bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-resolved FTS measurements of chemical kinetics and dynamics
Authors: Sloan J.J.
Published: February 2023

We have developed an instrument for carrying out submicrosecond time-resolved Fourier transform spectroscopic measurements on transient infrared spectra and have applied this to measurements of the spectra of intermediates and products from laser-initiated gas phase processes. We carry out the experiments in a low pressure flow reactor. Typically, we admit a molecular reagent and a precursor at the entrance of the reactor and photodissociate the precursor with an excimer laser, thereby creating a reactive fragment. The latter reacts rapidly with the molecular reagent, giving vibrationally and rotationally excited products. The excimer laser traverses the flowing gases at the centre of an observation region defined by a multipass Welsh optical cell which has its axis at right angles to the direction of the laser. The optical cell focuses the infrared chemiluminescence emitted by the reaction products into the entrance optics of a Michelson interferometer. We record the interferogram produced by the infrared detector of this interferometer at accurately known time intervals following the initiation of the reaction, using a data acquisition system which we have developed for fast time-resolved Fourier transform spectroscopy (TRFTS). Our implementation of TRFTS places no limit on the spectral resolution of the measurement, while providing a one microsecond time resolution. Typically, we use a spectral resolution which is adequate to resolve the vibrational - rotational spectra of hydrides and small molecules such as CO, NO, CO2, etc. Larger molecules are treated by using spectral simulation and deconvolution techniques to estimate the band intensities. In either case, the intensities of the transitions are used to calculate the populations of the vibrational-rotational states as a function of time after the initiation of the reaction. The dynamics of the process which forms the observed products are deduced from these data. The sum of the emission intensities gives a measure of the total amount of product formed, and the time dependence of the latter gives the overall kinetics of the process.
High Information Time-Resolved Fourier Spectroscopy
Authors: Guelachvili Guy
Published: February 2023

A new feature is added to High Information Fourier Spectroscopy: Time Resolution, which principle was first proposed in 1970 by Murphy and Sakai in Aspen.
High Resolution Fourier Spectrometry of the Nitrogen Molecular Ion
Authors: Davis Sumner P. , Nguyen An-Dien , Michaud Françoise , Roux Françoise
Published: February 2023

The spectrum of

N
2
+

has been and still is the subject of many investigations, mainly because of the role this ion plays in electric discharge plasmas, and atmospheric phenomena. Optical diagnostics and radiative modeling require accurate spectroscopic data (wavenumbers, molecular constants, transition probabilities) to predict the radiation of air, for example in the re-entry of spaces vehicles in the earth's atmosphere. A comparison between the experimental spectrum and a numerical simulation shows important disagreements when the perturbations are not modeled (1). The aim of the present work is to carry out a more complete deperturbation of the strongly perturbed

N
2
+

first negative system

B
2

Σ
u
+

→

X
2

Σ
g
+

. Line shifts of several cm-1 can be observed.
Fiber Optic Fourier and Double Fourier Interferometer: progress report
Authors: Zhao P. , Mariotti J.-M. , Léna P. , du Foresto V. Coudé , Perrin G.
Published: February 2023

Fiber optic Fourier transform spectrometer(FTS) may find its applications in gas sensing, space astronomy, etc. because of its compactness, low cost, etc.. Similarly, Fiber optic double Fourier interferometer is very attractive for double Fourier interferometric imaging(DFII) with telescope array. In both fiber optic FTS and fiber optic DFII, all optical operations are carried out with guided optics(optical fiber and directional coupler). Beams are transported in fibers. Beam splitting and combining are performed by directional couplers. Optical path delay is generated by stretching fibers(or, probably with combination with optical switchs) which are usually wrapped onto piezoelectric(p/z) tubes driven by high voltage.
Pressure Broadening in CO2
Authors: Johns J. W. , Lu Z.
Published: February 2023

Careful measurements of pressure broadening in CO2 have been made in the v3 band of CO2. The sample was contained in a 2m long multiple traversal cell set for four transits. The long pathlength allowed very low partial pressures of CO2 to be used. The temperature could be set anywhere between room temperature and 200 K and several recordings were made in this range. Nitrogen, oxygen and air (actually mixtures of pure nitrogen and oxygen since laboratory air contained far too much CO2) were used as collision partners at pressures up to 200 Torr. The spectrometer was a modified (1) Bomem DA8 instrument. With an InSb detector and a CaF2 beam splitter we were able to attain signal to noise ratios between 1000:1 and 2000:1.
Long-Path FTIR Spectroscopy at Low Temperatures
Authors: McKellar A.R.W.
Published: February 2023

A new absorption cell interfaced with a Bomem DA3.002 Fourier transform spectrometer has recently been put into operation. It is 5 m long and is capable of paths of up to 200 m at temperatures as low as 20 K. Compared to its 3.5m long predecessor,1,2 it gives longer paths, and, more importantly, has a larger optical aperture (f/25 vs. f/55). The result is improved sensitivity and the capability of higher spectral resolution. The enhanced throughput enables much better performance in the difficult "far" infrared region below the cutoff (≈ 1800 cm-1) of the InSb detector.
University of Denver Infrared Spectral Atlases
Authors: Goldman A. , Blatherwick R.D. , Murcray F.J. , Murcray D.G.
Published: February 2023

