Early Posting

Accepted papers to appear in an upcoming issue

Optica Publishing Group posts prepublication articles as soon as they are accepted and cleared for production. See the FAQ for additional information.

Virtually Measuring Layered Material Appearance

Kewei XU, Arthur cavalier, Benjamin Bringier, Mickaël Ribardière, and Daniel Meneveaux

DOI: 10.1364/JOSAA.514604 Received 30 Nov 2023; Accepted 17 Mar 2024; Posted 18 Mar 2024  View: PDF

Abstract: This paper describes the design and the implementation of a virtual gonioradiometer dedicated to theanalysis of layered materials BSDF. For a given material sample, interfaces between layers are representedby geometric meshes, associated with elementary reflectances. Light scattering is performed using pathtracing. Our system is composed of 5 hemispherical sensors, which cells have uniform solid angles, anda close-to-uniform geometry. The upper hemisphere captures the reflected radiance distribution, whilethe other 4 collect the light energy lost by the sample sides. Sensor resolutions can be set to gather veryfine details of the BSDF. With the proposed system, any type of virtual surface reflection and transmissioncan be simulated, with several controllable surface layers, and with any type of reflection configuration,including direct reflections, two bounces of reflection, or all contributions. A series of results are providedwith several types of layered materials, as well as discussion and analysis concerning the assumptionsmade with analytical layered BSDF models. We also propose an in-depth study of the side effects thatinevitably appear when measuring such (real) material configurations. Finally, our system will be freelyavailable to the community (open source dissemination). ©

Dynamic iterative correction algorithm for designing diffractiveoptical elements

Hu Chi, zhang jin, jiang shilei, and sun guobin

DOI: 10.1364/JOSAA.516657 Received 21 Dec 2023; Accepted 12 Mar 2024; Posted 12 Mar 2024  View: PDF

Abstract: When utilizing the Gerchberg-Saxton (GS) algorithm to design diffractive opticalelements, correction coefficients are introduced to improve the quality of the design results. Themain design idea is to correct the target information dynamically during the iterative calculationprocess. The effectiveness of the proposed method is demonstrated through the verification of beamshaping and phase-type hologram designs. Compared to the traditional GS algorithm, the results ofbeam shaping show that the light intensity nonuniformity and the RMSE (root-mean-square error)of the shaped spot are reduced by an order of magnitude. The results of phase-type holograms showthat the reconstructed image’s PSNR (peak signal-to-noise ratio) is improved by about 12dB. Finally,the paper also discusses the selection of correction coefficients, providing insights into the selectionof optimal design correction coefficients. The simulation and experimental results show that theimproved algorithm proposed in this paper is not only simple in design but also highly efficient inobtaining high-quality phase structure, which is of great help in designing high-quality diffractiveoptical elements.

Res-U2Net: Untrained Deep Learning for PhaseRetrieval and Image Reconstruction

Carlos Osorio Quero, Daniel Leykam, and Irving Rondon Ojeda

DOI: 10.1364/JOSAA.511074 Received 03 Nov 2023; Accepted 12 Mar 2024; Posted 12 Mar 2024  View: PDF

Abstract: Conventional deep learning-based image reconstruction methods require a large amount of training datawhich can be hard to obtain in practice. Untrained deep learning methods overcome this limitation bytraining a network to invert a physical model of the image formation process. Here we present a noveluntrained Res-U2Net model for phase retrieval. We use the extracted phase information to determinechanges in an object’s surface and generate a mesh representation of its 3D structure. We compare theperformance of Res-U2Net phase retrieval against UNet and U2Net using images from the GDXRAYdataset.

Simulating a turbulent video affected byspatiotemporally-varying blur and tilt usingtemporal cross-correlation of intermodal Zernikecoefficients

Or Maor and Yitzhak Yitzhaky

DOI: 10.1364/JOSAA.514892 Received 01 Dec 2023; Accepted 12 Mar 2024; Posted 12 Mar 2024  View: PDF

