The effects of different types of fluoride glass core fibers, from three main groups of fluorozirconate (ZrF 4 -based), fluoroaluminate (AlF 3 -based), and fluoroindate (InF 3 -based) fibers, were investigated in sensing salivary cortisol utilizing surface plasmon resonance (SPR) sensors. These sensors comprised multiple layers, including fluoride glass core, metal (Ag), dielectric, and dielectric grating (SiO 2 ). The comparison was conducted to evaluate the sensor's figure of merit (FOM) and limit of detection (LOD) at 830 nm wavelength while optimizing the thickness of metal layer for different concentration of cortisol and keeping other parameters constant. The largest FOM of 20.83 RIU −1 was observed for the composition of IZBSC (40 InF 3 -20 ZnF 2 -15 BaF 2 -20 SrF 2 -5 CaF 2 ) from InF 3 -based group, resulting in an exceptional LOD of 0.986 fg/mL with the intensity interrogation method. This represents a tremendous advancement compared to prior reported results. Furthermore, by implementing a topological insulator Bi 1.5 Sb 0.5 Te 1.8 Se 1.2 (BSTS) into this sensor with a ZBLAN fiber for the first time, the LOD was reduced to 0.54 fg/mL, demonstrating remarkable progress in cortisol sensing capability best to our knowledge.

This research investigates the light quality and thermal management of InGaN and InGaAlP Light Emitting Diodes (LEDs) under various light regulation methods. We compare Continuous Wave (CW) and Pulse-Width Modulation (PWM) modes, examining their impacts on luminous flux, temperature, total color shift, and angular color shift. Our findings reveal that the CW mode offers higher luminous flux and reduced temperatures, while the PWM mode ensures enhanced color stability across different currents and viewing angles, especially for white LEDs; however, this stability does not extend to other LED types. From both optical and visual performance perspectives, the study emphasizes optimizing the driving current to meet regulatory requirements and ensure consistent color perception. These insights are crucial for automotive lighting design, contributing to improved regulatory compliance and aesthetic quality.

For the purpose of meeting the requirements of wristworn wearable devices for human-computer interaction and for measuring human physiological parameters, especially dynamic physiological parameters, the collaborative work of various sensors is essential to provide sufficient perceptual information. This study introduces a Wrist Information Detection Sensor Based on Pinhole Imaging (WIDSP). This sensor utilizes the principle of pinhole imaging, employing an image sensor to capture motion and physiological signals at the wrist. Through the processing and analysis of image data, it can achieve the recognition of hand movements and the measurement of human physiological parameters. In the evaluation experiments, the displacement compensation function of WIDSP enhanced the recognition rate of mouse-like movements from 94.67% to 97.33%. Additionally, this sensor achieved a heart rate measurement with less than 2% error, demonstrating WIDSP's broad prospects in wrist information perception applications.

This work elucidates the intricate interplay between the structural complexity of double absorber layered perovskite solar cells and the presence of defects, offering crucial insights for advancing the field of photovoltaics. The study systematically investigates the impact of a heterostructure featuring two perovskite absorber layers on device efficiency and highlights the challenges associated with defects. Our comprehensive analysis underscores the significance of a precisely tuned conduction band offset within the heterostructure, a parameter critical for achieving superior charge transport properties and overall device performance. Moreover, deliberate introduction of acceptor defects emerges as a strategic avenue for enhancing the structural integrity and photovoltaic output of the solar cell. This research contributes to the evolving understanding of defect engineering in perovskite solar cells, providing an intricate perspective on defect dynamics to improve device functionality. The identified parameters and insights presented in this study facilitate and guide the design and fabrication of advanced perovskite solar cells, emphasizing the importance of tailored heterostructure configurations and defect management strategies.

This paper proposes ahybrid RF/FSO system based on RIS reflection to interfere with eavesdroppers in FSO eavesdropping scenarios, and analyzes and optimizes the physical layer security performance of this communication system. In this work, the RF link experiences Nakagama-m distribution, there is a singleantenna eavesdropper E 1 trying to eavesdrop on the RF link information, and the RIS reflection friendly interference signal is used to interfere with the RF link. The FSO link follows the Málaga (M) distribution. There is a single-antenna passive eavesdropper with optical eavesdropping equipment near the destination node to capture the optical signal sent by the relay and eavesdrop on the information. Based on the above communication model, we derive the Strict Positive Secrecy Capacity (SPSC) and Secure Outage Probability (SOP) under double eavesdropping, and use the Monte Carlo method to verify the correctness of the expressions. The impact of various parameters in the system on safety performance was analyzed. The results showed that the interference signal-to-noise ratio, time switching factor and energy conversion efficiency of the wireless power supply jammer, the increase in the number of RIS reflective elements, good weather conditions and better detection methods, etc. All influencing factors can improve physical layer security performance, which also lays a theoretical foundation for the application of hybrid RF/FSO systems where eavesdropping exists in both RF links and FSO links.

