bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymer Waveguide Taps for Optical Signal Distribution
Authors: Callender Claire L. , Robitaille Lucie , Noad Julian P.
Published: February 2023

GaAs optoelectronic integrated circuit (OEIC) technology is having an increasing impact in the areas of communications and signal processing, with applications such as high speed broad-band switching, high-speed interconnects for multiprocessor local area networks (LANs) and optically controlled phased-array antennas. A major component of the production of OEICs is the low cost, robust and reliable integration of optoelectronic devices for generating, amplifying and detecting optical signals. Recently, there has been considerable interest in the integration of photodetectors with optical waveguide circuits. Monolithic integration of metal-semiconductor-metal (MSM) detectors with semiconductor optical waveguides has been achieved by evanescent coupling from a waveguide layer into an absorbing detector layer grown epitaxially on top of the waveguide1,2. In this paper we examine the potential of polyimide waveguides as integrated light distribution systems in monolithic OEICs. Polymer guides can be formed on top of complex semiconductor circuitry by spin coating and photolithography. Polymer waveguides offer the advantages of ease of processing, low cost, and low optical losses. As well, vertical coupling facilitates alignment of light sources and detectors without additional components such as gratings or 45° facets.
Nonlinear Optical Properties of Self-Assembled Mainchain Polymer Films
Authors: Herman W.N. , Cline J.A. , Hoover J.M. , Chafin A. , Lindsay G.A. , Wynne K. J.
Published: February 2023

We report second harmonic generation measurements on multilayers of two interleaved mainchain polymers fabricated by Langmuir Blodgett (LB) deposition. LB processing1 offers advantages over electric-field poling in that it can be done at room temperature (hence the kT Brownian motion is much less) without the strong electric fields that can lead to film damage during corona poling. Mainchain polymers are inherently more stable than sidechain polymers because both ends of the chromophore are attached to the backbone of the polymer, whereas only one end of the chromophore is attached to the backbone in a sidechain polymer, and the other end is dangling free at one of the interfaces of each monolayer. Furthermore, only mainchain polymers that contain the chromophore in a head-to-head (syndioregic) configuration can have the chromophores ordered normal to the plane of the film by hydrophilic/hydrophobic forces. This is because a mainchain polymer containing chromophores in a heat-to-tail configuration will probably have all of the chromophores lying on the water, in the plane of the film with opposing dominant hyperpolarizability components.
Defeating the Nonlinearity-Transparency Tradeoff
Authors: Moylan Christopher R. , McComb I-Heng , Twieg Robert J. , Ermer Susan , Lovejoy Steven M. , Leung Doris S.
Published: February 2023

In order to be truly useful, nonlinear optical chromophores must have large molecular nonlinearities, high thermal decomposition temperatures, and low absorption coefficients at the application wavelengths. Yet it has been empirically observed that tradeoffs exist between nonlinearity and each of the other qualities (thermal stability and transparency). The ultimate success of organic nonlinear optical materials depends upon whether these tradeoffs can be defeated.
Anisotropic Self-Alignment of Supramolecular Amylose Inclusion of Chromophores for Second-Order Nonlinear Optical Materials
Authors: Kim Oh-Kil , Choi Ling-Siu , Zang He-Yi , He Xue-Hua , Shih Yan-Hua
Published: February 2023

Anisotropic alignment of nonlinear chromophores and their dipolar stability are the key issues1 of nonlinear optical (NLO) materials. Poling is a usual means in guest-host systems to bring about such an alignment2-4. Since poling is carried out around the glass transition temperature(Tg) of hosts5, and the temporal stability of chromophores depends primarily on Tg values of hosts, matrix materials for high-temperature stability are required to have high Tg such as with polyimides. However, the high-temperature poling causes problems in nonlinear chromophores, such as bleaching6-7, decomposition8,9 or loss of dipolar alignment10, unless they have very high decomposition temperatures. Also, a related problelm is a plasticizing effect8,11 of chromophores which lowers the Tg of the matrix with increasing chromophore concentration.
Chi-electric Relaxation: Frequency Domain Chromophore Dynamics in Nonlinear Optical Polymers
Authors: Cline J.A. , Herman W.N.
Published: February 2023

The orientational stability of nonlinear optical chromophores in polymer systems has been the subject of extensive research.1-8 A new experimental method of observing chromophore dynamics has been developed. The method is similar to dielectric relaxation measurements where the linear polarization of the material is induced by a sinusoidal electric field. However, this new method probes the orientation of just the chromophores through second harmonic generation (SHG). This method is unique because it yields information about chromophore dynamics in the frequency domain, whereas the bulk of the work is done in the time domain. The method is dynamic and the chromophores are in steady-state motion in response to a time varying electric field, as opposed to studies such as Boyd et al.4 where measurements are made with a static electric field. A description of the experimental method and a discussion of the results follows.
Coherent Detection of Freely Propagating Terahertz Radiation by Electro-optic Sampling in a Poled Polymer
Authors: Nahata Ajay , Heinz Tony F. , Auston David H. , Wu Chengjiu
Published: February 2023

We report the first demonstration of an electro-optic sampling technique that allows for the coherent detection of freely propagating terahertz radiation.
Measurements Of First Hyperpolarizabilities β:Anomalous Hyper-Rayleigh Scattering Results
Authors: Flipse Marinus C. , de Jonge Roel , Woudenberg Richard H. , Marsman Albert W. , van Walree Cornelis , Jenneskens Leonardus W.
Published: February 2023

