bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of Organic Thin Films by Laser Ablation Deposition for Electro-Optics Devices
Authors: Fujii Takeo , Shima Hiroki , Matsumoto Naotaka , Kannari Fumihiko
Published: February 2023

Various functions of organic materials in opto-electronics have been received much attention. Development of process technologies of various organic films, which are especially aimed for controlling their architectures in nanometer size, is also growing interest. Although inorganic films such as high-temperature ceramic superconducting materials or ferroelectric ceramics have been successfully fabricated in laser ablation deposition schemes, there is less experimental results available on organic thin film deposition with laser ablation.
Efficiency of photoassisted poling of azobenzene, stilbene and biphenyl dyes as studied by Stark spectroscopy
Authors: Haase W. , Grossmann S. , Saal S. , Weyrauch T. , Blinov L. M.
Published: February 2023

Besides the usual thermal assisted poling procedure the photoassisted poling reported for polymers containing azobenzene chromophores is of current interest. Usually the enhanced orientational mobility under illumination with visible light in the absorption band of the chromophore is explained by the trans⇔cis isomerization cycle of the azo dye, with a photoisomerization trans⇒cis and a thermal relaxation cis⇒trans. Because of the more compact shape of the cis isomer the rotational mobility is much higher than that of the trans isomer, thus polar orientation under electric DC field is possible. Since the memory of the polar orientation is lost only partially during the cis⇒trans transition, the trans isomers will achieve also a polar ordering [1-4]. This theory cannot be applied to systems containing stilbene dyes, where no thermal cis⇒trans relaxation is present. Investigations on systems containing stilbene dyes have also shown enhanced polar order in a poling process under illumination with visible light in the absorption range of the chromophore [5,6]. Thus the influence of heating of the sample (both macroscopically and microscopically in the vicinity of the dye molecule) must be discussed. The aim of this work is to compare the photoassisted poling behaviour of azo and stilbene dyes as well as of a non isomerizable biphenyl dye.
A Two Slit Electrooptic Coefficient Measurement Technique and Efficient In-Plane Poling of Polymer Thin Films
Authors: Garner Sean , Kalluri Srinath , Ziari Mehrdad , Steier William H. , Shi Yongqiang , Liang Zhiyong , Dalton Larry R.
Published: February 2023

Several techniques are in use for the characterization of the electrooptic properties of poled polymer thin films. Of these, three techniques - 1) extrapolation of electrooptic coefficient from second-harmonic generation data 2) attenuated total reflection (ATR)1 and 3) ellipsometry2,3 - are favored for their convenience and accuracy. However, these methods are mainly used for material characterization and it is difficult to adopt them for measurements of the material nonlinearity in certain practical device structures such as those poled in-plane by coplanar electrodes. The new technique that we will present here - a two slit interference modulation measurement - is capable of measuring the electrooptic coefficient for both material and device characterization. Moreover, in this method, waveguiding is not required and both the real and the imaginary parts of either r13 or r33 coefficients can be measured independently.
Frequency Doubling in a Poled Polymer Waveguide Using Anomalous Dispersion Phase-Matching
Authors: Kowalczyk T.C. , Singer K.D. , Cahill P.A.
Published: February 2023

Many technological advances can be realized from the development of coherent short wavelength sources, particularly in the fields of information display and storage. One approach to producing short wavelengths is to frequency double (existing and inexpensive) near-IR semiconductor lasers using a nonlinear optical process, second harmonic generation (SHG). Large intensities are necessary to drive such nonlinear interactions and these intensities can be achieved even with continuous wave lasers by spatially confining light to a waveguide. Waveguide geometry can be compact and may allow diffraction free propagation. Poled polymers are interesting materials for second harmonic generation because they have large nonresonant nonlinearities, low losses, and are easily processed.
Quasi-phasematched sum frequency generation in active-passive hybrid waveguides
Authors: Lehmann S. , Marowsky G.
Published: February 2023

Nonlinear optical interactions in waveguides have attracted considerable interest in the past few years. Various classes of materials have been investigated for this purpose. Of these, optically nonlinear polymers have been the focus of intensive research [1]. Their merits render them attractive for use in the development of optoelectronic devices. Quasi-phasematching is a versatile technique for second-order nonlinear processes. The phase-velocity mismatch between interacting waveguide modes at frequencies ωi (i = 1,2,3) is compensated for by a spatial modulation of the material nonlinearity with a period corresponding to the coherence length [2,3]. Active-passive hybrid waveguides combine the high optical quality of glass waveguides with the strong nonlinearity of poled polymers. Here, the guided modes interact via the evanescent field. For sum frequency (SF) generation in isotropic materials the phase mismatch is large, i.e. the coherence length is only a few microns, which increases by at least two orders of magnitude upon utilizing the mode dispersion of the waveguide [4].
Quasi-phase-matched Second Harmonic Generation in an Electro-optic Polymer Waveguide
Authors: Tomaru Satoru , Watanabe Toshio , Hikita Makoto , Amano Michiyuki , Shuto Yoshito , Itoh Hiroki , Yokohama Itaru , Asobe Masaki
Published: February 2023

