Silicon oxynitride (SiON) is a highly adaptable material platform for photonic integrated circuits owing to its refractive index tunability and full CMOS compatibility. In this work, an integrated surface plasmon resonance (SPR) sensor based on a robust SiON rib waveguide is demonstrated. The sensor geometry and modal properties were optimized using two-dimensional finite element method (FEM) simulations. The sensor performance was evaluated by direct edge coupling within the 550–915 nm spectral range. The influence of the plasmonic layer was first investigated by tracking the resonance dip for gold thicknesses of 20–40 nm with dimethyl sulfoxide (DMSO, n = 1.47) as the analyte. The response was then simulated matching approximately volumetric water-isopropyl alcohol (IPA) mixtures (n = 1.33–1.38), yielding an averaged sensitivity of 158 nm/RIU changing from 80 (water) up to 350 (IPA) nm/RIU that increases with the analyte refractive index. The results confirm that matching the SiON core refractive index to the target analyte enhances the evanescent coupling and thereby the sensitivity. The combination of index tunability, robust architecture, and simple CMOS-compatible fabrication makes the presented platform a versatile candidate for lab-on-a-chip sensing.
Single-shot phase-shifting interferometry (SSPSI) has emerged as a powerful solution for quantitative phase retrieval in situations where conventional multi-step phase-shifting techniques fail due to vibration, motion, or limited acquisition speed. By encoding the required phase diversity within a single interferogram, either spatially or computationally, SSPSI enables real-time and full-field measurement without sacrificing spatial resolution. This paper provides a comprehensive overview of the theoretical foundations, current methodologies, and remaining challenges of SSPSI. The basic principle of interferometric phase extraction is first revisited to establish the transition from classical N-step algorithms to single-frame strategies. Existing approaches are then classified according to the mechanism used to introduce phase shifts, including spatial-carrier encoding and digital or computational techniques such as Hilbert, Riesz, wavelet, and monogenic-signal–based analysis. Each family of methods is examined in terms of phase accuracy, robustness to noise, implementation complexity, and suitability for dynamic measurements. Particular attention is given to recent advances in digital and hybrid techniques that numerically generate π/2-shifted fringe patterns from a single image, enabling precise phase recovery without experimental modulation.
To meet the stringent ultra-reliable connectivity demands of 6G applications such as enhanced broadband and autonomous driving, optical wireless communication (OWC) is considered a key candidate technology. In this work, we investigate the performance of an intelligent reflecting surface (IRS)-aided OWC system by analyzing the signal-to-interference-plus-noise ratio (SINR), data rate, and sum rate through comprehensive MATLAB simulations. The impact of key system parameters on these performance metrics is systematically studied. Furthermore, an analytical expression for the optimal line-of-sight (LoS) channel gain is derived to maximize SINR, data rate, and sum rate. This optimization enables the selection of higher-order M-pulse amplitude modulation (M-PAM) schemes, thereby enhancing channel capacity (CC), spectral efficiency (SE), and energy efficiency (EE) of the IRS-aided OWC system. Simulation results demonstrate that for an SINR of 14.52 dB, 4-PAM is identified as the most suitable advanced digital modulation scheme for reliable data transmission. Additionally, the proposed system achieves a maximum sum rate of 32 Mbps for two mirror arrays and two blockages, which is approximately three times higher than the corresponding results reported in the existing literature. These findings highlight the substantial potential of IRS-assisted OWC systems as an enabling technology for future 6G networks.
Lentils are a key source of plant-based proteins, but their quality can be compromised by bruchids, insects that burrow inside the seeds, causing internal damage. Current detection methods rely on destructive testing, which is time-consuming, costly, and results in the loss of part of the batch. In this study, we demonstrate the potential of terahertz time-domain imaging in transmission as a non-destructive and effective method for detecting bruchids in lentils. The approach provides rapid and precise assessment, preserving the integrity of the samples and enabling quality control for the agro-industrial sector. Beyond accurate quality evaluation, this method holds promise for future applications in automated sorting systems, improving product valuation and market competitiveness. By leveraging terahertz technology, we present an innovative solution that aligns with the needs of producers, distributors, and consumers. This work is a qualitative proof-of-concept aimed at establishing physical feasibility. It does not estimate diagnostic performance (sensitivity/specificity); a powered validation on concealed larvae is planned.
