Optics and Photonics Research Papers (original) (raw)

2025, Journal of Biomedical Optics

We develop an optical fluorescent mapping system that is able to record the action potential wavefront propagation within cardiac tissue samples with high spatial and temporal resolutions. The system's main component, the fluorescence acquisition device (customized CCD camera), offers a high spatial resolution of 128ϫ128 pixels, with 12-bit digitization and a frame rate of 490 frames/s. The system is designed and implemented to image an area of approximately 20ϫ20 mm at its minimum object distance of 140 mm, corresponding to a spatial resolution of approximately 3 line pairs/mm. Experiments using this system with di-4-ANEPPS-stained canine cardiac tissues with stimulated action potentials through external electrodes result in successful mappings of the distribution and propagation of the action potential wavefronts, showing the system's sensitivity to the change in fluorescence intensity in regions of action potentials. These data demonstrate this optical mapping system as a powerful device in the study of cardiac arrhythmia mechanisms.

2025, IEEE Access

The ease of controlling waveguide properties through unparalleled design flexibility has made the photonic crystal fiber (PCF) an attractive platform for plasmonic structures. In this work, a dual analyte channel's highly sensitive PCF bio-sensor is proposed based on surface plasmon resonance (SPR). In the proposed design, surface plasmons (SPs) are excited in the inner flat portion of two rectangular analyte channels where gold (Au) strip is deposited. Thus, the surface roughness that might be generated during metal deposition on circular surface could be effectively reduced. Considering the refractive index (RI) change in the analyte channels, the proposed sensor is designed and fully characterized by the finite element method based COMSOL Multiphysics software. Improved sensing characteristics including wavelength sensitivity (WS) of 186,000 nm/RIU and amplitude sensitivity (AS) of 2,792.97 RIU -1 in the wide RI range of 1.30 to 1.43 is obtained. In addition, the proposed sensor exhibits excellent resolution of 5.38×10 -7 , signal to noise ration (SNR) of 13.44 dB, figure of merits (FOM) of 2188.23, detection limit (DL) of 101.05 nm, and detection accuracy (DA) of 0.0204 nm -1 . Outcomes of the analysis indicate that the proposed sensor could be suited for accurate detection of organic chemicals, bio-molecules, and biological analytes. INDEX TERMS Plasmonic, bio-sensor, photonic crystal fiber, finite element method, detection limit.

2025, Physical Review B

We address the concomitant metal-insulator transition (MIT) and antiferromagnetic ordering in the novel pyrochlore iridate Eu2Ir2O7 by combining x-ray absorption spectroscopy, x-ray and neutron diffractions and density functional theory (DFT) based calculations. The temperature dependent powder x-ray diffraction clearly rules out any change in the lattice symmetry below the MIT, nevertheless a clear anomaly in the Ir-O-Ir bond angle and Ir-O bond length is evident at the onset of MIT. From the x-ray absorption near edge structure (XANES) spectroscopic study of Ir-L3 and L2 edges, the effective spin-orbit coupling is found to be intermediate, at least quite far from the strong atomic spin-orbit coupling limit. Powder neutron diffraction measurement is in line with an allin-all-out magnetic structure of the Ir-tetrahedra in this compound, which is quite common among rare-earth pyrochlore iridates. The sharp change in the Ir-O-Ir bond angle around the MIT possibly arises from the exchange striction mechanism, which favors an enhanced electron correlation via weakening of Ir-Ir orbital overlap and an insulating phase below TMI . The theoretical calculations indicate an insulating state for shorter bond angle validating the experimental observation. Our DFT calculations show a possibility of intriguing topological phase below a critical value of the Ir-O distance, which is shorter than the experimentally observed bond length. Therefore, a topological state may be realized in bulk Eu2Ir2O7 sample if the Ir-O bond length can be reduced by the application of sufficient external pressure.

