Optical Function Research Articles

Safety of and chorioretinal circulation during repeated low-level red-light therapy for myopic children.

To evaluate the safety of repeated low-level red-light (RLRL) therapy in children, and the dynamic evolution of choroidal and retinal blood flow. This is a single-centre, randomised, single-blind, parallel-group clinical trial. Seventy myopic children were randomly assigned to either the intervention group [receiving RLRL therapy plus single-vision spectacle (SVS)] or the control group (wearing SVS). Participants underwent comprehensive ophthalmic examinations following their first irradiation, 9 months continuous RLRL therapy and stop of treatment. Quantitative analyses of choroidal and retinal microcirculation were analysed via optical coherence tomography angiography. Over 9 months of treatment, while the RLRL treatment demonstrated significantly less increases in refractive error and axial length compared with the SVS treatment (ps < 0.05), no abnormalities in fundus structure or visual function (mfERG, VEP and microperimetry) were detected (ps > 0.05). A single red-light exposure did not exert a significant influence on choroidal thickness (ps > 0.05). Upon continuous treatment, the RLRL group achieved peak values in these circulations at 9 months (ps < 0.05). Following cessation of exposure, all circulations exhibited a declining trend, reaching similar levels in both groups (ps > 0.05). As the frequency of red-light exposures intensified, there was a consistent surge in these circulations (ps < 0.05). Nine months of continuous RLRL exposure does not cause toxic side effects on retinal or optic nerve functions, and there is a time-dependent cumulative response in choroidal and retinal circulation.

Tunable silicon integrated quantum light source with on-chip FSR-free filters

In this work, we design and fabricate a telecom band quantum light source (QLS) on a silicon photonic chip, which integrates a piece of a long silicon waveguide as the nonlinear medium for spontaneous four-wave mixing (SFWM) and five narrow FSR-free bandpass filters based on a grating-assisted contra-directional coupler (GACDC). Two optical filtering functions of the silicon integrated QLS have been demonstrated. First, the QLS supports two tunable outputs of photon pair generations by four GACDC filters. A wavelength tunable range of 6 nm is demonstrated. Second, one GACDC bandpass filter is designed as an on-chip pump filter before the silicon waveguide. The performances of the QLSs with and without the on-chip pump filter are measured and compared. It shows that the on-chip pump filter has the effect to enhance the performance of the QLS by suppressing the Raman noise photons generated when a pump light propagated in optical fibers before it is injected into the chip. These results show that FSR-free filters would play important roles in developing silicon integrated QLSs.

Imaging system high dynamic range colorimetric calibration method based on a digital chain

Research on high dynamic range (HDR) color management imposes critical requirements on calibration methods between imaging systems and standard radiation. This paper proposes a colorimetric calibration method based on digital chain measurement for imaging systems. First, a HDR colorimetric calibration process model for imaging systems is constructed based on an imaging chain. It includes a light source, target reflectance, optical system parameters, spectral sensitivities, and color matching functions. Subsequently, visual tristimulus values and three-channel response values of an imaging system are obtained using the proposed model in response to the same target, and the target characteristic parameters are adjusted to simulate different HDR imaging scenarios. Following that, various regression algorithms can be employed for HDR colorimetric calibration of imaging systems. The experimental findings demonstrate that the method proposed in this paper boasts a broader dynamic range and denser sampling, thereby enhancing the accuracy of colorimetric characterization models and achieving superior resolution in color measurement.

Mid-infrared edge-enhanced imaging via angle-selective nonlinear filtering

We propose a novel, to the best of our knowledge, scheme for mid-infrared upconversion imaging with high tunability between bright-field and edge-enhanced modalities. The involved engineering of the nonlinear process favors shaping the optical transfer function of the imaging system. Consequently, a nonlinear angle-selective filter can be configured to perform an all-optical Fourier processing of the image, which highly depends on phase-matching parameters. We numerically demonstrate the ability to switch modalities between the bright-field and edge-enhanced imaging by tuning the crystal temperature and simultaneously acquiring both information by dichromatic illumination. Notably, the achieved reconfigurability is realized without changing the imaging settings, which contrasts with previous instantiations based on pump adaptation. Therefore, the proposed architecture of upconversion imagers would pave a novel way to implement layout-compact and all-optical processing for infrared images.

