bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Approach to High-Resolution FTS Design
Authors: Brault James W.
Published: February 2023

A major intercomparison campaign for the measurement of tropospheric OH was scheduled for September 1993 in the mountains near Boulder, CO, with our laboratory providing measurements of the OH concentration by spectroscopic detection of UV absorption in a 20 km path, to a retroreflector array across a wide valley and back. In early 1993, we decided to try to build a simple FTS that would be used to measure the concentration of CO - a crucial molecule in the photochemistry cycle for OH - on that same path using the 2-0 band in the near infrared. With a tight schedule and a low budget, some new design approach was needed; the resulting instrument, designed in collaboration with Roger Jakoubek of this Laboratory, appears to embody some ideas of general applicability.
Radiometry by FTS in the visible and UV regions
Authors: Thorne Anne
Published: February 2023

Much effort over many years has gone into evaluating and improving the wavenumber accuracy of FTS - the x-axis - but relatively little attention has been paid to the accuracy of the intensity measurements - the y-axis. This is particularly true of the UV region, where almost all spectrophotometry is done with grating instruments. We have used our high resolution UV FT spectrometer for making three different types of intensity measurements: branching ratios in emission, absorption cross-sections, and (at low resolution) lamp calibration. In the course of these measurements we have identified a number of sources of potential error, some known in advance and some discovered the hard way, some common to grating and FT spectrometers and some peculiar to FTS, and some that particularly affect the short wavelength region. This paper discusses the principal problems and the lessons we have learned. It also indicates some of the advantages (and the occasional disadvantage) that FTS has over grating spectrometry for radiometry in the UV.
Detector Nonlinearity Related Errors in Fourier Transform Spectroscopy and their Correction
Authors: Hanssen L. M. , Zhu C. J. , Zhang Z. M.
Published: February 2023

Due to the relatively high flux levels available in FT-IR spectrophotometers and the universal need for better signal to noise ratios, detectors are often operated in conditions under which their responsivity varies during the measurement. This can happen both during a single measurement (nonlinearity) as well as between measurements (nonequivalence). The results of measurements made under these conditions will contain errors. The quantity and spectral distribution of the errors will depend on both the instrument signature and the sample properties under investigation.
Design for a Fully Multiplexed Imaging Fourier Transform Spectrometer
Authors: Davis D. Scott
Published: February 2023

As described in recent publications1,2, the development of a new approach to multiplexed imaging is underway at the Naval Postgraduate School. The technique is expected to find a niche in sensitive astronomical and remote-sensing applications at long wavelengths (far infrared to submillimeter), particularly from high altitude aircraft and space-based platforms. At such wavelengths, various physical and technological constraints limit the development of focal plane array detectors, but single element, discrete detectors are available. The new multiplexed imaging method is called Kronecker product imaging (KPI), and it shares several attributes that are closely allied to the techniques of Fourier transform spectroscopy (FTS). Furthermore, it has been intended from the outset that KPI and FTS instrumentation can be easily combined into a hybrid, completely multiplexed imaging spectrometer, capable of both high spectral resolving power and fine spatial image resolution simultaneously.
Selection of Optimized Microwindows for Atmospheric Spectroscopy
Authors: Clarmann T. V.
Published: February 2023

Fourier transform instruments, such as the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), provide spectra covering wide frequency ranges. In atmospheric spectroscopy the measured spectrum is usually not analyzed simultaneously as a whole, but microwindows which are dedicated to certain target species are used for the inversion process. An optimum microwindow contains prominent transitions of the target species, leading to high sensitivities of the measured spectral signal to the target parameters, while the signal of transitions of non-target species shall be low. In the early days of atmospheric spectroscopy microwindows were defined and selected by experienced spectroscopists. Nowadays there is a growing need to define and select optimized microwindows in an objective and reproduceable manner.
Precision Wavelength Calibration for UV-visible FTS
Authors: Salit Marc L. , Sansonetti Craig J. , Travis John C. , Veza Damir
Published: February 2023

At the 1995 FTS topical meeting, our group presented a description of issues surrounding calibration of the wavenumber scale of our Chelsea Instruments UV/visible FTS.1 Inconsistencies observed when using wavelength standards from Ar II2 and 198Hg3 formed a large part of that discussion. We have continued to work on this problem, with the intent of resolving these discrepancies and probing the limits of precision of the wavenumber scale in FTS.
The PACE Mission: An Ultralite Solar Occultation Instrument for Simultaneous Infrared and Visible Measurements of Gases, Aerosols, Temperature, and Thin Cirrus
Authors: Rinsland Curtis P. , Farmer Crofton B. , Abrams Mark C. , Chu William P.
Published: February 2023

We have developed a concept for simultaneous solar occultation remote sensing of gases, aerosols, and thin cirrus in response to NASA's Announcement of Opportunity for Earth System Science Pathfinder (ESSP) Missions. The focus of our experiment is on the upper troposphere and lower stratosphere with the goal of filling critical gaps in the current climate research program. Specifically, the Particles, Atmosphere, and Climate Experiment (PACE) will

* Measure temperature, aerosols, ozone, water vapor, and thin cirrus clouds to diagnose the response of climate to human-induced forcings and their interactions.

