bluuebunny/crossref_metadata_2025 huggingface dataset:
SUBARU Adaptive Optics Program
Authors: Takami Hideki , Iye Masanori , Takato Naruhisa , Hayano Yutaka , Otsubo Masashi , Nakashima Koji
Published: February 2023

SUBARU telescope with 8.2 m diameter is being constructed atop Mauna Kea in the Hawaii island. It employs the thin-meniscus primary mirror that is supported by 260 actuators, providing the almost perfect surface figure for near infrared imaging. The atmospheric turbulence is now the dominant origin of image degradation. Therefore, the adaptive optics (hereafter AO) system is essential equipment for large ground telescopes.
Recent Results from the MARTINI III/WHIRCAM Infra-red Adaptive Optics System
Authors: Doel P. , Buscher D. , Dunlop C. , Sharples R. , Andrews N.
Published: February 2023

The MARTINI-III system is an infra-red adaptive optics system designed as a semi-common user instrument for use at the Ground-based High Resolution Imaging Laboratory (GHRIL) on the William Herschel Telescope (WHT). The optical layout of the system is shown in figure 1. Light from the Nasmyth focus of the WHT is incident on a six element adaptive mirror and is reflected back onto a toroidal mirror which refocuses the light at an off-axis point. Just before this re-imaged focus the light is split by a dichroic beamsplitter and the infra-red light reflected into the infra-red camera (WHIRCAM) arm. The visible light is passed to the wavefront sensing arm where it passes through a selectable sub-aperture mask and is imaged onto the wavefront sensor (an Astromed CCD15-11 camera) by a split lens assembly. The elements of this split lens are adjustable and these are used to align the images formed by each sub-aperture in a row on a 24x4 pixel region in the corner of the wavefront sensor’s CCD chip, each spot being centred on a 4x4 pixel square. On readout the 4x4 pixels are on-chip binned into a 2x2 quad-cell, the output of which is used to calculate the X and Y wavefront slopes. The system is designed to work in two modes, one an ‘unco-phased’ mode where the mirror segments are just controlled to remove the individual wavefront tip-tilt across each segment but no attempt is made to piston the six mirrors. The other a ‘co-phased’ mode where the segment slopes are used to reconstruct the piston values of each wavefront segment. The real-time reconstruction and control is performed with a Motorola 68020 microprocessor. Pixel scales on WHIRCAM of 0.05, 0.08 and 0.24 arcseconds can be selected giving fields of 12.8, 20.5 and 61.5 arcseconds respectively. A guide star of R-band magnitude 13th or brighter is required to be centred within this field.
CFHT Adaptive Optics Integration and Characterisation
Authors: Lai O. , Arsenault R. , Rigaut F. , Salmon D. , Gigan P. , Rouan D. , Crampton D. , Fletcher J.M. , Stilburn J. , Boyer C. , Jagourel P.
Published: February 2023

The Canada-France-Hawaii Telescope (CFHT) Adaptive Optics Instrument (PUEO’) is in its final stages of integration and calibration. First diffraction limited images produced with realistic turbulence conditions are presented, as well as operating characteristics.
Adaptive Optics Point Spread Function Retrieval from Wavefront Sensor Measurements
Authors: Véran Jean-Pierre , Rigaut François , Maitre Henri
Published: February 2023

We use wavefront sensor data, obtained directly during the acquisition of the science target, to retrieve the system point spread function, required for data reduction and image restoration. First results on simulated data are presented.
Conjugating AO Correction to Turbulence in the WHT AO System Design
Authors: Wells Martyn
Published: February 2023

One of the factors which limits the performance of a NGS AO system is the brightness of available stars. This, when combined with a requirement for a high sky coverage and a moderate Strehl ratio (see Table 1), means that reference stars up to about 1.5 arcmin from the science object have to be used.
Adaptive Optics in Western Europe
Authors: Merkle Fritz , Zeiss Carl
Published: February 2023

In Western Europe in the early seventies, main emphasis was put on high-power laser applications. Later, compensated imaging became the main driver, leading to the first routinely operated adaptive system in astronomy.
Spatial Light Modulator Structures for Adaptive Optics
Authors: Woods C. L.
Published: February 2023

Spatial light modulators have substantially improved in the past few years. Currently, commercial 256 by 256 pixel liquid crystal binary SLMs are available with an operating speed of a millisecond and a pixel spacing of 20 microns for a price of $15,000. Additional improvements in speed by orders of magnitude should be available in the next few years, and micro-mechanical flexure and deformable membrane devices will probably become available.
Two Decades of Atmospheric Site Characterization
Authors: Walters D. L.
Published: February 2023

Since the mid 1970's, a number of US Department of Defense programs have needed atmospheric-optical site characterization data that included the following: atmospheric-optical coherence length r0, isoplanatic angle θ0, thermal probe CT2 and acoustic echo-sounder data. In order to make these measurements, a suite of instruments were developed and have evolved to become reference standards.
A Study of Wavefront Reconstruction Methods
Authors: Ash D.L. , Solomon C.J.
Published: February 2023