Comparing Optical Quality and Simulated Defocus Curves: A Head-To-Head Analysis of Hydrophilic and Hydrophobic Trifocal Intraocular Lenses.

AT ELANA is a recently introduced trifocal intraocular lens (IOL) made of a hydrophobic material. The new IOL's optical function was examined against an equivalent version made of hydrophilic material. . The David J. Apple Center for Vision Research, Heidelberg, Germany. Laboratory investigation. This optical investigation was conducted on +20D samples of the AT ELANA and the AT LISA tri. The area under the modulation transfer function (MTFa) served as a quality criterion. Simulated visual acuity (VA) and defocus curves across +1 to -3.5D range were derived from an empirical formula according to ANSI Z80.35. Susceptibility to photic phenomena was evaluated by assessing the light distribution around a point light source. The two models demonstrated comparable optical quality. While at distance, a 4% improvement was noted with the AT LISA tri, the AT ELANA's near MTFa was 5% higher. Only a marginal difference (1%) was noted at intermediate. Both IOLs reached simulated VA of 0.0 logMAR far vision, 0.10 logMAR at 80 cm, and 0.05 logMAR at 40 cm. Still, the near range was slightly expanded with the hydrophobic model. The light-spread profile was comparable between the two trifocals. The AT ELANA and the AT LISA tri demonstrated comparable optical quality and similarities in the potential for inducing photic phenomena. This study suggests that the hydrophobic trifocal IOL may provide visual range comparable to its hydrophilic counterpart. However, the asphericity change may facilitate the selection of a model that more effectively addresses specific corneal aberrations.

Ab-initio atomistic insights into lead-free perovskites for Photovoltaics Technology

The primary objective of this manuscript is to enhance knowledge and comprehension of hexagonal perovskites KNiX3 (X=I, Br). The world is fascinated by halide perovskites because of their advancements in opto-electronic applications, particularly in the photovoltaic field. KNiI3 and KNiBr3 halide perovskites correspond to the two anion I and Br. Here we aim to investigate how opto-electronic applications are affected by the substitution of cations and anion. Within the framework of density functional theory (DFT), the structural, electronic, and optical properties have been computed using the PBE GGA approximation. Br-based perovskites have a shorter bond length than I-based compounds because iodine ions have a larger ionic radius than bromine ions. Thus, the lattice constant increases from I-based potassium halide perovskites to Br-based potassium halide perovskites. The values of the lattice constant match the results of experimental computations. The Density of States (DOS) curves and band structure are used to examine the contribution of the bands. From Br to I, there is a reduction in the band gap, indicating an improvement in photovoltaic applications. Various energy ranges are used to calculate the optical spectra, dielectric function, absorption coefficient, optical reflectivity, and refractive index. KNiX3 (X=I, Br) compound reveals low reflection value which is typically an excellent choice for photovoltaic and opto-electronic applications.

Efficient Rational Approximation of Optical Response Functions with the AAA Algorithm (Laser Photonics Rev. 18(11)/2024)

Efficient Rational Approximation of Optical Response Functions with the AAA Algorithm (Laser Photonics Rev. 18(11)/2024)

Ultrasonic Control of Polymer-Capped Plasmonic Molecules.

Plasmonic molecules (PMs) composed of polymer-capped nanoparticles represent an emerging material class with precise optical functionalities. However, achieving controlled structural changes in metallic nanoparticle aggregation at the nanoscale, similar to the modification of atomic structures, remains challenging. This study demonstrates the 2D/3D isomerization of such plasmonic molecules induced by a controlled ultrasound process. We used two types of gold nanoparticles, each functionalized with hydrogen bonding (HB) donor or acceptor polymers, to self-assemble into different ABN-type complexes via interparticle polymer bundles acting as molecular bonds. Post-ultrasonication treatment significantly shortens these bonds from approximately 14 to 2 nm by enhancing HB cross-linking within the bundles. This drastic change in the bond length increases the stiffness of the resulting clusters, facilitating the transition from 2D to 3D configurations in 100% yield during drop-casting onto substrates. Our results advance the precise control of PMs' nanoarchitectures and provide insights for their broad applications in sensing, optoelectronics, and metamaterials.