* Extend the Atmospheric Trace Molecule Spectroscopy (ATMOS) database by providing measurements of key gases with increased precision and tropospheric coverage.

* Extend the Stratospheric Aerosol and Gas Experiment (SAGE) database by providing aerosol and thin cirrus measurements with a new ability to measure horizontal inhomogeneity coupled with the ability to penetrate broken clouds.
Emission Fourier Transform Spectroscopy on Molecular Ions
Authors: Vervloet Michel
Published: February 2023

Emission spectra of molecular ions are most often recorded from electric discharge where parent molecules or fragments are ionized in excited states. These sources tend to generate sparks which give rise to many spikes in the interferograms and consequently make them unusable. In some cases, this problem can be overcome by creating excited ions of interest using Penning ionization.
Fourier Transform Spectroscopy in Solar Astronomy
Authors: Ayres Thomas R.
Published: February 2023

The FTS revolutionized many aspects of solar astronomy when introduced 20 years ago. The most profound impact was on infrared studies of molecules such as CO.
Testing and Improving the Radiometric Accuracy of FT-IR Transmittance Measurements
Authors: Kaplan S. G. , Hanssen L. M. , Datla R. U.
Published: February 2023

While FT-IR spectrophotometers have clear advantages over dispersive instruments in throughput and signal averaging, the same design elements that give these advantages can produce more complicated and severe sources of radiometric error in FTIR spectra compared to their dispersive counterparts. However, the high signal-to-noise ratio and good measurement repeatability afforded by FT-IR spectrophotometers are sometimes misinterpreted as low absolute radiometric uncertainty. While the complete radiometric characterization of even one FT-IR instrument is an ambitious long-term goal, it should be possible for users to both understand and reduce the various sources of radiometric error through the use of standard and diagnostic samples appropriate to the measurements of interest.
On the Design of Fourier Transform Spectrometers for Space-based Remote Sensing
Authors: Farmer C.B. , Brault J.W. , Goldman A. , Hinton D.E. , Murcray F.J. , Jennings D.E. , Puschell J.J. , Rinsland C.P. , Traub W.A. , Abrams M.C.
Published: February 2023

After some four decades of development, Fourier transform spectrometers have become the premier high resolution, broadband passive spectometer for laboratory and remote sensing applications. Following the four flights of the ATMOS instrument onboard the space shuttle, and with the development of emission sounders such as MIPAS (limb) and TES (nadir and limb), geostationary mesoscale sounders (GHIS), and polar meteorological sounders (IASI), the scientific role of FTS for remote sensing is indisputable. However, in general they remain less than ideal for space-based applications as a consequence of their size, mass, power, and telemetry requirements. A new concept for high resolution Fourier transform spectrometers suitable for space applications is described that reexamines each of the historical assumptions that have led to massive, large interferometers. The result will deliver the optical and radiometric performance of a high performance FTS such as ATMOS in a small (<0.25 m3), lightweight (20-25 kg) instrument with modest power requirements (<50 W), and with onboard data processing will have modest telemetry rates. Central to the concept is the realization that many of the historic assumptions about interferometer design are unnecessary, especially in a zero gravity environment.
A 10 to 140 Micron Beamsplitter: Recent Results
Authors: Traub W.A. , Johnson D.G. , Jucks K.W. , Dobrowolski J.A. , Laframboise G. , Rowell N.
Published: February 2023

We present results showing progress towards a beamsplitter made of polypropylene and germanium which is designed to cover the full spectral range from 10 to 140 micron wavelength.
A New Method for Tracing Rays through Graded Index Media
Authors: Sharma Anurag , Ghatak A.K.
Published: February 2023

Ray tracing in graded-index media forms an essential part of the design of inhomogeneous lenses. However, since the path of rays in such media are curved, in general, one has to solve the ray equation numerically, except in a few cases in which analytical solutions are possible (see, e.g., Refs.1-3). As such, some algorithms have been developed for tracing rays through a general medium(4-7). We present here a new numerical method for tracing rays through graded index media and have shown that this method requires much less computational effort (in comparison to other methods) for obtaining a desired accuracy. The method essentially consists of putting the ray equation in a convenient form by appropriately defining a new variable and solving the resulting equation using a standard numerical technique(8). In Sec.2, we have described the method and in Sec. 3, we have presented numerical results corresponding to graded index media which are of considerable practical importance and have also compared the computational effort with other methods(6,7).
Evaluation and Reduction of Aberrations in Distributed Index Rod Lenses
Authors: Iga Kenichi
Published: February 2023

Studies on evaluating and measuring aberrations of rod lenses which have mostly parabolic distribution of refractive index have been reviewed. Some efforts of reducing aberrations by controlling the fabrication process are also summarized.
Wavefront Aberration Measurements on GRIN-Rod Lenses
Authors: Cline T. W. , Jander R. B.
Published: February 2023

