Optical Pattern Research Articles

Dynamical structure of optical soliton solutions for M−fractional paraxial wave equation by using unified technique

This study deliberates the fractional form of the paraxial wave equation, which is used to investigate the self-focusing of optical waves in nonlinear media. The truncated time M−fractional derivative is used to get rid of the fractional order in the governing model. The several optical wave pattern of the paraxial wave equation can play an insignificant role to describe the dynamics of optical soliton solutions in optics and photonics for the study of various physical processes, including the propagation of light through optical systems, such as lenses, mirror, and fiber optics. In this framework, the newly introduced unified scheme is implemented to investigate optical soliton solutions of truncated time M−fractional Paraxial Wave (tM-fPW) equation. Under some conditions, the established solutions are expressed in terms of hyperbolic, trigonometric, and rational function forms with some free parameters. For the numerical values of the free parameters, we found optical periodic wave, the interaction of periodic wave and rogue wave, breather wave, linked rogue wave, periodic rogue wave solution, etc. For a corporeal explanation of the obtained solutions, we plotted among them with 3-D, density, and contour plots and analyzed the self-focusing of an optical pulse in nonlinear media.

Qualitative analysis and stationary optical patterns of nonlinear Schrödinger equation including nonlinear chromatic dispersion

Qualitative analysis and stationary optical patterns of nonlinear Schrödinger equation including nonlinear chromatic dispersion

Virtual experiments for the assessment of data analysis and uncertainty quantification methods in scatterometry

Geometrical dimensions in nanostructures can be determined through indirect optical measurements carried out by a scatterometer. This includes solving a non-linear regression task in which a physical model is fitted to the observed optical diffraction pattern. We developed a virtual experiment which produces simulated diffraction patterns in coherent Fourier scatterometry measurements including perturbations due to various error sources. We utilize this virtual experiment to assess the suitability of data analysis and uncertainty quantification methods employed in scatterometry. In addition to investigating relevant physical parameters we explore the impact of deviations between the regression model utilized for the analysis and the scatterometry model used to produce the virtual diffraction pattern. We choose coverage probabilities of interval estimates of the geometrical dimensions as the main metric for the assessment. One of our findings is that the discretization level, expressed as the number of retained Fourier orders, can be relaxed up to order 9 in our case study, which is relevant as calculation times strongly depend on this parameter. Another result is that the least-squares approach considered here for solving the regression task in combination with the propagation of variances yields uncertainties which have somewhat lower coverage probabilities than the envisaged 95%. It turned out that it was critically important to model the oxide layer in order to get proper estimates of the width, or ‘critical dimension’, of the sample, while the uncertainty of the side wall angle had the largest impact on the uncertainty of the measurands. Our findings can help establishing traceability of Fourier scatterometry and underline the usefulness of high-quality virtual experiments in connection with complex measurement principles. At the same time the presented case study can be seen as a generic approach that could be followed for assessing uncertainty quantifications in other applications as well.

71‐1: Data‐Driven and Optics‐Inspired Decomposition of Global Pupil Swim in VR/AR for an Improved Perception Model of Motion Discomfort

Users can observe dynamic distortion (or global pupil swim) during the usage of VR/AR headsets. Our earlier study correlated pupil swim to selected optic flow patterns corresponding to motion and mathematically modeled discomfort. This study decomposes global pupil swim as a linear sum of orthogonal basis patterns based on Zernike polynomials for improved applicability and for an improved perception model.

Indefinite and bidirectional near-infrared nanocrystal photoswitching.

Materials whose luminescence can be switched by optical stimulation drive technologies ranging from superresolution imaging1-4, nanophotonics5, and optical data storage6,7, to targeted pharmacology, optogenetics, and chemical reactivity8. These photoswitchable probes, including organic fluorophores and proteins, can be prone to photodegradation and often operate in the ultraviolet or visible spectral regions. Colloidal inorganic nanoparticles6,9 can offer improved stability, but the ability to switch emission bidirectionally, particularly with near-infrared (NIR) light, has not, to our knowledge, been reported in such systems. Here, we present two-way, NIR photoswitching of avalanching nanoparticles (ANPs), showing full optical control of upconverted emission using phototriggers in the NIR-I and NIR-II spectral regions useful for subsurface imaging. Employing single-step photodarkening10-13 and photobrightening12,14-16, we demonstrate indefinite photoswitching of individual nanoparticles (more than 1,000 cycles over 7 h) in ambient or aqueous conditions without measurable photodegradation. Critical steps of the photoswitching mechanism are elucidated by modelling and by measuring the photon avalanche properties of single ANPs in both bright and dark states. Unlimited, reversible photoswitching of ANPs enables indefinitely rewritable two-dimensional and three-dimensional multilevel optical patterning of ANPs, as well as optical nanoscopy with sub-Å localization superresolution that allows us to distinguish individual ANPs within tightly packed clusters.