Visual Outcomes of Children With Craniosynostosis.

Craniosynostosis can impact the visual development of a child. Historically, children with craniosynostosis, particularly when associated with a syndrome, had a significant risk of vision loss. The authors aimed to study the incidence of ophthalmic pathology in a modern, multidisciplinary craniosynostosis practice. Children aged 7 to 13 years attending face-to-face ophthalmic craniofacial clinics between February 2020 and June 2021 were included in a retrospective case note review. Visual acuity, ocular alignment, optic nerve function, and retinal nerve fiber layer (RNFL) condition using optical coherence tomography (OCT) were recorded. Forty-three children (30 girls) were assessed at a median age of 10.3 years (7.8-13.1). Eleven children had unicoronal synostosis, 15 had single-suture synostosis not involving the coronal, 14 had multisuture synostosis involving the coronal, and 3 had multisuture synostosis not involving the coronal. Thirty-two out of 43 had craniofacial surgery. Sixty-seven percent required glasses. Forty-nine percent had strabismus, 11/43 (26%) had squint surgery, and 2/43 (5%) had tarsorrhaphy for corneal protection. Four out of 43 (9%) had papilloedema detected; however, at the final review, 15/68 (22%) eyes showed RNFL changes on OCT imaging, none of whom had optic atrophy. Two children did not meet UK driving standards due to refractive amblyopia; no children were registered as sight impaired. In this cohort, optic atrophy and visual loss due to exposure keratopathy were not seen. A high incidence of strabismus, glasses wear, and amblyopia is persistent. Binocular visual impairment was rare in this cohort: 95% met UK driving standards. Visual outcomes appear to be improving coinciding with improved craniofacial care alongside multidisciplinary team working.

Beyond Moiré with Spatial Frequency Mastery via δ-Function Expansion Metasurface.

Mastering spatial frequency manipulation within momentum space is pivotal yet challenging, particularly in mitigating moiré patterns that significantly impair image quality across diverse applications. Conventional methods often require trade-offs in spatial resolution or fall short of completely eradicating unwanted frequencies, further burdened by complex post-processing demands. In this work, a novel coherent δ-function expansion technique implemented through an all-silicon metasurface, affording unparalleled synergistic control over arbitrarily selected spatial frequencies via refined k-space amplitude and phase modulations is introduced. This approach transcends traditional global methods by harnessing a sophisticated ensemble of multiple δ-functions, enabling a holistic manipulation of spatial frequencies. The periodicity introduced by this approach also enables the feasibility of infinitely spatial stitching expansion for metasurfaces while maintaining high energy utilization efficiency. The methodology excels in the meticulous removal of local moiré frequencies while concurrently facilitating numerous advanced optical functions, including mixed partial differentiation and noise suppression, all within the optical domain. This work heralds a significant leap forward in optical manipulation, presenting a viable, scalable alternative to complex electronic post-processing. Through this work, not only a longstanding challenge is addressed in optical physics but also open new avenues for research and application in photodetection and optical processing technologies.

Laser-induced reconfigurable wavefront control with a structured Ge2Sb2Te5-based metasurface

Phase change materials have been widely exploited in active metasurfaces due to their large index contrast. Despite recent advances in phase-change metasurfaces, it remains a challenge to integrate diverse reconfigurable optical functionalities into a single metasurface. Here, we demonstrate an effective strategy to realize reconfigurable wavefront control by combining a Ge2Sb2Te5-rod array with laser writing technology. Through arbitrarily modifying the position and power of laser source, the laser writing process helps to realize site-selective and multi-level phase change of Ge2Sb2Te5 rods. Due to multi-level switching for optical properties of Ge2Sb2Te5 material, the Ge2Sb2Te5-rod array offers complete phase control and high amplitude modulation. Subsequently, various optical devices are designed in numerical simulation, including a phase-only hologram, dynamic meta-deflectors, a grayscale image and a perfect absorber. The structured Ge2Sb2Te5-based metasurface with the combination of laser writing technology offers an effective way to explore various types of optical functionalities in the same device.

