Cross-talk-free, high extinction ratio, and ultra-compact all‑optical 4 × 2 encoder using graphene-based plasmonic waveguides.

This paper presents an all-optical 4 × 2 encoder based on graphene-plasmonic waveguides for operation in the wavelength range of 8-12 μm. The basic plasmonic waveguide consists of a silicon (Si) strip and a graphene sheet supported by two dielectric ridges. Surface plasmon polaritons (SPPs) are stimulated in the spatial gap between the graphene sheet and the Si strip.

An Optimal Internet of Things-Driven Intelligent Decision-Making System for Real-Time Fishpond Water Quality Monitoring and Species Survival.

Smart fish farming faces critical challenges in achieving comprehensive automation, real-time decision-making, and adaptability to diverse environmental conditions and multi-species aquaculture. This study presents a novel Internet of Things (IoT)-driven intelligent decision-making system that dynamically monitors and optimizes water quality parameters to enhance fish survival rates across various regions and species setups. The system integrates advanced sensors connected to an ESP32 microcontroller, continuously monitoring key water parameters such as pH, temperature, and turbidity which are increasingly affected by climate-induced variability.

Dielectric Metasurfaces for Broadband Phase-Contrast Relief-Like Imaging.

The visualization of transparent specimens in traditional light microscopy is impeded by insufficient intrinsic contrast, prompting the development of advanced contrast-enhancement methodologies to transmute minute phase discrepancies into detectable amplitude alterations. While existing methods excel in either phase-contrast imaging (contrast-enhanced image of whole objects) or relief-like imaging (deceptive three-dimensional images), it would be of great significance to seamlessly integrate both capabilities in the same device. Here, we propose a novel metasurface-assisted half-side phase-contrast technique capable of simultaneous phase-contrast and relief-like imaging across the visible spectrum, which is realized by introducing a ±π/2 phase shift to a half-side diffracted wave emitted by the objects.

A SURF and SVD-based robust zero-watermarking for medical image integrity.

Medical image security is paramount in the digital era but remains a significant challenge. This paper introduces an innovative zero-watermarking methodology tailored for medical imaging, ensuring robust protection without compromising image quality. We utilize Sped-up Robust features for high-precision feature extraction and singular value decomposition (SVD) to embed watermarks into the frequency domain, preserving the original image's integrity.

A reversible-zero watermarking scheme for medical images.

The paper addresses the issue of ensuring the authenticity and copyright of medical images in telemedicine applications, with a specific emphasis on watermarking methods. While several systems only concentrate on identifying tampering in medical images, others also provide the capacity to restore the tampered regions upon detection. While several authentication techniques in medical imaging have successfully achieved their goals, previous research underscores a notable deficiency: the resilience of these schemes against unintentional attacks has not been sufficiently examined or emphasized in previous research.

A Portable Fluorescent Lateral Flow Immunoassay Platform for Rapid Detection of FluA.

The spread of the FluA virus poses significant public health concerns worldwide. Fluorescent lateral flow immunoassay (LFIA) test strips have emerged as vital tools for the early detection and monitoring of influenza infections. However, existing quantitative virus-detection methods, particularly those utilizing smartphone-based sensing platforms, encounter accessibility challenges in resource-limited areas and among the elderly population.

A low-cost and portable fluorometer based on an optical pick-up unit for chlorophyll-a detection.

Chlorophyll-a (Chl-a) fluorescence detection is an important technique for monitoring water quality. In this work, we proposed an approach that employs the mass-produced low-cost optical pick-up unit (OPU) extracted from the high-definition digital versatile disc (HD-DVD) drive as the key optical component for our chlorophyll-a fluorometer. The built-in blue-violet 405 nm laser diode of the OPU acts as the excitation light to perform laser-induced fluorescence (LIF).

Wavelength-Independent Excitation Bessel Beams for High-Resolution and Deep Focus Imaging.