The accurate estimation of atmospherically distorted wavefronts is vital to both adaptive optics systems, and statistical deconvolution methods for image enhancement, as this places an absolute limit on the achievable resolution. Thus a clear understanding of the factors affecting the accuracy of wavefront estimation is essential.
A Sodium Guide Star Laser System for the Lick Observatory 3 Meter Telescope
Authors: Friedman Herbert W. , Erbert Gaylen V. , Gavel Donald T. , Kuklo Thomas C. , Malik Jody G. , Salmon J. Thaddeus , Smauley David A. , Thompson Gary R.
Published: February 2023

The use of sodium-layer laser guide stars for adaptive optics systems greatly enhances the sky coverage as compared to systems using natural guide stars. In order to demonstrate the feasibility of a sodium-layer guide star, a 20 W pulsed dye laser system has been designed and installed on the 3 meter Shane telescope at the Lick Observatory, Mt. Hamilton, California. The adaptive optics system used in conjunction with the laser guide star system has been described elsewhere1 and has already demonstrated diffraction limited images at the 2.2 micron wavelength using natural guide stars. The integration of the sodium laser guide star and the adaptive optics systems represents the first such installation on an astronomical telescope.
A Wavefront Generator for Adaptive Optics Testing
Authors: Marchetti Enrico , Ragazzoni Roberto
Published: February 2023

During day-light adaptive optics systems usually needs an artificial source in order to close the loop and provide checks for tests, upgrades and performances verifications. In this work the wavefront simulator for the Adaptive Optics system of the Telescopio Nazionale Galileo (TNG).
A New Generation Tip-Tilt System
Authors: Esposito S. , Fini L. , Ranfagni P.
Published: February 2023

The Arcetri Adaptive Optics group is in charge to design and build a closed loop control system for the reduction of astronomical image motion to be used in the Italian 3.6 meters “Telescopio Nazionale Galileo” (TNG) [4]. After the realization of an analog system prototype [1] the Arcetri Adaptive Optics Group has carried on the project of the final version of the control system that is scheduled to be ready for the telescope first light in middle ’96. The tip-tilt system is the first step in the implementation of a fully developed system which will also correct higher order terms.
Preliminary mechanical design of an adaptive secondary unit for the MMT-Conversion telescope
Authors: Del Vecchio C. , Gallieni W. , Salinari P , Gray P.M.
Published: February 2023

The potential advantages of using the secondary mirror of a telescope to perform adaptive correction of the wave front distorted by propagation through the atmosphere are known for long time. Among them are the drastic reduction of the number of optical surfaces, that increases the transmission and reduces the emissivity, and the possibility of providing adaptive corrections to different focal stations. The reduced emissivity makes adaptive secondary mirrors particularly attractive for work at infrared wavelengths where thermal background is of concern, provided that the design of the unit doesn’t affect emissivity in other ways (e. g., with high emissivity surfaces surrounding the secondary). Another desirable feature of an adaptive secondary (AS) is the capability of providing, in addition to wave front correction with many degrees of freedom, also a large (> 0.1 mm) range of motion to perform “chopping”, that is useful for sky subtraction even with modern two dimensional IR detectors. A conceptual approach to the design of an AS with the above features (+) was followed by a variety of studies and experiments that are still in progress (Bruns et al., Biasi et al., Biliotti et al., in this Conference). This paper reports the results of a preliminary study of the various problems related to the general layout, to the support of the optics and to the thermal aspects, in the specific case of the secondary mirror unit for the F/15 Cassegrain focus of the MMT Conversion telescope.
Force-Actuated Adaptive Secondary Mirror Prototype
Authors: Bruns Donald G. , Barrett Todd K. , Sandler David G. , Martin H.M. , Brusa Guido , Modisett Dave , Angel J.R.P. , Biasi Roberto , Gailieni Daniele , Salinari Piero
Published: February 2023

The new 6.5 m single mirror Multiple Mirror Telescope (MMT) will be equipped with adaptive optics capabilities. In particular, high resolution infrared astronomy will use a new adaptive secondary on a regular basis. Before we design the adaptive secondary in detail, we fabricated a smaller prototype mirror using similar actuators and actuator geometry. The prototype's purpose is to debug the components and allow comparisons with theoretical predictions. We are studying system interactions and looking for unexpected performance characteristics. Manufacturing techniques and reliability are also being tested, to reduce risks when building the adaptive secondary.
System Electronic Design for a Compact Deformable Mirror System
Authors: Rogers Sam , McDermott Scot
Published: February 2023

System design for an remotely controlled adaptive optics package to be mounted on the side of a large telescope involves many components. The design goals, hardware used (wavefront sensor, deformable optics and reconstructor hardware), the final system design, and some results from an experiment performed on the SOR 3.5 meter telescope will described in this paper.
Tip-Tilt Correction at the Anglo-Australian Telescope
Authors: Bryant J. J. , O'Byrne J. W. , Minard R. A. , Fekete P. W. , Cram L. E.
Published: February 2023

The first stage of the AAT adaptive optics program, allowing tip-tilt correction for images and spectroscopy in the near infrared has recently been implemented.
Prediction of Star Wonder Path With Linear and Non-linear Methods
Authors: Bonaccini D. , Gallieni D. , Giampieretti R.
Published: February 2023