Cascadable optical nonlinear activation function based on Ge-Si.

To augment the capabilities of optical computing, specialized nonlinear devices as optical activation functions are crucial for enhancing the complexity of optical neural networks. However, existing optical nonlinear activation function devices often encounter challenges in preparation, compatibility, and multi-layer cascading. Here, we propose a cascadable optical nonlinear activation function architecture based on Ge-Si structured devices. Leveraging dual-source modulation, this architecture achieves cascading and wavelength switching by compensating for loss. Experimental comparisons with traditional Ge-Si devices validate the cascading capability of the new architecture. We first verified the versatility of this activation function in a MNIST task, and then in a multi-layer optical dense neural network designed for complex gesture recognition classification, the proposed architecture improves accuracy by an average of 23% compared to a linear network and 15% compared to a network with a traditional activation function architecture. With its advantages of cascadability and high compatibility, this work underscores the potential of all-optical activation functions for large-scale optical neural network scaling and complex task handling.

Polarization-multiplexed zoom Moiré metalens for edge-enhanced imaging

Optical image processing with high operational efficiency has been applied as a pre-processing imaging system for image recognition. Edge-enhanced imaging as a high-efficiency optical image processing method is of great significance for feature extraction and target recognition. However, the edge-enhanced imaging system based on the 4F system and the spatial filter transforms mainly work under coherent light illumination conditions, without continuously zooming to track the spatial position of the target. Here, we demonstrate a polarization-multiplexed zoom Moiré metalens for edge-enhanced imaging under incoherent light illumination. Metalens is designed to generate polarization-dependent optical transfer functions that produce edge-enhanced images with a resolution of 1.2 µm by digital subtraction. Furthermore, continuous zoom at the range of 1-2× is realized by constructing a Moiré metalens composed of cascaded metasurfaces. The cascaded metasurfaces consist of two center-aligned dielectric metasurfaces, each with a Moiré phase sensitive to the rotation angle. By rotating the metasurface, the phase profile of the cascaded metasurfaces changes, and the effect of continuous zoom is realized. The focal length can be actively changed from 38 µm to 77 µm with the focusing efficiency of 50.3%. This metalens can be applied to machine vision, microscopic imaging, and promotes the development of multi-functional integrated optical systems.

Advances in Selective Detection of Cadaverine by Electronic, Optical, and Work Function Sensors Based on Cu-Modified B12N12 and Al12N12 Nanocages: A Density Functional Theory (DFT) Study.

This work explores Cu-modified B12N12 and Al12N12 nanocages for cadaverine diamine (Cad) detection using advanced density functional theory (DFT) calculations. The study found that Cu modification altered the geometry of the nanocages, increased the dipole moment, reduced the energy gap, and enhanced the reactivity. While pristine B12N12 and Al12N12 were not sensitive to Cad, the modified Cu(b64)B12N12 and Cu(b66)Al12N12 nanocages showed significantly higher electronic sensitivity (Δgap = 39.8% and 35.6%, respectively), surpassing the literature data. However, molecular dynamics (MD) revealed that the Cu(b66)Al12N12 nanocage is not stable in the long term, since the nanocage changes configuration to Cu(b64)Al12N12, which is less sensitive and has an even longer recovery time for Cad sensing. Adsorption energy analysis (Eads) showed a strong interaction of Cad/nanocages, while charge analysis suggested that the nanocages act as Lewis acids, accepting electrons from Cad. UV-vis spectra confirmed that Cu(b64)B12N12 responds optically to the presence of Cad. Furthermore, Cu(b64)B12N12 showed greater sensitivity to Cad compared to NO, H2, H2S, CO, COCl2, N2O, N2 gases, or H2O, showing high selectivity to diamine against interfering gases or water, standing out as a promising material for environmental applications in electronic, optical or work function sensors for cadaverine detection, even in humid environments.