GRIN-rod lenses currently have a variety of applications including imaging systems and microoptic lightwave components. Effective implementation of these lenses in such devices requires accurate evaluation of their optical properties. Transverse geometrical1,2 and interferometric3 techniques have been reported for the determination of the refractive index profile of GRIN-rod lenses and fiber preforms. These methods may be useful for initial measurements of lens rods, however, it is unlikely that they would adequately determine the quality of finished lenses. A fundamental limitation of transverse methods is that rays used to test the lens must pass through the entire lens cross section. It has been reported4 and we have confirmed that the index distribution at large radii frequently has relatively large deviations from the desired distribution. For microoptic lightwave components, lenses are used at subaperture values so the index profile beyond a certain maximum radius is incidental. Therefore, it is likely that results from transverse techniques may be distorted by unused portions of the lens.
Index Profiling of Distributed Index Lenses by A Shearing Interference Method
Authors: Kokubun Y. , Iga K.
Published: February 2023

The transverse interference method has been used as nondestructive index profiling of thin optical fibers1),2),3). It is difficult, however, to apply this method to thick samples such as distributed idnex rod lenses and preform rods, since the fringe shift is so large that it overflows from the field of the interference microscope.
Infrared Gradient Index Materials Fabrication
Authors: Miceli Joseph J.
Published: February 2023

One of the greatest limitations on the field of gradient index optics is a lack of technology for making gradient index materials. This is true not only for materials used in the visible portion of the spectrum, but also in the infrared. The current techniques of manufacturing gradient index materials in the visible include various ion exchange techniques, chemical vapor deposition and ion stuffing. Some of these techniques are also feasible using infrared materials. Work is being done within the Gradient Index Group at the University of Rochester to investigate the fabrication of infrared gradient index materials using the techniques of Czochralski crystal growth. This technique can be used to form alloys of two or more similar crystalline materials into gradient index material. Current work has been centered around the use of germanium and silicon.
Realisation of Schmitt Blades by Ion Exchange in Glass
Authors: Coutaz J.L. , Jaussaud P.C. , Chartier G.H.
Published: February 2023

A new technique is presented to realise Schmitt blades by ionic diffusion under electric field into adjacent areas. Shape of these areas and optical path in these areas may be adjusted very accurately results for such a device with 4 areas will be presented at the conference.
SELFOC Micro Lens with Spherical Surface
Authors: Yamamoto N. , Nishi H. , Nishizawa K. , Kitano I. , Kubo T. , Okada K.
Published: February 2023

Gradient index rod lenses have been successfully applied to imaging systems and micro-optical circuits in electro-optical systems. When the rod lens is used as a light-focusing micro device such as a pick-up lens in the video disk, a high numerical aperture (NA) is necessary in order to get a small focused spot. NA of the rod lens is determined by the quadratic gradient constant g of the refractive-index profile, the diameter, and the length of the lens. However, NA can be changed by making an end surface spherical even if those parameters are made constant. On the other hand, the spherical surface has the minus spherical aberration, so it becomes possible to compensate the plus aberration of the rod lens by the spherical surface.1)
Luminous Intensity of Gradient Index Lens Array
Authors: Toyama Minoru , Takami Manabu
Published: February 2023

SELFOC lens array (SLA) consisting of multiple gradient index lenses (SELFOC lenses) is used in a copying machine. Application to a facsimile (1) and Printer (2) is also studied as a new use of SLA.
Gradient-Index Rod Lens with High Optical Performance for Medical Use
Authors: Fujii K. , Akazawa N.
Published: February 2023

Gradient-index rod lenses (SELFOC® micro lens)1) have been widely used in medical optics devices, such as an endoscope which is an optical device for visualization in body cavities.2) The basic structure of the gradient-index rod lens of the endoscope is shown in Fig. 1. It consists of two types of gradient-index rod lenses which are called the objective lens and the relay lens. The object is imaged onto the rear face of the objective lens and this image is transfered to the back of the relay lens.
A Three Dimensional Superposition Array
Authors: Zinter J. Robert , Moore Duncan T.
Published: February 2023

Gradient index arrays exist in nature as compound eyes. This eye is composed of many individual ommatidia. Exner1 discovered that the corneal lens, in each ommatidia, of the water beetle Hydrophilus is composed of a gradient index material.
Gradient-Index Achromatic Doublet
Authors: Ichikawa Hiroyuki , Koshi Hiroshi , McLaughlin Paul O. , Toyama Minoru
Published: February 2023

In recent years, the application area of gradient-index has extended to optical communication1), photocopy machine, endoscope, facsimile, printer, optical disk system2) and so on.
Beam Propagation Analysis of Planar Micro-optical Components
Authors: Bava G.P. , Rosina P. , Montrosset I.
Published: February 2023

In the recent years a great effort has been addressed to the realization of planar micro-optics or GRIN devices |1,2|.
Y-Ȳ Diagram Analysis of Radial Gradient Index Lenses
Authors: Harrigan Michael E. , Loce Robert P. , Rogers John
Published: February 2023

The Y-Ȳ diagram of Delano1 has been shown to be useful in understanding the relationships and constraints between first order quantities of a wide range of optical systems from Gaussian beam propagation to zoom lens synthesis 2,3,4,5,6.
Electron-Beam Written Ultra-Micro Fresnel Lens Array with High-Efficiency Structure
Authors: Shiono T. , Higashino H. , Setsune K. , Yamazaki O. , Wasa K.
Published: February 2023