In adaptive optical systems using Shack-Hartmann wavefront sensors the optical wavefront is obtained measuring the star wonder or centroid of the reference object. The integration time of the wavefront sensor, especially in the case of natural guide star references, produces a phase lag of the servo-system which affects quite heavily the system performance in most cases, i.e. for faint sources.
Principles of Development of Adaptive Bimorph Optics
Authors: Safronov. ANdrey G.
Published: February 2023

A low-order correction adaptive optics, the so-called "small" adaptive optics, is obviously more preferable than the ordinary adaptive optics from the standpoint of technical introduction including the industrial-scaled one. In practice controllable bimorph mirrors may be considered as ideal means for use in such a system. Analysis of up-to-date state of bimorph optics have shown that up to the present days there were no industrial samples of bimorph mirrors as well as the industrial technology of their manufacturing. Developments on large-aperture bimorph mirrors have been totally lacking. Disadvantages of the presented before bimorph mirrors have hindered their wide introducing into the industrial laser optics and astronomical telescopes.
Review of astronomical adaptive optics systems on medium size (1.5-5m) telescopes
Authors: Rigaut François
Published: February 2023

We present an exhaustive review of adaptive optics systems with a vocation for astronomy. After a brief historical introduction, we review the different technological approaches and the results.
Review of Non Astronomical Active and Adaptive Optics Technologies
Authors: Fender Janet S. , Butts Russell R.
Published: February 2023

Active and adaptive optics developed by the defense and industrial communities for high performance optical telescopes and laser propagation are reviewed in this paper.
Status of the Advanced Electro-Optical System (AEOS) Adaptive Optics
Authors: Kenemuth John R. , McNally James J. , Passaro James R. , Berger Paul J. , La Fiandra Carlo , Abreu Rene
Published: February 2023

The Advanced Electro-Optical System (AEOS) is being developed as an upgrade to the Air Force Maui Space Surveillance Site (MSSS) on Haleakala, Maui, Hawaii. It consists of a new 3.6-m diameter telescope in an azimuth-elevation configuration mounted atop a pier approximately 60 ft above the local ground level. A bent-Cassegrain configuration provides for selection between three (3) sensor locations on the telescope trunnion and access to a coudé path through the elevation and azimuth axes to ground level. The coudé optics in the telescope provide a ± 150 μrad field of view over a 0.5 to 5.0 μm spectral band to a 941-actuator adaptive optics system located in the coudé path directly beneath the telescope at ground level (coudé room) which will provide dynamic compensation for atmospheric turbulence effects so that a significantly improved image quality may be achieved. A switching mirror located at the output of the adaptive optics system will provide a capability to direct either a compensated beam, or a beam which bypasses the adaptive optics system, to any of seven (7) optics laboratories concentrically located around the room which contains the adaptive optics system.
Focal Anisoplanatism Effect Affecting Techniques for Laser Guide Star Absolute Tilt Measurements
Authors: Riccardi A. , Ragazzoni R. , Esposito S.
Published: February 2023

We present calculations aimed at establishing the error resulting from the anisoplanatism effect when two auxiliary telescopes are used to obtain the overall backward wave-front tilt from a laser guide star.
Sodium Laser Guide Star Observations with FASTTRAC II
Authors: Groesbeck T. D. , Lloyd-Hart M. , Angel J. R. P. , McCarthy D. W. , Brusa G. , Gray P. M. , McLeod B. A. , Mohanty S. , Martinez T. , Jacobsen B. , Wittman D. M. , Ryan P. T. , Bruns D. G. , Sandler D. G.
Published: February 2023

The Center for Astronomical Adaptive Optics (CAAO) at the University of Arizona is developing a diffraction-limited adaptive optics (AO) system at infrared wavelengths utilizing a sodium laser guide star. This system (Lloyd-Hart et al., this conference), based on an adaptive secondary mirror with 300 actuators, will be placed in operation following the installation of the 6.5 m mirror upgrade at the Multiple Mirror Telescope (MMT) mount. As an interim step, we have built an adaptive optics system which provides tip-tilt correction for each of the 6 individual beams of the current MMT. This instrument, called FASTTRAC II, will produce a combined image at the diffraction limit of the 1.8 m primary mirrors (≲0.3″ at 2.2 μm) yielding moderately high resolution images in the near infrared. The current system incorporates the design philosophy of the 6.5 m system and provides a testbed for development of the system components in addition to serving as a significant scientific instrument in its own right.
Review of CCDs and Controllers: Status and Prospects
Authors: Beletic James W.
Published: February 2023

Wavefront sensor CCDs and controller electronics are reviewed, including functional systems and those in development. All major programs and manufacturers are presented and compared.
Principles of Action of Segmented Corrector
Authors: Smirnov Alexander P. , Reznichenko Vladimir V.
Published: February 2023

Determination of misalignment contributions of the optical system induced by individual elements errors and optimisation of "coarse" and "fine" corrections are the main purposes of the present paper. Function of the system perfomance dependability is investigated by means of a model of the adaptive segmented mirror telescope. The problem solution is found based on wave aberrationsd minimizattion in accordance with the corrector displacements. Position displacements of the secondary mirror in relation to thed primary one as well as these of peripheral in relation to the central one seem to be parameters of this dependence. A correlation between these parameters and temperature fluctuation range is found for this optical module. Maximization of the said parameters weighted sum within the minimization problem solutions domain provides necessary conditions for correction process optimisation and determination of optimal aligment of the system main elements.
Fast Steering Mirror Performance
Authors: Bruns D. , Esposito S. , Farinato J. , Ragazzoni R.
Published: February 2023

