Confinement of the light at the subwavelength scale makes photonic devices more efficient in applications such as optical filtering, switching, and sensing with their low dimensions. Metal-insulator- metal waveguide-b...
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Confinement of the light at the subwavelength scale makes photonic devices more efficient in applications such as optical filtering, switching, and sensing with their low dimensions. Metal-insulator- metal waveguide-based configurations present many paths for manipulating light at the wide range of the electromagnetic spectrum. For that purpose, in this study, a wavelength demultiplexer (WDM) based on a metal-insulator-metal (MIM) waveguide is numerically investigated by finite difference time domain (FDTD) method. Proposed WDMs have cascade polygon resonators. After optimizing the fundamental filter, this structure is formed as 1xN demultiplexers. The proposed demultiplexers have two- and three channels. The minimum full width at half-maximum (FWHM) value for these channels is 20.02 nm and the maximum quality factor value is 47.7 at 954.9 nm wavelength. The minimum crosstalk value is obtained as -30.37 dB for this study. The proposed 1xN demultiplexers have potential tools to design low-cost integrated optical circuits for specific wavelengths.
Rapid, simultaneous detection of organic chemical pollutants in water is an important issue to solve for protecting human health. This study investigated the possibility of developing an in situ reusable optical senso...
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Rapid, simultaneous detection of organic chemical pollutants in water is an important issue to solve for protecting human health. This study investigated the possibility of developing an in situ reusable optical sensor capable of selective measurements utilizing a chalcogenide transducer supplemented by a hydrophobic polymer membrane with detection based on evanescent waves in the mid-infrared spectrum. In order to optimise a polyisobutylene hydrophobic film deposited on a chalcogenide waveguide, a zinc selenide prism was utilized as a testbed for performing attenuated total reflection with Fourier-transform infrared spectroscopy. To comply with the levels mentioned in health guidelines, the target detection range in this study was kept rather low, with the concentration range extended from 50 ppb to 100 ppm to cover accidental pollution problems, while targeted hydrocarbons (benzene, toluene, and xylene) were still detected at a concentration of 100 ppb. Infrared measurements in the selected range showed a linear behaviour, with the exception of two constantly reproducible plateau phases around 25 and 80 ppm, which were observable for two polymer film thicknesses of 5 and 10 mu m. The polymer was also found to be reusable by regenerating it with water between individual measurements by increasing the water temperature and flow to facilitate reverse exchange kinetics. Given the good conformability of the hydrophobic polymer when coated on chalcogenide photonic circuits and its demonstrated ability to detect organic pollutants in water and to be regenerated afterwards, a microfluidic channel utilising water flow over an evanescent wave optical transducer based on a chalcogenide waveguide and a polyisobutylene (PIB) hydrophobic layer deposited on its surface was successfully fabricated from polydimethylsiloxane by filling a mold prepared via CAD and 3D printing techniques. Optimisation of the functionalisation of infrared chalcogenide sensors for accidental water poll
Millimeter-scale slide optical waveguides (OWGs) show the potential to break the barrier of easy-to-use and versatility for total internal reflection (TIR) fluorescence technology. In this paper, multi-frequency struc...
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Millimeter-scale slide optical waveguides (OWGs) show the potential to break the barrier of easy-to-use and versatility for total internal reflection (TIR) fluorescence technology. In this paper, multi-frequency structured illumination (SI) patterns resulting from the evanescent field (EF) on the surface of a millimeter-scale polymer slide OWG are observed by measuring the fluorescence intensity distribution of fluorescent dyes deposited on the top of theOWG. The frequency, intensity, and stability of the SI patterns show a strong dependence on the coupling angle of the incident light (changing with the incident position). The distribution of multi-frequency SI patterns in the frequency space is demonstrated for different numerical aperture (NA) imaging systems (NA= 0.3, 0.6, and 0.8), indicating the potential for enhanced resolution for low NA systems with a simple and cheap polymer slide. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.