Optical spectroscopy study of damage in ion-irradiated 3C-SiC epilayers on a silicon substrate

Epitaxial cubic (100) 3C-SiC films on a (100) silicon wafer were irradiated at room temperature with 2.3-MeV Si+ or 3.0-MeV Kr+ ions up to a fluence of 1 × 1016 cm−2. The evolutions of the epilayer and the substrate were followed as a function of ion fluence by using micro-Raman spectroscopy, optical absorption, and diffuse reflectance spectroscopy in the UV-visible and near infrared range. Raman spectra evidence the amorphization of SiC films at an estimated dose of about 0.1 displacement per atom (dpa) for both ion irradiations. The narrow peaks of the Raman-allowed TO and LO modes of SiC and Si are recorded in the virgin sample, together with few peaks assigned to zone-edge modes of SiC arising from the intrinsic disorder in the strained films. Those crystal phonon peaks broaden or disappear with increasing fluence. The spectra finally exhibit broad extra peaks assigned to the formation of Si–Si and C–C wrong homonuclear bonds in the local order of the amorphous phase. The optical transmission and diffuse reflectance spectra feature interference fringe patterns in the SiC film that are smoothened out with irradiation due to the matching of refractive indices of the amorphous SiC film and Si substrate. The evolution of the refractive index of SiC and optical gap of Si are deduced from those spectra. The respective roles of ballistic effects and electronic excitations in the radiation damage of both SiC and Si are discussed for those two ions with about the same electronic stopping power and about one order-of-magnitude difference in nuclear stopping power. The damage is dominated by the nuclear collision processes and rather well correlated with the estimated irradiation dose in dpa. Optical spectra show that electronic excitations induce damage recovery of the amorphized substrate below the SiC/Si interface. Raman spectra and optical absorption/reflection spectra yield complementary pictures of the radiation damage.

Ligand-Crosslinking Strategy for Efficient Quantum Dot Light-Emitting Diodes via Thiol-Ene Click Chemistry.

While solution-processable colloidal quantum dots (QDs) offer cost-effective and large-scale manufacturing, they can be susceptible to subsequent solution processes, making continuous processing challenging. To enable complex and integrated device architectures, robust QD films with subsequent patterning are necessary. Here, we report a facile ligand-crosslinking strategy based on thiol-ene click chemistry. Thiol molecules added to QD films react with UV light to form radicals that crosslink with QD ligands containing carbon double bonds, enabling microscale photo-patterning of QD films and enhancing their solvent resistance. This strategy can also be extended to other ligand-capped nanocrystals. It is found that the swelling of QD films during the process of binding with the thiol molecules placed between the ligands contributes to the improvement of photoluminescence and electroluminescence properties. These results suggest that the thiol-ene crosslinking modifies the optoelectronic properties and enables direct optical patterning, expanding the potential applications of QDs.

Identification of Cyprodinil + Fludioxonil to Manage Soybean Red Crown Rot Using the Microplate-Based High-Throughput Screening and Pot Assay.