Atmospheric and laboratory atlases were generated from spectra obtained with the University of Denver Michelson type interferometer balloon-borne spectrometer systems for solar absorption spectra. Prior to 1987, only 0.02 cm-1 resolution spectra were available but since then 0.002 cm-1 resolution spectra are used. The stratospheric atlases cover many spectral intervals and also provide tables of line positions and identifications. High sun spectra are used for solar lines identifications. Latest editions of these atlases include selected sections in the 760-1950 cm-1 and 800-1700 cm-1 regions at 0.02 cm-1 and 0.002 cm-1 resolutions respectively. In addition to the stratospheric atlases, the University of Denver ground-based and laboratory spectra atlases will be presented. The laboratory spectra of many molecules relevant to stratospheric chemistry have been obtained.
A Method of Remotely Measuring Trace Gases in the Atmosphere Using Thermal Emission Fourier Transform Spectroscopy and Singular Value Decomposition of Atmospheric Spectra
Authors: Hayden Andreas
Published: February 2023

There is a need by civilian and government agencies for a means of passively detecting and measuring trace gases from remote sites. The techniques described in this paper may be used for remote monitoring of: adherence to environmental standards and regulations, process control, and local and global environmental conditions. Using an emission Fourier Transform Spectrometer (FTS) coupled with our Orthogonal Background Suppression (OBS) techniques we have been able to quantitatively measure the column density (nc) of trace gases in simulations and controlled releases under strong background conditions.
Overview of ATMOS and Lessons Learned
Authors: Gunson Michael R.
Published: February 2023

This paper presents an overview of the atmospheric trace molecule spectroscopy (ATMOS) experiment from four Space Shuttle flights with a discussion of future prospects and challenges for this technique.
Recent progress in the spectroscopy of atmospheric molecules
Authors: Flaud J.-M.
Published: February 2023

During recent years a number of molecules of atmospheric interest have been studied in the laboratory in order to obtain the best possible spectral line parameters: line positions, intensities, widths and variation of these parameters with respect to temperature. The spectral line parameters are indeed essential to perform reliable and precise retrievals of optical remote sensing measurements in the atmosphere. The present talk will be devoted to the presentation of recent improved results concerning three molecules of atmospheric interest, namely ozone, nitric acid and nitrogen dioxide stressing mainly recent progress in theoretical models. It is indeed usually not possible to derive complete sets of spectral line parameters from experiment only.
Recent Advances in Submillimeter Remote Sensing and Analysis
Authors: Carlotti Massimo
Published: February 2023

The spectral region of submillimeter-waves (from 10 cm-1 to 200 cm-1) has proven to be suitable for the remote sensing of the atmosphere in terms of the number of species that can be observed, the intensity of the transitions that produce spectral features, and the diurnal coverage of the emission measurements that can be obtained. Fourier Transform spectrometers have been built for this purpose at the Istituto di Ricerca sulle Onde Elettromagnetiche (IROE) [1] and at the Smithsonian Astrophysical Observatory (SAO) [2]. Both instruments had several successful flights in which they measured the emission of the atmosphere, from a balloon-borne platform, with the limb-scanning observation technique. The analysis of the spectra has two main objectives:

i) identification of atmospheric constituents through the assignment of the observed spectral features to specific transitions,

ii) determination of the altitude distribution (profile) of the molecules that have been identified.
Practical Wavelength Calibration Considerations for UV-Vis FTS
Authors: Salit Marc L. , Travis John C. , Winchester Michael R.
Published: February 2023

Wavelength accuracy is a key characteristic of FTS, and impressive results are available with relative ease. Assuming adequate signal-to-noise ratio, wavelength uncertainty arises from two primary phenomena — the effect of using a finite size aperture (and photon detector), and from cosine errors arising from imperfect alignment of the sample and reference beams. These effects are typically small enough to ensure uncalibrated accuracy of about 1 part in 105. Significant improvement can be attained through a single point, multiplicative calibration approach, which has been reported to reduce uncertainties to several parts in 108. In fact, relative line positions for strong lines within a given spectrum can be determined with a precision of several parts in 109. [1]
Measurements of Spectral Lineshape Parameters of Important Infrared-active Gases in Planetary Atmospheres at Relevant Temperatures
Authors: Nemtchinov V. , Li Z. , Varanasi P.
Published: February 2023

Twenty-five years of experience with cooling spectroscopic samples to planetary atmospheric temperatures in the laboratory, the acquisition of a state-of-the-art Fourier-transform spectrometer, and an accurate non-linear least-squares line-fitting routine have enabled us to obtain infrared line intensities, collision-broadened linewidths, lineshifts, and some aspects of the collision-broadened lineshape with unprecedented accuracy. We present in this paper some of the results obtained in our laboratory in the fundamental bands of CO, CO2, N2O, CH4, CH3D, C2H2, and NH3 at temperatures and other conditions relevant to various planetary atmospheres. A critical comparison with other published work, including some well-known spectroscopic databases, and some revealing trends as to the variation of the spectral line parameters with temperature are presented.
Measurements of the Instrumental Lineshape of a High Resolution Ftir Using a 3.39 µm HeNe Laser
Authors: Bell William , Paton-Walsh Clare , Vance Alan
Published: February 2023

