonstrated [5] that PR polymeric materials can exhibit light-induced refractive index modulation amplitudes as high as Δn = 7 × 10-3 at 1 W/cm2 writing intensity, and applied field of 90 V/µm. As shown in Fig. 1, such a high index modulation leads to complete diffraction and periodic energy transfer between the probe and diffracted beams in four-wave mixing (FWM) experiments and also, to net gain coefficients in excess of 200 cm-1 in two-beam coupling (TBC) experiments [5]. These results demonstrate that PR polymeric materials can reach performance levels that are competing with those of the best inorganic crystals, but with better processing capabilities.
High Efficiency Photorefractive Polymer with Immunity to Crystallization
Authors: Poga C. , Twieg R. J. , Moerner W. E.
Published: February 2023

In the few years since the first report of a photorefractive (PR) organic polymeric material [1], much research has been done [2] to improve the material characteristics in order to meet the requirements necessary for applications such as holographic optical storage. A potentially useful polymeric system would combine a wide variety of properties in the same material, such as high diffraction efficiency, long dark lifetime, fast response, excellent optical clarity, just to name a few.
In situ trimming of polymer optical waveguides by rapid photobleaching for tuning device specifications
Authors: Chen Antao , Marti-Carrera Felix Ignacio , Chuyanov Vadim , Garner Sean , Steier William H. , Mao Shane S. H. , Ra Younsoo , Dalton Larry R. , Shi Yongqiang
Published: February 2023

Electrooptic (EO) polymer is very attractive for ultrahigh speed optical waveguide modulators and switches because of its good speed match between the traveling microwave and optical wave. High-speed EO polymer modulators that operate at frequencies as high as 113 GHz have been demonstrated(1). Besides such advantages as high frequency response, flexible processing capability, low cost, and ease of integration with VLSI circuitry, we will demonstrate an additional advantage of EO polymer - the ability of post-fabrication device trimming.
Application of Surface Relief Gratings Created on Azobenzene Functionalized Polymer Films as Phase Masks
Authors: Li Lian , Jiang Xin Li , Kim Dong-Yu , Kumar Jayant , Tripathy Sukant
Published: February 2023

Holographic recording of surface relief gratings has recently been reported in side chain azo containing polymers by Kumar, Tripathy and coworkers [1-10] and Rochon, Natansohn and coworkers [11-13] It has been demonstrated that large surface modulation (>3000Å) could be inscribed in thin films of these polymers when an Argon ion laser radiation at 488 nm with a modest intensity (a few tens of mW/cm2) is used to record the gratings. This grating formation process strongly depends on the polarization states of the recording beams [4]. The gratings appear to be almost sinusoidal and recording of crossed gratings has been demonstrated[1]. These gratings are very stable when they are kept below the glass transition temperature (Tg) of the polymer. The gratings can be erased by either heating the grating sample above Tg or exposing it to a single laser beam at appropriate wavelength and with appropriate polarization [10]. This process allows a one step fabrication of complicated surface profile without the need of any pre or post processing of the polymer samples. Complex surface profiles, for example, well defined beat structures and blazed gratings have been recorded on these polymer films [8]. Since this surface relief grating formation process provides the one step processing and large surface modulation on the polymer films, such process is expected to have significant potential applications for various optical devices including diffractive optical elements.
Application of UV Cured Epoxy Resin to Polymeric Optical Waveguide Components
Authors: Tomaru Satoru , Enbutsu Koji , Hikita Makoto , Yoshimura Ryoko , Imamura Saburo , Maruno Tohru , Kobayashi Junya
Published: February 2023

Many polymeric optical waveguides have been studied for use in the field of optical interconnection [1-3] because they offer such advantages as routing flexibility, process compatibility with electronic devices, and mass productivity. In particular, their application to multimode optical waveguide devices in the 0.85 µm wavelength region is attractive because polymeric materials generally have low loss. We have already realized polymeric multimode optical devices for optical interconnection[4,5].
Integrated electrooptic polymer devices for optical communications
Authors: Shi Yongqiang , Wang Wenshen , Bechtel James H. , Steier William H. , Dalton Larry , Fetterman Harold R.
Published: February 2023

The rapid development in high speed optical communications has prompted a large demand in electrooptic (EO) modulators and switches which are currently made of LiNbO3 and semiconductor materials. In order to reduce manufacturing cost and driving voltage, and extend the bandwidth of the EO devices, an intense research in EO polymer materials and devices is underway.
Phase stability of guest/host photorefractive polymers studied by light scattering experiments
Authors: Hendrickx E. , Volodin B. L. , Steele D. D. , Maldonado Rivera J. L. , Wang J. F. , Kippelen B. , Peyghambarian N.
Published: February 2023