2025

In line bisection tasks, right-brain damaged patients with unilateral spatial neglect (USN) exhibit a rightward deviation with respect to the objective midpoint of the stimulus, while in neurologically unimpaired participants a reversed bias ("pseudoneglect") has been consistently reported. In a study with healthy subjects, suggested the existence of partially independent mechanisms involved in word and line bisection, not only linguistic but also visuo-perceptual. Furthermore, both lexical and syntactic factors are shown to modulate the reading performance in patients with neglect dyslexia . A series of studies involving USN patients were conducted in order to investigate the spatial and linguistic encoding of orthographic material through a bisection task. In Study I, right-brain damaged patients with USN, right-brain damaged patients without USN, and matched controls were asked to manually bisect words (5-10-13 letters) and lines of comparable length (Exp. 1), and words with final sequences differing on the prediction made concerning how the word should have been read (stressed on the penultimate or antepenultimate syllable; Exp. 2). Study II required the bisection of words and lines of different lengths, radially oriented. In Study III, patients were asked to bisect affirmative and interrogative sentences varying on the syntactic structure, compared to letter strings and lines (Exp. 1), and sentences in which lexical and syntactic alterations were introduced (Exp.2). Data from Study I demonstrated that most USN patients show a rightward deviation similar for words and lines, with the bias increasing with stimulus length. However, in individual patients USN can affect the bisection of lines and orthographic material with various degrees of severity, demonstrating that at least partially independent mechanisms interact during bisection . Furthermore, the ortho-phonological information contained in the final part of a word could act as a cue, modulating the bisection error in patients and healthy subjects. In Study II, radial words are re-oriented during bisection, reaching their canonical orientation. Finally, the linguistic nature of the stimulus induces facilitation in USN patients, who show a reduced error deviation in case of sentences with respect to letter strings and lines (Study III), even when lexical and syntactic alterations were introduced. In conclusion, visuo-perceptual and linguistic information (both lexical and possibly syntactic) modulates the allocation of attention in word and sentence bisection.

2025, Cortex

Unilateral spatial neglect (USN) syndrome has been rarely diagnosed in association with a concurrent status epilepticus. Some reports described patients affected by seizure-related USN together with additional clinical signs, motor or... more

2025, Journal of Clinical Medicine

Personalized medicine has the potential to improve our ability to maintain health and treat disease, while ameliorating continuously rising healthcare costs. Translation of basic research findings to clinical applications within regulatory compliance is required for personalized medicine to become the new foundation for practice of medicine. Deploying even a few of the thousands of potential diagnostic biomarkers identified each year as part of personalized treatment workflows requires clinically efficient biosensor technologies to monitor multiple biomarkers in patients in real time. This paper discusses a critical component of a regulatory system, a microcavity optical biosensor for label-free monitoring of biomolecular interactions at physiologically-relevant concentrations. While most current biosensor research focuses on improving sensitivity, this paper emphasizes other characteristics a biosensor technology requires to be practical in a clinical setting, presenting robust microcavity biosensors which are easy to manufacture and integrate with microfluidics into flexible and redesignable platforms making the microcavity biosensors deployable for continuous monitoring of biomarkers in body fluids in the clinic, in dense 2D random arrays for high-throughput applications like drug-library screening in interactomics, and of the secretory behavior of single cells in the laboratory.

2025, Current biology : CB

Eyes with refractive error have reduced visual acuity and are rarely found in the wild. Vertebrate eyes possess a visually guided emmetropisation process within the retina which detects the sign of defocus, and regulates eye growth to align the retina at the focal plane of the eye's optical components to avoid the development of refractive error, such as myopia, an increasing problem in humans [1]. However, the vertebrate retina is complex, and it is not known which of the many classes of retinal neurons are involved [2]. We investigated whether the camera-type eye of an invertebrate, the squid, displays visually guided emmetropisation, despite squid eyes having a simple photoreceptor-only retina [3]. We exploited inherent longitudinal chromatic aberration (LCA) to create disparate focal lengths within squid eyes. We found that squid raised under orange light had proportionately longer eyes and more myopic refractions than those raised under blue light, and when switched between...

2025, International Journal of Periodontics and Restorative Dentistry

2025, Physical Review B

Experimentally observed narrowing of spectral holes in a glass under hydrostatic pressure confirms our theoretical finding that the external pressure, in addition to increasing the frequencies of soft localized modes, also reduces their number. This occurs because the majority of soft localized modes in glasses is shown to have a negative cubic anharmonicity. For that reason the applied pressure not only enhances the stiffness of these modes, but also transforms a fraction of them into tunneling two-level systems, whereas the simultaneous reverse transformations of some other two-level systems into soft localized modes are less numerous.