We describe here how a 3.39 µm HeNe laser can be used to measure the instrument lineshape of a high resolution FTIR used for remote sensing of the stratosphere.
Progress in FTIR Applications for Gas Analysis
Authors: Stuffier Timo , Bittner Herman , Eisenmann Thomas , Mosebach Herbert
Published: February 2023

New applications for remote sensing and laboratory measurements for gas analysis using FTIR systems from Kayser-Threde and another manufacturer are presented in this paper. It represents a summary of the latest progress in FTIR technology induced as feedback from different customer applications, currently running research projects, and hardware optimizations.
Progress on the NIST IR-vis-UV Fourier transform spectrometer
Authors: Nave Gillian , Sansonetti Craig J. , Griesmann Ulf
Published: February 2023

Two years ago, NIST acquired a high-resolution Fourier transform spectrometer (FTS) from the Los Alamos National Laboratory [1, 2], The instrument has an unapodized spectral resolution of 0.0025 cm-1. We currently have optics and detectors to cover the wavelength range 200 nm to 2.5 μm, and will soon obtain a CaF2 beamsplitter to extend the range to around 8 μm and a KCL beamsplitter to cover the region 8-18 μm.
Measurements of the Schumann-Runge Bands of O2 with VUV-FT Spectrometer and Synchrotron Radiation Source
Authors: Yoshino K. , Esmond J.R. , Parkinson W.H. , Thorne A.P. , Murray L.E. , Cox G. , Learner R.C.M. , Ito K. , Imajo T. , Mastsui T. , Cheung A. S.-C. , Leung K.-S.
Published: February 2023

Current research on the Earth’s upper atmosphere requires molecular parameters of unprecedented detail and accuracy. State-of-the-art models of the vacuum-ultraviolet (VUV) absorbing properties of the atmosphere call for absorption cross sections with details on the scale of the Doppler linewidths (i.e., 0.1 to 0.15 cm−1 at 295 K). As a consequence, spectroscopic data at resolving powers of the order of 106 are needed. Current particular needs are for ultrahigh resolution absorption cross section data for some bands of NO and O2 in the UV to VUV region. To meet some of these requirements, we have used a UV Fourier transform (FT) spectrometer at Imperial College (IC) to measure the Herzberg I bands of O2 [1,2] and the δ (0,0) band of NO [3]
Laser-Induced Fluorescence and High-Resolution Fourier-Transform Spectrometry
Authors: Bacis R.
Published: February 2023

The invention and development of Fourier transform spectrometers (F.T.S.) in France, at Laboratoire Aimé Cotton, marked a turning point in the acquisition of high-quality spectroscopic data, mainly after implementation of the third generation apparatus (1). F.T.S. are now widely used in absorption spectroscopy (mid-and near infrared), but have also been used to study emission spectra. The first high resolution F.T. molecular electronic spectra recorded in emission were obtained in 1977 (2, 3). Shortly afterwards, laser induced fluorescence (L.I.F.) was recorded on an F.T.S. introducing selectivity via the excitation mechanism, and allowing fluorescence to be recorded from the laser line (visible) out to a few pm in regions inaccessible to other dispersive techniques (4,5). The main advantages of this technique are now well known (6). It has been proved invaluable in the study of the crowded spectra of high temperature molecules (e.g. transition metal halides), and in the characterisation of low lying excited electronic states. This paper uses examples of recent work on CuCl2 to illustrate the advantages of using a cold source (free-jet expansion) and the use of optical-optical double resonance techniques to study lithium and iodine dimers.
Improved Time-resolved Fourier Spectroscopy
Authors: Weidner H. , Peale R. E.
Published: February 2023

Fourier spectroscopy is widely acknowledged as a powerful tool for steady-signal spectroscopy. It is becoming popular also for time-resolved measurements with step-scan interferometers providing for the widest range of possible time constants and repetition rates. The simpler, more numerous continuously scanning interferometers have seemed less suitable for time-resolved measurements because such data acquisition needs to be more or less closely synchronized to the continuous stream of sampling requests issued by these instruments. Of the several schemes for TRS with continuous-scan instruments, the interleaved or stroboscopic technique least restricts the time constant and repetition rate of the transient events, but this method is prone to artifacts and noise [1,2,3]. Small variations of the interferometer-mirror speed are a source of noise and possibly artifacts [3,4], Our “Event-Locked” data acquisition / analysis method eliminates these problems by reducing the need to synchronize the data acquisition to the scanning motion of the mirror, which simultaneously simplifies the experiment [5].
Airborne Emission Spectrometer
Authors: Rider David , Beer Reinhard , Worden Helen
Published: February 2023

The Airborne Emission Spectrometer (AES) is a Fourier transform spectrometer designed for remote sounding of the troposphere from an aircraft platform. The instrument covers the 650 cm-1 to 4350 cm-1 spectral range with a resolution of better than 0.1 cm-1. The primary focus of AES investigations is to study the distribution of tropospheric ozone and the factors controlling the formation and distribution of tropospheric ozone. However, having access to a wide variety of atmospheric constituents, the instrument has proven to be useful in several remote sensing applications. The instrument has been deployed on NASA’s DC-8, P-3B and C-130Q aircraft, collecting infrared spectra over a wide range of targets and atmospheric conditions.
Infrared Chemical Imaging
Authors: Lewis E. Neil , Kidder Linda H. , Levin Ira W. , Kalasinsky Victor F. , Lester David S.
Published: February 2023