Spot-size converters (SSCs) are key for efficient coupling of light between waveguides of different sizes. While adiabatic tapers are well suited for small size differences, they become impractically long for expansio...
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Spot-size converters (SSCs) are key for efficient coupling of light between waveguides of different sizes. While adiabatic tapers are well suited for small size differences, they become impractically long for expansion factors around x100, which are often required when coupling integrated waveguides and free-space beams. Evanescent couplers and Bragg deflectors can be used in this scenario, but their operation is inherently limited in bandwidth. Here, we propose a solution based on a parabolic dielectric interface that couples light from a 0.5 mu m wide waveguide to a 285 mu m wide waveguide, i.e., an expansion factor of x570. We experimentally demonstrate an unprecedented bandwidth of more than 380 nm with insertion losses below 0.35 dB. We furthermore provide analytical expressions for the design of such parabolic spot-size converters for arbitrary expansion factors. (c) 2025 Optica Publishing Group. All rights, including for text and data mining are reserved.
Herein, stacked nanosheets of barium and antimony are fabricated using a vacuum deposition technique under a vacuum pressure of 10-5 mbar onto cleaned glass substrates. The Zintl Ba/Sb nanosheets exhibit an amorphous ...
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Herein, stacked nanosheets of barium and antimony are fabricated using a vacuum deposition technique under a vacuum pressure of 10-5 mbar onto cleaned glass substrates. The Zintl Ba/Sb nanosheets exhibit an amorphous nature of growth with equal atomic contents. Notably, they present interesting properties such as low average roughness, high light transmittance and absorption, and low reflectance. Two optical transitions within energy bands with values of 3.40 eV and 0.75 eV are determined for these stacked nanosheets. Additionally, Ba/Sb nanosheets displayed dielectric lens and optical filter characteristics with high optical conductivity exceeding 5.0 (Omega cm)-1, 20 (Omega cm)-1, and 100 (Omega cm)-1 in the infrared, visible, and ultraviolet ranges of light, respectively. The optical conductivity parameters, including the free charge carrier density, drift mobility, and plasmon frequency, exhibit values in the ranges of 1.3-25x1019 cm-3, 3.53-9.41 cm2/versus, and 3.92-17.18 GHz, respectively. Moreover, Ba/Sb nanosheets display characteristics of terahertz band filters, demonstrating terahertz cutoff frequency values of 18-100 THz in the incident photon energy range of 1.13-3.64 eV. On the other hand, temperature-dependent electrical conductivity measurements on these stacked nanosheets reveal the domination of two impurity levels centered at 136 meV and 500 meV, with one being dominant below and the other above 380 K, respectively. The features of the Ba/Sb nanosheets reported here highlight their potential as optical filters, surface plasmon resonators, and terahertz band filters.
Integrated optics play important role in the development for optical network devices, optical processing, instrumentation and quantum information device. Here, multimode interference (MMI) coupler is one of basic comp...
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Integrated optics play important role in the development for optical network devices, optical processing, instrumentation and quantum information device. Here, multimode interference (MMI) coupler is one of basic component preferred for these integrated optic devices in which MMI coupler based on general interference (GIMMI) has been focused for large scale integrated optic devices because of compact size in comparison to MMI coupler based restricted interference (RIMMI). In this paper, we have reviewed different GIMMI structures reported previously. Different waveguide materials are mentioned and compared for fabrication of GIMMI device. The coupling behaviors and modal analysis of GIMMI couplers and their different tapered structures are estimated by using simple model based on sinusoidal modes showing reduced coupling lengths in down tapered structures in comparison to other structures. The excess loss, polarization dependence loss and crosstalk versus fabrication tolerances are obtained to compare their performances revealing almost same losses and fabrication tolerance. The paper reports the use of the GIMMI coupler in wavelength multiplexing, power splitting, switching, optical processing. Finally, Quantum optic application of GIMMI coupler is shown indicating high quantum fidelity of 50:50 coupling ratio.