The large optical nonlinearities, the accessibility of molecular engineering, and the intriguing physics of quadratic nonlinear optics made both chemists and physicists explore the field of organic chromophores for nonlinear optics. Furthermore, the potential of polymers derived from these nonlinear optical chromophores for applications within telecommunications led to a considerable interest from industry.
Enhanced Cerenkov-Radiative SHG with UV Induced Nonlinear Optical Susceptibility-Corrugation
Authors: Sato Heihachi , Matsuno Hiroaki , Seo Iwao
Published: February 2023

It has been well recognized that introducing corrugative configuration into nonlinear optical (NLO) susceptibility χ(2) results in an extreme enhancement of SHG power with quasi-phase-matching (QPM) scheme. The authors et al have also demonstrated significant SHG enhancement with the NLO corrugation even in the Cerenkov-radiative schemes1-3. In these recent works the NLO corrugations have been electrically introduced with either contact-electrode or corona discharges. However, organic polymers have, in general, tendency to change their optical properties, i.e. refractive index and NLO susceptibility, with ultra-violet (UV) sbsorption. Fortunately, it has been found from spectroscopy that vinylidene cyanide/vinyl acetate (VDCN/VAc) copolymer has a strong absorption band around 200 nm wavelength. In addition, it has also been preliminarily expected that the UV irradiation tends to reduce or dissipate its NLO susceptibility and the refractive index due to dissociation of the side chain in VDCN/VAc co-polymer. In the present paper we shall thus attempt to enhance the Cerenkovian SHG power with a periodic or chirped NLO χ(2) corrugation by irradiating ArF 193 nm laser source, together with discussion of the optimum UV irradiation.
A Study of Neodymium-Chelate-Doped Polymer Waveguides
Authors: Lin Sihan , Feuerstein Robert J. , Mickelson Alan R.
Published: February 2023

The promise of switched high speed optical interconnects has stimulated research on electro-optic (EO) polymeric devices due to their potentially low cost and the flexibility of fabrication, as well as the possibility of forming multilayer structures [1-3]. As in other integrated optical (IO) devices, loss in polymer devices is a serious issue and a major limitation to the application of IO devices.
Electro-optic And Second Harmonic Generation Studies Of Dye-Doped Polymers
Authors: Ghebremichael Fassil , Lackritz Hilary S.
Published: February 2023

The linear electro-optic (EO) effect, in conjunction with second harmonic generation (SHG) has been used to study temperature and electric field effects on dye-doped guest-host systems. An interferometric technique with in-situ poling was used to probe the poling field- induced molecular alignment of the chromophores as a function of temperature. The doped polymer systems were thin films of 4-dimethylamino-4'-nitrostilbene or disperse red 1 chromophores doped into poly(methyl methacrylate). For small poling fields, this technique revealed the linear dependency of the electro-optic-coefficient, r, and thus the second order susceptibility χ(2) of the material, on low poling fields. It was also possible to detect the β-relaxation, the secondary transition occurring below the glass transition temperature, which until now has not easily been seen in studies using optical techniques.
Towards a physical interpretation of the activation volume for chromophore reorientation in corona poled polymers
Authors: Brower Shane C. , Hayden L. Michael
Published: February 2023

Recently we reported1,2 on a technique for measuring the decay of the second order optical susceptibility χ(2) as a function of temperature and pressure in poled nonlinear optical (NLO) polymeric materials. This approach utilizes second harmonic generation (SHG) to monitor the rotational reorientation of the NLO chromophores in such systems and yields structural information directly related to the reorientation process in poled polymers.
Design and Synthesis of Soluble Thermally Stable Nonlinear Optical Chromophores Based on the Dicyanomethylenepyran Moiety
Authors: Lovejoy Steven. M. , Ermer Susan , Leung Doris S. , Dirk Carl W. , Kalamegham Priya , Zhang Lixia , Moylan Christopher R.
Published: February 2023

For several years we have been developing polyimide-based electro-optic materials based on commercially available components. In 1992, we described a proof-of-principle all-polyimide triple stack Mach-Zehnder modulator using DCM (4-(dicyanomethylene)-2-methyl-6-(p-di-methylaminostyryl)-4H-pyran) in Amoco Ultradei 3112 polyimide as the active core layer with Amoco Ultradei 4212 polyimide cladding layers.1 During the course of our work we found that some commercial preparations of DCM contained a significant amount of a less soluble, more thermally stable impurity which we identified as the bis condensation product arising from the synthesis of DCM itself.2 This impurity, DAD, and several analogs were synthesized, and their physical and NLO properties were investigated.3 Figure 1 shows the synthetic scheme used for their preparation.
Permanent All Optical Poling of An Octupolar Dye
Authors: Zyss Joseph , Samuel Ifor , FIORINI Céline , Charra Fabrice , Nunzi Jean-Michel
Published: February 2023