A fast steering mirror actuated with electromagnetic voice coils has been designed and built, shown in Figure 1. The mirror diameter is 100 mm, and made with 19 mm thick fused silica. Since only 1 milliradian angular deflections are required in typical astronomical applications, the mirror is held in place with a stiff, two-dimensional flexural pivot. Voice coil actuators are arranged in push-pull pairs about two orthogonal axes, resulting in a high torque against the mirror, but negligible piston excitation. To further control the system performance, a reaction mass inside the optical head cancels most of the external vibration.
Status of the Design of an Adaptive Secondary for the 6.5m conversion of the MMT telescope
Authors: Brusa Guido , Gray Peter , Vecchio Ciro Del , Salinari Piero , Gallieni Walter
Published: February 2023

The advantages of using an adaptive secondary mirror for astronomical high resolution observations are very attractive. The drastic reduction of optical surfaces along the optical train of the adaptive system will allow a very compact system with high transmission and low emissivity. Also such a system has the potentiality of a very high actuator density.
Liquid Crystal Spatial Modulators with Segmented Mirror for Adaptive Optics.
Authors: Reznichenko Vladimir V. , Nicitin Vladislav V. , Onokhov Arkadi P. , Isaev Michail V. , L.Ivanova Natalia , Beresnev Leonid A. , Haase Wolfgang
Published: February 2023

We have developed efficient optically controlled liquid-crystal optically addressed spatial light modulators that possess modulation parameters for reflected light.
Design of optical wavefront corrector based on liquid crystal concept
Authors: Reznichenko Vladimir V. , Nicitin Vladislav V. , Onokhov Arkadi P. , V.Isaev Michail , L.Ivanova Natalia
Published: February 2023

A mack-up of a nematic liquid crystal (LC) phase corrector has developed for application in adaptive optical systems. Both design features of the optical addressed spatial light modulators and requirements to its are concedered. Optical surface processing technology is investigated for preperation of the modulator individual components. The modulator electro-optical responses obtained show the wider potentialities of the device application as a phase corrector.
Temporal Performance Characterization of a Liquid Crystal Phase Modulator
Authors: Kudryashov A. , Gonglewski J. , Love G. D. , Browne S. , Highland R.
Published: February 2023

Liquid crystal phase modulators or retarders have the potential to induce controlled, repeatable, dynamic aberrations into optical systems at low cost, low complexity, and high flexibility. We discuss the performance of a transmissive nematic device with 69 phase delay cells in a hexagonal pattern developed for the Phillips Laboratory by Meadowlark Optics. The emphasis on this research is the production and measurement of time varying phase distortions.
Phase Diversity Imaging: Report of Experiments and Simulations
Authors: Gonsalves Robert A. , Ebstein Steven M. , Nisenson Peter , Shelton Chris
Published: February 2023

We report research results on phase diversity imaging, a technique for pre and post processing of atmospherically degraded images. The method uses an in-focus image and an out-of-focus Image to deduce the aberrating wavefront introduced by the atmosphere and telescope; and deconvolves the measured images to produce a near-diffraction-limited estimate of the object.
Review of Industrial Applications
Authors: Merkle Fritz
Published: February 2023

Summary not available.
Adaptive Optics at MPE: Astronomical Results and Future Plans
Authors: QUIRRENBACH A.
Published: February 2023

We have used the Adaptive Optics system ADONIS at the ESO 3.6 m telescope on La Silla, Chile, to obtain high-resolution images of the R136 complex in the young massive cluster 30 Doradus in the Large Magellanic Cloud. Within our 12.″8 × 12.″8 field-of-view, we find more than 500 stars in our H and K near-infrared images. Combining these data with Hubble Space Telescope observations in the visual wavelength range, and comparing the brightness and colors with stellar models, we can determine the mass of each individual star. We have thus been able to construct the stellar mass function in the central crowded area down to ~ 5 solar masses. The inclusion of the infrared data obtained with Adaptive Optics in this analysis reduces the uncertainty due to varying amounts of extinction towards the individual stars. In addition, we find about 60 red sources that went undetected by the Hubble observations; these are probably young low or intermediate-mass pre-main-sequence stars, which are still embedded in dense circumstellar gas. We can constrain the age of the starburst in the center of 30 Doradus to about 3 to 5 Myrs. The mass function appears to vary between the innermost 0.4 pc and the outer region, indicating mass segregation on a time scale of only 105 to 106 years.
Phasing of Elements of a Primary Mirror of AST-10
Authors: Lukin V. , Fortes B.
Published: February 2023

It is pertinent to note that the applications of adaptive optics (AO) for implementation of the total potential of such a high-power telescope as AST-10 imposes heavy demands on the quality of production, adjustment and phasing of a primary mirror (PM). The atmospheric turbulence was a controlling factor of the image quality for previous generations of telescopes.
ADAPTIVE OPTICS LONG EXPOSURE POINT SPREAD FUNCTION RETRIEVAL FROM WAVEFRONT SENSOR MEASUREMENTS: TESTS ON REAL DATA
Authors: Véran J.-P. , Rigaut F. , Rouan D. , Maître H.
Published: February 2023