Laser‐Induced Graphene Smart Textiles for Future Space Suits and Telescopes

AbstractNovel materials with high electrical, optical, and thermal functionalities are crucial in next‐generation space missions. Astronauts’ well‐being demands continuous health monitoring, while stray light suppression and heat dissipation are vital for space telescopes. Here, it is demonstrated that laser‐induced graphene (LIG), patterned with femtosecond laser pulses, serves as a versatile material for temperature/strain sensing, stray light absorption, and heat management for smart spacesuits and telescopes. LIG exhibits a superior temperature coefficient of resistance (−0.068% °C⁻¹), gauge factor of 454, optical absorption (97.57%), and heat diffusivity (6.376 mm2 s−1) via a single platform. Furthermore, thermal‐vacuum tests confirm LIG's reliability and readiness for space missions. Under vacuum conditions (≈10−3 Torr) and repeated temperature changes ranging from −20 to 60 °C over a period of ≈40 h, the temperature/strain sensor, and optical absorbers maintain the functionality.

Effect of supplementation with lutein, zeaxanthin, and omega-3 fatty acids on macular pigment and visual function in young adults with long-term use of digital devices: study protocol for a randomized double-blind placebo-controlled study.

Growing evidence emphasizes the importance of xanthophyll carotenoids and omega-3 fatty acids in eye health. However, the beneficial effects of such supplementation have not been thoroughly discussed among adults with high screen exposure. Current trial evidence on lutein bioavailability is contradictory, and the interactions of dietary intervention with host-related factors remain elusive. This study aims to investigate the comparative effectiveness of supplementation with macular xanthophylls and omega-3 fatty acids on macular pigment optical density (MPOD) and visual function, access the bioavailability of free lutein and lutein ester, and explore the complex interplay between genetic variations, intestinal microbiota, and the dietary intervention in Chinese adults with long-term exposure to digital devices. The Lutein, Zeaxanthin, and Omega-3 (LZO) clinical trial is a 24-week multicenter, randomized, double-blind, placebo-controlled trial of 600 participants recruited from research centers, universities, and communities. Individuals are eligible to participate if they are aged over 18 years and use digital devices for over 8 h daily in the last 2 years, and will be randomized to six arms. A total of three visits will be scheduled at baseline, 12 and 24 weeks. The primary outcome is the change in MPOD over the 24-week intervention. The secondary outcomes are changes in visual function (visual acuity, best-corrected visual acuity, contrast and glare sensitivity, critical flicker fusion, reaction time, visuognosis persistence, symptoms and signs of dry eye, retinal thickness, and optical quality), and changes in serum lutein and zeaxanthin concentrations, and erythrocyte membrane omega-3 fatty acids. Genetic variations will be determined using genome-wide genotyping at baseline. 16S rRNA gene sequencing will be utilized to assess microbiome compositional changes before and after intervention. The trial is anticipated to establish early interventions to prevent photochemical ocular damage and delay the onset of vision impairment in young adults with long-term repeated exposure to screen-based electronic devices, and provide valuable insights for the development of precision nutrition strategies for maintaining eye health. www.clinicaltrials.in.th, Identifier, TCTR20220904002.

Processing wheat straw into a near-infrared light selective transmission film

This research focuses on the development of near-infrared light selective transmission film (NIR-LSTF) utilizing wheat straw biomass, extracting lignocellulose and lignin through the acetic acid method. Employing a hydrogel-based approach, lignin was encapsulated and underwent self-assembly both within and atop the hydrogel, enabling initial integration with cellulose. Hot pressing facilitated the thorough amalgamation of lignin into the cellulose matrix, enhancing the NIR-LSTF's resistance to environmental wear and creating a dense structure that minimizes light loss and reflection, thus outperforming traditional materials in optical efficiency and functionality. Moreover, the presence of lignin imparts the material with unique selective absorption characteristics, effectively blocking nearly all ultraviolet light and visible light (approximately 100 % at 610 nm and 78 % at 780 nm), while maintaining a high transmittance rate (∼90 %) in the near-infrared spectrum. This property underscores the films' significant potential in applications demanding near-infrared transparency. The efficacy of NIR-LSTF in the realms of infrared surveillance and privacy protection was assessed, yielding favorable experimental outcomes. This study paves a new pathway for the valorization of agricultural waste biomass within the near-infrared optical domain.