The predominant class of molecular systems considered so-far towards applications in the realm of quadratic nonlinear optics has been derived from the all-pervading "molecular diode" template as exemplified by paranitroaniline-like molecules. The underlying basic paradigm consists in the dipolar anchoring of an interacting couple of electron donor and acceptor groups to a conjugated π electron linkage(1). The virtue of such a configuration is to provide a significant electronic charge displacement in the ground state which is further enhanced upon directional optical excitation towards the charge-transfer level. This basic mechanism has been confirmed by nearly two decades of experiments in solutions, crystals and polymer media with the two-level quantum model providing solid theoretical support(2). Both the Electric Field Induced Second Harmonic (EFISH) experiment and the current poled polymer technology essentially depend on the existence and magnitude of a strong ground state dipole μ contributing to the μ.E coupling potential between individual molecules and the externally applied de poling field E.
Potentials of Ionic Organic Chromophores for Second-Order Nonlinear Optical Thin Film Materials
Authors: Nakanishi H. , Duan X.-M. , Okada S. , Oikawa H. , Matsuda M.
Published: February 2023

Organic second-order nonlinear optical materials, in competition with inorganic materials, must fulfill the conditions of both large susceptibilities and short cutoff wavelength, together with processability, mechanical strength, chemical, thermal and temporal stabilities. Enormous numbers of conjugated compounds have already been investigated. Almost all of them are, however, electrically neutral molecules, and do not conquer the tradeoff issues between susceptibility and cutoff wavelength. Ionic organic compounds have been investigated little for this purpose, even though they generally have several advantages as follows. In the case of single crystals, alignment of the ionic chromophore can be controlled into a polar structure by changing the counter ions [1-3]. Thus, there is no need to modify the chemical structure of the chromophore itself after having determined the ionic species with large hyperpolarizability (β). Mechanical properties, especially hardness, of the ionic crystals are better than those of neutral crystals. In addition, high melting point and/or thermal stability is also expected.
Arrays of Flip-Chip Mounted, Surface-Illuminated, Crystalline-Organic Optoelectronic Modulators on Glass Substrates
Authors: Yap D. , Burrows P.E. , Forrest S.R.
Published: February 2023

Thin films of organic molecular crystals are promising optoelectronic materials. Some of these crystalline organic materials can have very high optical nonlinearities. Conventional optoelectronic devices are usually formed on crystalline semiconductor substrates such as GaAs, InP or silicon which have a good lattice match with the optoelectronic material. In contrast, by using the ultrahigh vacuum process of organic molecular-beam deposition (OMBD), the crystalline organic materials can be deposited on highly lattice-mismatched substrates without generating defects.1 Thus, devices can potentially be fabricated on a variety of substrates such as glasses, semiconductors, ceramics and polymers. This feature enables selection of the substrate to be based on considerations such as microwave or thermal properties, manufacturability or cost rather than being limited by the substrate’s lattice match. Furthermore, it opens the door to a variety of new applications that require conformally embedded optoelectronic modules or large-area sheets of optoelectronic devices.
Photomechanical Multistability and Logic in a Polymer Optical Fiber
Authors: Welker D. J. , Kuzyk M. G.
Published: February 2023

Optical multistability and optical logic both operate on the principle that light can interact with itself through an intensity dependent refractive index. More precisely, an intensity dependent phase shift is responsible. This implies that multistability can originate in both a refractive index change or a physical path-length change within a material. While the refractive index mechanism has been routinely studied, the implications of the length change mechanism has been largely ignored. In this contribution, we show that an intensity dependent length change can be used to build a new class of devices. In particular, we show that mechanical and optical multistability in a polymer optical fiber Fabry-Perot interferometer can be used in the design of a mesoscale all-optical vibration suppressor and an optical positioner.
Photochromic Diarylethenes for Erasable Optical Memory.
Authors: Irie Masahiro
Published: February 2023

Photon-mode optical recording offers advantages over magnet-optic or phase change recording, which utilizes light as a heat source for recording, with regard to resolution, speed of writing, and multiplex recording capability. One of the candidates for the photon-mode recording media is organic photochromic media(1). Although much effort has been made in this field in the past, the photochromic materials still await practical application. The limitation is due to the lack of suitable materials which fulfill the requirements for the reversible recording media(2). The requirements for the use are: 1. Archival storage capability. 2. Low fatigue (write/erase cycles can be repeated many times). 3. High sensitivity at diode laser wavelengths and rapid response. 4. Non-destructive readout capability. 5. High contrast even if the thin film thickness is thin.
Photoinduced Refractive Index Changes in PMMA Films Including a Photochromic Fugide
Authors: Morino S. , Yamazaki T. , Machida S. , Yamashita T. , Horie K.
Published: February 2023

Photochemical reactions such as photochromic reactions, photodegradation and photocrosslinking, change optical properties of the samples during their reactions, and are applicable for optical memories, optical switching devices, and so on[1~3].
EO Polymer Devices for Fiber Optics Gyros and Other Applications
Authors: Ashley Paul R. , Cites Jeffrey S.
Published: February 2023

Integrated photonic components based on polymeric materials have been developed which enhance the integration of fiber optic gyroscopes. New active and passive polymeric materials, device designs, and component integration on optoelectronic substrates are reviewed.
Push-pull Polymer Integrated Mach-Zehnder Modulators
Authors: Wang Wenshen , Shi Yongqiang , Lin Weiping , Olson David J. , Bechtel James H.
Published: February 2023