We have developed a new Fourier transform infrared chemical imaging technique1 which, when coupled with powerful multivariate data processing methods, allows the visualization of intrinsic chemical distributions in biological samples and other composite materials. Integrating spectroscopy with sample visualization and digital image processing is a potent combination of what have traditionally been two distinct methods for studying the chemistry and morphology of a sample. This synergy has been referred to as chemical imaging or hyperspectral imaging and has wide ranging implications for material characterization. In the infrared spectral region the technique relies on the use of infrared focal-plane array detectors composed of either indium antimonide (InSB), mercury cadmium telluride (MCT) or arsenic doped silicon (Si:As). These arrays, which were originally developed for defense related applications, constitute an emerging commercial technology. The arrays can be used in conjunction with standard Cassegrainian infrared optics and step-scan Michelson infrared interferometers to construct imaging systems capable of collecting tens of thousands of spatially resolved infrared spectra and images with less than 1 minute of data acquisition time.2 The data sets contain both spatial and spectral information and typically consist of hundreds of images resolved in frequency space (wavenumbers, cm-1), with each image containing many tens of thousands of pixels. Using a microscope, each pixel can sample a region as small as 2 μms2 of a sample surface.
Protein Reactions Monitored by Time-Resolved Step-Scan FTIR Spectroscopy
Authors: Gerwert Klaus
Published: February 2023

Time-resolved step-scan FTIR difference-specroscopy allows monitoring of protein-reactions with nanoseconds time-resolution at atomic resolution. The technique monitors reaction of prosthetic groups, like cis-trans isomerization, movements of the protein backbone and protonation changes or H-bond changes of aminoacids.
Multipassing a Cryogenic Sample: Use of a White-Type Cell with 8 Passes for Studying Solid Hydrogen
Authors: Mengel Markus , Winnewisser Brenda P. , Winnewisser Manfred
Published: February 2023

The use of a White-type multipass arrangement external to the optical head of a cryostat for Fourier transform spectroscopy of solid H2 was explored in previous work from our laboratory [1, 2]. The present measurements were made by extending from 4 to 8 passes through the cell within the liquid-He vaporization cryostat (Janis Research Inc., Model 10 DT) [3]. This multireflection system was mounted inside the sample chamber of the Bruker IFS 120 HR interferometer as shown in Fig. 1. Water absorptions were minimized by evacuating the whole spectrometer. All six windows of the cryostat and of the sample cell were equipped with an antireflection coating which was optimized for the spectral range 7500 - 9000 cm-1.
Infrared and Near Infrared Spectra of Sunspots
Authors: Bernath P.F. , Ram R.S. , Wallace L.
Published: February 2023

L. Wallace of Kitt Peak National Observatory has been reducing the infrared and near infrared spectra of sunspots. These spectra were recorded with the Fourier transform spectrometer associated with the McMath-Pierce Solar Telescope of the National Solar Observatory in Tucson, AZ. The sunspot and the photospheric infrared spectra are available in the form of four atlases1.
Airborne-Infrared Fourier Transform Spectroscopy
Authors: Larson Harold P.
Published: February 2023

The role of FTS in airborne astronomy is assessed from its past scientific achievements and its future potential on SOFIA, NASA’s next-generation airborne observatory (2.5-m telescope in a 747 aircraft).
Solar absorption measurements of stratospheric OH in the UV with a Fourier Transform Spectrometer
Authors: Notholt J. , Schütt H. , Schrems O. , Keens A.
Published: February 2023

Solar absorption measurements of OH in the UV have been performed using a FTS (Fourier Transform Spectrometer). The experiments have been carried out in the high Arctic at Ny-Ålesund (79°N, 12°E) during summer 1996. The analysis was done in two ways; (i) by utelizing the Doppler shift of two spectra, recorded on the east and west side of the solar disk, or (ii) by studying single solar absorption spectra recorded in the middle of the solar disc. The results of both analysis methods agree and give total columns of about 6×1013 molec. cm−2 for SZA (Solar Zenith Angles) of 60°.
Astronomy with an imaging Fourier-transform spectrometer
Authors: Maillard J.P.
Published: February 2023

A 3-D spectrometer is a particularly useful instrument in astronomy where many sources are extended objects or star clusters. With the advent of bidimensional array detectors the throughput advantage of a Fourier-transform spectrometer (FTS) can be exploited to create this type of instrument. The coupling of the FTS of the CFH Telescope, which is a step-scan interferometer, to a near-infrared camera has been realised. With this combination, spectro-imaging in any bandpass between 1 and 2.5 μm is possible within a circular 24” field of view, at seeing-limited spatial resolution. Spectral resolution in any spectral domain within these limits, up to 30,000 is choosable. Illustrations are given by the study of several typical objects.
Gradient Index Imaging Optics Today
Authors: Marchand Erich W.
Published: February 2023