Quasi-phase-matched(QPM) technique is very attractive for realizing frequency conversion devices, because it is easy to realize frequency conversion with high efficiency and to obtain a collimating beam. Therefore, many QPM studies have been undertaken mainly using LiNbO3 waveguides.[1-3] On the other hand, nonlinear organic materials have received considerable attention due to their large nonlinear coefficient. However, there have been few reports on quasi-phase-matched frequency conversion using these materials[4,5] because they are difficult to fabricate into waveguides with a precise periodic poling structure.
Thin Films of Organic Salts with Large Optical Non-Linearities by Organic Vapor Phase Deposition.
Authors: Burrows P.E. , Forrest S.R. , Buma T. , Sapochak L.S. , Schwartz J. , Ban V.S. , Forrest J.L.
Published: February 2023

Recently, single crystals of organic and organometallic salts1-3 have been shown to possess extremely large second order (χ(2)) NLO effects leading to a high second harmonic generation (SHG) efficiency. The naturally non-centrosymmetric crystal structures of these compounds eliminates the need for external poling as required for guest-host polymeric systems. Furthermore, these salts have a high optical damage threshold and sufficient stability with respect to temperature to withstand many conventional semiconductor fabrication processes. In particular, highly pure single crystals of the salt, 4'-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST)1, have been shown to have a value of χ(2) at least 103 times greater than that of urea.
Effects of Drawing on Second-Order Nonlinear Optical Coefficients of Poled Polymers
Authors: Watanabe T. , Tao X. T. , Nakayama M. , Kim J. , Deguchi T. , Miyata S.
Published: February 2023

Recently organic nonlinear optical (NLO) materials have been extensively investigated because of their large second-order nonlinear optical coefficients and ultra fast response in the field of optoelectronics[1]. In order to obtain a highly efficient second harmonic generation (SHG), the materials match the phase velocity over the long propagation distance for light at fundamental and harmonic waves. To realize phase-matching, a general technique is using natural birefringence in certain anisotropic crystal to compensate the refractive index dispersions between the fundamental and second harmonic wavelength and fulfill nω = n2ω. The advantages of birefringence phase-matching is that one can satisfy this condition relatively easy by rotating the crystal. Recently the bulk-type phase-matched SHG was observed for the first time from poled polymers with large positive birefringence[2]. The conversion efficiency of this SHG device is not enough because of small nonlinear optical coefficients. Large off-diagonal tensor components are required to improve the conversion efficiency of bulk type SHG devices. However the molecular design concept and their assembly to optimize off- diagonal tensor component are not clear. In this presentation, the effects of drawing on second order nonlinear optical coefficients of poled polymers will be discussed using A type main chain polymers and a side chain polymer.
Diagnostics of femtosecond laser pulses using films of poly(p-phenylenevinylene) (PPV).
Authors: Luther-Davies B. , Samoc M. , Samoc A. , Woodruff M. , Swiatkiewicz J. , Trebino R. , Delong K.W.
Published: February 2023

Poly(p-phenylenevinylene), abbreviated PPV, is a conjugated polymer having a very high third-order optical nonlinearity which we are investigating for possible use in ultrafast photonic switching at 800 nm [1]. A result from these investigations is that PPV can be very useful as an active material in devices used to diagnose very short laser pulses.
Optically initiated orientation of nonlinear photoisomers
Authors: Hill R. A. , Knoesen A. , Yankelevich D. R. , Twieg R.
Published: February 2023

Second order nonlinearities can be imposed in a disordered polymer film by poling. Electric field poling is the most common technique but poling can also be achieved optically. In optical poling, a sample is irradiated with linearly polarized light and the nonlinear molecules undergo successive isomerizations, contractions and relaxations and eventually become aligned perpendicular to the incident polarization.1 This photoisomerization can also increase the mobility of the nonlinear molecules within the polymer and permit improved alignment to an electric field.2 The previous reports of optically induced reorientation have used continuous-wave illumination and required long exposure times.3-11However, the trans-cis photoisomerization has been shown to be extremely fast.12 We are investigating the dynamics of the trans-cis isomerization and orientation of nonlinear stilbene molecules in the presence of an electric field by monitoring the changes in the second order nonlinearity. In our research we have used short optical pulses to initiate molecular reorientation by photoisomerization. The unstable cis-isomer of azobenzene is used to enable a transition between two states which both involve the stable trans-isomer. Because of the extreme speed with which the photoisomerization can be initiated, it could find an application in digital optical storage.
Electroluminescence from conjugated polymers
Authors: Friend Richard
Published: February 2023

Conjugated polymers can be processed as thin films, and can be used as the emissive or charge-transport layers in thin-film electroluminescent diodes. I will discuss the present understanding of the operation these devices, including the improvement to the efficiency that can be produced by the use of heterojunction devices.
Current Conduction and Electroluminescence Mechanisms in Molecular Organic Light Emitting Devices.
Authors: Forrest S.R. , Burrows P.E. , Shen Z. , Bulovic V. , McCarty D.M. , Thompson M.E.
Published: February 2023