Nonlinear optical (NLO) polymers have been used to demonstrate broadband electro-optic (E-O) modulators in laboratories [1-3]. Because of the small and nondispersive dielectric constants of polymer materials, over 100 GHz modulation can be achieved with a simple integrated microstrip line circuit [3]. However, in order for these polymer modulators to be usable in commercial fiber-optic data links, several other device performance figures have to be improved. In addition to the often-discussed thermal stability issue, the halfwave voltage, optical insertion loss, optical power handling capability, and bias control stability are all of vital importance to the commercial application of polymer E-O modulators. Future polymer photonic devices must have a balanced overall performance, with a much lower cost, broader bandwidth, and competitive thermal, photochemical and bias control stability. We have reported our fabrication and testing of integrated Mach-Zehnder modulators using a double-end-crosslinked NLO polymer LD-3 [4-5]. The LD-3 based modulators have exhibited higher thermal stability, photochemical stability and low optical insertion loss compared to the E-O modulators based on the PUR-DR19 polymer [2]. However, because the LD-3 polymer has a lower E-O coefficient r33, and the corona poling schedule was not optimized, our LD-3 modulators exhibited a higher halfwave voltage which is not acceptable in most applications. In this paper, we report our new device fabrication technique that effectively reduced the halfwave voltage by one-half using an optical push-pull structure in M-Z modulators.
Nonlinear Optical Chromophores Containing Fused Terthiophene As A New Type of Electron Relay
Authors: Kim O.-K. , Fort A. , Barzoukas M. , Lehn J.-M.
Published: February 2023

Thiophene-based D-A molecules have been actively sought recently, exploiting interesting results indicating that the incorporation of a thiophene unit or the replacement of a phenylene moiety by thienylene in the relay of a D-A molecule enhanced the molecular hyperpolarizability (μβ(0)) significantly (1-3). Accordingly, it is expected that oligothiophenes give a larger contribution to the μβ(0) compared to oligophenylenes. As in the case of polyenes, the rigidification of thiophenes (by cyclization) has also been known to enhance charge-transfer in push-pull D-A molecules, as indicated by a bathochromic shift of absorption bands and a stronger solvatochromism compared to the flexible counterpart (4,5). A further indication for the effectiveness of fused thiophenes as relay is demonstrated by the fact that their absorption maxima increase linearly with the number of rings up to five (6). Aside from the electronic features, another merit of thiophenes is their inherent thermal stability from which thiophene-containing chromophores will benefit (2,3).
Mode Coupling Effects in Plastic Optical Fibers
Authors: Jiang G. , Shi R.F. , Garito A.F.
Published: February 2023

In optical fibers for data transmission applications, a most important characteristic along with total attenuation is the optical bandwidth that defines the limit of information carrying capacity.1 Besides compensation for modal dispersion through a parabola-like graded index profile, mode coupling is a mechanism important to increased fiber bandwidth performance. Mode coupling changes the length dependence of the bandwidth, or equivalently, the inverse pulse broadening, from linear to square root behavior, usually through extrinsic features which might include micro bends, diameter variations, micro voids, cracks etc. In this paper, we report the observations of mode coupling effects in plastic optical fibers (POFs) using time-domain bandwidth measurements of high quality step index (SI) POF.2-4 Our results are directly verified by independent measurements of the far-field radiation patterns.
Polymer Thin Film Overlays for Passive Side Polished Fiber Devices
Authors: Lee S. G. , Sokoloff J. P. , Sasabe H.
Published: February 2023

Side polished fibers (SPF) are interesting devices because they represent a method of altering a light wave's amplitude or phase as it travels in an optical fiber. This eliminates many of the practical problems associated with fiber-optic devices made up of components, such as the optical mode-mismatches and losses resulting from "pigtailing" an optical fiber to a non-fiber device component. In SPFs a portion (~1 mm in length) of the fiber clad is polished away permitting the light wave to interact with an overlay material placed on the polished area. A variety of overlays have been used with SPFs to make both passive and active SPF devices.1
Multifunctional Photoresponses in Carbazole Main-Chain Polymers
Authors: Wada Tatsuo , Zhang Yadong , Kimura-Suda Hiromi , Aoyama Tetsuya , Choi Su-An , Sasabe Hiroyuki
Published: February 2023

Electronic and optical properties of organic charge-transfer (CT) compounds have attracted a lot of attention from both fundamental science and practical applications. Remarkable progress have been made in development of electroactive CT materials such as organic metals, conducting polymers, and organic photoconductors (OPCs). Among them, OPCs are widely used for electrophotographic applications. Besides photoconductive properties, it has been elucidated experimentally and theoretically that organic inter- and intracharge transfer compounds exhibit large nonlinear optical (NLO) responses. We have investigated the third-order NLO properties of polymeric CT materials based on poly-n-vinylcarbazole (PVK) complexed with 2,4,7-trinitrofluorenone (TNF) in terms of the complex composition.1 The values of χ(3) (-3ω; ω,ω,ω) increased linearly with the content of CT complex in the film. Recently large refractive index changes have been demonstrated in organic photorefractive polymers based on PVK/TNF systems.2 Carbazole compounds play a significant part in electroactive and NLO applications. In order to utilize the unique properties of polymer backbone, acceptor-substituted carbazole moiety was incorporated into the main chain through either 3,6- or 3,9-linkage. In this paper we discuss the multifunctional photoresponses in various carbazole main-chain polymers with shoulder-to-shoulder, head-to-tail, and hyper-branched arrangements as shown in Figure 1.
High Glass Transition Temperature Syndioregic Second Order Nonlinear Optical Polymers in Langmuir-Blodgett-Kuhn Films
Authors: Roberts M. J. , Lindsay G. A. , Stenger-Smith J. D. , Hollins R. A. , Chafin A. P. , Gratz R. G.
Published: February 2023