In a fabrication of micro optical components, the electron-beam (EB) writing technique has potential for submicron patterning and flexibility for the design. Recent progress in the EB writing technique has shown a feasibility of a blazed relief structure1. In a micro Fresnel lens, the blazed relief structure improves the focusing efficiency. An array of such micro Fresnel lenses can be applied for optical instruments including line scanners, copying machines, CCD image sensors, and interfaces in future optical computer.
Microlens Arrays Produced by a Photolytic Technique
Authors: Borrelli N. F. , Morse D. L.
Published: February 2023

A new process is described whereby excellent quality microlenses can be photolithographically patterned onto a glass. The glass whe exposed to Ultraviolet light followed by a thermal development initiates the formation of noble metal particles which in turn serve as nuclei for the growth of a microcrystalline phase from the homogeneous glass. This thermo-optically developed crystallized region is slightly more dense than the homogeneous glass. The contraction of the exposed region squeezes the soft unexposed glass beyond the original surface during the thermal schedule. When the appropriate photomask is used, opaque circles on a clear background, this effect produces spherical segments due the surface energy minimization. See Figure 1 for schematic of process and Figure 2 for actual SEM photomicrograph of formed lenses.
Index Profile Formation Process in a Planar Microlens by Electro-Migration
Authors: Sugiyama H. , Iga K.
Published: February 2023

One of methods for fabricating a distributed-index planar microlens1) is a selective ion-exchange or electro-migration technique, which introduces metal ions into a glass substrate through a circular window mask. Although the ion-exchange technique is valid to simplify the fabrication process, the electromigration method which enable us to control the index distribution can realize a lens with a large NA and small aberration. However, its index profile formation process has not fully been clarified. In this study, on the basis of the previous work2), we have introduced a local field effect for simulating the process and obtained better agreement with an actual semispherical distribution.
Estimation of Planar Microlens by Oblique Ray Tracing
Authors: Misawa S. , Iga K.
Published: February 2023

We presented the meridional ray tracing method for a planar microlens with 3-D distributed index and aspheric boundaries, and estimated its N.A. and spherical aberration1),2). But the off-axial characteristics of this lens has not been estimated. In this paper, we aim to estimate a planar microlens by more general ray tracing which includes the calculation of path length.
Fabrication of polymer radial index gradients utilizing a new cross-linking polymer
Authors: Gardner Leo R. , Moore Duncan T.
Published: February 2023

Radial GRIN lenses have met with industrial success as focusing devices for desktop copiers, endoscopes, and fiber optic couplers. In all of these applications, however, the radius of the GRIN lens needed is small and the current limitations in controlling the diffusion depth and Δn of manufacturable GRIN materials has not overly hampered these particular applications. If, however, larger diameter radial GRIN lenses could be manufactured, the technology could be employed in a host of larger aperture imaging systems where the benefits of radial GRIN lenses could be utilized.
Large Diameter Radial Gradient-Index Glass
Authors: Caldwell J. Brian , Kindred Douglas S. , Moore Duncan T.
Published: February 2023

The ion exchange technique is widely used to produce radial index gradients in glass.(1,2) The depth of the index profile produced by this technique is typically only a few millimeters or less. In order for radial gradients to be used in large scale imaging systems, however, much larger index profile depths are required. In this paper a radial gradient sample is presented which is 37 millimeters in diameter. The sample was produced by using conventional ion exchange techniques.
Gradient Index Lenses Made by Double Ion Exchange Process
Authors: Ohmi S. , Sakai H. , Asahara Y.
Published: February 2023

Gradient index (GRIN) rod lenses with parabolic index profiles have a variety of application including imaging systems and optical communication systems.1) There are a number of techniques that could be used for making these radial gradients in the glass. Ion exchange is probably the most widely and successfully used technique in the fabrication of GRIN rod lens for optical communication applications, because it is the simplest in terms of instrumentation and control. In conventional ion exchange techniques, T1 ions in a glass rod are exchanged for K or Na ions in a molten salt.2,3) There appears to be some problems in T1 ions, namely high toxicity and low diffusion rate in the glass. Ag ions also offer great potential for making large numerical aperture lenses because of their high refractive index in the glass. However, silver oxide cannot be introduced into the glass in significant quantities by melting.
A Model for Gradient Formation in Polycrystalline Germanium - Silicon Alloy Crystals via Czochralski Crystal Growing
Authors: Miceli Joseph J. , Naughton Denis P.
Published: February 2023

A mathematical model has been developed that describes the silicon composition gradient produced in germanium-silicon alloy crystals which have been formed via Czochralski crystal growing. This model is based on the naturally occuring segregation effect of silicon in germanium. In addition the refractive index of the alloy is described in terms of its relation to the band gap energy, which is itself dependent on the silicon concentration. A relationship between refractive index and the silicon compositon of the alloy is then derived.
Measurement of the Refractive Index Profile in Polycrystalline Germanium-Silicon Alloy GRIN Crystals
Authors: Naughton Denis P. , Miceli Joseph J.
Published: February 2023