In recent years, we developed plasticized guest-host photorefractive polymers with a glass transition temperature below room temperature.1 However, in these guest/host polymers a gradual crystallization of the chromophores (50% wt.) limits the shelf lifetime of the samples. The lifetime of DMNPAA(2,5-dimethyl-4-(p-nitrophenylazo) anisole) : PVK(poly-vinylcarbazole) : ECZ(N-ethylcarbazole) : TNF(tri-nitrofluorenone) samples with 50% wt. of DMNPAA was found to vary between a few hours and a few months depending on the starting materials and the processing conditions. Here we present a new guest/host photorefractive composite based on isomeric mixtures of the chromophore NPADVBB (4-(4’-nitrophenylazo)l,3-di[(3”or 4”-vinyl)benzyloxy] benzene). These composites exhibit a performance level that is identical to that of DMNPAA-based samples but have an estimated shelf lifetime of several years at room temperature.
Reduced Hole Mobility in Photorefractive Polymers due to the Chromophore Dipole Moment
Authors: Goonesekera Arosha , Ducharme Stephen
Published: February 2023

The recent demonstrations of low-cost high performance photorefractive polymers has encouraged more detailed studies of charge carrier transport mechanisms in photorefractive polymers as charge transport is a limiting factor in the sensitivity of these materials. The photorefractive effect is a mechanism for non local refractive index grating formation in an electro-optic material due to nonuniform illumination, through photoconduction and linear electro-optic response. The speed of photorefractive effect which remains low at present, is proportional to photoconductivity, hence improved understanding of transport mechanisms is vital. This report describes the negative effect the dipole moment of the non-linear chromophore has on the hole mobility in photorefractive polymers.
Optical Limiting Mechanisms in a Neat Liquid Phthalocyanine Thin Film
Authors: Flom Steven R. , Pong Richard G.S. , Shirk James S. , Bartoli F.J. , Snow Arthur W.
Published: February 2023

This paper describes some of the novel physical, photophysical, and optical properties of a new material, lead tetrakis-(β-ethyl-terminated-polyethyleneoxide)phthalocyanine (PbPc(β-PEO)4). These novel properties were achieved by molecular engineering of the long polyethylene oxide (PEO) side chains. In the material described here, the PEO side chains are O(CH2CH2O)nCH2CH3 and have an average molecular weight of 350 implying that n=7. PbPc(β-PEO)4 is a viscous liquid in the pure form. It readily forms thin films of high optical quality by capillary action. By comparison, the usual unsubstituted phthalocyanine forms polycrystalline thin films that sublime only at temperatures above 400C. The feature of this material most important to our group is that this neat liquid maintains many of the photophysical properties of the phthalocyanine electronic system. Here we emphasize the physical properties that are useful for optical limiting applications.
Nonlinear Optics of Chiral Media
Authors: Verbiest Thierry , Van Elshocht Sven , Beelen Gunter , Boutton Carlo , Kauranen Martti , Persoons André
Published: February 2023

Chiral media interact differently with left- and right-hand circularly-polarized light. In linear optics this gives rise to optical activity effects like circular dichroism, optical rotation and optical rotatory dispersion. Optical activity effects also occur in nonlinear optics. For example, second-harmonic generation from chiral surfaces is different for left- and right-hand circularly-polarized fundamental excitation.[1,2]
Bacteriorhodopsin Opto-Electronic Synapses
Authors: Shelton David P.
Published: February 2023

In recent years there has been a resurgence of interest in artificial neural networks, and several optical implementations have been investigated [1]. Neural networks are intrinsically parallel computers, and optics can provide the massive parallelism and interconnectivity they require. The key components of neural networks are the synapses between the neurons, which are the locus of signal processing, learning, and memory. Bacteriorhodopsin (BR) has photochromic properties which will enable one to construct functionally complete synapses in the form of a thin-film optically-addressed spatial light modulator. Here we present measurements of properties of bacteriorhodopsin relevant to synaptic functions.
Beam Splitting in Nonlinear Polymeric Waveguide Induced by Photobleaching
Authors: Wilkosz Aaron , Sarkisov Sergey
Published: February 2023

Optical beam splitting has been first reported for photorefractive waveguides built by titanium diffusion in LiNbO3 [1,2]. The effect has been qualitatively explained as an appearance of spatial dark solitons in self-defocusing nonlinear medium [3]. Optical splitting has also been observed in pure self-defocusing Kerr media in a two dimensional configuration [4,5] similar to that of a slab waveguide. The splitting effect in this case is apparently associated with dark spatial solitons. This paper presents theoretical and experimental data and discusses a theoretical model developed to study optical beam splitting induced by photobleaching a dye-doped polymeric waveguide, where instant refractive index reaction to light intensity redistribution is replaced by permanent index decrease associated with dye photobleaching.