Abstract: Videos captured in long-distance horizontal imaging through the atmosphere, suffer fromdynamic spatiotemporal movements and blur caused by the air turbulence. Simulations of atmosphericturbulence in such videos, which have been conducted in the past, are difficult to compute. Our goal inthis research is to develop an effective simulation algorithm of videos affected by atmospheric turbulencecharacterized by spatiotemporally-varying blur and tilt, when supplied with a given image. Weaccomplish this via extending an already-established way that simulates atmospheric turbulence in asingle image, by incorporating turbulence properties in the time domain that include both the tilts andblurring effects. This study also extends our previous work that simulated turbulence, but did not considerthe space-varying property of the blur. This is done by employing the relationship between turbulenceimage distortions and the intermodal correlations of the Zernike coefficients in time and space, and alsovia analyzing the spatiotemporal matrix that represents the spatial correlation of movements betweendifferent frames. The proposed method can facilitate the production of simulations, given turbulenceproperties that include turbulence strength, object distance, and height. The simulation is applied tovideos with low and high frame-rates, and the differences between them are analyzed. The proposedmethod can prove useful when generating machine-learning algorithms that apply to videos affected byatmospheric turbulence, which require large labeled video datasets (with controlled turbulence andimaging parameters) for training.

Influence of corneal astigmatism on near andfar vision in eyes with bifocal intraocularlenses

JongIn You and Mooseok Jang

DOI: 10.1364/JOSAA.517377 Received 03 Jan 2024; Accepted 12 Mar 2024; Posted 12 Mar 2024  View: PDF

Abstract: Here, we present a full wave propagation model that quantitatively assesses the effectof astigmatism on visual functions in eyes with diffractive bifocal IOLs. The proposed modelwith bifocal IOLs evaluated the image quality of each focus at varying degrees of cornealastigmatism with the metrics of modulation transfer function and light-in-the-bucket. Theresults show that corneal astigmatism alters the distance-near image quality balance.Positive(Negative) astigmatism has more detrimental effects on far(near) vision. Additionally,bifocal IOLs are more vulnerable to corneal astigmatism, highlighting the need to considermultifocal toric IOLs with astigmatism greater than 1.0D. The numerical results closely agreedwith previous relevant clinical findings, suggesting the clinical usability of the presentedmethod in predicting the postoperative visual function of patients.

Stokes vector characterization by strongly measuring weak values

Francisco De Zela, Carlos Montenegro La Torre, Max Jara, and Jean Paul Marrou

DOI: 10.1364/JOSAA.516469 Received 19 Dec 2023; Accepted 11 Mar 2024; Posted 12 Mar 2024  View: PDF

Abstract: We report the implementation of a non-standard procedure to perform Stokespolarimetry, which was recently proposed by considering weak value measurements. Ourprocedure is not restricted to weak measurements, but applies for both weak and strong couplingsbetween the observable being measured, the polarization (spin) vector, and the measuringdevice, the “pointer”. In optics, the polarization-pointer coupling is usually implemented witha birefringent crystal. This applies in the weak coupling regime. We overcame this limitationby using an alternative setup, in which one can go from weak to strong couplings by tuning amoveable mirror. We carried out our proof-of-concept experiments with a laser beam, the imageof which was recorded and processed on a charge coupled device. Our results illustrate that someconcepts, originally introduced in a quantum context, in fact refer to properties that are commonto both quantum and classical phenomena.

Diffraction of pseudo nondiffracting Besselbeam by a circular perfect electromagneticconductor disc

Husnu Deniz Basdemir

DOI: 10.1364/JOSAA.516314 Received 18 Dec 2023; Accepted 11 Mar 2024; Posted 11 Mar 2024  View: PDF

Abstract: This study examined the diffraction of a pseudo nondiffracting Bessel beam by aperfect electromagnetic disk. The geometric optics beam waves were written from the geometryof the problem and related boundary conditions. The diffracted beam waves were derived byutilizing the relation between geometric optics and diffracted waves at the transitionboundaries, considering the high frequency asymptotic expression of the scattered wave. Theuniform scattered beam waves were expressed in terms of Fresnel functions with the uniformgeometrical theory of diffraction method. Thus, finite magnitudes were read at the transitionboundaries. Finally, the obtained uniform expressions were investigated numerically fordifferent groups of parameters.

Degree of paraxiality of radially polarized twistedMulti-Gaussian Schell-model beams

jinping Cheng, ying feng, Hao Wu, Tao Wang, and Miaomiao Tang

DOI: 10.1364/JOSAA.516407 Received 19 Dec 2023; Accepted 11 Mar 2024; Posted 11 Mar 2024  View: PDF

Abstract: Degree of paraxiality (DOP) of a radially polarized twisted multi-Gaussian Schell model(RPT MGSM) beam is discussed, and the influence of the source parameters on its DOP is studied. It isshown that the parameters of the beam source, including the boundary characteristic, the beam waistwidth, the coherence width of the source correlation, and the twist factor, have a significant impact onthe DOP of the RPT MGSM beam. To explain the behaviors of DOP, the far-field divergence angle ofthis beam is also discussed.