2025, Journal of a sustainable global south

Dental treatments generally need length of time period. The dental care consist of several steps and these steps should be performed in the cramped space which is patient's mouth (oral cavity). Thus, dentists have potential on suffering for musculoskeletal injuries which may affect their quality of work. This is a descriptive study (observation and interviews) with cross-sectional approach. This study conducted observation on several ergonomic aspects include task, organizational, and environment; following with interviews on how were dental students performing scaling procedures The mean time of dental students in performing scaling was 28,38 ± 1,03 minutes, this period of time also cover all the time needed for several adjusting working positions taken by dental students on purpose to cover scaling on all of the teeth surfaces and regions. Dentists have risk for potential injuries resulted from non-ergonomic working attitude and static position. This indicated from increasing of Nordic Body Map scores after performing scaling with mean scores 13,87 ± 1,56, increasing eyes train scores up to 2,2 ± 0,27, and increasing work load which was calculated from hearth rate 23,45 ± 2,70 beats/menit. This study also assesses organizational and working environment which may affect dental students on performing scaling. The total ergonomic approach may be employed to solve the identified problems from ergonomic assessment on the scaling procedures performed by dental students at Dentistry Udayana University. Thus, it is expected that the approach can be solve the problems complained by dental students while performing scaling procedure, as well as assistant operators, patients, and others related parties without creating unnecessary side effects causing by the purposed adjustment.

2025, Optics Express

We describe the application of cavity ring-down spectroscopy (CRDS) to the detection of trace levels of ethylene in ambient air in a cold storage room of a fruit packing facility over a several month period. We compare these results with those obtained using gas chromatography (GC), the current gold standard for trace ethylene measurements in post-harvest applications. The CRDS instrument provided real-time feedback to the facility, to optimize the types of fruit stored together, and the amount of room ventilation needed to maintain sub-10 ppb ethylene levels for kiwi fruit storage. Our CRDS instrument achieved a detection limit of two partsper-billion volume (ppbv) in 4.4 minutes of measurement time.

2025, IEEE Photonics Journal

Sampling is the primary functional step of an analogue to digital conversion, required for sensing, measurement, signal processing, metrology, and various data communication applications. Here we present, for the first time, to the best of our knowledge, the optical sampling of different microwave signals with sinc-pulse sequences with a very compact integrated silicon photonics ring modulator. By a simple time interleaving with three branches, the employed ring modulator enables ultra-compact photonic integrated analog to digital converters with a sampling rate of three times the RF bandwidth of itself and of the used photodetector and electronic devices. Therefore, its analogue bandwidth is 50% higher than the RF bandwidth of the incorporated electronics and photonics. Thus, the method might enable high-bandwidth analogue to digital converters with ultra-compact footprint and lower power consumption for future communication systems, sensors, and measurement devices.

2025, Journal of the Optical Society of America B

The spatial structure of Raman-converted radiation was investigated numerically and experimentally for the case when the pump is a conical beam produced by an axicone from multimode laser radiation. Both conical and axial Stokes beam generation was found to be possible. The improvement of the laser beam quality was demonstrated numerically and supported by experiment on Raman conversion in barium nitrate crystal. The laser beam with the beam quality factor M 2 = 11 was converted into the axial Stokes beam with M 2 = 3.5 at the conversion efficiency of 20%. A two-times increase in the Stokes beam brightness was obtained.

2025, Journal of the Optical Society of America B

The two-Stokes generation of a Q-switched microchip laser with intracavity stimulated Raman scattering frequency conversion and multiwave mixing has been investigated theoretically and experimentally. The dependences of the output power and the pulse repetition rate of the Nd:LaSc 3 ͑BO 4 ͒ 3 (Nd:LSB)-Cr:YAG-BaWO 4 microchip laser on the pump power have been experimentally obtained and the shapes of the fundamental, first Stokes, and second Stokes pulses have been recorded. The effect of the intracavity multiwave mixing on the characteristics of the both Stokes pulses and their shapes has been analyzed. The modeling of the output parameters and the calculated pulse shapes agree well with the obtained experimental results.

2025, Revista Mexicana De Fisica

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2025, Journal of Electronic Materials

A theoretical demonstration of a high-quality-factor photonic crystal (PC) temperature sensor in the near-infrared frequency domain is presented. The sensor is based on coupling of Tamm plasmon polaritons (TPPs) existing at the graphene-PC interface and graphene plasmon polaritons (GPPs) existing at the graphene surface. This leads to the appearance of a TPP-GPP hybrid mode in one-dimensional ternary photonic crystals (1D TPC) truncated by a dielectric layer between graphene monolayers. For a transverse magnetic (TM) polarized wave, the excited TPP-GPP hybrid modes are localized within the range 180-270 THz or 1.11-1.67 µm. Excellent control over the resonance frequency is established via Kretschmann configuration excitation that covers the temperature range spanning from 1 K to 1500 K with high coupling efficiency and high quality factor (QF) of the order of 10 5. It has been proved that the QF is strongly governed by temperature. The design parameters of the sensor are optimized so that temperature sensitivity of 5.75 fm∕K is achieved, with an excellent figure of merit of the order of 10-4 K-1 and high detection accuracy of the order of 10 11. The proposed sensor exhibits a high temperature detection limit or temperature resolution of 3.915 × 10-4 K. A comparative analysis of the sensor parameters in the near infrared wavelength is provided, and the wavelengths are resolved at the femtometer length scale with very high QF.