Nonlinear optical processes lie at the heart of frequency tunable coherent light sources, including entangled photon sources and squeezed states of light, and they have become ubiquitous in fields ranging from ultrafa...
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Nonlinear optical processes lie at the heart of frequency tunable coherent light sources, including entangled photon sources and squeezed states of light, and they have become ubiquitous in fields ranging from ultrafast spectroscopy to quantum information processing. van der Waals materials have recently emerged as dynamically tunable and highly nonlinear optical platforms with ultracompact footprints. In particular, semiconducting materials like transition metal dichalcogenides possess large optical nonlinearity, orders of magnitude higher than standard nonlinear bulk crystals, and promise interesting opportunities toward the miniaturization of nonlinear optical devices down to the nanoscale. In this Perspective, we outline ongoing and future research directions in the field of nonlinear optics with layered semiconductors, with special focus on the control and tunability of their optical nonlinearities.
We report on the quantitative hard x-ray phase microscopy obtained with a laboratory source equipped with an x-ray planar waveguide. The waveguide, acting as a small secondary source with increased coherence, allows f...
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We report on the quantitative hard x-ray phase microscopy obtained with a laboratory source equipped with an x-ray planar waveguide. The waveguide, acting as a small secondary source with increased coherence, allows for phase contrast microscopy to be measured from a phase-only one-dimensional object. We analyzed different strategies and their performances for the case studied of low absorbing one-dimensional sample. It was found that the phase-only approximation for the sample enables the best performance in phase retrieval. Results obtained from experimental data are supported by phase retrieval performed on simulated data allowing an estimation of the performance of the algorithms. The ability to perform quantitative phase contrast microscopy with waveguides is an important advance for this novel x-ray phase contrast method, well suited to compact laboratory setups. (C) 2014 Elsevier B.V. All rights reserved.
We introduce a topology-optimized metal structure that attains broadband wavefront engineering of guided terahertz waves. While the recent demonstrations of dielectric-free terahertz lenses composed of curved metal su...
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We introduce a topology-optimized metal structure that attains broadband wavefront engineering of guided terahertz waves. While the recent demonstrations of dielectric-free terahertz lenses composed of curved metal surfaces facilitate low-loss and point source-coupled beamforming for the fundamental transverse-electric guided terahertz waves, such designs are significantly constrained in bandwidth due to the frequency dispersion of the mode. To address this challenge, this article employs topology optimization to tailor the effective refractive index profile via the surface structure, achieving broadband manipulation of guided terahertz waves. Experiments around 300 GHz demonstrate the capability to produce a directional beam with an about 15 mm waist from a point source over a 50 GHz bandwidth. Our approach presents a versatile design framework for integrated terahertz systems.
Guided waves play a crucial role in non-destructive testing, offering a reliable and efficient means for inspecting structures and materials. In this paper, we present the implementation of a wave finite element metho...
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Guided waves play a crucial role in non-destructive testing, offering a reliable and efficient means for inspecting structures and materials. In this paper, we present the implementation of a wave finite element method for extracting dispersion curves, providing a feasible approach for analysing guided wave propagation in structures characterized by complex geometries and diverse material properties. Various numerical examples are investigated, including layered composites, functionally graded materials, rail sections, and metastructures, showcasing the versatility of the method. Mode sorting is a serious problem associated with this method crucial for distinguishing different guided wave modes. A mode sorting algorithm based on modal assurance criteria is implemented which can effectively trace different guided wave modes. To enhance accuracy, dispersion calculations are assisted by incorporating micro -modelling techniques for composite materials. Furthermore, the influence of initial stress on dispersion curves is examined, revealing that the effects of tensile and compressive stresses can vary at different frequencies and for different modes. Attenuation or damping is inherent in every structure and material, significantly influencing wave propagation. The article also investigates viscoelasticity and damping, expanding the method's applicability by introducing a novel approach to calculate attenuation using the frequency domain modulus for computing complex angular frequencies. The present method offers a fast, accurate, and feasible solution for extracting dispersion curves in structures with intricate geometries and material properties.
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