Utilizing Joukowsky Transformation in the Design ofOptical Fiber for Elliptical-to-Circular Mode Conversion

Shuaikang Fu, Ping Jiang, Yan Qin, Jianing Liu, and Yang Huajun

DOI: 10.1364/JOSAA.515412 Received 07 Dec 2023; Accepted 10 Mar 2024; Posted 11 Mar 2024  View: PDF

Abstract: This study addresses the challenge of enhancing coupling efficiency between optical fibers and ellipticalGaussian beam emitted by semiconductor lasers, particularly in fiber communication systems. We introduce a novel method for fiber design utilizing the Joukowsky transformation to facilitate efficient modetransformation from elliptical to circular, thereby augmenting the coupling efficiency with both singlemode and multimode fibers. Theoretical analysis and numerical simulations demonstrate that the fiberwith a structurally transitional core maintains high-efficiency mode transformation across various lengths,and its structure has been optimized accordingly. Additionally, our investigation reveals that the designedfiber’s ability to preserve polarization states, which could have significant implications in precision opticalapplications. The proposed design offers an innovative approach to improving performance in opticalcommunication systems, especially in wavelength-division multiplexing (WDM) transmission systemsand fiber lasers.

EFNet: Enhancing feature information for 3D object detection in LiDAR point clouds

xin meng, Yuan Zhou, Kaiyue DU, Jun Ma, Jin Meng, Aakash Kumar, Jiahang Lv, JONGHYUK kim, and Shifeng Wang

DOI: 10.1364/JOSAA.511948 Received 09 Nov 2023; Accepted 10 Mar 2024; Posted 12 Mar 2024  View: PDF

Abstract: With the development of autonomous driving, there has been considerable attentionon 3D object detection using LiDAR. Pillar-based LiDAR point cloud detection algorithms areextensively employed in the industry due to their simple structure and high real-timeperformance. Nevertheless, the pillar-based detection network suffers from significant loss of3D coordinate information during the feature degradation and extraction process. In the paper,we introduce a novel framework with high performance, termed EFNet. The EFNet uses theEnhancing Pillar Feature Module (EPFM) to provide more accurate representations of featuresfrom two directions: pillar internal space and pillar external space. Additionally, the Head UpModule (HUM) is utilized in the detection head to integrate multi-scale information andenhance the network's information perception ability. The EFNet achieves impressive resultson the nuScenes datasets, namely 53.3% NDS and 42.4% mAP. Compared to the baselinePointPillars, EFNet improves 8% NDS and 11.9% mAP. The results demonstrate that theproposed framework can effectively improve the network's accuracy while ensuringdeployability.

Optimized Stokes imaging for highly resolved optical speckle fields, part III: Topological analysis of polarimetric states distributions with optimized data representations

Jonathan Staes and Julien Fade

DOI: 10.1364/JOSAA.516717 Received 21 Dec 2023; Accepted 09 Mar 2024; Posted 11 Mar 2024  View: PDF

Abstract: In this last article of a three-paper series focusing on Stokes polarimetry of opticalspeckle fields resolved at the individual speckle grain scale, experimental results are provided ontest samples of varying nature and polarization properties, and are analyzed extensively. Forthis purpose, a review of the classical ways of displaying Stokes polarimetric information isprovided. Then, some original alternative graphical representations are introduced that ensureoptimal readability and interpretability of the Stokes imaging data in the context of speckle fieldpolarimetry, and it is shown how they can be adapted to various observation scales. Finally, thesetools are implemented in order to provide a topological analysis of the distribution of the states ofpolarization across a speckle pattern, and in the vicinity of polarimetric singularities of the field.

Optimized Stokes imaging for highly resolved optical speckle fields, part II: Optimal acquisition & estimation strategies

Jonathan Staes and Julien Fade

DOI: 10.1364/JOSAA.516702 Received 21 Dec 2023; Accepted 09 Mar 2024; Posted 14 Mar 2024  View: PDF

Abstract: In this second article of a three-paper series focusing on Stokes polarimetry ofoptical speckle fields resolved at the individual speckle grain scale, a theoretical study basedon numerical simulations is presented in order to establish the optimum sensing, estimationand processing strategies that guarantee the best precision, accuracy and robustness for Stokespolarimetry in this specific context. In particular, it is demonstrated that the so-called StateOf Polarization Analysis by Full Projection on the Poincaré space (SOPAFP) approach can beoptimized in order to ensure best estimation performance. These numerical simulations also makeit possible to establish that the SOPAFP approach provides better results in terms of robustness toresidual experimental imperfections of the setup when compared to classical Stokes polarimetryapproaches.