Bessel beams are attaining keen interest in the current era considering their unique non-diffractive, self-healing nature and their diverse applications spanning over a broad spectral range of microwave to optical frequencies. However, conventional generators are not only bulky and complex but are also limited in terms of numerical aperture (NA) and efficiency. In this study, we experimentally develop a wavelength-independent Bessel beam generator through custom-designed metasurfaces to accomplish high resolution and large depth-of-focus imaging.

Broadband generation of accelerating polygon beams with large curvature ratio and small focused spot using all-dielectric metasurfaces.

Self-accelerating polygon beams have drawn growing emphasis in optics owing to their exceptional characteristics of multiple self-accelerating channels and needle-like field distributions. Various approaches have been proposed to generate polygon beams, such as using spatial light modulators (SLMs) or plasmonic metasurfaces. However, SLMs impede the miniaturization of the optical system and both approaches are subject to low efficiencies and demand an extra physical lens with a long focal length for Fourier transform, which limits the quality and the diverse variability of polygon beams.

Generation of high-uniformity and high-resolution Bessel beam arrays through all-dielectric metasurfaces.

Bessel beam arrays are progressively attracting attention in recent years due to their remarkable non-diffracting nature and parallel manipulation capabilities in diverse applications. However, the poor phase discretization of conventional approaches such as spatial light modulators leads to low numerical aperture (NA) beam arrays due to the limitation imposed by the Nyquist sampling theorem and poor uniformity of the beam intensity. The key contribution of this study is to experimentally demonstrate the generation of high-uniformity and high-resolution Bessel beam arrays by utilizing all-dielectric metasurfaces.

Detection and Classification of Multi-Type Cells by Using Confocal Raman Spectroscopy.

Tumor cells circulating in the peripheral blood are the prime cause of cancer metastasis and death, thus the identification and discrimination of these rare cells are crucial in the diagnostic of cancer. As a label-free detection method without invasion, Raman spectroscopy has already been indicated as a promising method for cell identification. This study uses a confocal Raman spectrometer with 532 nm laser excitation to obtain the Raman spectrum of living cells from the kidney, liver, lung, skin, and breast.

Patient-related factors associated with severe heat-related illnesses in Karachi: A hospital perspective.

In 2015, Karachi saw its first ever epidemic of severe heatrelated illnesses that resulted in an extraordinary number of hospital admissions, especially in the intensive care, for fatal heat stroke within-hospital mortality of 3.7%.We conducted this study to elucidate the patient-related factors that lead to an increase in hospital admissions with heat-related illnesses in a tertiary care hospital.

Polarization Insensitive, Broadband, Near Diffraction-Limited Metalens in Ultraviolet Region.

Metasurfaces in the ultraviolet spectrum have stirred up prevalent research interest due to the increasing demand for ultra-compact and wearable UV optical systems. The limitations of conventional plasmonic metasurfaces operating in transmission mode can be overcome by using a suitable dielectric material. A metalens holds promising wavefront engineering for various applications.

Shift of the surface plasmon polariton interference pattern in symmetrical arc slit structures and its application to Rayleigh metallic particle trapping.

In symmetric nano/micro metal slit structures, interference patterns are produced by counter-propagating surface plasmon polaritons (SPPs) in the the center of structures, which can be employed to improve the resolution of microscopy and surface etching and to realize particle trapping. This paper focuses on the shift of the SPP interference patterns in the symmetric arc slit structures. The excitation models with one incident beam and two incident beams are established and analyzed respectively, and methods to shift the SPP interference patterns via adjusting the tilt angle and initial phase of the excitation beams are compared.

High-Efficiency, Broadband, Near Diffraction-Limited, Dielectric Metalens in Ultraviolet Spectrum.

Ultraviolet (UV) optical devices have plenteous applications in the fields of nanofabrication, military, medical, sterilization, and others. Traditional optical components utilize gradual phase accumulation phenomena to alter the wave-front of the light, making them bulky, expensive, and inefficient. A dielectric metasurface could provide an auspicious approach to precisely control the amplitude, phase, and polarization of the incident light by abrupt, discrete phase changing with high efficiency due to low absorption losses.