Electroluminescence (EL) from vacuum deposited organic molecular heterojunction (HJ) devices can potentially yield red, green and blue light at levels of brightnesses and efficiencies adequate for viable flat panel displays1. However, to date, there has been little detailed analysis of the origin of EL and the current conduction mechanisms in these novel devices. The spatial distribution of EL in HJ devices using tris-(8-hydroxyquinoline) aluminum (Alq3) as the light emitting layer has been measured and shown to occur within a few hundred Ångstroms of the organic HJ.2 This was assigned to excitons created at the organic HJ subsequently diffusing into the bulk organic layer before radiatively recombining. Charge injection mechanisms in such structures, however, were not elucidated. In polymeric OLEDs, tunneling3 into the conduction bands of the organic material has been invoked to explain the observed current-voltage (I-V) and EL characteristics. However, given the low carrier mobilities characteristic of many organic materials and the difficulties in measuring and interpreting band offset data, the validity of simple band structure and tunneling models remains unclear.
TN and GHLCDs Fabricated by Non-Rubbing Techniques and an Overview of LCDs in Japan
Authors: Kobayashi S. , Iimura Y. , Saitoh T. , Suzuki H. , Hashimoto T. , Sugiyama T. , Katoh K.
Published: February 2023

Amorphous TN(twisted by 90°) and amorphous highly twisted chiral nematic (N*)(twisted by 300°) are utilized for fabricating TN and GHLCDs, respectively, and furthermore, photopolymer films are utilized for fabricating TNLCD and hybrid aligned N-LCD. These NLC alignment techniques are non-rubbing techniques and they make it possible to overcome the disadvantages of current rubbing technique. An overview of LCDs in Japan is also given.
Accelerated Degradation Studies of MEH-PPV*
Authors: Radousky H.B. , Madden A. D. , Pakbaz K. , Hagler T. W. , Lee H. W. H. , Lorenzana H. E. , Fox G. A. , Elliker P. R.
Published: February 2023

MEH-PPV is of interest due to its potential use as the active element in electroluminescent devices.1 The usefulness of these devices is limited at the present due to a variety of degradation mechanisms.2-3 We have studied one class of degradation in MEH-PPV using photoluminescence (PL).
New Polymers for Second-Order Nonlinear Optics
Authors: Lindsay G. , Stenger-Smith J. , Chafin A. , Hollins R. , Merwin L. , Yee R. , Nissan R. , Nadler M. , Henry R. , Wynne K. , Ashley P. , Hayden L. , Herman W.
Published: February 2023

Progress on mainchain syndioregic polymers for χ(2) applications is reported, An electro-optic coefficient, r33, of 8.5 pm/V @ 1.3 microns and loss of < 1 dB/cm was measured in a Mach-Zehnder interferometer waveguide fabricated by parallel plate electrode poling and photobleaching. This EO film has been stable at ambient room temperature for many months, and the long term thermal stablility is estimated to be ≥125°C if protected from UV radiation and air. Preliminary results on the preparation of a series of related polymers designed for low temperature fabrication of χ(2) thin films will be reported.
Polyurethane based polymers with improved stability of electrooptic properties
Authors: Zieba J. , Park C.-K. , Swedek B. , Prasad P.N. , Lee Kwang-Sup , Moon Ki-Jeong , Shim Hong-Ku
Published: February 2023

In the presented work we have investigated the basic chemical and optically nonlinear properties of two types of polyurethane based second order active nonlinear polymers.
Light Induced Spatial Modulation of Second-Order Optical Nonlinearity Via a Photoconducting Layer
Authors: Cohen Rami , Berkovic Garry
Published: February 2023

Poling organic polymers containing hyperpolarizable dye species can produce high second-order nonlinearities. One limitation for application to second harmonic generation is the difficulty to achieve phase matching. A solution may be periodic spatial modulation of the nonlinearity to achieve quasi phase-matching [1].
Two-photon absorption based optical recording in organic planar waveguide
Authors: Piyaket Ram , Cokgor Ilkan , McCormick Frederick B. , Esener Sadik , Dvornikov Alexander S. , Rentzepis Peter M.
Published: February 2023

Two-photon absorption based three-dimensional (3-D) memories have been investigated and demonstrated over the last years, providing potentials for high memory densities and parallel access for fast data rates. Figure 1 illustrates the basic principle by which information is stored and retrieved in these 3-D memories. Two photons with appropriate combined energy (for example, λ = 1064 and 532 nm) are introduced into the memory and are absorbed simultaneously by the memory material which consists of spirobenzopyran (SP) in a PMMA host matrix).1 The simultaneous absorption of the two photons by the photochromic molecule results in a bond dissociation transforming it into a new form with different properties, including the absorption spectrum as shown in Fig. 1. These two different molecular forms are defined as the non-written and written forms of the memory. When properly excited, the new molecular form emits fluorescence which can be detected during the read-out process. The peak fluorescence occurs at 660 nm.
Control of The Photoinduced Micro-Patterning of Nonlinear Organic Thin Films: From Molecular to Photonic Engineering
Authors: Brasselet Sophie , Zyss Joseph
Published: February 2023