The optical path or equivalently the refractive index as a function of spatial coordinate in gradient index germanium-silicon alloy crystals has been measured using A.C interferometric techniques. The interferometer is capable of high phase resolution and is computer controlled for real time data processing. Three crystals grown via the Czochralski method were measured. These results were compared to a theoretical model of the refractive index profile which is based on the dynamics of the growth process and the physical properties of germanium/ silicon alloys [1,2].
Design and Fabrication of 25mm Diameter Axial Gradient Singlets
Authors: Manhart Paul K. , Pagano Robert J. , Sherman Paul T.
Published: February 2023

Several F/3 single element axial gradient index lenses with a focal length of 75 mm have been fabricated and tested with emphasis being on performance and repeatability. The lens material was made via a fusion/diffusion process. This paper discusses the results of this endeavor.
Gradient Index Lens Array Through-focus Modulation Transfer Function Modeling
Authors: Herloski Robert
Published: February 2023

Radial gradient index (GRIN) fiber lenses are becoming more and more common in a variety of optical devices, especially photocopying machines. In these machines arrays of GRIN lenses are used to form compact unity magnification lenses. These arrays are commercially available from the Nippon Sheet Glass Co. under the trade name SELFOC1 lens array, or SLA.
Ion Exchanged Waveguides: Round-Robin Measurements of Propagation Characteristics
Authors: Pelli Stefano , Righini Giancarlo C. , Scaglione Antonio , Rimet Roger , Schanen Isabelle , Bräuer Andreas , Dannberg Peter , Yip Gar-Lam , Noutsious Peter , Liñares Jesus , Reino Carlos Gomez , Mazzi Giulio , Gonelia Francesco
Published: February 2023

The accurate determination of the optical characteristics of waveguides is a crucial parameter in the development of integrated optical devices. In this paper we have focused our attention on the problem of the accuracy of the measurement of the propagation constants of the modes and of the optical losses of a waveguide.
Planar optical waveguides in glass by diffusion of copper films
Authors: Marquez H. , Salazar D. , Razon E. , Paez G.
Published: February 2023

Ion-exchanged passive waveguide components fabricated in glass have been considered as an important method for fabricating passive integrated optical devices. These components show potential for low production cost, immunity to optical damage, and low losses for propagation and coupling with commercial fiber interfacing [1-3].
Refractive Index Profile Determination of Graded-index (GRIN) Waveguides from Near-Field Measurements
Authors: Chen L. , Pham T.H. , Haumont S. , Noutsios P.C. , Yip G.L.
Published: February 2023

Knowledge of the refractive index profile (RIP) of graded-index (GRIN) waveguides can yield important characteristics necessary for photonic device design involving ion-exchanged waveguides in glass, proton-exchanged guides in LiNbO3, or other GRIN fabrication techniques. Thus, it is very important to establish an efficient, non-destructive and accurate method to determine the RIP. In the literature, many such methods have been proposed [1, 2, 3] one of which includes the well-established inverse method of RIP reconstruction from near-field measurements of the fundamental mode intensity distribution [4, 5]. Profiles for planar and channel guides have been determined by measuring the near-field intensity with infrared vidicon tubes that need to be corrected for their non-linear response. In this paper, we propose a more accurate approach using a CCD camera to image the near-field pattern and a frame grabber to capture it pixel-by-pixel. Once this pattern is measured, a simple numerical solution of the Helmholtz equation is carried out to determine the RIP from its digitized near-field image.
Couplin of Single-Mode Fibers to GRIN Waveguides by Butt-Joining
Authors: Ríos Susana , Gómez-Reino Carlos
Published: February 2023

The use of guided-wave optical devices will depend on how well they can be coupled to optical fibers. There are many works about coupling efficiences between optical fibers and waveguides which also evaluate waveguide transmission losses [1,2]. The aim of this work is to evaluate the coupling efficiency between a step-index single-mode fiber and a planar single-mode GRIN waveguide by butt-joining. In this way the coupling efficiency between a step-index single-mode fiber of 4μ core diameter and three single-mode planar ion-exchanged waveguides fabricated in this laboratory has been calculated and measured as well as the waveguide transmission losses. The results agree with the theoretical calculations.
Bistable Bright Solitons in Nonlinear Monomode Optical Fiber
Authors: Michinel H.
Published: February 2023

It is well known that for certain class of nonlinearities the soliton solution of the generalized nonlinear Schrödinger equation (GNSE) becomes multistable(1). The existence of this kind of solitons is related to the type of dependence of nonlinear susceptibility on the intensity of light.
Glass structure and ion exchange
Authors: Houde-Walter S. N.
Published: February 2023

Measurable degradation in the image quality of radial and spherical gradient lenses can be caused by what might seem to be excruciatingly small perturbations from ideal gradient-index profiles. These are controlled by a number of empirically determined fabrication parameters that include glass composition, salt melt composition, thermal history, applied electric field and multiple diffusion steps.
Chemical Structure and Concentration Dependence of the Diffusion Coefficient in Silver/Sodium Ion-Exchanged Aluminosilicate Glasses
Authors: Inman J.M. , Houde-Walter S.N. , McIntyre B.L.
Published: February 2023