Recent progress has been made toward the goal of processing polymers at low temperature to produce all-polymeric nonlinear optical films which may ultimately find application as active waveguides. Our previously reported work [1] has utilized the Langmuir-Blodgett-Kuhn (LBK) technique to produce such films but the noncentrosymmetric order in those films was lost when heated above 80 °C. New polymers were designed to yield ordered films with higher thermal stability by eliminating the long alkyl side chains (Figure 1). The glass transition temperature (Tg) of the bulk polymer is about 240 °C, and the upper limit on short term thermal baking stability is about 320 °C [2].
Thiophene Based Hydrazones: a New Class of Nonlinear Optical Molecular Crystals
Authors: Bosshard Christian , Feng Pan , Wong Man Shing , Bösch Martin , Meier Urs , Günter Peter
Published: February 2023

Crystalline solids are often regarded as the best choice of material form for practical use as optical frequency converters because of the excellent long-term orientational stability and extremely high density of active components. Such materials can be combined with inexpensive diode lasers for optic parametric generation of a broad range of optical frequencies [1, 2]. We here report on our on-going efforts in the development of novel and highly efficient second-order nonlinear optical crystalline materials for frequency conversion, based on the hydrazone derivatives 5-(methylthio)-thiophenecarboxaldehyde-4-nitrophenylhydrazone (MTTNPH) and 5-nitro-2-thiophene-carboxaldehyde-4-methylphenylhydrazone (NTMPH).
Electro-optic Modulation in Waveguides Based on Single Crystal Films of Organic Materials
Authors: Xu Jianjun , Thakur M.
Published: February 2023

Optical amplitude modulators are important components for optical signal processing and telecommunication. Organic single crystal materials have excellent stability, and high figures of merit for electro-optic applications. In this work, two different methods of electro-optic modulation have been studied: i) using direct fabrication of organic single crystal waveguides and end-fire coupling and ii) using evanescent coupling from fiber to organic single crystal film overlay.
Fabrication of vertical tapers in polymer thin films by oxygen reactive ion etching with a shadow mask for photonic device applications
Authors: Chen Antao , Marti-Carrera Felix Ignacio , Garner Sean , Chuyanov Vadim , Steier William H.
Published: February 2023

The taper structure is the key component of an on-chip mode size transformer for efficient fiber coupling. The taper provides a smooth transition between two waveguide sections with different mode sizes with minimum radiation loss. The tapered mode size transformer has become a standard approach for efficient fiber coupling with semiconductor lasers and amplifiers[1]. Various taper fabrication techniques are developed for semiconductor and LiNbO3 devices[2-5], but most of them are not applicable to polymer waveguides. Oxygen reactive ion etching is the primary method to etch a polymer film. For most polymer waveguides, the major part of fiber coupling loss is due to the mode size mismatch between the waveguide and fiber in the vertical direction, therefore a vertical taper is needed to reduce the fiber coupling loss. In this paper, a reactive ion etching (RIE) technique with a shadow mask is demonstrated. A similar technique has been reported for etching submicron tapers in InP with methane plasma[5]. Our approach can effectively create tapers several microns deep and a few millimeters long with oxygen plasma which is required for multilayer polymer waveguide structures.
Ionization-assisted Deposition of Polyurea Thin Films for NLO Applications
Authors: Usui H. , Kikuchi H. , Tanaka K. , Miyata S. , Watanabe T. , Knoll W. , Bock H.
Published: February 2023

Polymeric material needs a poling process to align the dipole moment for activating optical nonlinearity. The major problem is the relaxation of dipole orientation, which is to be solved by designing a molecular structure of higher rigidity. However, it leads to a contradiction that the thermally stable polymer, like the linear main-chain NLO polymer, is difficult to align the dipole orientation by the poling procedure. This paper will propose a new concept in film formation of NLO polymer, integrating the dipole orientation process with the polymerization and film deposition. The authors have investigated the film formation of organic materials by using the ionization-assisted deposition method. It is a unique method that involves the ionization of evaporated material in the course of vacuum deposition, and grows the films with an assistance of the ionized particles that are accelerated toward the substrate. It is reported that polymeric thin films can be synthesized on the substrate surface by co-deposition of bifunctional monomers. If the polymerization proceeds under an electric field, the dipole orientation could take place much effectively, because the electric field influences the highly mobile monomers. Our objective is to control the dipole orientation in the film formation process by utilizing the electric field that is generated by the substrate bias voltage and by the electric charge carried by the deposition ions. Polyurea (PU) was chosen for the film material because of its thermal stability and optical transparency. Moreover, its dipole moment is built in the backbone, making this material attractive as a stable optical nonlinear material.
High Performance Electro-Optic Polymer Waveguide Modulator
Authors: Hwang W.-Y. , Lee H.-M. , Oh M.-C. , Park H. , Lee H.-J. , Lee M.H. , Ahn J.H. , Han S.G. , Won Y.H.
Published: February 2023