The manufacture of optical molds for generating optical components in continuous or batch production has become a great challenge as freeform components are increasingly required. New manufacturing techniques have emerged to meet these technological demands; however, freeform optics present previously unseen manufacturing challenges as traditional optical workshops are designed to produce components with spherical shapes. The mold technique is widely used for batch production, but the main challenge is mold manufacturing. Therefore, the manufacturing process of a toroidal 6061 aluminum optical mold is presented, using a CNC milling machine. To evaluate the finish of the toroidal surface, null screen tests and coordinate measurements were used as these methods allow changes in slopes across the entire surface to be measured in a single evaluation, which is not possible with other tests. The results obtained show that implementation is feasible at a reduced cost, with a Peak to-Valley (PV) error of 0.1806 mm and an Root Mean Square (RMS of 0.0402 mm in the surface finish, which can be further improved by taking the polishing stage as a guide.
Membrane diffraction imaging is one of the most widely used imaging technologies today, which offers the advantages such as lightweight design, large aperture, foldability, and low cost. However, the system imaging quality degrades because of the multiple order diffraction generated by the diffractive elements in practical applications. To eliminate the effects of multiple diffraction orders from the diffractive elements and optimize imaging quality, the system images are post processed. Iterative optimization algorithms are commonly used for image post processing. Particle swarm optimization is a commonly used iterative optimization algorithm, which is often used to search for optimal solutions within the solution space. The particle swarm optimization algorithm has the features of few parameters, simple behavior, and fast iteration speed, which can rapidly and effectively optimize imaging. This paper optimizes the simulated imaging of a diffraction imaging system based on Fresnel zone plates by adopting the particle swarm optimization algorithm. Optimize the system image based on known point spread functions and the system image. System imaging is optimized under the premise of known point spread functions and system imaging. The iteration speed is enhanced, reducing the number of iterations by approximately 99.6% compared to the random parallel gradient descent algorithm. Simultaneously, contrast is improved by about 5.4%, while gradient optimization effectiveness increases by approximately 25.4% after optimization by the particle swarm algorithm. Finally, the derived restoration model was applied to other images, achieving overall improvements in all evaluation metrics.
Optical inter-satellite links are a promising technology for constructing satellite backbone networks, owing to their high data transmission capacity and lightweight terminals. To circumvent the data-rate bottlenecks and structural complexity associated with optical-electrical-optical conversion, all-optical signal processing is essential. This paper addresses a common challenge at the relaying nodes of satellite backbone networks: handling concurrent access requests from multiple laser links. We propose and validate an all-optical data access system based on an optical time-lens. The system demonstrates robust performance and high modulation format compatibility. It successfully processes intensity-modulated, phase-modulated, and hybrid-format inputs entirely in the optical domain. The system’s reliability is further confirmed under practical conditions, including uneven wavelength spans and unequal data rates among the accessing links. It achieves bit-error rates below 10−7 and supports optical inter-satellite link transmission distances exceeding 4,500 km, even under hybrid modulation formats. With its simple structure and high compatibility, the proposed system offers a scalable solution for future multi-format satellite backbone networks.
BackgroundVascular occlusion tests (VOTs) are widely used to assess microvascular function with near-infrared spectroscopy (NIRS), but protocols vary substantially, particularly in occlusion pressure and anatomical site. Most studies focus on the upper arm or thigh, with few studying distal limbs such as the wrist, highlighting the importance of standardizing wrist-based arterial occlusion pressures.MethodsTo address this gap, the present study examined the effects of two fixed occlusion pressures, 150 mmHg and 200 mmHg, applied at the wrist on the local muscle oxygenation dynamics. A total of 21 healthy participants underwent an 8-min experimental protocol comprising a 1-min baseline (no pressure), 3-min occlusion, and 4-min reperfusion period. Muscle oxygenation was continuously monitored from the thenar eminence of the occluded hand using a commercial near-infrared spectroscopy (NIRS) device (Moxy, Hutchinson, USA).ResultsReactive hyperemia responses at the two pressures were compared for five distinct metrics: amplitude of muscle oxygen saturation (SmO2)(p=0.0065), time to maximum SmO2(p=0.235), and three first-derivative features: time to peak slope (p=0.694), peak slope value (p=0.019), and full width at half maximum (FWHM) (p=0.46). Statistically significant differences were observed in amplitude of SmO2, and peak slope value. However, the temporal metrics such as time to max SmO2, time at peak slope value, and FWHM, were not significantly different.ConclusionOverall, this study supports the potential of wrist-based AOP protocols and highlights the importance of selecting appropriate occlusion pressures and anatomical sites to optimize vascular response while minimizing patient discomfort. Given the wrist’s anatomical advantages, incorporating wrist-based occlusion into daily practice and clinical assessments may enhance its translational potential as a pressure occlusion site.