Ion exchange is often used to alter the index of refraction of a glass to fabricate waveguide and micro-optics devices, usually resulting in a gradient index. However, in order to efficiently design such devices it is necessary to be able to accurately predict and control the ion exchange. One important complication that must be accounted for is the Mixed Mobile Ion Effect (MMIE), also known as the Mixed Alkali Effect, in which many of the glass properties vary from additivity when two species of monovalent cations are present. This effect, although extensively documented, is poorly understood. As a result, parameters and conditions for ion exchanges are usually determined through a tedious trial-and-error process. We have found that insight into ion-exchange processes, including the MMIE, can be gained from studies of glass structure. We have studied silver-for-sodium exchange in a series of aluminosilicate glasses, commercially important for ion-exchanged waveguides. In this work we relate the results of our previous structural studies to MMIE and the concentration dependence of the diffusion coefficient.
Measurement of refractive index and dispersion in axial gradient material using prism refractometry
Authors: Pagano Robert J. , Manhart Paul K. , Sherman Paul T.
Published: February 2023

Axial gradient material is now fabricated via controlled diffusion of glass plates for a wide variety of optical applications. The variation in both refractive index and dispersion, through this new optical material, challenges current refractive index measurement techniques. To provide accurate characterization of refractive index, as a function of thickness, at multiple wavelengths, a prism refractometer was constructed. Multiple laser lines are spatially filtered and passed through a right-angle prism of gradient material. A movable exit slit selects the region under test along the angled back face of the prism. The selected slit of radiation is then retro-reflected back through the prism and the refracted angle is measured directly. By scanning the exit slit along the prism back face, the refractive index variation through the prism is measured at multiple wavelengths. This paper describes, in detail, the test method summarized above and reports on the precision and accuracy of this laboratory test.
General Method to Fit Refractive Index of Planar Microlenses to Simplified Formula
Authors: Acosta Eva , Rios Susana , Oikawa M. , Iga K.
Published: February 2023

We present a general method to find a simplified formula for the refractive index profile of planar microlenses in terms of functional expressions containing a lower number of coefficients compared to the usual matrix fit.
Simultaneous single-shot imaging of H and O atoms in premixed turbulent flames using femtosecond two-photon laser-induced fluorescence
Authors: Ruchkina Maria , Raveesh Meena , Dominguez Armand , Bood Joakim , Brackmann Christian
Published: February 2023

A method based on femtosecond two-photon excitation has been developed for simultaneous visualization of interference-free fluorescence of H and O atoms in turbulent flames. This work shows pioneering results on single-shot simultaneous imaging of these radicals under non-stationary flame conditions. The fluorescence signal, showing the distribution of H and O radicals in premixed CH4/O2 flames was investigated for equivalence ratios ranging from ϕ = 0.8 to ϕ = 1.3. The images have been quantified through calibration measurements and indicate single-shot detection limits on the order of a few percent. Experimental profiles have also been compared with profiles from flame simulations, showing similar trends.
Two-dimensional photonic crystals as selective filters for thermophotovoltaic applications
Authors: Zhang Shouhao , Huang Bohui , Bian Yubo , Han Chengzhi , Tian Dai , Chen Ximeng , Qiu Jiawen , Zhu Anwen , Yang Aixiang , Shao Jianxiong
Published: February 2023

The optical properties and performance of the two-dimensional photonic crystal (2D PhC) filters at normal incidence were simulated, and the best geometric parameters were obtained with the help of a global optimization program. The honeycomb structure has better performance, including high in-band transmittance, high out-band reflectance, and low parasitic absorption. The power density performance and conversion efficiency can reach 80.6% and 62.5%. Furthermore, the deeper cavity structure and multi-layer structure were designed to improve the performance of the filter. The deeper one can reduce the influence of transmission diffraction, increases the power density performance and conversion efficiency. The multi-layer structure reduces the parasitic absorption significantly and increases the conversion efficiency to 65.5%. These filters have both high efficiency and high power density, avoid the challenge of high-temperature stability faced by emitters, also easier and cheaper to fabricate compared to the 2D PhC emitters. These results suggest that the 2D PhC filters can be used in thermophotovoltaic systems for long-duration missions to improve the conversion efficiency.
TGPS: dynamic point cloud down-sampling of the dense point clouds for Terracotta Warrior fragments
Authors: Liu Jie , Song Da , Geng Guohua , Tian Yu , Yang Mengna , Liu Yangyang , Zhou Mingquan , Li Kang , Cao Xin
Published: February 2023