The development of electrooptic polymers now stands at the onset of technological fruition as a result of almost two decades of intense molecular engineering studies and of the more recent maturing of semiconductor compatible integrated optics fabrication processes. Nevertheless, the full potential of organic systems for nonlinear optics(1) and related applications may not have been fully exploited so-far within the paradigmatic orientational scheme of a dipolar molecular diode structure coupled with an externally applied poling electric field at thermal equilibrium. In particular, such a configuration makes it difficult to implement (quasi)-phase matched gratings for (cascaded) quadratic NLO, guarantee polarization independant telecom device behaviour or engineer other propagative (e.g. soliton generation) or QED (e.g. microcavity) configurations. A different approach, whereby all-optical photoinduced processes are called-upon instead of thermally equilibrated ones and traditional 1-D systems are traded for more general 3-D multipolar molecules (e.g. octupolar, dipolar or a combination of these) opens-up new possibilities to adress these issues. It permits indeed to micro-pattern and control with subwavelength accuracy a continuous or pixellised spatial χ(2) tensorial distribution whereby the magnitude and ratios of macroscopic tensorial coefficients are balanced at will by phase and ellipsometric adjustment of the writing beams2.
Self-Imaging Holographic Optical Waveguides
Authors: Grebel H. , Graziani J. L. , Vijayalakshmi S. , Shacklette L.W. , Stengel K. M. T. , Eldada L. , Norwood R. , Yardley J. T.
Published: February 2023

Periodic structures exhibit an effect known as self-imaging[1-3]. The complex, amplitude distribution of the field, u(x,y,z) is self-similar such that, u(x,y,z) = u(x,y,z + L
s
). Here we address self-imaging by use of transverse gratings which extend throughout the entire waveguide (Figure 1). By use of photolithographic techniques in photopolymers, one has a simple means to match waves having dissimilar propagation constants without much loss.
Characterization of Electro-Optic Polymer Films using Decal Deposited Reflection Fabry-Perot Modulators
Authors: Wu L.-M. , Prêtre Ph. , Hill R. A. , Knoesen A.
Published: February 2023

Electro-optic (EO) properties of nonlinear optical polymers (NLPs), of key interest in any device application, are most widely measured with ellipsometric(1, 2) or interferometric methods.(3) The major drawbacks of these techniques are: a) with ellipsometry, the Pockels coefficients cannot be extracted independently, b) refractive indices must be obtained from other measurements, and c) these methods ignore multiple reflection effects in stratified samples. Waveguiding methods such as attenuated total reflection (ATR) measurements are capable of a complete linear optical and EO characterization of NLPs.(4) But the ATR prism complicates the angular scans, and waveguiding conditions over a large spectral range are difficult to fulfill with a single sample.
Recent Advances in the Translation of Large Microscopic Nonlinearities to Large Macroscopic Nonlinearities in Electro-Optic Polymer Films
Authors: Harper Aaron W. , He Mingqian , Wang Fang , Chen Jinghong , Zhu Jingsong , Sun Sam S. , Dalton Larry R. , Chen Antao , Garner Sean M. , Yacoubian Araz , Steier William H. , Chen Datong , Fetterman H.R.
Published: February 2023

Typical electro-optic polymers are characterized by second-order nonlinear optical (NLO) chromophores arranged polar-asymmetrically in an amorphous polymer matrix. It is believed that the electro-optic activity of workhorse NLO chromophores (e.g., DANS and Disperse Red) are of insufficient magnitude to be viable candidates for commercial device-quality materials.1 Consequently, much effort has been directed in the past few years toward the development of chromophores with device-quality magnitudes of molecular optical nonlinearities. Unfortunately, the translation of these so-called high-β chromophores to the expected bulk electro-optic activities in polymers generally has not been achieved. Recently, we have shown that this lack of electro-optic activity is due primarily to strong intermolecular electrostatic interactions between chromophores, which tend to align the chromophores in an antiparallel fashion, resulting in no net polar asymmetry in the bulk material.2,3
Four Photon Absorption in the Single Crystal Polymer PTS
Authors: Shim Hoon , Liu Mingguo , Stegeman George
Published: February 2023

Conjugated polymers belong to a class of materials which has proven to be one of the most fascinating and challenging developed to date for nonlinear optics. They, most specifically bis paratoluene sulfonate (PTS), have been shown to exhibit the largest third order nonlinearities and the strongest two photon absorption of any known material. [1] These properties are a direct consequence of the π-electron delocalization which occurs over multiple double and triple carbon bonds along the backbone chain. The strong one and two photon absorption which occurs in PTS implies that the one and two photon active excited states might also be accessible through even higher order nonlinear processes which satisfy the same symmetry relations between the ground and excited states. Although there have been sporadic reports of three and four photon absorption in semiconductors, four photon absorption has never been unambiguously measured in an organic solid state material before. [2] Here we report observation of four photon absorption in PTS at 1600 nm.
Third-order nonlinear optical property of platinum group metal complexes with square planar configurations
Authors: Kodzasa Takehito , Ushijima Hirobumi , Matsuda Hiro , Kamata Toshihide
Published: February 2023

The developments of novel materials having large third-order nonlinear optical susceptibility χ(3) and fast response give a considerable interest as the key subjects for future optoelectronic technology. It was proved in former researches that the large low dimensional delocalization field for optically excited electron is effective for large χ(3) value. Third-order optical nonlinearities of many materials, mainly inorganic semiconductors or organic conjugated polymers, have been investigated. Many inorganic materials have studied for their large χ(3) and thermal stability. On the other hands, organic nonlinear optical materials also have been noted, because they have advantages of fast optical response, architectural flexibility and ease of fabrication.
Fabrication of the One-Dimensional Superlattice in the Epitaxially Grown Film of Platinum Dioxime Complexes
Authors: Yamamoto Kaoru , Kamata Toshihide , Yase Kiyoshi , Yoshida Yuji , Mizukami F. , Ohta T.
Published: February 2023