Finite background solitons are a significant area of research in nonlinear dynamics, as they are commonly found in various complex physical systems. Understanding how finite background solitons are generated and determining the conditions required for their excitation is crucial for detecting and applying dynamic characteristics. We used the Darboux transformation method to obtain explicit analytical solutions for the Akhmediev breather, the Kuznetsov-Ma soliton, and the Peregrine soliton of the cubic-quintic nonlinear Schrödinger equation. This equation is typically used as a model to control the propagation of ultrashort pulses in highly nonlinear optical fibers. We also provide the conditions required for the existence of these different breather solutions and discuss their interesting dynamical properties, such as oscillation period, propagation direction, and peak amplitude. We systematically discuss the excitation conditions and phase diagrams of the breathers by analyzing modulation instability. These results and associated formulas can also be extended to vector or multi-component systems, the breathing dynamics of which remain to be explored.

Fiber nonlinearity is the bottleneck of optical communication systems and is commonly addressed by applying various nonlinearity mitigation and compensation techniques. In general, nonlinearity mitigation techniques offer modest improvements with minimal computational complexity, while nonlinearity compensation techniques provide significant performance gains at the expense of higher computational complexity. This motivates us to propose a joint nonlinearity mitigation and compensation approach in which the nonlinear effects during signal propagation are reduced to compensate for the residual nonlinearity at a lower complexity. Specifically, in this paper, we study the combination of symbol rate optimization (SRO) and perturbation-based nonlinearity compensation (PB-NLC) for a pre-chromatic dispersion compensated (pre-CDC) transmission of polarization multiplexing, digital sub-carrier multiplexing, and wavelength division multiplexing (PM-DSCM-WDM) optical communication system. We highlight the interplay between SRO and PB-NLC and demonstrate that joint SRO and PB-NLC provides considerable performance gain, significant complexity reduction, and an additional degree of freedom to balance performance-complexity trade-offs when compared to applying only PB-NLC in a conventional PM-WDM system. We observe that the pre-CDC transmission manifests a unique property that enables the distribution of PB-NLC computational complexity between transmitter and receiver. Leveraging the distinctive property, we propose a split PB-NLC technique for the PM-DSCM-WDM system. This technique combines the benefits of both pre-PB-NLC and post-PB-NLC, resulting in a modest performance improvement while maintaining the same computational complexity as post-PB-NLC.

The orbital angular momentum (OAM) states are used for OAM modulation and OAM multiplexing in free-space optical (FSO) communication systems to enhance the transmission quality and capacity. Although a few impactful methods had been developed to measure static OAM states, the fast and accurate recognition of dynamic OAM states in FSO communications remains a challenge due to the OAM crosstalk easily induced by the atmospheric turbulence. In this paper, we present a new simple statistical recognition method realized by utilizing the turbulence-induced crosstalk distribution, other than the routine way to use the spatial intensity patterns. The proposed method is based on acquiring the priori OAM crosstalk distribution of the training optical data, and then using similarity analysis to recognize the OAM states of the information optical data. Its availability and accuracy are validated through the computer simulations. The recognition accuracy under relatively strong turbulence conditions can be improved by using wavefront compensation and specific distance calculation.

In this paper, the feasibility of employing a fast intensity modulator and a chirped fibre Bragg grating to build a dispersion-tuned mode-locked swept laser (DTML-SS) for OCT at 850 nm is evaluated. Stable mode-locking is achieved by applying 50 ps pulses at 1 GHz to the modulator, obtaining 35 nm tuning range at 10 KHz sweep rate and 1 mm axial range.

We consider visible light communication (VLC) using phosphorescent white light-emitting diodes (LEDs) and two different receiver types – a simple receiver for moderate data rate requirements and a sophisticated receiver for higher data rate requirements equipped with an optical blue filter. We address the question, whether it is viable to support both heterogeneous receiver types simultaneously, using a single LED-based transmitter, and characterize the trade-offs associated with a common waveform. In particular, with regard to a simplistic transmitter and receiver structure, we propose a “nested” pulse-position modulation (nPPM) scheme and show that it improves upon conventional time sharing, when the bit rate of the simple receiver is supposed to be retained, while realizing a higher bit rate for the sophisticated receiver. An analysis of the available signal-to-noise ratio at the receiver for a practical setting combined with analytical and simulated error performance results corroborates the feasibility of our approach. Furthermore, we devise an end-to-end signal model, which includes the electrical properties of the LED as well as interference effects associated with optical filtering, and assess the influence on the resulting error performance. Due to its simplicity, our nPPM scheme may be particularly relevant for future mass-market VLC deployments as well as for proprietary solutions.