The dense point clouds of Terracotta Warriors obtained by a 3D scanner have a lot of redundant data, which reduces the efficiency of the transmission and subsequent processing. Aiming at the problems that points generated by sampling methods cannot be learned through the network and are irrelevant to downstream tasks, an end-to-end specific task-driven and learnable down-sampling method named TGPS is proposed. First, the point-based Transformer unit is used to embed the features and the mapping function is used to extract the input point features to dynamically describe the global features. Then, the inner product of the global feature and each point feature is used to estimate the contribution of each point to the global feature. The contribution values are sorted by descending for different tasks, and the point features with high similarity to the global features are retained. To further learn rich local representation, combined with the graph convolution operation, the Dynamic Graph Attention Edge Convolution (DGA EConv) is proposed as a neighborhood graph for local feature aggregation. Finally, the networks for the downstream tasks of point cloud classification and reconstruction are presented. Experiments show that the method realizes the down-sampling under the guidance of the global features. The proposed TGPS-DGA-Net for point cloud classification has achieved the best accuracy on both the real-world Terracotta Warrior fragments and the public datasets.
Polarization-sensitive narrowband infrared photodetection triggered by optical Tamm state engineering
Authors: Yu Yuanfang , Zhong Fan , Chu Qiongqiong , Li Ruizhi , Zhang Fengyuan , Zhang Ye , Lu Junpeng , Liu Hui , Ni Zhenhua
Published: February 2023

Polarization-sensitive narrowband photodetection at near-infrared (NIR) has attracted significant interest in optical communication, environmental monitoring, and intelligent recognition system. However, the current narrowband spectroscopy heavily relies on the extra filter or bulk spectrometer, which deviates from the miniaturization of on-chip integration. Recently, topological phenomena, such as the optical Tamm state (OTS), provided a new solution for developing functional photodetection, and we experimentally realized the device based on 2D material (graphene) for the first time to the best of our knowledge. Here, we demonstrate polarization-sensitive narrowband infrared photodetection in OTS coupled graphene devices, which are designed with the aid of the finite-difference time-domain (FDTD) method. The devices show narrowband response at NIR wavelengths empowered by the tunable Tamm state. The full width at half maximum (FWHM) of the response peak reaches ∼100 nm, and it can potentially be improved to ultra-narrow of about 10 nm by increasing the periods of dielectric distributed Bragg reflector (DBR). The responsivity and response time of the device reaches 187 mA/W and ∼290 µs at 1550 nm, respectively. Furthermore, the prominent anisotropic features and high dichroic ratios of ∼4.6 at 1300 nm and ∼2.5 at 1500 nm are achieved by integrating gold metasurfaces.
Privacy protection for 3D point cloud classification based on an optical chaotic encryption scheme
Authors: Liu Bocheng , Liu Yongxiang , Xie Yiyuan , Jiang Xiao , Ye Yichen , Song Tingting , Chai Junxiong , Liu Meng , Feng Manying , Yuan Haodong
Published: February 2023

In allusion to the privacy and security problems in 3D point cloud classification, a novel privacy protection method for 3D point cloud classification based on optical chaotic encryption scheme is proposed and implemented in this paper for the first time. The mutually coupled spin-polarized vertical-cavity surface-emitting lasers (MC-SPVCSELs) subject to double optical feedback (DOF) are studied to generate optical chaos for permutation and diffusion encryption process of 3D point cloud. The nonlinear dynamics and complexity results demonstrate that the MC-SPVCSELs with DOF have high chaotic complexity and can provide tremendously large key space. All the test-sets of ModelNet40 dataset containing 40 object categories are encrypted and decrypted by the proposed scheme, and then the classification results of 40 object categories for original, encrypted, and decrypted 3D point cloud are entirely enumerated through the PointNet++. Intriguingly, the class accuracies of the encrypted point cloud are nearly all equal to 0.0000% except for the plant class with 100.0000%, indicating the encrypted point cloud cannot be classified and identified. The decryption class accuracies are very close to the original class accuracies. Therefore, the classification results verify that the proposed privacy protection scheme is practically feasible and remarkably effective. Additionally, the encryption and decryption results show that the encrypted point cloud images are ambiguous and unrecognizable, while the decrypted point cloud images are identical to original images. Moreover, this paper improves the security analysis via analyzing 3D point cloud geometric features. Eventually, various security analysis results validate that the proposed privacy protection scheme has high security level and good privacy protection effect for 3D point cloud classification.
Energy-efficient routing based on a genetic algorithm for satellite laser communication
Authors: Jing Yinji , Yang Zhenghao , Zhao Yongli , Wang Hua , Wang Wei , Rahman Sabidur , Zhang Jie
Published: February 2023

Low earth orbit satellite laser communication has become an important part of communications due to its large capacity and low latency. The lifetime of the satellite mainly depends on the recharge and discharge cycles of the battery. The low earth orbit satellites frequently recharge under sunlight and discharge in the shadow, which leads satellites to age quickly. This paper studies the energy-efficient routing problem for satellite laser communication and builds the satellite ageing model. Based on the model, we propose an energy-efficient routing scheme based on the genetic algorithm. Compared with shortest path routing, the proposed method improves the satellite lifetime by about 300%, and the performances of the network are only slightly degraded, the blocking ratio increases by only 1.2%, and the service delay increases by 1.3 ms.
Two-photon fluorescence imaging using a tunable spectral window based on fiber supercontinuum
Authors: Chen Zhongyun , Huang Jiangfeng , Huang Xinyuan , Gao Xiujuan , Zhou Yifu , Fu Ling
Published: February 2023