Current astronomical adaptive optics (AO) systems are not able to fully correct the atmospheric turbulence. As a result, the quality of the AO long exposure images is degraded by a residual blur which significantly reduces the contrast of the fine details [1]. Removing this residual blur is the field of image restoration (deconvolution) and since this problem is general to many imaging applications, many different methods have already been developed. To achieve an accurate restoration however, an accurate estimation of the system Point Spread Function (PSF) is usually required. For adaptive optics imaging, the shape of the PSF depends on how well the deformable mirror is able to compensate for the wavefront distortions. This “degree of correction” in turn depends on the size and magnitude of the object used as a reference for wavefront sensing, but also on the characteristics of the turbulence, which is known to be a non-stationary process. As a results, the AO PSF is highly variable [2]. The usual way around this problem involves dedicating of significant portion of the observing time to the sole acquisition of a point source, from which the current PSF is estimated.
CTIS-GAN: computed tomography imaging spectrometry based on a generative adversarial network
Authors: Wu Luoxiang , Cai Weiwei
Published: February 2023

Computed tomography imaging spectrometry (CTIS) is a snapshot hyperspectral imaging technique that can obtain a three-dimensional (2D spatial + 1D spectral) data cube of the scene captured within a single exposure. The CTIS inversion problem is typically highly ill-posed and is usually solved by time-consuming iterative algorithms. This work aims to take the full advantage of the recent advances in deep-learning algorithms to dramatically reduce the computational cost. For this purpose, a generative adversarial network is developed and integrated with self-attention, which cleverly exploits the clearly utilizable features of zero-order diffraction of CTIS. The proposed network is able to reconstruct a CTIS data cube (containing 31 spectral bands) in milliseconds with a higher quality than traditional methods and the state-of-the-art (SOTA). Simulation studies based on real image data sets confirmed the robustness and efficiency of the method. In numerical experiments with 1000 samples, the average reconstruction time for a single data cube was ∼16ms. The robustness of the method against noise is also confirmed by numerical experiments with different levels of Gaussian noise. The CTIS generative adversarial network framework can be easily extended to solve CTIS problems with larger spatial and spectral dimensions, or migrated to other compressed spectral imaging modalities.
Optical design of multilayer antireflection coatings for indoor solar cell applications
Authors: Kubota Shigeru , Ahmmad Bashir , Hirose Fumihiko
Published: February 2023

Multilayer antireflection coatings (ARCs) for solar cells are conventionally designed to enhance the photocurrent level obtained at normal incidence. This is mainly because outdoor solar panels are usually placed such that they can receive strong midday sunlight at a nearly vertical angle. However, in the case of indoor photovoltaic devices, the direction of light changes considerably with changes in the relative position and angle between the device and light sources; therefore, it is often difficult to predict the incident angle. In this study, we explore a method to design ARCs suitable for indoor photovoltaics by essentially taking into account the indoor lighting environment, which is different from the outdoor conditions. We propose an optimization-based design strategy that aims to enhance the average level of the photocurrent generated when a solar cell receives irradiance randomly from all directions. We apply the proposed method to design an ARC for organic photovoltaics, which are expected to be promising indoor devices, and numerically compare the resultant performance with that obtained using a conventional design method. The results demonstrate that our design strategy is effective for achieving excellent omnidirectional antireflection performance and allows the realization of practical and efficient ARCs for indoor devices.
LIBS and Raman spectroscopy in tandem with machine learning for interrogating weatherization of lithium hydride
Authors: Pinson Ryan E. , Giminaro Andrew V. , Dugan Christina L. , Jenkins Phillip R. , Patnaik Anil K.
Published: February 2023

Lithium compounds such as lithium hydride (

L
i
H

) and anhydrous lithium hydroxide (

L
i
O
H

) have various applications in
industry but are highly reactive when exposed to moisture and

C
O

2

. These reactions create new molecular
compounds that degrade applications. Environmental conditions such as
temperature and moisture are examples of environmental conditions that
are of interest for these reactions. To interrogate the effects of
such weatherization, experiments were conducted in an environmental
chamber (Plas-Labs 890-THC glove box) employing a pulsed laser and an
echelle spectrograph in a novel single setup to conduct both Raman
spectroscopy and laser-induced breakdown spectroscopy (LIBS) in
tandem. These measurements in conjunction with data fusion and machine
learning techniques are used to develop training and testing of
environmental conditioning of Li compounds. Modeling of environmental
characterizations involving lithium-based compounds enabled by the
presented measurements and analytical techniques has significant
implications on industrial technologies, such as batteries, and other
nuclear applications.
Inverse design of a photonic moiré lattice waveguide towards improved slow light performances
Authors: Nasidi Ibrahim , Hao Ran , Jin SangZhong , Li Erping
Published: February 2023