100 AD Greeks and Egyptians observe astronomical refraction

1854 Maxwell's fisheye lens

1900 Wood lens invented

1944 Luneburg lens

1954 Fletcher's analysis of GRIN rod (Fletcher, Murphy, and Young, Proc. Roy Soc. , London, 223, 216 1954).
Gradient-index Optics in Eye Design
Authors: Campbell Melanie C.W.
Published: February 2023

A gradient index crystalline lens modulates image quality across a spherical retina and balances the aberrations of other dioptric components. The rat eye demonstrates the pressures of lifestyle on lens and eye design.
Ray Tracing in Anamorphic Gradient Index Media
Authors: Moore Duncan T. , Stagaman Joan M.
Published: February 2023

There are a number of optical systems for which the power or magnification in one meridian is different from that of the other meridian. Lenses with cylindrical surfaces are used to achieve this effect, but it is difficult to fabricate such components with close tolerances. The introduction of inhomogeneous lenses in which the index profile is anamorphic produces the same effect and also eliminates the need for non- spherical surfaces. Fewer components are necessary to achieve performance comparable to that of a homogeneous system, since there are additional degrees of freedom associated with the index of refraction profile.
Design of Gradient Index Optical Systems
Authors: Moore Duncan T.
Published: February 2023

The design of gradient index optical systems has advanced to the point where gradients can now be treated in much the same way as homogeneous degrees of freedom. Although many authors have restricted their gradients to radial type geometries with only plano surfaces, these limitations have for some time been overcome, and therefore, gradients bounded by curves or aspheric surfaces are now possible, at least in theory. The analytic tools for describing the performance of gradient index systems have been well described. These lens systems can now be evaluated from aberration theory, ray trace analysis, modulation transfer functions, and wavefront aberrations. At least one optimization routine has been written which permits the gradient profile to be varied in the same way as other construction parameters in homogeneous lenses. Therefore, the tools are in place for the automatic design of many different types of lens systems.
Graded-index sphere lens with hemispherical rod cladding
Authors: Kikuchi K. , Morikawa T. , Shimada J. , Sakurai K.
Published: February 2023

As optical circuit elements for the optical communication and the optical information processing, small and high performance lenses of a simple design suited for objective functions are required. So far self- focusing rod lenses have been playing an important role as ones partially satisfying the above requirements.1,2)
Imaging Capabilities of a Long Gradient Index Rod
Authors: Atkinson Leland G. , Moore Duncan T. , Sullo Nancy J.
Published: February 2023

Bundles of small diameter homogeneous optical fibers have been used extensively to transmit spatial information. Because these fibers are non-imaging, the resolution of the bundle is limited by the size of the individual fibers, and the total number of points that can be transmitted is limited by the number of fibers in the bundle. There is also a significant light loss because of the cladding surrounding each fiber. For example, if the core diameter is 10μ and the total diameter 15μ, less than half the incident light can be transmitted. If the index of refraction in a fiber is made to vary continually outward from the optical axis such that the surfaces of constant index are cylinders, the fiber will now be an imaging system. If the fiber is increased in diameter and the parameters chosen correctly, equivalent amounts of spatial information can be transmitted over this single gradient index rod. The total number of resolution points will be limited by the diameter of the rod and the diameter of the image spot.
Requirements And Measurement Techniques For GRIN-rod Lenses In Optical Fiber Components
Authors: Tomlinson W. J. , Wagner R. E.
Published: February 2023

Optical fiber communications systems require a variety of optical components, such as directional couplers, switches, wavelength multiplexers, etc., and most of the components that have been reported to date use graded-refractive-index rod lenses (GRIN-rod lenses).1 A very important parameter for the evaluation of such components is the insertion loss, and in most cases the major loss contributions are from imperfections of the lenses and from mechanical misalignments. In this paper we describe analysis techniques which make it possible to separate the effects of lens imperfections and misalignments, and from which we determine the lens characteristics required to achieve specified losses. We also review the various techniques available for measuring GRIN-rod lens characteristics, and compare the achievable accuracies of the techniques with that required for the analysis of fiber components.
Experimental Determination of the Chromatic Properties of Gradient Index Materials
Authors: Ryan Danette P.
Published: February 2023

The design and tolerancing of gradient index lenses represent an advance in the area of lens design. The data necessary for the design of a gradient index optical component includes information about the index of refraction profile and the chromatic dependences of the gradient profile. The usefulness of the lens design thus hinges upon the accuracy to which these properties can be measured.
Gradient Index Lens Fabrication Processes: A Review
Authors: Mukherjee Shyama P.
Published: February 2023

Processes for producing index-of-refraction variations in optical materials (e.g., glasses, plastics, and single crystals) are reviewed in the context of fabricating graded index lenses for optical imaging systems. The following criteria are considered: (a) the underlying scientific principles, (b) size and shape of lenses in which the gradient can be produced, (c) index levels and maximum index differences obtainable, (d) degree of control over gradients produced, (e) wavelength regions in which the transparency can be obtained, and (f) nature of materials: glasses, plastics, or crystals.
A Light-Focusing Plastic Rod of Methyl Methacrylate - Vinyl Phenylacetate
Authors: Koike Yasuhiro , Kimoto Yoshihiko , Ohtsuka Yasuji
Published: February 2023