Red crown rot (RCR), caused by the soilborne fungus Calonectria ilicicola, is an emerging soybean disease in Taiwan, and fungicide screening is desired to identify effective management for C. ilicicola. This study screened 11 fungicides, including azoxystrobin, boscalid, cyprodinil, cyprodinil + fludioxonil, difenoconazole, fluopyram, flutolanil, mancozeb, prochloraz, pyraclostrobin, and tebuconazole, for their inhibitory effects on the mycelial growth of 10 C. ilicicola field isolates. Subsequently, a microplate-based high-throughput screening (MHTS) method was established to measure the fungicide sensitivity in a population composed of 80 C. ilicicola isolates to three effective fungicides, cyprodinil + fludioxonil, fluopyram, and tebuconazole. The MHTS was optimized for multiple factors, including the optical scanning pattern, absorption wavelength, conidial concentration, and measurement timing based on the quality controls of Z' factor and the log-phase growth curve. The population mean EC50 estimated by MHTS were 0.14, 2.34, and 2.46 ppm to cyprodinil + fludioxonil, fluopyram, and tebuconazole, respectively. In addition to the in vitro assessment, fungicide efficacy was evaluated by coating cyprodinil + fludioxonil, fluopyram, or tebuconazole on soybean seeds in the pot assay. The results showed that cyprodinil + fludioxonil significantly reduced both postemergence damping-off and disease severity, while fluopyram and tebuconazole reduced only the postemergence damping-off but not disease severity. Based on the MHTS and the pot assay results, this study demonstrated cyprodinil + fludioxonil to be a potential fungicide to manage soybean RCR.

Integrated optical pattern generation on thin-film lithium niobate with electro-optic modulators and phase-change material cells

Reconfigurable photonic integrated circuits enable high-bandwidth signal shaping with the prospect for scalability and compact footprint. Cointegration of electro-optical tunability with nonvolatile attenuation through functional materials allows for implementing photonic devices that operate on both phase and amplitude. Based on this approach, we propose an integrated photonic design for optical pattern generation deploying a continuous-wave laser and a single electrical function generator. We employ the nonvolatile and reconfigurable phase-change material Ge2Sb2Te5 (GST) as a tunable attenuator for an integrated photonic circuit on the lithium-niobate-on-insulator (LNOI) platform. The GST can be switched between its amorphous and crystalline phases, leading to an optical contrast of ≅18dB. Combining this with integrated electro-optical modulators with a 4 GHz bandwidth in LNOI enables the generation of short optical pulses, based on the principles of inverse discrete Fourier transform.

Photodarkening, Photobrightening, and the Role of Color Centers in Emerging Applications of Lanthanide-Based Upconverting Nanomaterials

Upconverting nanoparticles (UCNPs) compose a class of luminescent materials that utilize the unique wavelength-converting properties of lanthanide (Ln) ions for light-harvesting applications, photonics technologies, and biological imaging and sensing experiments. Recent advances in UCNP design have shed light on the properties of local color centers, both intrinsic and controllably induced, within these materials and their potential influence on UCNP photophysics. In this review, we describe fundamental studies of color centers in Ln-based materials, including research into their origins and their roles in observed photodarkening and photobrightening mechanisms. We place particular focus on the new functionalities that are enabled by harnessing the properties of color centers within Ln-doped nanocrystals, illustrated through applications in afterglow-based bioimaging, X-ray detection, all-inorganic nanocrystal photoswitching, and fully rewritable optical patterning and memory.

Optoelectronic Trajectory Reconfiguration and Directed Self-Assembly of Self-Propelling Electrically Powered Active Particles.

Self-propelling active particles are an exciting and interdisciplinary emerging area of research with projected biomedical and environmental applications. Due to their autonomous motion, control over these active particles that are free to travel along individual trajectories, is challenging. This work uses optically patterned electrodes on a photoconductive substrate using a digital micromirror device (DMD) to dynamically control the region of movement of self-propelling particles (i.e., metallo-dielectric Janus particles (JPs)). This extends previous studies where only a passive micromotor is optoelectronically manipulated with a translocating optical pattern that illuminates the particle. In contrast, the current system uses the optically patterned electrode merely to define the region within which the JPs moved autonomously. Interestingly, the JPs avoid crossing the optical region's edge, which enables constraint of the area of motion and to dynamically shape the JP trajectory. Using the DMD system to simultaneously manipulate several JPs enables to self-assemble the JPs into stable active structures (JPs ring) with precise control over the number of participating JPs and passive particles. Since the optoelectronic system is amenable to closed-loop operation using real-time image analysis, it enables exploitation of these active particles as active microrobots that can be operated in a programmable and parallelized manner.

"Lotus root": a novel optical coherence tomography imaging pattern in spontaneous coronary artery dissection.

"Lotus root": a novel optical coherence tomography imaging pattern in spontaneous coronary artery dissection.