Enhancing thermoelectric and radiation shielding performance of novel LaFe0.8Mn0.2Sb12 skutterudites for energy applications

We explore the structural, optoelectronic, and thermoelectric properties of LaFe0.8Mn0.2Sb12 skutterudites using first-principles computations and semi-classical Boltzmann Transport equations. These materials are classified as semiconductors exhibiting band gaps of 0.55 eV and 1.8 eV for spin-up and down polarizations. Valence band maxima (VBM) and conduction band minima (CBM) lie on the gamma points, indicating direct band gaps for both spin channels. The band structure, density of states, and optical characteristics reveal that the material is a semiconductor. The optical reflectivity and complex dielectric function were calculated for a wide range of photon radiation to understand these compounds' optical properties. The transport parameters were investigated using electrical conductivity, thermal conductivity, the Seebeck coefficient, the power factor, the heat capacity, and the figure of merit determined using the Boltztrap code. The LaFe0.8Mn0.2Sb12 has a Seebeck coefficient of 5.77×10−6 V/K (Up), whereas the down channel has a 4.2×10−6 V/K. The highest figure of merit is 0.99, and as a result, the theoretical findings provide a robust foundation for upcoming experimental research. In this study, utilize the Phy-X program to evaluate the radiation shielding capabilities of LaFe0.8Mn0.2Sb12, focusing on critical parameters like mass attenuation coefficients (γmac) and half-value layers (γhvl), essential for optimizing protection against hazardous ionizing radiation. Computational study of energy-renewable and thermoelectric properties enables experimenters to investigate fresh applications for predicting photovoltaic materials with atomic-level accuracy.

Tunable and polarization-dependent electromagnetically induced transparency analogy in graphene-based terahertz metasurfaces

In this paper, we theoretically and numerically demonstrate a tunable and polarization-dependent electromagnetically induced transparency analogy based on graphene terahertz metasurfaces. The unit cell of the metasurface consists of three-layer graphene strips embedded in a silicon grating. The dynamic adjustment of the transparent window can be achieved by changing the coupling distance between the graphene layers and the polarization direction of the incident lights. The operation mechanism behind the phenomenon can be attributed to the near-field interaction and electromagnetic coupling of modes in graphene strips. Furthermore, the full wave electromagnetic simulations obtained by the finite-difference time-domain method agree well with the theoretical fitting results based on the three-harmonic oscillator model. In addition, by changing the Fermi levels, it can not only realize the outstanding slow-light effects with a maximum group index of 3750 but also obtain the four-frequency asynchronous optical switch function in terahertz regions. Therefore, our proposed metamaterial device may have potential applications in image switching, optical switches, slow-light device, optical communication, and optical storage.

Dielectric metasurface Fresnel zone plates for polarization conversion

Abstract Conventional Fresnel zone plates (FZPs) can only achieve a single focusing function and require the combination with other optical elements to achieve multiple optical functions. This contradicts the development trends for miniaturized, integrated and multifunctional optical devices. However, the emergence of metasurfaces offers new solutions for this problem. In this paper, we design two different types of multifunctional metasurface Fresnel zone plates (MFZPs). One is based on amplitude modulation, and the other is based on phase modulation, both of which can achieve linear polarization conversion and focusing functions. The realization of these functions is based on the ability of silicon diatomic nanopillars to decouple and control the amplitude, phase, and polarization of electromagnetic waves. The designed ultrathin dielectric metasurface effectively combines the functions of conventional half-wave plates and FZPs, thereby reducing the volume of the optical system. The designed MFZPs have enormous potential for application in integrated and compact optical systems.