2025, The Journal of Organic Chemistry

Singlet molecular oxygen (a 1 ∆ g ) has been produced and optically monitored in time-resolved experiments upon nonlinear two-photon excitation of photosensitizers that contain triple bonds as an integral part of the chromophore. Both experiments and ab initio computations indicate that the photophysical properties of alkyne-containing sensitizers are similar to those in the alkenecontaining analogues. Most importantly, however, in comparison to the analogue that contains double bonds, the sensitizer containing alkyne moieties is more stable against singlet-oxygenmediated photooxygenation reactions. This increased stability can be advantageous, particularly with respect to two-photon singlet oxygen imaging experiments in which data are collected over comparatively long time periods.

2025, Optics Express

Ultrasound and photoacoustics can be utilized as complementary imaging techniques to improve clinical diagnoses. Photoacoustics provides optical contrast and functional information while ultrasound provides structural and anatomical information. As of yet, photoacoustic imaging uses large and expensive systems, which limits their clinical application and makes the combination costly and impracticable. In this work we present and evaluate a compact and ergonomically designed handheld probe, connected to a portable ultrasound system for inexpensive, real-time dualmodality ultrasound/photoacoustic imaging. The probe integrates an ultrasound transducer array and a highly efficient diode stack laser emitting 130 ns pulses at 805 nm wavelength and a pulse energy of 0.56 mJ, with a high pulse repetition frequency of up to 10 kHz. The diodes are driven by a customized laser driver, which can be triggered externally with a high temporal stability necessary to synchronize the ultrasound detection and laser pulsing. The emitted beam is collimated with cylindrical micro-lenses and shaped using a diffractive optical element, delivering a homogenized rectangular light intensity distribution. The system performance was tested in vitro and in vivo by imaging a human finger joint.

2025, 2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC

Photoacoustic microscopy (PAM) research, as an imaging modality, has shown promising results in imaging angiogenesis and cutaneous malignancies like melanoma, revealing systemic diseases including diabetes, hypertension, coronery artery, cardiovascular disease from their effect on the microvasculature, tracing drug efficiency and assessment of therapy, monitoring healing processes such as wound cicatrization, brain imaging and mapping,

2025, Sen'i Gakkaishi

This paper describes the immobilization of uricase by entrapment. The entrapping membrane was prepared by the cross-linking of chitosan with polyethylene glycol diglycidyl ether (diepoxy compound). The properties of the immobilized enzyme were investigated and compared with those of the native uricase. The enzyme activity of the immobilized uricase were found to be more dependent on temperature and pH than that of the native enzyme. The uricase immobilized membrane was sufficiently stable for 30 days allowing for the determination of uric acid concentration. The uric acid sensor was constructed using a hydrogen peroxide electrode. 1.

2025, Physical Review Letters

We demonstrate that meandering as well as regular spiral waves can form in a well-controlled culture layer of rat ventricle cells and that the meandering spiral wave, in particular, can generate an alternant rhythm. These observations are made possible by a newly developed, noninvasive phase contrast macrooptics that is simple but highly effective in visualizing the contractile motion of the populations of cardiac cells.

2025

Photorefractive (optical) damage Alternative Non-photorefractive ions recently were found by the Ashtarak group are tetravalent ions (Hf4+, Zr4+, etc), which were found to be very efficient with a threshold around -2-3mol%. Doping with an appropriate impurity ion and/or to change the stoichiometry of the crystal. The most effective on this day -MgO. Threshold -5-6mol%

2025, Optical Materials

It has been established by Raman scattering study that the optical damage in nominally pure LiNbO 3 crystals presents an irreversible part. This irreversible fraction of the optical damage is induced only by the high-intensity (I P 25 kW/cm 2 ) exposition for a long time, and it has accumulative character with exposure time. This irreversible effect has been shown to be related to the optical fatigue of the material. The consequent needle-like domain inversion was considered to cause accumulative deterioration of the material, i.e., a fatigue due to the continuous electric field application, relating to the high space-charge field induced by inhomogeneous high-intensity illumination.