Nonparaxial accelerating waves as superposition ofnondiffracting Bessel-lattice optical fields

Israel Julián Macías, Gabriel Martinez-Niconoff, Gilberto Silva-Ortigoza, and Carolina Rickenstorff

DOI: 10.1364/JOSAA.518866 Received 16 Jan 2024; Accepted 07 Mar 2024; Posted 07 Mar 2024  View: PDF

Abstract: In the first part of this work, we introduce a monochromatic solution to the scalar wave equation in freespace, defined by a superposition of monochromatic nondiffracting half Bessel-lattice optical fields, whichis determined by two scalar functions, one is defined on frequency space and the other is a completeintegral to the Eikonal equation in free space. We obtain expressions for the geometrical wavefronts, thecaustic region, and the Poynting vector. We highlight that, this solution is stable under small perturbationsdue that this solution is characterized by a caustic of the hyperbolic umbilical type. In the second part, weintroduce the corresponding solution to the Maxwell equations in free space.

Generalized neutral axes in non-depolarizing opticalsystems

Guy Perrin

DOI: 10.1364/JOSAA.518345 Received 22 Jan 2024; Accepted 05 Mar 2024; Posted 05 Mar 2024  View: PDF

Abstract: The polarizing properties of optical systems are often characterized by their action on specific polarizationstates. For example, half-wave plates are used to rotate linear polarizations and quarter-wave plates to turna linear polarization into an elliptical polarization and into a circular polarization if the linear polarizationmakes a 45◦ angle with the slow and fast axes of the quarter-wave plate. Phase shifts introduced by theoptical train of an interferometer may lead to coherence losses and the existence of neutral axes – in thesense of linear polarizations whose polarization state is not modified by the optical system – is then ofimportance to maximize fringe contrast. Neutral axes do not systematically exist. The purpose of this paperis to investigate how this notion can be generalized to define generalized neutral axes for optical systems.Generalized neutral axes are defined as linear polarizations whose polarization state is not modified by theoptical system except for their orientation. It is shown that such generalized neutral axes exist for someclasses of optical systems. A scheme is proposed with quasi-unitary Jones matrices – which are introducedin this paper – to give an approximate description of optical systems when generalized neutral axes do notexist. This formalism is a new scheme to describe the polarizing properties of non-depolarizing opticalsystems.

Optimized Stokes imaging for highly resolved optical speckle fields, part I: Optimized experimental setup

Jonathan Staes and Julien Fade

DOI: 10.1364/JOSAA.516693 Received 21 Dec 2023; Accepted 27 Feb 2024; Posted 27 Feb 2024  View: PDF

Abstract: In this first article of a three-paper series focusing on Stokes polarimetry of optical speckle fields resolved at the individual speckle grain scale, a review of the state of the art techniques for such experimental investigations is first provided. An optimized experimental setup is then extensively described which allows polarimetric Stokes measurements on such complex interference patterns to be carried out at each location of the speckle field without disturbing the wavefront. Specific calibration procedures are also described in order to provide the estimation of trustful polarimetric properties of light across a resolved speckle field.

Matrix-based integral transformations for Stokesimaging with partially polarized and partially coherentlight

Wei Wang and Mitsuo Takeda

DOI: 10.1364/JOSAA.517693 Received 03 Jan 2024; Accepted 22 Feb 2024; Posted 27 Feb 2024  View: PDF

Abstract: With the aid of the matrix-based integral transforms, called matrix convolution and matrix direct correlation, weprovide a simplified expression for the space-domain and frequency-domain calculations of polarization imagingwith partially polarized and partially coherent light. As an example of practical interest, a formula for Stokesimaging, based on the generalized Stokes parameters, is presented, in which a hypermatrix-based transmissioncross-coefficient matrix is introduced to represent the combined effects of diffraction and aberrations of apolarization-dependent imaging system and a partially-polarized and partially-coherent illumination system. Thecoherent limit and the incoherent limit in Stokes imaging are discussed with the optical transfer matrix, alongwith its frequency response for a diffraction-limited incoherent polarization imaging system. A generalizedconcept of the apparent transfer matrix is introduced to deal with the nonlinearity inherent in the polarizationimaging system under partially coherent illumination.