Learning-based super-resolution interpolation for sub-Nyquist sampled laser speckles

Information retrieval from visually random optical speckle patterns is desired in many scenarios yet considered challenging. It requires accurate understanding or mapping of the multiple scattering process, or reliable capability to reverse or compensate for the scattering-induced phase distortions. In whatever situation, effective resolving and digitization of speckle patterns are necessary. Nevertheless, on some occasions, to increase the acquisition speed and/or signal-to-noise ratio (SNR), speckles captured by cameras are inevitably sampled in the sub-Nyquist domain via pixel binning (one camera pixel contains multiple speckle grains) due to finite size or limited bandwidth of photosensors. Such a down-sampling process is irreversible; it undermines the fine structures of speckle grains and hence the encoded information, preventing successful information extraction. To retrace the lost information, super-resolution interpolation for such sub-Nyquist sampled speckles is needed. In this work, a deep neural network, namely SpkSRNet, is proposed to effectively up sample speckles that are sampled below 1/10 of the Nyquist criterion to well-resolved ones that not only resemble the comprehensive morphology of original speckles (decompose multiple speckle grains from one camera pixel) but also recover the lost complex information (human face in this study) with high fidelity under normal- and low-light conditions, which is impossible with classic interpolation methods. These successful speckle super-resolution interpolation demonstrations are essentially enabled by the strong implicit correlation among speckle grains, which is non-quantifiable but could be discovered by the well-trained network. With further engineering, the proposed learning platform may benefit many scenarios that are physically inaccessible, enabling fast acquisition of speckles with sufficient SNR and opening up new avenues for seeing big and seeing clearly simultaneously in complex scenarios.

DMD-based optical pattern recognition using holograms generated with the Hartley transform

High-speed optical reconstruction of holographic and diffractive optical elements is widely used in encryption and recognition, 3D-displays, beam shaping, nanofabrication, visualization, etc. This paper proposes the use of amplitude holograms generated by the Hartley transform (HT) as filters in an incoherent correlator. The real computations using the HT are faster and less computationally intensive than the standard complex transforms. Generated holograms using HT and Fourier transform (FT) were compared. It is demonstrated that the diffraction efficiency of HT-based holograms is not inferior to the FT case. The reconstruction quality is better in metrics (NSTD, MSE, SNR, RMS contrast, SSIM) by 2–10%. An optical incoherent correlator based on two digital micromirror devices (DMDs) was constructed. DMDs have very high frame rates (up to 30 kHz) that provides its great potential for application in fast recognition problems. The object images were displayed on the first DMD. The holograms generated with the HT were binarized and displayed on the second DMD. The objects were successfully recognized. Thus, HT-based amplitude holograms can be successfully used instead of FT-based amplitude holograms.

Application of artificial neural networks for stress state analysis based on the photoelastic method

The present article proposes an evolutionary development of the photoelasticity method for measuring stresses based on annular photoelastic sensors application along with stress pattern recording with the aid of a digital camera and its recognition using artificial neural networks. The analysis of the modern application of the photo-elasticity method for various problems within the theory of strength is presented. The principle of operation of photoelastic sensors based on the photoelasticity effect is considered. Optical patterns in an annular photoelastic sensor are presented for various values of the horizontal stress. The calculation of the stress state of the sensor for the following full-scale experiment has been performed, the estimate of the threshold conditions under which the sensor can be applied has been performed. As a result of a laboratory experiment, a dataset of 1500 isochromatic images has been assembled. A subspecies of a neural network, namely a convolutional neural network, has been applied as a machine learning algorithm. Different combination of models and optimizers have been employed. The application of downhole sensors for continuous monitoring of alterations in the rock mass stress state and the integration of this data into a digital field model based on Internet of Things technologies has been proposed.

Efficient ultrafast laser writing with elliptical polarization

Photosensitivity in nature is commonly associated with stronger light absorption. It is also believed that artificial optical anisotropy to be the strongest when created by light with linear polarization. Contrary to intuition, ultrafast laser direct writing with elliptical polarization in silica glass, while nonlinear absorption is about 2.5 times weaker, results in form birefringence about twice that of linearly polarized light. Moreover, a larger concentration of anisotropic nanopores created by elliptically polarized light pulses is observed. The phenomenon is interpreted in terms of enhanced interaction of circularly polarized light with a network of randomly oriented bonds and hole polarons in silica glass, as well as efficient tunneling ionization produced by circular polarization. Applications to multiplexed optical data storage and birefringence patterning in silica glass are demonstrated.