2025, Applied Physics Letters

In this letter, we demonstrate that, at mesoscales, nonferroelectric liquid films of poly͑dimethyl siloxane͒ exhibit significant electrostriction not present in the corresponding bulk state. Remarkably, the observed electrostrictive effect has a response time Ͻ20 s in contrast to Ͼ5 ms recorded in conventional bulk ͑ferroelectric͒ polymers. The emergence of this fast electrostrictive strain in thin films is explained in terms of the amalgamation of two contrasting dynamic features-the influence of a highly mobile, viscous layer ͑at the air/film interface͒ on the less-mobile, but fast responding, solid-like layer at the film/substrate interface. The effect is observed for thickness below 200 nm.

2025, Langmuir

The real (n) and imaginary (k) refractive indices of an immobilized monolayer of 27 nucleotide (nt) single stranded DNA (ssDNA) and the corresponding double stranded DNA (dsDNA) are measured in the 255-700 nm range. Multiple techniques are used to obtain consistent estimation. The coverage is ∼6.5% with an average interchain distance of tethered ssDNA molecules of ∼11.8 nm, which is significantly larger than the "footprint" of the chain on the surface. The measured increase in n by ∼5% between the ssDNA and the dsDNA is 20% smaller than the expected change due to doubling of the molecular weight. The change in k is not significant, indicating that the electron delocalization effect expected in dsDNA due to base pair stacking is not important at optical frequencies.

2025, Vision, Reading Difficulties, and Visual Stress

The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

2025

A power efficient, battery powered optogenetic headstage for doing in-vivo experiments with freely moving genetically modified animals is presented. The proposed system is designed with commercial off-the-shelf components, and is based on a Bluetooth Low Energy (BLE) System-on-Chip (SoC) with an integrated antenna and a programmable ARM Cortex-M3 microprocessor core able to control the circuit. The optical signal is generated using a compact laser diode (LD) suitable for a wearable headstage. LD produces light in a highly concentrated way considerably improving the LD-optical fiber coupling efficiency. The proposed optogenetic system is shown to provide 120 mW/mm 2 at the fiber tip with a current consumption of 60mA, considerably lower than LED-based systems. The system is remotely controlled by a smartphone app where the user can define optical stimulations patterns settings (optical power, frequency, duty cycle, etc.). It is also powerful enough to be ready to house additional optogenetics functionalities, like electrochemical sensing of the cell response, without significant modifications, thus being the basis of an integrated optogenetic platform.

2025, Optics Express

The top-of-atmosphere (TOA) radiation field from a coupled atmosphere-ocean system (CAOS) includes contributions from the atmosphere, surface, and water body. Atmospheric correction of ocean color imagery is to retrieve water-leaving radiance from the TOA measurement, from which ocean bio-optical properties can be obtained. Knowledge of the absolute and relative magnitudes of water-leaving signal in the TOA radiation field is important for designing new atmospheric correction algorithms and developing retrieval algorithms for new ocean biogeochemical parameters. In this paper we present a systematic sensitivity study of water-leaving contribution to the TOA radiation field, from 340 nm to 865 nm, with polarization included. Ocean water inherent optical properties are derived from bio-optical models for two kinds of waters, one dominated by phytoplankton (PDW) and the other by non-algae particles (NDW). In addition to elastic scattering, Raman scattering and fluorescence from dissolved organic matter in ocean waters are included. Our sensitivity study shows that the polarized reflectance is minimized for both CAOS and ocean signals in the backscattering half plane, which leads to numerical instability when calculating water leaving relative contribution, the ratio between polarized water leaving and CAOS signals. If the backscattering plane is excluded, the water-leaving polarized signal contributes less than 9% to the TOA polarized reflectance for PDW in the whole spectra. For NDW, the polarized water leaving contribution can be as much as 20% in the wavelength range from 470 to 670 nm. For wavelengths shorter than 452 nm or longer than 865 nm, the water leaving contribution to the TOA polarized reflectance is in general smaller than 5% for NDW. For the TOA total reflectance, the water-leaving contribution has maximum values ranging from 7% to 16% at variable wavelengths from 400 nm to 550 nm from PDW. The water leaving contribution to the TOA total reflectance can be as large as 35% for NDW, which is in general peaked at 550 nm. Both the total and polarized reflectances from water-leaving contributions approach zero in the ultraviolet and near infrared bands. These facts can be used as constraints or guidelines when estimating the water leaving contribution to the TOA reflectance for new atmospheric correction algorithms for ocean color imagery.