A large number of studies have been done for multiple quantum wells of inorganic semiconductor, because confined electronic system in a thin layer shows various properties essential for optoelectronic application. Since the quantum size effect increases when the electron system approaches lower dimension, fabrication of higher order confined structures has been attempted to advance the properties. On the other hand, there are many substances having one-dimensional structure in the nature. It can be thought that the one-dimensionality is prospective to realize a higher order confined system.
Enhanced Degenerate Four-Wave Mixing in an Endohedral Metallofullerene Through Metal-to-Cage Charge-Transfer
Authors: Marciu D. , Figura C. , Wang S. , Heflin J.R. , Burbank P. , Stevenson S. , Dorn H.C.
Published: February 2023

Since the initial discovery and development of a technique for macroscopic preparation of the archetypal and most abundant fullerene C60, a wealth of fullerene-based structures have been produced including higher fullerenes, charge-transfer complexes, fullerene derivatives, superconducting exohedral-doped fullerenes, and carbon nanotubes. One of the most intriguing fullerene classes is the endohedral fullerene in which the spheroidal molecular structure is employed to encapsulate a small number of atoms (one to four) internal to the cage.1,2 Until recently, the difficult separation process of endohedral fullerenes had limited their availability to submilligram levels. Consequently, initial studies of these materials had primarily been restricted to electron paramagnetic resonance (EPR) and linear spectroscopy. EPR measurements demonstrated that, for the case of La@C82, the La atom transfers three electrons to the fullerene cage and resides in the +3 oxidation state.2 Metal-to-cage charge transfer appears to be a common feature of transition metal-containing endohedral metallofullerenes. Meanwhile, nonlinear optical studies of empty-cage C60 and C70 have shown that these materials possess both large third order susceptibilities χ(3)(−ω4;ω1,ω2,ω3)3 (~10-11 esu) and strong optical limiting behavior.4,5 We report here the first nonlinear optical measurements of an endohedral metallofullerene and find a dramatic enhancement in the third order nonlinear optical response. Degenerate four-wave mixing (DFWM) experiments on solutions of the endohedral metallofullerene Er2@C82 show that the metal-to-cage charge transfer provides a mechanism for increasing χ(3)(−ω4;ω1,ω2,ω3) by orders of magnitude relative to empty-cage fullerenes.
Precise Determination of Electro-Optic Coefficients for Poled Polymeric Films with Ellipsometric Technique
Authors: Lee M. H. , Lee H. J. , Hwang W.-Y. , Oh M.-C. , Ahn J.-H. , Han S. G. , Won Y. H.
Published: February 2023

The electro-optic (EO) effect was the earliest nonlinear optical(NLO) phenomenon discovered. The EO effects are the change in the refractive index resulting from the application of a dc or a low frequency electric field. NLO polymeric materials have been of great interest because of their potential use for optical devices. Poled polymers are one of the promising materials for EO applications. Our purpose is to measure the linear EO effects of poled polymeric films precisely. In this paper, the determination of the linear EO coefficients of poled polymeric films with the ellipsometric reflection technique has been discussed in detail. The interference effects were introduced with the spurious signal. The magnitude and phase retardation of the spurious signal were obtained empirically. We have analyzed and demonstrated experimentally with DANS and DR1 side chain poled polymer.
Two-photon Fluorescence Cross Section Measurements Calibrated Using Hyper-Rayleigh Scattering
Authors: Kaatz Philip , Shelton David P.
Published: February 2023

Two-photon fluorescence of Rhodamine B (RhB) measured relative to hyper-Rayleigh scattering of para-nitroaniline (pNA) gives the absolute two-photon absorption cross section of RhB at λ = 1064 nm, δ = 2.2 ± 0.2 × 10-50 cm4 s, and is 3-9 × smaller than previous results.
Modeling Relaxation Mechanisms in Nonlinear Optical Polymer Films
Authors: Singer K.D. , Dureiko R.D.
Published: February 2023

The thermal and temporal relaxation of polar order in polymeric electro-optic materials remains an important problem in the realization of these materials in applications. Fortunately, much progress has occurred in the development of more stable high- temperature materials. These developments, however, require that a regime for accelerated testing be established. Thus, measurement techniques and associated models which can connect the time and temperature behavior of new materials need to be refined. To this end, we report here on progress in the development of a new frequency domain technique for measurement, as well as progress on the development of a widely applicable model for chromophore orientational relaxation.
Molecular-Level Engineering of Polymer-Based Light-Emitting Devices
Authors: Rubner Michael
Published: February 2023

Molecular-level processing schemes have been utilized to fabricate light emitting thin film devices from a variety of materials including conjugated polymers and polymers containing tris-chelated Ru(II) complexes.
Wavefront Analysis of Non-Spherical Surfaces
Authors: Hemenger Richard P.
Published: February 2023

By specializing to the problem of axial imaging by surfaces with rotational symmetry a complete wavefront analysis is possible. Applications to multifocal lenses are given.