Electro-optic (EO) polymers have been utilized to fabricate many waveguide devices such as modulators, switches, and polarization control devices [1]-[3]. Up to now, most of the research activities have been focused on electro-optically active materials to improve the device performances. In contrast, less attention has been paid on cladding materials.
Linear and Second-Order Nonlinear Optical Properties of Urethane-Urea Copolymers
Authors: Tsuchimori Masaaki , Watanabe Osamu , Okada Akane
Published: February 2023

Nonlinear optical (NLO) polyurethanes have been intensively studied to develop electro-optic devices, because they have not only large second-order NLO coefficients (d33) but also good temporal stability of d33 at room temperature [1,2]. We have reported that introducing urea groups into main chains of polyurethanes, namely urethane-urea copolymers, improves the temporal stability at elevated temperatures [3]. The copolymers have many advantages, for example easiness of synthesis, relatively high intrinsic viscosity [η] (molecular weight), easiness of poling process, and applicability of photobleaching method [4]. In the present work, linear and second-order nonlinear optical properties of the copolymers are discussed.
Vertical tapered mode size transformer in polymer waveguides for efficient fiber coupling
Authors: Chen Antao , Chuyanov Vadim , Marti-Carrera Felix Ignacio , Garner Sean , Steier William H. , Chen Jinghong , Sun Shajing , Mao Shane S. H. , Ra Younsoo , Dalton Larry R.
Published: February 2023

Recent years have seen significant progress in photonic devices based on electrooptic (EO) and passive polymers. Recently an EO polymer modulator that works at a record high speed of 113 GHz has been reported(1), and a system demonstration incorporating EO polymer modulators has also been made(2). As polymer waveguide devices are entering fiber optic telecommunication and data communication systems, practical issues concerned by system designers have become increasingly important. One of such issues is the insertion loss of the polymer device.
Mechanisms of chromophore reorientation probed with in-situ, pressure second harmonic generation
Authors: Hayden L. Michael , Strutz Shane J.
Published: February 2023

Research to determine the mechanisms which tie chromophore reorientation to polymer relaxation is crucial to the development of thermally stable NLO polymers.1 Most of the work to date has been performed above or near the glass transition temperature where the decay of the NLO properties of the material is tied to the glass transition and the α-motion of the polymer backbone. Devices which rely upon permanently poled polymer films for their NLO characteristics are not designed to operate near or above the glass transition because their nonlinear properties would quickly dissipate. A study of the coupling between polymer motion and chromophore reorientation below the glass transition temperature is necessary to gain insight into the reorientional dynamics of the chromophores at common device temperatures. Using the results of elevated temperature studies to predict the behavior of the NLO properties below T
g
may not be accurate if the mechanisms responsible for chromophore reorientation are not the same in both regimes.
Kinetics of Photoinduced Orientation of Azo-dyes in Alignment Layers
Authors: Kosa T. , Palffy-Muhoray P.
Published: February 2023

Optical buffing of alignment layers [1] for liquid crystal device applications has generated considerable interest recently. In order to make efficient use of optical alignment, detailed understanding of photoinduced orientation of azo-dye molecules in the alignment layer and the coupling between the dye and the bulk liquid crystal is necessary. A simple model for the latter has already been proposed [2]. In this paper we study the time evolution of photoinduced anisotropy in azo-dye doped polyimide films. The orientational kinetics of chromophores in polymers is also of interest to the χ(2) materials community.
Observation of Switching Phenomena in Non-ether PPQ Planar Waveguide with Two-wavelength Nonlinear Prism Coupling
Authors: Zhou Jun , Cao Zhuangqi , Chen Yingli , Chen Yixin , Sun Meng , Sun Diechi , Li Fuming
Published: February 2023

In the past two decades, third-order nonlinear optical properties of organic and polymeric materials have attracted considerable attention to realize all-optical signal processing devices.1,2 Especially, the large off-resonance third-order optical nonlinearities of conjugated organic polymers with delocalized π--electron systems, such as polydiacetylenes3,4, are considered to be potential candidates. Although conjugated polymer is reported to have large χ(3) and fast response time, many of them are highly intractable materials that are difficult to process to form the low-loss waveguide structures required for their application5. Recently, many techniques for fabricating low-loss planar waveguides in thin films of solution processible conjugated polymer have been developed7,8 besides third-order nonlinear optical polymers that exhibit low absorption have been reported6 Furthermore, numerous different schemes which aim is all-optical switching and all-optical logic operations have been suggested for practical devices. They are included in nonlinear prism and grating couplers and nonlinear directional couplers9,10, such as two-channel nonlinear directional couplers, nonlinear Mach-Zehnder interferometers, nonlinear distributed-feedback grating reflectors and adiabatic polymer-glass-waveguide all-optical switch11,12. However, though the prism coupler has attracted partially significant attention both theoretically13 and experimentally14, as so far we know the nonlinear prism coupling to organic polymer waveguide has only been demonstrated in single beam experiments on intense-dependent nonlinear effects15.
Conjugated Polymers as Materials for Thin Film Solid State Lasers
Authors: Hide F. , Diaz-Garcia M.A. , McGehee M. , Schwartz B. J. , Heeger A. J.
Published: February 2023