2025, Yasmin Mohamed Attia

تقترح هذه الورقة البحثية نموذجاً نظرياً جديداً لطبيعة الفوتون يتجاوز التصور التقليدي لازدواجية الموجة-جسيم من خلال الفرضية الاساسية هي أن الفوتون ليس كيانًا بسيطًا بل له بنية داخلية معقدة تتكون من "أوتار مضغوطة حساسة" تعمل كأجهزة... more

2025, Nature Communications

Proteins possess a complex and dynamic structure, which is influenced by external signals and may change as they perform their biological functions. We present an optical approach, distance-encoding photoinduced electron transfer (DEPET), capable of the simultaneous study of protein structure and function. An alternative to FRET-based methods, DEPET is based on the quenching of small conjugated fluorophores by photoinduced electron transfer: a reaction that requires contact of the excited fluorophore with a suitable electron donor. This property allows DEPET to exhibit exceptional spatial and temporal resolution capabilities in the range pertinent to protein conformational change. We report the first implementation of DEPET on human large-conductance K + (BK) channels under voltage clamp. We describe conformational rearrangements underpinning BK channel sensitivity to electrical excitation, in conducting channels expressed in living cells. Finally, we validate DEPET in synthetic peptide length standards, to evaluate its accuracy in measuring sub-and near-nanometer intramolecular distances.

2025, Periodicals of Engineering and Natural Sciences (PEN)

In this study, a plasmonic photonic crystal fiber (PCF) sensor was designed with an internal gold layer between the liquid holes and the air holes. The study shown that the thickness of the gold layer, the radius of the air holes and the radius of the liquid holes all have a significant effect on the sensitivity of the sensor, where a wavelength sensitivity of (10,500 nm/RIU) was achieved at certain simulation conditions. Under these chosen conditions, the relationship of resonance wavelength with the refractive index of the liquid was linear and this gives flexibility to extend the range of the refractive index of the analyte without changing the sensor design. Approaching or moving away of the holes from center in the proposed design has a fundamental role in determining the sensor characteristics.

2025, Journal of Molecular and Cellular Cardiology

2025, Electronics

Time-gating of single-photon avalanche diodes (SPADs) was commonly used as a method to reduce dark noise in biomedical imaging applications where photon events are correlated with a reference clock. Time-gating was also used to obtain timing information of photon events by shifting the gate windows applied to a SPAD array. However, in this approach, fine timing resolution comes at the cost of a lengthened measurement time due to the large number of counts required for each shift. As a solution, we present a multi-time-gated SPAD array that simultaneously applies shifted gate windows to an array of SPADs, which has the potential to reduce the measurement time compared to a single time gate window. Compared to similar works, this design has fully integrated the multi-gate generation using shared circuitry which also functions as a coarse time-to-digital converter. The proposed array, fabricated in the TSMC 65 nm standard CMOS process, achieved a median dark count rate (DCR) of 37 kHz,...

2025, From füberphysics to Information Mechanics Part 11: Discrete Energy Exchange and the Physical Limits of Quantum Computation

We examine the implications of a discrete energy quantization framework, inspired by (a, b) variables in relativistic models, for the physical realization of quantum computation. This framework postulates that all energy exchanges occur in integer multiples of a fundamental quantum , especially when measured from a preferred symmetrical frame corresponding to the isotropic velocity of the cosmic microwave background. We explore whether such a discretization introduces limits to idealized exponential quantum computing using entangled qubits. Our analysis supports 't Hooft's recent claim that unbounded exponential computation may be unrealistic due to the fundamentally discrete and deterministic nature of physical interactions.

2025, Journal of Telecommunication, Electronic and Computer Engineering

Silicon based photonics have generated strong interest in recent years, mainly in optical waveguide interconnects for microelectronic circuits. This paper presents a single mode condition (SMC) of SOI-based rib waveguide for high-speed Optical Interconnect (OI) implementation at a circuit level. In OptiBPM, a correlation analysis between two parameters, etched rib thickness (r) and effective index (neff) was investigated to identify the effects of width (W) on the rib waveguide. The waveguide performance of the OI links such as output power, propagation loss and propagation delay was recorded based on OptiSPICE simulation. A wavelength (λ) of 1550 nm has the advantages of low power loss and delay which makes it reliable for high-speed OI applications.