A wavefront analysis using elementary methods is possible for the case of axial imaging by an arbitrary rotationally symmetrical surface. Optically this approximates an eye fitted with a centered multifocal simultaneous vision contact lens. The essential assumption is that paraxial optics holds at each surface except one surface of the contact lens.
Corneal Topography and the Hirschberg Test.
Authors: Brodie Scott E.
Published: February 2023

An alternative approach to the problem of reconstucting the topography of the cornea by measurement of images formed by the corneal reflecting surface may be had by considering the effect of aspherical corneal topography on the "Hirschberg Test," a traditional clinical maneuver for the estimation of ocular misalignment.
An Experimental Model of Bifocal Vision
Authors: Zhang Xiaoxiao , Bradley Arthur , Ye Ming , Thibos Larry
Published: February 2023

Contact and intraocular lens designers and manufacturers have
considered many strategies to provide presbyopes with good near and
distant vision. In particular, considerable effort has been made
recently to design simultaneous vision bifocal contact and intraocular
lenses (CL and IOL). These simultaneous vision bifocals create dual
images simultaneously on the retina (we will refer to this as
monocular diplopia). Very little is known about the visual impact of
such an optical situation.
Sculptured Surfaces for the Design and Evaluation of Aspherics
Authors: Dürsteler Juan C.
Published: February 2023

New designs of Aspherics, in the most general sense of the word (including PAL’s), demand higher degrees of freedom in the mathematical formalism that supports the surface definition. The last 20 years have seen the arising of powerful surface design methods that have been succesfully exploited in different areas such as: aeronautics (wings and bodies of planes), naval craft (ship hulls, sails), car body design and so on. These methods, generally known as Sculptured Surface methods have a high number of degrees of freedom, which make them ideal for the design of PAL’s and Aspherics in general.
Fitting Varifocal Lenses: Strain as a Function of the Orientation of the Eyes
Authors: Menozzi M. , Buol A. v. , Krueger H. , Miège Ch. , Pedrono C.
Published: February 2023

Prolonged or intense oculomotoric muscle use may cause strain. This strain is rearly perceived because at many visual tasks the strain remains subliminal due to the small amount by which the eyes are displaced from their muscular equilibrium. However, some visual tasks require a large angular displacement of the eyes in relation to the head. In such cases, the displacement is not maintained for a long time. Either the eyes move back to their initial position or, if the point of fixation has to be maintained, head movements are performed in order to compensate the displacement of the eyes in relation to the head. Hartmann (1987) showed that with an increasing angular change of the direction of fixation, eye displacement is increasingly achieved by the help of head movements. If only an energetically point of view is considered, changes in direction of fixation should preferably be carried out by movements of the eyes rather than by movements of the head due to the big difference between the moment of inertia of the eyes and the one of the head.
Zemike polynomial description of ophthalmic surfaces
Authors: Webb Robert H.
Published: February 2023

Surfaces of interest in vision research are often nearly spherical. A useful descriptor for such surfaces is one which allows comparison to a sphere or to other simple surfaces. Zernike polynomials1 provide such a descriptor. We show here ways in which this complete set of functions may be used to describe the wavefront necessary for perfect correction of refractive error and the retina, and with modification, the cornea.
A Noninvasive Alternative to Radial Keratotomy
Authors: Horner Douglas G. , Wheeler William H. , Soni P. Sarita , Gerstman Daniel R. , Heath Gordon G.
Published: February 2023

Over the last 20 years a number of new procedures have been introduced to reduce myopia and astigmatism. These procedures fall into two categories, those involving surgery and those utilizing contact lenses.1,2 All of them attempt to flatten the curvature of the cornea in order to reduce its refractive power.
Ocular Aberrations and Accommodation
Authors: Atchison David A. , Collins Michael J. , Wildsoet Christine F.
Published: February 2023

It has been generally considered that on the visual axis in monochromatic light, the eye is limited only by diffraction effects for pupil diameters up to 2mm1 and thereafter is predominantly affected by spherical aberration. Most eyes are considered to suffer from positive spherical aberration when unaccommodated, which tends to negative spherical aberration upon accommodation2-4. For positive spherical aberration, rays passing through the periphery of the pupil intercept the optical axis in front of the rays passing nearer the centre of the pupil.
Creating Ophthalmic Standards in Practice
Authors: Campbell Charles , Humphrey Allergan
Published: February 2023

International standards for the ophthalmic industry and the ophthalmic professions are created by the International Standards Organization in its Technical Committee 172 (Optics). Within this technical committee (TC 172) two subcommittees, Subcommittee 7 (Ophthalmic, Endoscopic and Metrological Instruments and Test Methods) (SC 7) and Subcommittee 8 (Ophthalmic Optics) (SC 8) are primarily involved with the work on ophthalmic optics. The subcommittees are composed of experts, chosen by the sponsoring national bodies for their expertise in the areas which are under consideration for standardization. In this way the countries which are members support the effort of standard writing while at the same time insuring that their interests are represented in the process.
Optical Properties of Bifocal Intraocular Lenses
Authors: Kusel R.
Published: February 2023