Optically pumped gain narrowing and lasing have been demonstrated in submicron thick films, neat and undiluted, of photoluminescent conjugated polymers. The dramatic collapse of the emission line width occurs at very low pump energy thresholds (~10 μJ/cm2). Gain narrowing is found in over a dozen different conjugated polymers representing a variety of molecular structures, including poly(p-phenylenevinylene), poly(p-phenylene) and polyfluorene derivatives; the emission wavelengths in these materials span the visible spectrum. The short gain lengths in conjugated polymers are attributed to the high density of chromophores, the large density of states associated with the interband (π-π*) transition in quasi-one-dimensional systems, and the Stokes shift which minimizes self-absorption and allows optical pumping to the excited state without simultaneously stimulating emission (thereby yielding population inversion). Lasing and gain narrowing are compared for a soluble poly(phenylene vinylene) derivative using two different resonant structures: planar waveguides and microcavities. In both cases, the gain narrowing threshold is at 0.05 - 0.1 μJ per 10 ns pulse focused to approximately 1.5 mm. Single mode microcavity lasers are obtained when a cavity resonance occurs at the wavelength where the gain of the polymer is a maximum. Low threshold lasing (threshold more than an order of magnitude below that observed in planar waveguides and microcavities) has also been demonstrated using distributed feedback in a planar chip film configuration.
Liquid Crystalline Polymers for Electroluminescence
Authors: Bradley D.D.C. , Grell M. , Brandon K.L. , Turner M.L. , Bentley P. , Dunmur D.A. , Woo E.P. , Inbasekaran M.
Published: February 2023

Organic electroluminescence is attracting strong interest for applications in lighting and displays. Polymer devices offer some advantages for low cost processing over large areas and with extended molecular architectures there is the possibility of polarised emission. This is attractive for backlighting liquid crystal displays and also for development of sources for optoelectronics. In order to achieve polarised emission there is a need to obtain highly oriented samples. Further, to allow construction of efficient electrolumiescent diodes it is necessary to achieve this orientation in thin films deposited on suitable electrode surfaces. We believe that mesophase formation is an attractive approach to achieve these dual goals and we have thus undertaken a programme of work to produce liquid crystalline polymers with the dual attributes of charge transport and light emission capability that can allow application in electroluminescence devices. This paper reports on recent progress in materials preparation, processing and device fabrication.
Origin of Optical Gain and Stimulated Emission in Conjugated Polymers
Authors: Spiegelberg Ch. , Schülzgen A. , Morrell M. M. , Allemand P. M. , Kippelen B. , Peyghambarian N.
Published: February 2023

Recent reports on a spectrally narrow emission peak have generated a lot of excitement in the scientific community. Hide et al. [1] and Frolov et al. [2] reported dramatic photoluminescence (PL) line narrowing in a variety of PPV derivative films for exciton densities above 1017 cm-3, indicating stimulated emission (SE). The SE linewidth (7 to 9 nm) has been attributed to either amplified spontaneous emission [1] or superradiance [2].
Low Vision Aid Using High-Minus Intra Ocular Lens
Authors: Garnier B. , De Lega X. Colonna
Published: February 2023

We analyzed the theoretical performances and some clinical investigational results of a new low-vision aid system first described by CHOYCE and subsequently studied by DONN, KOESTER and BAYLEY.
The Effect of the Visual Stumulus on the Eye's Refractive State Monitored with the Aerial Retinal Image
Authors: Navarro R. , Geslin D. , Losada M. A. , Artal P.
Published: February 2023

Lately a method to record the aerial retinal image of a point test after double pass through the optical media of the eye was developed at the Instituto de Optica (Santamaría et al. 1987). Until now we used a point source as fixation target so that it served as the stimulus for accommodation. Here we explore how the visual stimulus affects the shape of the point spread function (PSF), or equivalently the modulation transfer function (MTF). For that purpose, we compare gratings with point sources to determine how they can affect or modify the refractive state of the eye, and in consequence, the shape of the PSF and MTF.
Task Performance As A Measure of Vision
Authors: Sheedy James E. , Harris Michael G. , Bailey Ian L.
Published: February 2023

An important function of vision is to provide us with sensory information to efficiently perform tasks - especially occupational-type tasks. In the research laboratory and the clinic we often measure and quantify various aspects of the visual sense such as visual acuity, stereoacuity, contrast sensitivity, amplitude of accommodation, etc. These and many other measures of visual performance each has an effect upon the performance of occupational-type tasks.
Isomorphic Corneal Topography
Authors: Siegel Irwin M. , Young Joshua A.
Published: February 2023

Measurements obtained from computer-based videokeratographic instruments have focussed on accurate representations of corneal power, in diopters or equivalent radii lengths. Zones of power arranged in discrete (annular) widths correspond to hemi-chord lengths of the familiar bulls-eye reflected corneal ring pattern. Often these zones are color-coded for dioptric equivalence and yield quick assessment of corneal power change as a function of distance from the apex. Whether the final image is of the former sort or even configured into a "3-D chicken wire" frame, the information provided is still only about discrete power boundaries -- a sort of corneal power profile. While the sense of corneal topography may be implied in such profiles accurate representation of the true corneal surface is clearly missing. Using data derived from a clinical videokeratography unit we have been able to computer-generate an image (in X,Y,Z coordinates) which we believe to be isomorphic to the actual corneal surface.
Measure and Assessment of Ophtalmic Surfaces Using Least-Squares Interpolation
Authors: Frechilla Mariano
Published: February 2023