Slow light waveguides in photonic crystals are engineered using a conventional method or a deep learning (DL) method, which is data-intensive and suffers from data inconsistency, and both methods result in overlong computation time with low efficiency. In this paper, we overcome these problems by inversely optimizing the dispersion band of a photonic moiré lattice waveguide using automatic differentiation (AD). The AD framework allows the creation of a definite target band to which a selected band is optimized, and a mean square error (MSE) as an objective function between the selected and the target bands is used to efficiently compute gradients using the autograd backend of the AD library. Using a limited-memory Broyden-Fletcher-Goldfarb-Shanno minimizer algorithm, the optimization converges to the target band, with the lowest MSE value of 9.844×10−7, and a waveguide that produces the exact target band is obtained. The optimized structure supports a slow light mode with a group index of 35.3, a bandwidth of 110 nm, and a normalized-delay-bandwidth-product of 0.805, which is a 140.9% and 178.9% significant improvement if compared to conventional and DL optimization methods, respectively. The waveguide could be utilized in slow light devices for buffering.
Discrimination of thermal, molecular orientation, and pure electronic refractive nonlinearities using the polarization-resolved Z-scan technique
Authors: Moysés R. M. , Barbano E. C. , Misoguti L.
Published: February 2023

We have investigated how the polarization-resolved Z-scan technique is able to distinguish and discriminate three types of nonlinear effects—thermal, orientational, and ultrafast electronic nonlinearities—when acting simultaneously. Here employing a high-repetition-rate ultrafast laser, we excite these three nonlinearities in pure and contaminated CS2 solvent. Using 200 fs laser pulses, we could detect and measure the contribution of pure electronic, orientational, and, more importantly, identify the growth of cumulative thermal effect as the laser repetition rate increases. Also, we have verified that the source of the thermal effect is mainly due to two-photon (one-photon) absorption for pure (contaminated) CS2.
Chiral polarization response of a nanophotonic device
Authors: Sadgrove Mark , Sugawara Masakazu , Mitsumori Yasuyoshi , Edamatsu Keiichi
Published: February 2023

Nanophotonic devices are becoming increasingly important for enabling the controlled and efficient production of photons in well defined modes of optical resonators and waveguides. A particular class of such devices which has seen extensive application in recent years is that of evanescently coupled waveguides which can be used to create fiber-coupled single photon sources or to couple light to other nanophotonic systems. However, evanescent coupling typically results in equal intensities coupled to either port of the waveguide, leading to a 50% if it is desired to send photons to a particular receiver.
Orientation of the NV centers are determined using the cylindrical vector beam array
Authors: Li Ziyan , Zhang Ning , Guo Ji , Guo Qiang , Yu Tingting , Zhang Mengshi , Wang Guanxue , Gao Xiumin , Zhang Xuedian
Published: February 2023

The determination of nitrogen-vacancy centers plays an important role in quantum information sensing. Efficiently and rapidly determining the orientation of multiple nitrogen-vacancy center s in a low-concentration diamond is challenging due to its size. Here, we solve this scientific problem by using an azimuthally polarized beam array as the incident beam. In this paper, the optical pen is used to modulate the position of beam array to excite distinctive fluorescence characterizing multiple and different orientations of nitrogen-vacancy centers. The important result is that in a low concentration diamond layer, the orientation of multiple NV centers can be judged except when they are too close within the diffraction limit. Hence, this efficient and rapid method has a good application prospect in quantum information sensing.
Integral imaging reconstruction system based on the human eye viewing mechanism
Authors: Gu Yue-Jia-Nan , Zhang Jin , Piao Yan , Deng Li-Jin , Wang Qi
Published: February 2023

For integral stereo imaging systems based on lens arrays, the cross-mixing of erroneous light rays between adjacent lenses seriously affects the quality of the reconstructed light field. In this paper, we proposed a light field reconstruction method based on the human eye viewing mechanism, which incorporates simplified human eye imaging into the integral imaging system. First, the light field model for specified viewpoint is established, and the distribution of the light source for each viewpoint is accurately calculated for the EIA generation algorithm of fixed viewpoint. Second, according to the ray tracing algorithm in this paper, non-overlapping EIA based on the human eye viewing mechanism is designed to suppress the amount of crosstalk rays fundamentally. The actual viewing clarity is improved with the same reconstructed resolution. Experimental results verify the effectiveness of the proposed method. The SSIM value is higher than 0.93, which verifies that the viewing angle range is increased to 62°.
One-step crack-free fabrication of chip-scale lithium niobate through dispersion engineering of femtosecond pulses
Authors: Wu Qiang , Zhou Xu , lu Yao , Liu Haibo , Xu Xitan , Chen Lu , Li Zhixuan , Wang Rui , Guo Jin , Xu Jingjun
Published: February 2023

Femtosecond-laser micromachining is of tremendous interest to various disciplines including optics, material science, and biomedicine. The continued effort in optimizing laser-matter interactions has, for example, greatly promoted the application of lithium niobite in the fields of nonlinear photonics, on-chip integrated photonics, and quantum optoelectronics. However, fragmentations and cracks commonly accompanying the laser machining process leave the further application of lithium niobate having to face very complicated post-processing procedures. Here, we propose a crack-free micro-structure fabrication method using dispersion-engineered femtosecond laser pulses. This achievement is based on a thorough investigation into the influence of femtosecond laser temporal dispersion on the lithium niobite machining process. We find our approach can improve the terahertz transmittance by about 5.8 times compared to the general case. Our findings may further promote the development of lithium niobite for optoelectronics, integrated devices, terahertz technology, and industrial applications, as well as offer insights into simple realization of precision machining of other forms of hard and brittle materials.
Inverse Design of Nanophotonic Devices using Dynamic Binarization
Authors: Butz Marco , Abazi Adrian , Ross Rene , Risse Benjamin , Schuck Carsten
Published: February 2023