The light-focusing plastic rod (LFR) with a quadratic distribution of refractive index expressed as Eq.(l) in the center region of radius Rc could be prepared by two different processes, namely by two-step copolymerization [1-6] and by photocopolymerization [7-10].
A Planar Micro-Lens with Distributed Index Made of Plastics
Authors: Iga K. , Oikawa M. , Sanada T.
Published: February 2023

A distributed index rod lens with nearly parabolic refractive index distribution in its radial direction has been widely applied to imaging systems or micro-optical circuits [1],[2]. In this paper we propose a new class of distributed index lens; a planar micro-lens. A lot of lens samples or their array can be monolithically fabricated in one substrate by diffusing dopants through a mask. Planar micro-lenses may be applied to optical imaging systems, micro-optical circuits, focusers and so on.
The Usefulness of Gradient Property Materials
Authors: Guenther B. D.
Published: February 2023

The various types of gradient properties and their utilization are reviewed with emphasis on Army applications.
Optical Fiber Components Using GRIN-Rod Lenses
Authors: Knerr R. H.
Published: February 2023

This paper will review the current application of GRIN-rod lenses in optical components, such as couplers, switches, wavelength multiplexers, etc., for use in optical fiber systems.
Imaging with a Linear Array of Conventional (nongradient) Lenses, an Alternative to Arrays of Gradient Index Rods
Authors: Moorhusen Robert W.
Published: February 2023

Linear arrays of conventional simple lens elements, arranged as shown on figure 1, were proposed as copier optics as early as 1966. These, so called, "Strip Lenses" present an erect image made up of a large number of overlapping registered images. This image orientation is identical to that formed by a Selfoc* lens. The Selfoc lens, which is a linear array of gradient index rods (or fibers), has been effectively utilized in a number of small copiers recently.2
Non-Gaussian Imaging Properties of Gradient-Index Fiber Lens Arrays
Authors: Rees James D.
Published: February 2023

This report explores non-Gaussian (where the object and image planes are not coincident with the Gaussian 1X object and image planes) imaging with GRIN lens arrays. These arrays are commercially available under the trade name SELFOC1 lens arrays.
Fabriction and Testing of a Gradient Index Binocular Objective
Authors: Kindred Douglas S. , Moore Duncan T.
Published: February 2023

In a previous paper1, a design was presented for a two element binocular objective having an axial gradient index positive lens and a homogeneous negative lens. The performance of the resulting binocular was shown to be comparable to the original system, having a three element homogeneous objective. Recently, a prototype binocular has been fabricated using this design. Details of the fabrication and testing, as well as a review of the design, will be presented.
Raytracing In Grin Systems : Estimation of Optimum Extrapolation Interval
Authors: Sharma Anurag , Ghatak A.K.
Published: February 2023

Rays in gradient-index (GRIN) optical systems have to be traced by solving the ray equation numerically. We have earlier reported /1-4/ a very fast numerical method based on a new form of the ray equation which is solved by a numerical technique, e .g., the Runge-Kutta method.
Ray Tracing in a Cylindrical Medium with Inverse-Square-Law Index Profile: Theory and Application
Authors: Irrera Fernanda , Someda Carlo G.
Published: February 2023

It is well know /1/ that analytical ray tracing in GRIN rods has been successful, so far, for a limited number of index profiles. This lead to the development of very satisfactory numerical techniques (e.g., see again /1/). Nevertheless, enlarging the class of media which can be studied analytically remains an interesting goal. Recently, we investigated /2/ analytical modal solutions of the scalar wave equation in cylindrical waveguides, where the index is proportional to r-2 (r = radius, cylindrical coordinates). This model, which was first proposed by Marcatili /3/ for analyzing lossless tapers and bends, turns out to be useful also for studying waveguides where the index profile is not circularly symmetrical /4/. Here, we report on the analysis of the same index distribution, under the viewpoint of ray tracing.
Characterization of Planar Microlenses Made by Ion Exchange Diffusion
Authors: Zhu X. -F. , Iga K.
Published: February 2023

Several years ago, we proposed and demonstrated the distributed-index planar microlens1, which was made with a glass substrate by a selective ion exchange technique.
Graded Index Ti: LiNbO3 Waveguides: Process Optimization
Authors: Ramaswamy R.V. , Horton T. , Suchoski P.G.
Published: February 2023

Channel waveguides with minimum mode size, and electrode patterns that maximize the overlap integral between the guided optical field and the applied modulating field are essential for efficient operation of Ti diffused LiNbO3 modulators, switches and other active guided wave devices. Previous efforts have concentrated on improving the coupling efficiency of Ti:LiNbO3 waveguides to single mode fibers. A total fiber-waveguide-fiber insertion loss of 1 dB at 1.32 μm in a z-cut LiNbO3 crystal was achieved [1] by carefully selecting the fabrication parameters so that the TE and TM modal width and depth nearly matched that of a single mode fiber, specifically for guides with Ti strip widths in the range of 6 -10 μm. These waveguides, however, are not quite suitable for efficient active, guided wave device operation, due to their large mode size. Instead, minimum mode size waveguides are required for the maximization of the overlap integral between the optical and modulating fields. It is recognized that the coupling of suchwaveguides to single mode fibers will result in a large mode mismatch loss. In order to reduce this coupling loss to a reasonable value, it is necessary to incorporate a tapered transition [2] between the small mode size LiNbO3 guide and the single mode fiber.
Buried Na+-Ag+ Ion-Exchanged Glass Waveguides: Theory and Experiment
Authors: Cheng H.C. , Ramaswamy R.V. , Srivastava R.
Published: February 2023