The assessment of optical surfaces of use in the Ophtalmic Optics is a field of increasing interest. Not only is needed in the areas of aspheric and progressive addition lenses (PAL's), but also corneal topography benefits from these methods.
Distortion of Progressive Addition Lenses
Authors: Baumbach P. , Guilino G.
Published: February 2023

It is necessary to distinguish between monocular and binocular perception of lens distortion. Monocular distortion is seen as a local change in size inside the visual field or as a distortion of straight lines or right angles. In its binocular form, the different distortion in the two lenses (assuming binocular single vision) has a spatial effect which impairs stereopsis. A spectacle wearer with spherical minus power lenses will interpret a surface in space which is actually level as having a convex curvature.
Influence of Progressive Addition Lenses on the Identification of Peripheral Visual Images
Authors: Semmlow John L. , Pedrono Claude , Bonnin Thierry
Published: February 2023

The distortion produced by progressive addition lenses reduces performance in tasks requiring identification of peripheral images. A psychophysical test is described to assess the peripheral deficit produced by these lenses.
Corneal Analysis with a Rectilinear Photokeratoscope
Authors: Shimmick John , Munnerlyn Charles
Published: February 2023

Photorefractive keratectomy (PRK) involves precisely sculpting a lens on the anterior cornea by excimer laser photoablation (1). Consequently, patient positioning relative to the laser must be within certain predefined tolerance levels (2), and the procedure should be centered on the patient's line of sight (3).
New Developments in Ophthalmic Laser Technology
Authors: Puliafito Carmen
Published: February 2023

Summary not available at time of publication.
Intraoperatve Corneal Topographic Measurement Using Phase-Shifted Projected Fringe Contouring
Authors: Lange Steven R. , Thall Edmond H.
Published: February 2023

Interest in corneal topography has increased in recent years as a consequence of developments in corneal surgery. There are commercial corneal measurement systems for office use but no surgical instrument is available. Intuitively, it would seem useful for surgeons to have the capability to monitor changes in corneal shape intraoperatively. Indeed, some authorities have expressed the opinion that intraoperative evaluation of corneal topography would be a significant advance. This paper describes a prototype device for intraoperative measurement of corneal topography and gives preliminary clinical results.
Polynomial Approximations of Corneal Surfaces And Corneal Curvature Topography
Authors: Howland H. C. , Glasser A. , Applegate R.
Published: February 2023

Machines for the measurement of corneal topography typically produce a colored topographic map of the mean curvature of the cornea. (1). From the examination of a number of such maps of normal corneas it has been found that the normal cornea is most curved at its apex and flatter in the periphery. By contrast, a cornea flattened by corneal surgery will typically be flatter in its center and steeper in the periphery (2).
Gradient Index Profile Calculation using Cubic Splines
Authors: Munger R. , Campbell M.C.W. , Kröger R.
Published: February 2023

Accurately modelling the refractive index gradient of the crystalline lens is essential in understanding the optical properties of the vertebrates visual system. A method of indirectly measuring the refractive index profile in intact crystalline lenses was devised by Campbell1 (based on work2 measuring refractive index profiles in optical fibers) and subsequently used by others to measure refractive index distributions in rat3, rock bass4, bovine5 and humans6. The total deviation of a set of parallel laser beams incident on the lens parallel to the optical axis or the equator are measured. For a spherically symmetric lens the index of refraction, n(r), at a distance r from the center of the lens can be calculated from the deviation angles, ψ(y), using the following set of equations, here ρ is the lens radius and y the perpendicular distance between a ray and the optical axis.
Light damage to the neural retina with aging-the protective role of macular pigment
Authors: Haegerstrom-Portnoy G. , Torio J. , Torio L. , Valenzuela V.
Published: February 2023

Previous studies have demonstrated loss of retinal function with
increasing age in the absence of disease. The short-wavelenght
sensitive cone pathways have been shown to be particularly vulnerable
to aging effects (eg. Haegerstrom-Portnoy, et al., 1989; Werner and
Steele, 1988; Johnson et al., 1988). A potential cause of neural loss
with age is visible light exposure over a lifetime. The ocular
photochemical light damage action spectrum shows an exponential rise
with decreasing wavelength (Ham et al., 1976). One possible method to
determine if a life-long exposure to visible light contributes to
neural loss is to examine S-cone sensitivity across the retina. If
light contributes to damage, the fovea may show less damage due to the
protective role of the yellow macular pigment. In a previous study
(Haegerstrom-Portnoy, 1988), I showed that the S cone loss with aging
was not evenly distributed across the retina but that
parafoveal locations showed considerably more loss, consistent with
the hypothesis that macular pigment protects the fovea from light
damage. The purpose of the present study is to strengthen this
argument. Macular pigment density is very variable at any one age
(e.g. Pease et al., 1987) but shows no significant change with age in
cross-sectional studies beyond age 2 years (Bone et al., 1988). If
macular pigment does protect the fovea, there should be a direct
relationship between macular pigment density and the foveal/parafoveal
difference in S cone sensitivity. The results of this study shows that
such a relationship indeed exists.