2025, Physical Review Letters

We demonstrate experimentally and theoretically the existence of excitable optical waves in semiconductor microcavities. Although similar to those observed in biological and chemical systems, these excitable optical waves are self-confined. This is due to a new dynamical scenario, where a stationary Turing pattern controls the propagation of waves in an excitable medium, thus bringing together the two paradigms of dynamical behavior (waves and patterns) in active media.

2025

The wave function has been with us for one hundred years and constitutes the core of quantum mechanics (QM). It is disconcerting that we still don't know the nature of the matter waves that the equation represents. Photon waves have some commonality with matter waves and at least we know their constituents: kinetic energy, momentum, and electromagnetic (EM) oscillations. In fact, photon waves exhibit most of the puzzling features of QM including probability and collapse. Piecing together the clues the photon gives us is the best way to make progress on the wave function and the major issues confronting QM: duality, collapse, probability, constant velocity, even nonlocality and the measurement problem.

2025, Journal of Neuroscience Methods

Since optical imaging (OI) of intrinsic signals was first developed in the 1980s, significant advances have been made regarding our understanding of the origins of the recorded signals. The technique has been refined and the range of its applications has been broadened considerably. Here we review recent developments in methodology and data analysis as well as the latest findings on how intrinsic signals are related to metabolic cost and electrophysiological activity in the brain. We give an overview of what optical imaging has contributed to our knowledge of the functional architecture of sensory cortices, their development and plasticity. Finally, we discuss the utility of OI for functional studies of the human brain as well as in animal models of neuropathology.

2025, Journal of Synchrotron Radiation

The 19ID undulator beamline of the Structure Biology Center has been designed and built to take full advantage of the high flux, brilliance and quality of X-ray beams delivered by the Advanced Photon Source. The beamline optics are capable of delivering monochromatic X-rays with photon energies from 3.5 to 20 keV (3.5-0.6 A ˚wavelength) with fluxes up to 8-18 Â 10 12 photons s À1 (depending on photon energy) onto cryogenically cooled crystal samples. The size of the beam (full width at half-maximum) at the sample position can be varied from 2.2 mm Â 1.0 mm (horizontal Â vertical, unfocused) to 0.083 mm Â 0.020 mm in its fully focused configuration. Specimen-to-detector distances of between 100 mm and 1500 mm can be used. The high flexibility, inherent in the design of the optics, coupled with a -geometry goniometer and beamline control software allows optimal strategies to be adopted in protein crystallographic experiments, thus maximizing the chances of their success. A largearea mosaic 3 Â 3 CCD detector allows high-quality diffraction data to be measured rapidly to the crystal diffraction limits. The beamline layout and the X-ray optical and endstation components are described in detail, and the results of representative crystallographic experiments are presented.

2025, Journal of Visualized Experiments

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The optical modes are frequently referred to as "whispering gallery modes" (WGM) or "morphology dependent resonances" (MDR) and exhibit high optical quality factors. Some proposed applications of micro-cavity optical resonators are in spectroscopy 1 , micro-cavity laser technology 2 , optical communications 3-6 as well as sensor technology. The WGM-based sensor applications include those in biology 7 , trace gas detection

2025, IOP SCIENCE

Recent advancements in diffractive optical elements have renewed interest in equal-intensity multifocal diffractive lenses with a wide range of applications. In this paper, we present a new family of zone plates based on the space-filling Hilbert curve, termed the Hilbert zone plate (HZP). The focusing capabilities of the HZP are extensively investigated through both theoretical analysis and experimental validation. It is shown that the HZP can generate eight double nearly equal-intensity focus points along the optical axis under plane wave illumination. This distinctive optical characteristic of the HZP represents a significant enhancement over traditional zone plates, which are limited to four equalintensity focus points. The proposed equal-intensity multi-focal HZP has potential applications in optical imaging, multi-plane lithography, laser processing, wavefront measurements, three-dimensional optical tweezers, and various advanced optical technologies.

2025, Journal of Biomedical Optics

A general physiological model for the hemodynamic response during altered blood flow, oxygenation, and metabolism is presented. Calculations of oxy-, deoxy-, and total hemoglobin changes during stimulation are given. It is shown that by using a global hyperoxic or mild hypoxic challenge it is possible to normalize the activation response in terms of the fractional changes in the cerebral blood volume, tissue oxygenation index, and oxygen extraction ratio, which are independent of the optical pathlength. Using a dual wavelength spectrometer, the method is validated by measuring pathlength-independent hemodynamic responses during mild hypercarbia in a rat model. Phantom experiments showed that the changes in optical pathlength were small as the hemoglobin concentration was varied over a wide range. The determination of quantitative parameters facilitates the use of continuous-wave transcranial methods by providing a means by which to characterize activation response across subjects.