We here describe a nanosecond, multi-line laser source that preserves partial linear polarization after transmission through a 100-m large-core graded-index (GRIN) fiber. The system generates narrow emission lines between 473 and 600 nm, evenly spaced by the silica Raman shift of ∼440 cm-1, from a Q-switched nanosecond pump coupled into the fiber. Despite multimode propagation, the cascaded beams emerge close to diffraction-limited Gaussian profiles due to nonlinear mode self-cleaning, while the residual pump remains multimodal. Across the emission lines, the degree of linear polarization (DoLP) ranges from 0.1 to 0.6 depending on the wavelength. As an application, we demonstrate single-shot, multiwavelength spectro-polarimetric reflectance, simultaneously measuring DoLP at all cascaded lines. To our knowledge, this is the first demonstration of wavelength-dependent polarization retention through a 100-m large-core GRIN fiber.
This study presents a novel approach for achieving high-quality and large-scale microscopic ghost imaging by integrating deep learning-based denoising with computational ghost imaging techniques. By utilizing sequenced random speckle patterns of optimized sizes, we reconstructed large noisy images with fewer patterns while successfully resolving fine details as small as 2.2 μm on a USAF resolution target. To enhance image quality, we incorporated the Deep Neural Network-based Noise2Void (N2V) model, which effectively denoises ghost images without requiring a reference image or a large dataset. By applying the N2V model to a single noisy ghost image, we achieved significant noise reduction, leading to high-resolution and high-quality reconstructions with low computational resources. This method resulted in an average Structural Similarity Index (SSIM) improvement of over 324% and a resolution enhancement exceeding 33% across various target images. The proposed approach proves highly effective in enhancing the clarity and structural integrity of even very low-quality ghost images, paving the way for more efficient and practical implementations of ghost imaging in microscopic applications.
The research in the area of terahertz (THz) radiation is a subject of intense discussion in the international scientific community owing to its various applications in the fields of defense systems, security, interstellar studies, imaging, and agriculture. Although most of these applications have captured the attention of researchers in recent years, the development of a THz radiation source that meets specific requirements remains a challenging task. In this regard, the emission frequencies of terahertz quantum-cascade lasers (THz QCLs) can be fine-tuned by adjusting the thickness of the quantum well and the height of the barriers. The electron distribution among three periods of a hybrid active region design QCL structure is numerically simulated to estimate the optical gain spectra and electric field strength values. The results of the numerical simulations are compared with those of the experimental investigations by fabricating a 23 μm-thick active region THz QCL wafer by using the molecular beam epitaxy (MBE) technique. The wafer is split into six portions (A–F) to investigate the transport and the lasing properties. The electrical power dissipated at 10 K for the 23 μm-thick active region THz QCL stripe processed from the central portion (B) of the wafer is found to be approximately 56 W at the current density value of 0.53 kAcm−2. The thick active region THz QCL investigated in the present work operates in both pulsed and continuous-wave modes at the desired emission frequencies, which is a unique feature of the interlaced design. The optical output power of the 23 μm-thick active region THz QCL stripe compared to the 12 μm-thick active region is enhanced, attributed to improved mode confinement. Therefore, optimal performance in the pulsed mode can be achieved with thick active region THz QCL stripes fabricated near the center of the parent wafer. Nevertheless, thin active region THz QCLs are more suitable for continuous-wave operation due to reduced heat dissipation.
Precision glass molding (PGM) enables high-accuracy, efficient production of complex optical components, yet interfacial adhesion between mold and glass surfaces remains a significant barrier, impacting both quality and mold durability. This review comprehensively examines the factors influencing adhesion behavior, including the roles of material selection, surface wettability, process parameters, and thermodynamic principles in defining interfacial performance. Through a detailed analysis of anti-adhesion materials and optimized process strategies, such as controlled temperature, pressure, and atmospheric conditions, this work elucidates mechanisms that mitigate adhesion and extend mold life. Thermodynamic modeling, including work of adhesion calculations, provides a quantitative foundation for predicting interfacial behavior, offering guidance for material and process optimization in PGM applications. The findings provide a multi-dimensional framework for addressing adhesion challenges in PGM, setting the stage for enhanced efficiency and quality in precision optics manufacturing.