Apart from monofocal intraocular lenses (IOL) increasing numbers of bifocal IOLs are implanted. Besides the basic refractive power necessary for far vision these lenses have an additional refractive power which allows near vision. Since two images are superimposed upon each other, the contrast of the retinal image is reduced. If the correct lens is implanted the patient needs no glasses, otherwise he will need only monofocal glasses.
Dispersion in Ophthalmic Lenses
Authors: Davis John K. , Waido Richard P.
Published: February 2023

Dispersion causes lateral chromatic aberration, lowering off-axis contrast. Visual and analytical experiments are in crude quantitative agreement. Older and recent studies are presented and compared.
Non-prescription sunglasses - how good are they in relation to BS2724:1987?
Authors: Fowler Colin
Published: February 2023

Mass produced sunglasses constitute a large worldwide market. These articles are promoted both as protective devices, and also as objects of fashion. But how good are they at achieving their optical design function?
Designing Multifocal Contact Lenses and IOL's
Authors: Hemenger Richard P.
Published: February 2023

I describe a straightforward procedure for designing multifocal contact lenses or IOL's having desired optical properties.
The Stiles-Crawford effects in normal and anomalous color vision.
Authors: Walraven Pieter L.
Published: February 2023

Stiles and Crawford (1933) showed sixty years ago that the sensitivity of the retina varies with the place of entry of the light in the pupil, and thus with the direction of incidence of light upon the retina. Sensitivity is generally greatest near the centre of the pupil and progressively decreases for more eccentric entry points. This phenomenon is known in the literature as the Stiles-Crawford effect of the first kind (SCE I). The hue shift associated with the SC-effect was discovered by both investigators (Stiles 1937) in a further study of the retinal direction effect. This effect is called the chromatic Stiles-Crawford effect, often also referred to as the Stiles-Crawford effect of the second kind (SCE II).
The Effect of the Eye's Chromatic Aberration on Eccentric Photorefraction
Authors: Roorda Austin , Bobier William R. , Campbell Melanie C.W.
Published: February 2023

Photorefraction describes a family of techniques used to measure the refractive state of the eye. The technique is commonly used for children or uncooperative subjects whose limited attention span prevents accurate measurements using the traditional techniques, such as retinoscopy. The technique can be separated into two methods, eccentric and coaxial photorefraction. All methods employ a small light source at a camera which is directed toward the eye. Some of the light reflected back from the eye enters the camera aperture. The result is a photorefracted pattern whose size is determined by the parameters of the experiment, particularly the refractive state of the eye and the pupil size. Both methods have limited working ranges and a dead zone in which changes in refractive error cannot be measured.
An Optical Method for Mapping the Power and Cylinder of Multifocal Progressive Lenses
Authors: Keren Eliezer , Berman Reuben , Hochner Michel
Published: February 2023

The fast progress in the design and manufacture of complex lenses for visual correction has not been accompanied by a comparable progress in test and measurement equipment. The traditional focimeter averages an area of several millimeters, and requires a tedious process of scanning several thousand points on the surface, which would take hours to complete. The power is measured using a beam in a direction normal to the back surface, which in general does not correspond to normal usage.
Photoacoustic Detection of Atmospheric Absorptions Using a cw Ring Dye-Laser
Authors: Reddy K. V.
Published: February 2023

The intracavity dye-laser photoacoustic-detection technique is extremely sensitive permitting detection of weak absorptions in benzene1 with cross sections as low as 10−27 cm2 at 9.3 kpa (70 Torr) of vapor pressure (absorption coefficient α ~ 10−9 cm−1). The high sensitivity of this technique makes it useful for detecting weak atmospheric absorptions in the near-IR and visible regions. Atmospheric absorption characteristics of high- and low-energy lasers (for example the chemical iodine laser at 1.315 μm and the blue/green laser at 496 nm) are required for selecting and optimizing a particular laser for communications and military applications requiring a long pathlength in the atmosphere. The photoacoustic detection technique is advantageous because it directly measures only the absorption loss which is the principal source of thermal blooming in high-energy laser propagation. Moreover, the small size of photoacoustic cells makes them ideal for quantitative studies of collisional broadening, lineshape, temperature dependence, and the simulation of real-time airborne variations. Similar studies are tedious and time-consuming tasks with large-volume multipass cells.
Photoacoustic Measurement of Refractive Index Profile in Glass Waveguides
Authors: Cheng Ken , Swimm Randall , Yeung Peter
Published: February 2023

Photoacoustic measurements provide a method of indirectly measuring the refractive index profile in glass waveguides. This technique therefore allows an independent verification of index profile measurements made using the conventional prism coupling method.
Photo-acoustic Study of Zircon-based Ceramic Pigments and Glasses Containing High Concentrations of Copper and Cobalt
Authors: Parke S. , Warman G.P. , Mellor J.H.
Published: February 2023

Zircon stains for the ceramics industry have been produced commercially since 1949. At present the commercial stains are mainly zircon (ZrO2.SiO2) doped with vanadium, praseodymium or iron to produce blue, yellow or pink colours respectively. A research programme is in progress to study the factors controlling the colours of these zircon-based glaze stains and photo-acoustic spectroscopy has been used to monitor the colours of stains prepared by different routes. Spectra of coral pink tiles reveal a broad absorption between 600 nm and 350 nm which is yet to be identified. A blue glaze has a spectrum which suggests the presence of V4+ but the yellow glaze has a sharp cut-off near 470 nm which is quite uncharacteristic of the spectrum expected from Pr3+. Single crystal specimens of the doped zircon are being prepared and these too will be examined photo-acoustically. An attempt will also be made to obtain transmission measurements.
Acoustic Detection of Magnetic Resonance
Authors: Coufal H.
Published: February 2023