Glass waveguides are generally fabricated by ion-exchange process by immersing the glass substrate in a molten salt mixture. These waveguides have the maximum index change at the glass surface, and their index profile depends upon the diffusion time, the melt temperature, the compositions of the glass and the melt, and on any applied electric field. The surface waveguides can be buried by immersing them in pure salt bath and carrying out diffusion in one more step with or without external field. Burying the waveguide under the glass surface reduces the scattering losses arising from the surface irregularities. The buried profile can be tailored to give desired waveguide characteristics by changing the process parameters. Both planar and channel Na+-Ag+ ion-exchanged buried waveguides have been reported [1-3]. Since the silver melt concentration used in these studies was relatively large (NAg ⩾ 0.1 mole fraction), the resultant surface index change was also large (Δn ~ 0.1), giving rise to either multimode waveguides or very shallow single-mode guides, incompatible with single-mode fibers. Moreover, the interdiffusion coefficient under these conditions is concentration dependent, a fact that makes the solution of the diffusion equation more cumbersome.
Propagation constants and coupling lengths in graded-index single-mode waveguide structures: A path integral approach
Authors: Hawkins Raymond J.
Published: February 2023

A novel technique, numerical path integration, has been developed as a tool for computer-aided integrated-optical device design. The features that recommend its use are (i) computational simplicity and (ii) the ability to accomodate arbitrarily graded refractive-index distributions. In this paper we present a brief overview of the theory behind numerical path integration and present applications of this method to analyze Ti:LiNbO3 waveguide structures, illustrating both the accuracy of the method as well as its ability to provide meaningful information in real device design.1
25 Years of GRIN in Rochester
Authors: Moore Duncan T.
Published: February 2023

Summary not available.
An Heuristic Solution for the Arbitrary Index Distribution and Ray-Trajectory-Angular-Frequency Aberration Linkage
Authors: Il’in Vladimir Gl.
Published: February 2023

The applied gradient index optics is 25 years old today. And almost all the time the long-thin-GRIN-rod-lenses with good imaging capability being the most dramatic examples of GRIN systems were a challenge for fabrication, investigation and actual design. It is well known that the ion-exchange diffusion technology yields the best results in achieving smooth, controllable and reproducible refractive index distributions. But even in that case we can not avoid some discrepancies of actual index distributions from the ideal or prescribed ones. For actual design these discrepancies are to be accurately measured and characterized, and it must be pointed out, that for the low numerical aperture GRIN rod lenses with the index difference of about 0.003 we are dealing with discrepancies of the order of 0.00005 in marginal areas of the rod and even less in the main paraxial area.
A Y-branch Wavelength Multi/Demultiplexer by K+ and Ag+ Ion-exchange for λ=1.31 and 1.55μm-Device Fabrication and Measurement Results
Authors: Xiang F. , Yip G.L.
Published: February 2023

An optical waveguide Y-branch, with a small branch angle and two asymmetric arms, can function as a wavelength multi/demultiplexer (see Fig.1)[1,2]. A small branch angle θ will cause the Y-branch to perform as a mode splitter. Two asymmetric arms, differing either in the geometric shape or refractive index, will yield two intersecting waveguide dispersion curves between the two wavelengths to be demultiplexed. The intersection is designed to be between λ2 = 1.31μm and λ1 = 1.55μm as shown in Fig.2. Thus, the effective index of arm 1 will be higher than that of arm 2 at λ1 = 1.55μm and lower at λ2 = 1.31μm. The waves at λ1 and λ2 from the main branch can then be separated into arm 1 and arm 2, respectively [2]. Generally, the stronger asymmetric two branch arms are, the higher will be the extinction ratios, which are defined as the ratios of the output power from the two arms.
Annealed proton-exchanged planar lithium tantalate waveguides fabricated in concentrated and diluted pyrophosphoric acid
Authors: Kan Dennis , Yip Gar Lam
Published: February 2023

Lithium tantalate is a promising substrate for electro-optical integrated-optical devices because of its low sensitivity to optical damage and its high electro-optic coefficient. The annealed proton-exchange technique[1] (APE), which includes an additional annealing step after proton-exchange, is being established as a reliable method for producing stable, low-loss devices with little reduction in the electro-optic constant (from the bulk value). For the optimal design and fabrication of APE waveguide devices, accurate characterization data are necessary.
Li+ for Na+ and Na+ for Li+ Ion Exchange in Alumina Borate Glasses
Authors: Bentley Julie L. , Rouke Jennifer L. , Kindred Douglas S. , Moore Duncan T.
Published: February 2023