The development of integrated photonic systems, both on-chip and fiber-based, has transformed quantum photonics by replacing bulky, fragile free-space optical setups with compact, efficient, and robust circuits. Photonic platforms incorporating fiber-connected sources of correlated and entangled photon pairs offer practical advantages, such as operation at room temperature, efficient integration with telecom infrastructure, and compatibility with mature and efficient semiconductor fabrication processes for cost-effective and large-scale optical circuits. The stability and scalability of integrated quantum photonics platforms have facilitated the generation and processing of quantum information in the temporal domain within a single spatial mode. Time-bin encoded states, known for their robustness against decoherence and compatibility with existing fiber-optic infrastructure, have shown to be an efficient paradigm for advanced applications like quantum secure communication, information processing, spectroscopy, imaging, and sensing. This review examines recent advancements in fiber- and chip-based platforms for generating non-classical states and their applications as quantum state processors in the time domain. We discuss the generation of pulsed quantum frequency combs using microring resonators and intra-cavity mode-locked laser schemes, enabling co- and cross-polarized quantum photonic states. Additionally, the versatility of these resonator chips for entanglement generation is emphasized, including two- and multi-photon time-bin entangled schemes. We highlight the development of time-bin entanglement analyzers in fiber architectures, featuring ultrahigh stability and post-selection-free capabilities, which enable precise and efficient characterization of two- and higher-dimensional time-bin entanglement. We also review scalable on-chip schemes for quantum key distribution, demonstrating low quantum bit error rates and compatibility with higher-dimensional quantum communication protocols. Further, methods for enhancing temporal resolution in detection schemes, crucial for time-bin encoding, are presented, such as the time-stretch sampling technique using electro-optic modulation. These innovations, relying on readily available, telecom-based fiber-optic components, provide practical, scalable, and cost-effective solutions for advancing quantum photonic technologies. Looking forward, time-bin encoding is expected to play a pivotal role in the advancement of quantum repeaters, distributed quantum networks, and hybrid light-matter systems, advancing the realization of globally scalable quantum technologies.
IntroductionApart from discussing general issues related to the application of freeform telescopes, this work presents a design of ultra-compact high-resolution freeform telescope dedicated to CubeSat application associated with Earth surface imaging from Low Earth Orbit (LEO), providing high resolution (Ground Sampling Distance, GSD <5 m) and 20 km width of the observed Earth strip.MethodsThe telescope was designed in a three-mirror off-axis configuration according to the <0.5U volume constraint. Freeform surfaces were described by shifted polynomial equations. In order to prevent optimization falling into numerous local minima of multi-variate merit function, the new design strategy was proposed. The optical design commercial software was supplemented by add-on responsible for dynamically modifying the set of variables in the loop during the optimization process.ResultsThe designed 250 mm f/4.9 telescope meets the assumed operational and volumetric criteria. It fits into the volume of 5 × 10 × 10 cm cuboid. It is diffraction limited across the whole (3o) field of view.DiscussionFreeform optics design technology was successfully applied to design a miniature space telescope. The proposed design algorithm proved to be computationally efficient. It enabled to obtain the excellent imaging of the designed telescope, which from mathematical perspective becomes a challenging multi-variable optimization task, unattainable with the standard optimization procedures included in the commercial optical design software.
The advent of X-ray Free Electron Lasers (XFELs) has opened unprecedented opportunities for advances in the physical, chemical, and biological sciences. With their state-of-the-art methodologies and ultrashort, and intense X-ray pulses, XFELs propel X-ray science into a new era, surpassing the capabilities of traditional light sources. Ultrafast X-ray scattering and imaging techniques leverage the coherence of these intense pulses to capture nanoscale structural dynamics with femtosecond spatial-temporal resolution. However, spatial and temporal resolutions remain limited by factors such as intrinsic fluctuations and jitters in the Self-Amplified Spontaneous Emission (SASE) mode, relatively low coherent scattering cross-sections, the need for high-performance, single-photon-sensitive detectors, effective sample delivery techniques, low parasitic X-ray instrumentation, and reliable data analysis methods. Furthermore, the high-throughput data flow from high-repetition rate XFEL facilities presents significant challenges. Therefore, more investigation is required to determine how Artificial Intelligence (AI) can support data science in this situation. In recent years, deep learning has made significant strides across various scientific disciplines. To illustrate its direct influence on ultrafast X-ray science, this article provides a comprehensive overview of deep learning applications in ultrafast X-ray scattering and imaging, covering both theoretical foundations and practical applications. It also discusses the current status, limitations, and future prospects, with an emphasis on its potential to drive advancements in fourth-generation synchrotron radiation, ultrafast electron diffraction, and attosecond X-ray studies.