A simple device allowing the detection of acoustically magnetic resonance phenomena in conventional CW-spectrometers using field modulation is described. Results obtained with this technique are compared with conventional detection methods. Modulation frequency and amplitude data, as well as the dependence of the signal on thermal properties of the sample and the coupling gas, are discussed. It is shown that signal intensities reflect the detection scheme much more than the spectral characteristics caused mainly by the excitation mechanism.
Picosecond Photoacoustics Using an Elliptical Acoustic Cell
Authors: Heritier Jean-Marc , Fouquet J.E. , Jackson Kenneth , Siegman A.E.
Published: February 2023

We report the development of a photoacoustic cell in the form of an elliptical cylinder, in which the acoustic impulse generated by a laser beam passing along one focal line is focused onto a cylindrical piezoelectric transducer located along the other focal line. The sensitivity and clean impulse response of this cell will be employed in photoacoustic experiments presently under way using single and multiple groups of picosecond laser pulses.
Improvements of an acoustic window cell
Authors: Helander Per
Published: February 2023

A new type of photoacoustic cell has been developed. It consists of a sapphire-window and a piezoelectric crystal mounted tightly together in a metal frame (Figure 1). The sapphire-window is sensing temperature variations in the sample due to absorption of pulsed radiation. The sapphire is then exhibiting a periodical length expansion which is measured with the piezoelectric crystal. The new cell is in some senses similar to the acoustically closed cell using a gas volume and a microphone to measure the variation in the sample temperature. It has for instance the same chopper frequency dependence. The methods for depth discrimination2 and for absolute determination of absorption coefficient suggested for the closed cell3-6 can therefore be applied to this new cell. The main difference to the usual cell is that this new cell is open and is well suited for measurements on liquids. Measurements on liquids have been done by Patel et al7 using a hydrophone. An open photoacoustic cell gives the experimentator additional freedom. The sample can be affected during the measurement for instance by addition of substances or by exposure to a controlled atmosphere. The cell can also be modified to allow the sample to flow through the cell which gives the possibility to make on line measurements in a system with flowing liquids. The new cell gives the additional freedom to measure from the bottom or from one side as well as from the top of a sample volume.
Detection of EPR in Metallo-Organic Complexes Using the Photoacoustic Effect
Authors: Goldammer E.v. , Netzelmann U. , Pelzl J. , Vargas H.
Published: February 2023

The photoacoustic effect recently has been applied to the detection of microwave absorption in metallic compounds /1,2/ and in insulating materials /3/. Although the calorimetric detection in EPR is already a well established technique, its combination with the acoustic response of a transducer gas may deliver some new information.
Photoacoustic Chopping Frequency Studies on Uncoated Sapphire and Zinc Selenide
Authors: Fernelius Nils C.
Published: February 2023

Photoacoustic chopping frequency studies similar to those reported elsewhere1-4 have been performed on uncoated CVD ZnSe samples at 10.6 μm and on uncoated sapphire, A12O3, samples at 1.3 μm.
Image Formation by Integrated Scanning
Authors: Burt J.A.
Published: February 2023

In conventional optical instruments, imaging implies that all the rays passing through the lenses and reflecting from the mirrors of the instrument converge in the image plane in such a manner that a magnified duplicate of the object plane is formed. However, this correspondence between the object and the image need not always be present in an optical instrument, in which case we say the instrument is non-imaging. We do not consider such an instrument in this report. We do wish to discuss, however, a loosely-defined class of optical systems called scanning systems. This class includes systems with multiple transmitters and receivers, complicated scanner motions, synthetic apertures, etc. We direct our attention, however, only to systems where the object is time-sequentially scanned by a spatially localized beam. Furthermore, the entire instantaneous image, or intermediate image, produced by the scanning system is integrated according to some summation law. The integrated signal constitutes the intensity of the image point corresponding to the object point being scanned at that instant. When all integrated image points are displayed on a map according to their corresponding object positions we have the integrated scan image, and hence we call this system integrated scanning.
Nonergodicity and Light Scattering from Polymer Gels
Authors: Chaikin P. M.
Published: February 2023

The intensity and time correlation function of light scattered from polymer gels change as different parts of the sample are explored because the sample is nonergodic (time averages differ from ensemble averages) as a result of finite rigidity, which leads to constrained inhomogeneities. We describe a direct technique for ensemble averaging by moving the sample.
High-Speed Flow Measurements in a Two-Stroke Engine by Photon-Correlation Laser Velocimetry
Authors: Fansler Todd D. , French Donald T.
Published: February 2023

The two-stroke-cycle engine has recently attracted renewed interest as a potential passenger-car powerplant because of its high specific power output. The performance and emissions of these engines have long been recognized to depend critically on scavenging,the gas-exchange process which removes combustion products from the cylinder and brings in fresh air. Nevertheless, comparatively little quantitative experimental information on the scavenging flow fields in practical two-stroke engines is available.