The complexity of applications addressed with photonic integrated circuits is steadily rising and poses increasingly challenging demands on individual component functionality, performance and footprint. Inverse design methods have recently shown great promise to address these demands using fully automated design procedures that enable access to non-intuitive device layouts beyond conventional nanophotonic design concepts. Here we present a dynamic binarization method for the objective-first algorithm that lies at the core of the currently most successful inverse design algorithms. Our results demonstrate significant performance advantages over previous implementations of objective first algorithms, which we show for a fundamental TE00 to TE20 waveguide mode converter both in simulation and in experiments with fabricated devices.
Terahertz anti-resonance hollow-core fiber for label-free and nondestructive detection of circulating tumor cells
Authors: He Zhe , Luo Yueping , Huang guorong , de La Chapelle Marc Lamy , Tian Huiyan , Xie Fengxin , Shi Jia , yang xiang , Fu Weiling
Published: February 2023

Circulating tumor cells (CTCs) can be used as important biomarkers to reflect the progress and malignancy of tumors. However, current CTC detection technologies have some limitations for clinical applications due to their complexity, low specificity and high cost. Herein, we develop a terahertz anti-resonance hollow core fiber (THz AR-HCF) biosensor for CTC detection. Through simulation and experiment comparisons, the low-loss property of the THz AR-HCF is verified, and a suitable fiber is selected for biosensing applications. By measuring different cell numbers and different types of cancer cells, a good linear relationship between THz transmittance and the numbers of cells between 10 and 106 was found. Meanwhile, different types of tumor cells can be distinguished by comparing THz transmission spectra, indicating that the biosensor has high sensitivity and specificity for CTC detection. The biosensor only required a small amount of sample, as low as 100 μl, and enables label-free and nondestructive quantitative detection. Flow cytometry results showed that the cell viability was as high as 98.5±0.26% after whole assay process and there was no statistically significant difference compared with the negative control. This study demonstrated that the proposed THz AR-HCF has great potential for highly sensitive, label-free and nondestructive detection of CTCs in clinical samples.
Alpha oscillatory activity is causally linked to working memory retention
Authors: Chen Xueli , Ma Ru , Zhang Wei , Zeng Ginger Qinghong , Wu Qianying , Yimiti Ajiguli , Xia Xinzhao , Cui Jiangtian , Liu Qiongwei , Meng Xueer , Bu Junjie , Chen Qi , Pan Yu , Yu Nancy Xiaonan , Wang Shouyan , Deng Zhi-De , Sack Alexander T. , Laughlin Myles Mc , Zhang Xiaochu
Published: February 2023

Although previous studies have reported correlations between alpha oscillations and the “retention” subprocess of working memory (WM), causal evidence has been limited in human neuroscience due to the lack of delicate modulation of human brain oscillations. Conventional transcranial alternating current stimulation (tACS) is not suitable for demonstrating the causal evidence for parietal alpha oscillations in WM retention because of its inability to modulate brain oscillations within a short period (i.e., the retention subprocess). Here, we developed an online phase-corrected tACS system capable of precisely correcting for the phase differences between tACS and concurrent endogenous oscillations. This system permits the modulation of brain oscillations at the target stimulation frequency within a short stimulation period and is here applied to empirically demonstrate that parietal alpha oscillations causally relate to WM retention. Our experimental design included both in-phase and anti-phase alpha-tACS applied to participants during the retention subprocess of a modified Sternberg paradigm. Compared to in-phase alpha-tACS, anti-phase alpha-tACS decreased both WM performance and alpha activity. These findings strongly support a causal link between alpha oscillations and WM retention and illustrate the broad application prospects of phase-corrected tACS.
Health services for aboriginal and Torres Strait Islander children in remote Australia: A scoping review
Authors: Dossetor Phillipa J. , Freeman Joseph M. , Thorburn Kathryn , Oscar June , Carter Maureen , Jeffery Heather E. , Harley David , Elliott Elizabeth J. , Martiniuk Alexandra L. C.
Published: February 2023