IntroductionSeveral population-based clinical studies suggest that increased Pulse Wave Velocity (PWV) is highly associated with increased cardiovascular disease (CVD) mortality, which is one of the leading causes of death worldwide. Current methods for CVD detection are invasive, expensive, and contact methods, which are not friendly for skin-sensitive patients.MethodsIn this study, we investigated the use of remote photoplethysmography (rPPG) on the neck region using a high-speed camera (2000 frames per second (fps)) to resolve the drawbacks of CVD detection and overcome the limitations of current PWV measurement techniques. Pearson correlation and cross-correlation were used for signal processing and generating the projection map of potential major vessels. A reference signal is selected for the region of interest based on peak value and modulation depth variation. The signal distance and pulse transit time (PPT) between the local and reference signals were calculated using the cross-correlation method and then fitted into a linear regression model for PWV calculation.ResultsThe results revealed areas on the neck that positively and negatively correlated with the selected reference signals, potentially representing the distribution of the main neck vessels - carotid artery and jugular vein- and, consequently, the upstream and downstream blood circulation directions.DiscussionThis research implies the feasibility of touchless estimation of local PWV using a high-speed camera, expanding the potential applications of remote photoplethysmography in aiding the diagnosis of CVD.
In this paper, the authors explore the potential of an exotic multi-graphene layer/Si nanowire (MGL/SiNW) pin device as a switch in the THz frequency domain. The device is developed by the incorporation of multiple SiNWs into its intrinsic region. In contrast, cap and bottom layers are developed by the incorporation of multiple graphene layers. The electrical characterization of the proposed exotic pin device is carried out by developing a quantum-rectified Schrodinger–Poisson drift-diffusion (QRSP-DD) model. The developed QRSP-DD model is validated by analyzing experimental and simulation observations under similar operating conditions. After establishing its validity, the same model in conjunction with the PSpice simulator is used to obtain the switching characteristics of MGL/SiNW pin-based series-shunt and shunt single-pole single-throw (SPST), single-pole double-throw (SPDT), and single-pole multiple-throw (SPMT) switches in the THz frequency domain. The analysis proves that the MGL/SiNW pin-based SPMT switch offers low resistance (0.56 Ω), high isolation (91.15 dB), and low insertion loss (0.007 dB) at 5 THz frequency compared to its SiNW counterpart.
Introduction: This work presents a prototype electromagnetic actuation deformable mirror (DM) assembly with stress-resilient face sheet design.Methods: The DM face sheet design includes slender micromachined silicon pillars that are integrated with a silicon face sheet to reduce unpowered face sheet surface distortion caused by actuator adhesion stress.Results: The assembled deformable mirror prototype allowed bi-directional actuation with total stroke exceeding 20 μm. A two-step control method was used to improve the prototype dynamic performance, allowing settling time on the order of 1 ms. Prescribed references shapes were made on the prototype deformable mirror using closed-loop control.Discussion: While the simplified DM produced in this work has only 19 actuators and therefore has limited capacity to control complex shapes, the design and fabrication processes described and demonstrated in this work provide a promising approach to development of high-stroke magnetic DMs.
The significant brightness contrast between stars and orbiting planets often hinders the detection of exoplanets. This paper presents the development and validation of an experimental setup and digital filtering techniques for a rotational shearing interferometer (RSI) aimed at enhancing exoplanet detection. The method leverages controlled phase shifts and spatial frequency modulation through Risley and Dove prisms to isolate faint planetary signals from dominant starlight. Laboratory experiments use HeNe lasers to simulate a star-planet system, and spatial filters ensure precise wavefront alignment. The interferometer’s rotational shearing capabilities enhance the accuracy of phase alignment, allowing for significant suppression of starlight and improved detection of planetary signals. Additionally, applying Fourier-based digital filtering techniques further enhances detection sensitivity by reducing background noise. Experimental results demonstrate an 80% reduction in noise and up to a 20% increase in detection sensitivity compared to traditional interferometric methods. The RSI’s performance represents a significant advancement in interferometric techniques, suggesting its potential for real-world astronomical applications. However, further optimization is required to address challenges associated with space-based observations. This work sets the foundation for future research aimed at refining optical configurations and digital filtering techniques for exoplanet detection.