Rapid discrimination of Candida species based on optical diffraction pattern.

Candidiasis occurs mainly in immunocompromised patients. Rapid detection of Candida species can play a major role in the successful management of fungal infections and treatment monitoring. Detection and discrimination of five common strains of Candida species was performed using the optical elastic scattering diffraction pattern of their colonies. Using laser light with 632 nm wavelength and the designed optical system, optical diffraction patterns of C. albicans (ATCC12261), C. tropicalis (ATCC20336), C. glabrata (15545), C. guilliermondii (20216), and C. parapsilosis (22019) were recorded, processed and analyzed. The results of our study show that based on the different structure of Candida species and dissimilar structure of their colonies, the difference between acquired diffraction patterns are recognizable. In addition, through extraction of statistical feature of the diffraction pattern images and using classification techniques, the detection and discrimination could be performed in a semi-automatic way. The analysis of the colonies of five different Candida species by the optical diffraction patterns generated from the interaction of the laser with colonies' structures demonstrated that the technique had the potential to be applied for the detection and discrimination of various species.

Customized Design of Aperiodic Liquid Crystal Grating for Generation of Multiple Optical Patterns

Liquid crystal (LC) grating has drawn extensive attention due to its merits, including tunability, easy preparation process, cost effectiveness, and high diffraction efficiency. However, limited efforts have been made to explore LC grating for the generation of customized diffraction patterns, despite the fact that the patterning size of LC molecular director orientation has been tremendously reduced even to subwavelength scale via high-precision photoalignment techniques. Here, we propose a versatile method based on the binary particle swarm optimization algorithm to efficiently design aperiodic LC gratings for customized optical patterns generation, including needle beam, multi-foci, and hollow beam. The optical performance of the LC gratings was simulated using both the vectorial Rayleigh–Sommerfeld method (with discrete zero or π phase, in this article) and the actual director orientations. These results matched each other well, which proves the effectiveness of the optimization method based on discrete phase. This study paves the way for designing LC gratings with engineered functionalities, which may find applications in optical tweezers, laser delivery systems, and laser scanning imaging.

Digging Deeper through Biological Specimens Using Adaptive Optics-Based Optical Microscopy

Optical microscopy is a vital tool for visualizing the cellular and sub-cellular structures of biological specimens. However, due to its limited penetration depth, its biological applicability has been hindered. The scattering and absorption of light by a wide array of biomolecules causes signal attenuation and restricted imaging depth in tissues. Researchers have put forth various approaches to address this, including designing novel probes for imaging applications and introducing adaptive optics (AO) technology. Various techniques, such as direct wavefront sensing to quickly detect and fix wavefront deformation and indirect wavefront sensing using modal and zonal methods to rectify complex aberrations, have been developed through AO paradigms. In addition, algorithmic post-processing without mechanical feedback has been utilized to correct the optical patterns using the matrix-based method. Hence, reliable optical imaging through thick biological tissue is made possible by sensorless AO. This review highlights the latest advancements in various AO-based optical microscopy techniques for depth-resolved imaging and briefly discusses their potential in various biomedical applications.

Chloroplast and outside-chloroplast interference of light inside leaves

Our research explored leaf optical patterns when light falls on the leaf’s inner surface and interacts to chloroplasts pigments or with the outside-chloroplast components (structural apparatus) of leaves. Six species of variegated leaves were used to detect effects of chlorophylls (green leaves), carotenoids (yellow leaves – without chlorophylls) and outside-chloroplasts components (albino leaves – without functional chloroplasts) to deep our understand of behavior of light inside leaf beyond spectral interference of pigments. High absorbance at wavelengths shorter than 530 nm in albino leaves (absence of chloroplasts) in addition to high scattering at longer wavelengths (considering the 400–700 nm range) were detected. Changes in measurements of chlorophyll fluorescence spectroscopy performed simultaneously on both side of leaves and using a high fluorescence in red absorption (R) to low effects on fluorescence in far-red (FR) as a proxy, the ratio of fluorescence (R/FR) were associated to differences in penetrability of different wavelengths. From the leaf optical system point of view, internal reflectance and degenerate chlorophyll quantum state are important physical mechanisms that maximize the absorption of wavelengths of low absorptivity, as in the case of green light.