2025

The aim of this work is to develop a small on-chip bioimpedance sensing device (BISD) to rapidly detect and quantify cells with a specific phenotype in a heterogeneous population of cells (e.g., human CD4 + cells in blood, for monitoring HIV-infected individuals) using a minimal sample volume and minimal preparation. The transducers, gold/titanium microelectrodes (100x100µm and 80x80µm), have been fabricated on glass substrates. The microelectrode surface is non-covalently modified sequentially with protein G', human albumin, monoclonal anti-human CD4 antibody, and mouse IgG. The anti-human CD4 antibody binds CD4 + cells present in human blood. The basic function of the microelectrodes was characterized using electrochemical cyclic voltammetry before and after protein G' deposition. The binding of biomolecules, protein G' and antibodies, as well as cells was detected by precisely measuring the electrical current, as a function of frequency (1-8 kHz), that flowed between the microelectrode and the much larger reference electrode. This current was measured using a specially designed very low-noise amplifier based on instrument-grade operational amplifiers. This measurement was plotted as impedance, using the constant-amplitude voltage applied between the two electrodes. We have conducted a series of AC impedance and output voltage measurements with various sizes of gold microelectrodes with adsorbed protein layers, as well as with the CD4 + cells. When a sample of human peripheral blood mononuclear cells (PBMCs) was incubated on the biosensor, an increase in impedance was observed; this increase was due to the presence of CD4 + cells, which cause a decrease in the current flow. Incubation of the captured cells with FITC-labeled antihuman CD4 antibody verified that all captured cells were CD4 + , demonstrating the selectivity of the BISD system. The BISD system is a promising tool for the detection of CD4 + cells in HIV-infected individuals, and for the detection and quantification of antigen:antibody or receptor:ligand interactions.

2025, American Journal of Physiology-Heart and Circulatory Physiology

In cardiac arrest due to ventricular fibrillation (VF), moderate hypothermia (MH, 33°C) has been shown to improve defibrillation success compared with normothermia (NR, 37°C) and severe hypothermia (SH, 30°C). The underlying mechanisms remain unclear. We hypothesized that MH might prevent reentrant excitations rotating around functional obstacles (rotors) that are responsible for the genesis of VF. In two-dimensional Langendorff-perfused rabbit hearts prepared by cryoablation ( n = 13), action potential signals were recorded by a high-resolution optical mapping system. During basic stimulation (2.5–5.0 Hz), MH and SH caused significant prolongation of action potential duration and significant reduction of conduction velocity. Wavelength was unchanged at MH, whereas it was shortened significantly at SH at higher stimulation frequencies (4.0–5.0 Hz). The duration of direct current stimulation-induced ventricular tachycardia (VT)/VF was reduced dramatically at MH compared with NR and S...

2025, Physical Review Letters

2025, PLoS ONE

Diagnosis of retinal vascular diseases depends on ophthalmoscopic findings that most often occur after severe visual loss (as in vein occlusions) or chronic changes that are irreversible (as in diabetic retinopathy). Despite recent advances, diagnostic imaging currently reveals very little about the vascular function and local oxygen delivery. One potentially useful measure of vascular function is measurement of hemoglobin oxygen content. In this paper, we demonstrate a novel method of accurately, rapidly and easily measuring oxygen saturation within retinal vessels using in vivo imaging spectroscopy. This method uses a commercially available fundus camera coupled to two-dimensional diffracting optics that scatter the incident light onto a focal plane array in a calibrated pattern. Computed tomographic algorithms are used to reconstruct the diffracted spectral patterns into wavelength components of the original image. In this paper the spectral components of oxy-and deoxyhemoglobin are analyzed from the vessels within the image. Up to 76 spectral measurements can be made in only a few milliseconds and used to quantify the oxygen saturation within the retinal vessels over a 10-15 degree field. The method described here can acquire 10-fold more spectral data in much less time than conventional oximetry systems (while utilizing the commonly accepted fundus camera platform). Application of this method to animal models of retinal vascular disease and clinical subjects will provide useful and novel information about retinal vascular disease and physiology.

2025, Journal of Biomedical Optics