Two-photon excitation fluorescence (TPEF) microscopy has evolved into a versatile tool in biological research. However, the multiplexing capability of TPEF microscopy is limited by the narrow spectral bandwidth of the light source. In this study, we apply a photonic crystal fiber in TPEF microscopy to broaden the excitation source bandwidth. We tuned the spectral window using a spatial light modulator as a programmable diffraction grating that was placed behind a prism pair. In addition, we combined a grating pair to compensate for dispersion to improve the two-photon excitation efficiency. The combination of a broad spectrum and a programmable grating enabled fast spectral window tuning rate on a time scale of tens of milliseconds. We demonstrate the performance of our method by imaging live B16 cells labeled with four emission spectrum overlapped fluorescent proteins.
Host heterogeneity and epistasis explain punctuated evolution of SARS-CoV-2
Authors: Nielsen Bjarke Frost , Saad-Roy Chadi M. , Li Yimei , Sneppen Kim , Simonsen Lone , Viboud Cécile , Levin Simon A. , Grenfell Bryan T.
Published: February 2023

Identifying drivers of viral diversity is key to understanding the evolutionary as well as epidemiological dynamics of the COVID-19 pandemic. Using rich viral genomic data sets, we show that periods of steadily rising diversity have been punctuated by sudden, enormous increases followed by similarly abrupt collapses of diversity. We introduce a mechanistic model of saltational evolution with epistasis and demonstrate that these features parsimoniously account for the observed temporal dynamics of inter-genomic diversity. Our results provide support for recent proposals that saltational evolution may be a signature feature of SARS-CoV-2, allowing the pathogen to more readily evolve highly transmissible variants. These findings lend theoretical support to a heightened awareness of biological contexts where increased diversification may occur. They also underline the power of pathogen genomics and other surveillance streams in clarifying the phylodynamics of emerging and endemic infections. In public health terms, our results further underline the importance of equitable distribution of up-to-date vaccines.
The nutrient-responsive CDK Pho85 primes the Sch9 kinase for its activation by TORC1
Authors: Deprez Marie-Anne , Caligaris Marco , Rosseels Joëlle , Hatakeyama Riko , Ghillebert Ruben , Sampaio-Marques Belém , Mudholkar Kaivalya , Eskes Elja , Meert Els , Ungermann Christian , Ludovico Paula , Rospert Sabine , De Virgilio Claudio , Winderickx Joris
Published: February 2023

Yeast cells maintain an intricate network of nutrient signaling pathways enabling them to integrate information on the availability of different nutrients and adjust their metabolism and growth accordingly. Cells that are no longer capable of integrating this information, or that are unable to make the necessary adaptations, will cease growth and eventually die. Here, we studied the molecular basis underlying the synthetic lethality caused by loss of the protein kinase Sch9, a key player in amino acid signaling and proximal effector of the conserved growth-regulatory TORC1 complex, when combined with either loss of the cyclin-dependent kinase (CDK) Pho85 or loss of its inhibitor Pho81, which both have pivotal roles in phosphate sensing and cell cycle regulation. We demonstrate that it is specifically the CDK-cyclin pair Pho85-Pho80 or the partially redundant CDK-cyclin pairs Pho85-Pcl6/Pcl7 that become essential for growth when Sch9 is absent. Interestingly, the respective three CDK-cyclin pairs regulate the activity and distribution of the phosphatidylinositol-3 phosphate 5-kinase Fab1 on endosomes and vacuoles, where it generates phosphatidylinositol-3,5 bisphosphate that serves to recruit both TORC1 and its substrate Sch9. In addition, Pho85-Pho80 directly phosphorylates Sch9 at Ser726, and to a lesser extent at Thr723, thereby priming Sch9 for its subsequent phosphorylation and activation by TORC1. The TORC1-Sch9 signaling branch therefore integrates Pho85-mediated information at different levels. In this context, we also discovered that loss of the transcription factor Pho4 rescued the synthetic lethality caused by loss of Pho85 and Sch9, indicating that both signaling pathways also converge on Pho4, which appears to be wired to a feedback loop involving the high-affinity phosphate transporter Pho84 that fine-tunes Sch9-mediated responses.
Multi-attribute decision-making method based on q-rung orthopair probabilistic hesitant fuzzy schweizer-sklar power weighted hamy mean operator
Authors: Chen Zhiyuan , Shen Di , Yu Fuping , Tang Xinlei , Zhang Zhe
Published: February 2023

In order to further improve the computing power of the information aggregation operator in the q-rung orthopair probabilistic hesitant fuzzy environment, this paper proposes a multi-attribute decision-making method based on the q-rung orthopair probabilistic hesitant fuzzy Schweizer-Sklar power weighted Hamy mean operator. Firstly, the algorithm of q-rung orthopair probabilistic hesitant fuzzy set is improved based on the Schweizer-Sklar T-norm. In order to better reflect the degree of hesitation of decision-making experts, a new q-rung orthopair probabilistic hesitant fuzzy distance measure is proposed, which provides a basis for subsequent power weighted calculations. Furthermore, considering the correlation between attributes and the influence of data extremes, some information aggregation operators and their power weighted forms are proposed. Finally, a multi-attribute decision-making model based on the q-rung orthopair probabilistic hesitant fuzzy Schweizer-Sklar power weighted Hamy mean operator is established, and the reliability and validity of the research content in this paper are verified through decision-making examples and comparative analysis.