In Australia, there is a significant gap between health outcomes in Indigenous and non-Indigenous children, which may relate to inequity in health service provision, particularly in remote areas. The aim was to conduct a scoping review to identify publications in the academic and grey literature and describe 1) Existing health services for Indigenous children in remote Australia and service use, 2) Workforce challenges in remote settings, 3) Characteristics of an effective health service, and 4) Models of care and solutions. Electronic databases of medical/health literature were searched (Jan 1990 to May 2021). Grey literature was identified through investigation of websites, including of local, state and national health departments. Identified papers (n = 1775) were screened and duplicates removed. Information was extracted and summarised from 116 papers that met review inclusion criteria (70 from electronic medical databases and 45 from the grey literature). This review identified that existing services struggle to meet demand. Barriers to effective child health service delivery in remote Australia include availability of trained staff, limited services, and difficult access. Aboriginal and Community Controlled Health Organisations are effective and should receive increased support including increased training and remuneration for Aboriginal Health Workers. Continuous quality assessment of existing and future programs will improve quality; as will measures that reflect aboriginal ways of knowing and being, that go beyond traditional Key Performance Indicators. Best practice models for service delivery have community leadership and collaboration. Increased resources with a focus on primary prevention and health promotion are essential.
A systematic review of dengue outbreak prediction models: Current scenario and future directions
Authors: Leung Xing Yu , Islam Rakibul M. , Adhami Mohammadmehdi , Ilic Dragan , McDonald Lara , Palawaththa Shanika , Diug Basia , Munshi Saif U. , Karim Md Nazmul
Published: February 2023

Dengue is among the fastest-spreading vector-borne infectious disease, with outbreaks often overwhelm the health system and result in huge morbidity and mortality in its endemic populations in the absence of an efficient warning system. A large number of prediction models are currently in use globally. As such, this study aimed to systematically review the published literature that used quantitative models to predict dengue outbreaks and provide insights about the current practices. A systematic search was undertaken, using the Ovid MEDLINE, EMBASE, Scopus and Web of Science databases for published citations, without time or geographical restrictions. Study selection, data extraction and management process were devised in accordance with the ‘Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies’ (‘CHARMS’) framework. A total of 99 models were included in the review from 64 studies. Most models sourced climate (94.7%) and climate change (77.8%) data from agency reports and only 59.6% of the models adjusted for reporting time lag. All included models used climate predictors; 70.7% of them were built with only climate factors. Climate factors were used in combination with climate change factors (13.4%), both climate change and demographic factors (3.1%), vector factors (6.3%), and demographic factors (5.2%). Machine learning techniques were used for 39.4% of the models. Of these, random forest (15.4%), neural networks (23.1%) and ensemble models (10.3%) were notable. Among the statistical (60.6%) models, linear regression (18.3%), Poisson regression (18.3%), generalized additive models (16.7%) and time series/autoregressive models (26.7%) were notable. Around 20.2% of the models reported no validation at all and only 5.2% reported external validation. The reporting of methodology and model performance measures were inadequate in many of the existing prediction models. This review collates plausible predictors and methodological approaches, which will contribute to robust modelling in diverse settings and populations.
Exploring water, sanitation, and hygiene coverage targets for reaching and sustaining trachoma elimination: G-computation analysis
Authors: Sullivan Kristin M. , Harding-Esch Emma M. , Keil Alexander P. , Freeman Matthew C. , Batcho Wilfrid E. , Bio Issifou Amadou A. , Bucumi Victor , Bella Assumpta L. , Epee Emilienne , Bobo Barkesa Segni , Seife Gebretsadik Fikre , Sanha Salimato , Kalua Khumbo M. , Masika Michael P. , Minnih Abdallahi O. , Abdala Mariamo , Massangaie Marília E. , Amza Abdou , Kadri Boubacar , Nassirou Beido , Mpyet Caleb D. , Olobio Nicholas , Badiane Mouctar D. , Elshafie Balgesa E. , Baayenda Gilbert , Kabona George E. , Kaitaba Oscar , Simon Alistidia , Al-Khateeb Tawfik Q. , Mwale Consity , Bakhtiari Ana , Westreich Daniel , Solomon Anthony W. , Gower Emily W.
Published: February 2023

Background

Trachoma is the leading infectious cause of blindness. To reduce transmission, water, sanitation, and hygiene (WaSH) improvements are promoted through a comprehensive public health strategy. Evidence supporting the role of WaSH in trachoma elimination is mixed and it remains unknown what WaSH coverages are needed to effectively reduce transmission.

Methods/Findings

We used g-computation to estimate the impact on the prevalence of trachomatous inflammation—follicular among children aged 1–9 years (TF1-9) when hypothetical WaSH interventions raised the minimum coverages from 5% to 100% for “nearby” face-washing water (<30 minutes roundtrip collection time) and adult latrine use in an evaluation unit (EU). For each scenario, we estimated the generalized prevalence difference as the TF1-9 prevalence under the intervention scenarios minus the observed prevalence. Data from 574 cross-sectional surveys conducted in 16 African and Eastern Mediterranean countries were included. Surveys were conducted from 2015–2019 with support from the Global Trachoma Mapping Project and Tropical Data.

When modeling interventions among EUs that had not yet met the TF1-9 elimination target, increasing nearby face-washing water and latrine use coverages above 30% was generally associated with consistent decreases in TF1-9. For nearby face-washing water, we estimated a ≥25% decrease in TF1-9 at 65% coverage, with a plateau upon reaching 85% coverage. For latrine use, the estimated decrease in TF1-9 accelerated from 80% coverage upward, with a ≥25% decrease in TF1-9 by 85% coverage. Among EUs that had previously met the elimination target, results were inconclusive.

Conclusions

Our results support Sustainable Development Goal 6 and provide insight into potential WaSH-related coverage targets for trachoma elimination. Targets can be tested in future trials to improve evidence-based WaSH guidance for trachoma.