In optical design, the index of refraction profile of a gradient-index element is usually expressed by a polynomial expansion. [1] Although mathematically - convenient, this type of representation cannot be constrained by manufacturing parameters during optimization. In the past, this has resulted in a trial and error fabrication process which has made the implementation of many designs difficult. A preferred method from a manufacturing standpoint would be to design the lens in terms of the actual fabrication parameters by developing diffusion models and incorporating them into a lens design program. This paper discusses a Li+-Na+ diffusion model which has been developed for an alumina borate glass system. Results of the model are compared to experimental gradient index profiles.
The Preparation of Macro Axial Gradient Index Glasses for F/3 Singlet Lenses
Authors: Xu Xiaojie J. , Savard Michael E.
Published: February 2023

Macro-size axial gradient index glasses with different refractive index profiles have been produced by fusing together layers of glasses of progressively different indices of refraction. Smooth, step-free gradients are formed by controlled diffusion within and across the layers. The refractive index profiles and wavefront distortions of the lens blanks made from these materials were characterized. Different F/3 singlet lenses were designed and fabricated using these gradient glasses. The performance of these gradient lenses were tested using MTF and interferogram methods. These lenses, having only spherical surfaces, have practically no spherical aberration, and the on-axis performance reached diffraction limit. The methods of preparation of the gradient materials are discussed as well as the advantageous properties of macro gradients in optics.
Chromatic Dispersion of Selected Gradient-Index Glasses
Authors: Saxer Christopher E. , Moore D. T.
Published: February 2023

The degree to which gradient-index (GRIN) elements can be effectively used in optical systems depends partly on the ability to characterize them. This paper discusses measurements of the chromatic dispersion and birefringence made with a multi-wavelength, harmonic phase-shifting interferometer1 on several types of gradient-index glasses.
Eye Contact GRIN Lenses
Authors: Koike Yasuhiro
Published: February 2023

Additional design by controlling the radial graded-index (GRIN) inside a lens medium has generated considerable interest especially in reducing spherical aberration or increasing optical power. However in the case of glass materials, it is difficult to prepare large dimensional GRIN materials with about 10 mm diameters. On the other hand, polymer materials are suitable for obtaining a large dimension such as 10mm - 100mm1).
Sol-Gel Method for Making Radial Gradient-Index Glass in the SiO2-TiO2-R2O System
Authors: Caldwell J. Brian
Published: February 2023

The use of sol-gel methods to make titanium silicate gradient-index (GRIN) glass is now well established [1-9]. The basic technique consists of the following steps: 1) make a titanium silicate gel from Si and Ti alkoxides, 2) soak the gel in an acid bath to partly leach and thus create a concentration gradient of Ti, 3) arrest the leaching process by soaking the gel in an appropriate solvent such as alcohol or water, 4) dry the gel, 5) sinter the gel by controlled heating to a high temperature. This technique can be used to produce transparent monolithic radial gradient-index glass rods up to 8mm or more in diameter with a nearly parabolic index profile. A drawback of this technique is that the concentration of titania in the final glass article is limited by devitrification to less than 10 mole percent. As a result, the largest index change so far achieved in the TiO2-SiO2 system is about 0.027 [8].
The Effects of Lens Grin Profiles on Phakometric Measurements
Authors: Moroney Michael J. , Campbell Melanie C. W. , Munger Rejean , McCurdy Boyd
Published: February 2023

The in vivo dimensions and shape of the posterior crystalline lens surface in eyes are often calculated based on information taken from the image of that surface as viewed through the lens and the cornea. It is therefore necessary to choose a schematic eye model that successfully describes the optical properties of the interior of the lens in order to accurately determine the dimensions of its posterior surface. For simplicity the schematic eye models often assume that the refractive index of the lens is constant, although it is known to have a gradient of refractive index1. Evaluation of the resulting errors in calculations of the posterior lens surface dimensions have not previously been published. It will be shown that the gradient can have a profound effect on the image of the posterior lens surface of the lens in the Cichlid fish. The purpose of this paper is to investigate the effects of simplistic models on the calculations of the position, radius of curvature, and shape of the posterior lens surface in humans.
Integrated Imaging Fiber Optics with Multiple Grin Lenses
Authors: Dhadwal Harbans S. , Khan Romel R.
Published: February 2023

Design and fabrication of an integrated imaging fiber optic probe (IFOP) (comprising a monomode optical fiber which is fusion spliced to a short length of a graded index multimode fiber) for delivery of either a collimated beam or a focused spot to a remote location, has been reported earlier.1 A short section of a multimode graded index fiber (GFL) with quadratic index profile has focusing properties similar to those of spherical lenses and Sclfoc2 graded index lenses manufactured by NSG2. Advantages of GFL over Selfoc lenses include miniaturization, narrower beam delivery for a certain distance and alignment-free lens system since the GFL is fused to the monomode fiber. Applications in areas such as photon correlation spectroscopy3 and fiber optic connectors4 have been evaluated. Variations in the image distance and magnification can be obtained by controlling the length of the GFL and is limited by the properties (namely the refractive index profile) of the GFL under use.
Further Consideration of Parallel Image Recognition System Using Planar GRIN Microlens Array
Authors: Nakagawa K. , Okano H. , Katayama T. , Iga K.
Published: February 2023

Optical parallel processing[1] is expected to be one of the powerful methods for dealing with a large amount of image information because of its very high processing speed and parallelism. To optically handle image information processing, image multiplexing is an indispensable technique. We proposed an image recognition system using planar GRIN microlenses[2] (PML) which utilizes the high density image multiplexing ability of PMLs.