Ni2(+) is a toxic heavy metal pollutant with cumulative and irreversible toxicity, requiring reliable monitoring methods. This study developed a single-mode.tapered multimode.single-mode (STMS) microfiber sensor with a Ni2+ ion-imprinted chitosan (Ni2(+)-II-CS) thin film on its surface for specific detection. The sensor demonstrated excellent stability in deionised water, with wavelength fluctuations of only 0.0155 nm within 20 min. Its detection limit is as low as 1.01 nM (far below the World Health Organization (WHO) drinking water standard of 1.19 mu M), with a response time of less than 8 min, during which approximately 90% of the total wavelength shift is completed. In pond water sample tests, the sensor demonstrated strong selectivity, with wavelength shifts induced by interfering ions (e.g., Cu2+, Cd2+, Cr3+, K-+,K- Na+, and Pb2+) being less than 20% of that for Ni2+ under the same concentration (100 nM). It also maintained reliability over a 10-day testing period, with a test relative standard deviation (RSD) = 8.9%. Spiked recovery rates obtained from pond water validation experiments ranged from 93.22% to 115.12% RSD <= 4.17%), validating its accuracy in practical applications. This cost-effective, miniaturized platform provides a rapid and reliable solution for ultrasensitive Ni2+detection in environmental monitoring

Multimode hollow-core anti-resonant (MM-HC-ARF) fiber based on tellurite glass for mid-infrared (mid-IR) applications, which supports eight core modes, namely LP01, LP11, LP21, LP02, LP31, LP12, LP41 and LP22. The designed fiber uses tellurite glass as the base material and a novel structure with double-nested tubes to divide the cladding region, which can effectively suppress mode couplings between the core and the cladding modes. The structural parameters of the MM-HC-ARF are optimized using the finite element method, and the confinement loss (CL) and bending loss (BL) of every core mode are analyzed. The simulation results demonstrate that within the 2.5-3.5 mu m wavelength range, the CL of all modes reaches its minimum at 3 mu m. Among them, the fundamental LP01 mode exhibits the lowest CL of 7.6 x 10-6 dB m-1, while the differential group delay remains above 0.1 ps m-1 throughout this spectral range. Furthermore, when the bending radius exceeds 11 cm, the BL of all modes remains below 0.02 dB m-1. The proposed double-nested-tube MM-HC-ARF structure exhibits significant potential for applications in optical communication systems.

This paper presents a double-cladding (DC) Raman probe utilizing DC hollow-core anti-resonant fiber (HC-ARF). The core region constructed from HC-ARF is designated for the transmission of pump light, while the inner cladding, made of silica glass, is employed for the collection and transmission of Raman signals. The outer cladding, featuring a low refractive index, establishes a significant refractive index contrast with the inner cladding, thereby facilitating the efficient collection of Raman signal light from the inner cladding. By comparing the confinement loss (CL) and other properties of four distinct HC-ARF structures, along with an analysis of the energy transmission performance of the inner cladding structure, we validate the rationale behind the selected configurations for the core, inner cladding, and outer cladding. The HC-ARF used in the core region demonstrates a CL of 8.57 x 10-6 dB m-1 for its LP01 mode, a high-order mode extinction ratio of 243, and notable bending loss. The inner cladding attains a numerical aperture of up to 0.9, indicating that the fiber can effectively collect Raman light signals. This fiber achieves a high level of integration, facilitating both low-loss transmission of pump light and efficient collection and transmission of signal light simultaneously. By utilizing optical fiber Raman detection technology, real-time imaging of tissues can be achieved, assisting doctors in monitoring and making decisions during surgical procedures.

In this paper, a polarization beam splitter (PBS) based on dual hollow-core negative-curvature fibre (DHC-NCF) is designed. The two cores of the DHC-NCF consist of eight vertically arranged claddings, which show a parallel cladding structure. The structural parameters of the PBS are calculated by the finite element method. The final simulation results show that the designed PBS has a splitting length of 2.55 cm and a wide bandwidth of up to 380 nm in the range of 1.52 similar to 1.90 mu m. Higher-order mode extinction ratio (HOMER) is greater than 100 in the corresponding band, showing good single-mode characteristics as well. The PBS has important application prospects in fibre optic communication, fibre optic gyroscope, and fibre optic sensing.

A simple photonic crystal fiber (PCF) arranged in a square geometry with two gold-coated air holes and one material-infiltrated core is proposed. A broadband polarization filter and a temperature sensor can be achieved based on the same simple PCF structure, with a hollow core separately filled with liquid crystal and toluene. The polarization filtering and sensing properties of the proposed PCF were studied using the finite element method (FEM). Numerically results show that variations in the diameter of both the liquid crystal-infiltrated central hole and the cladding air holes have a slight effect on the polarization filter characteristics. The polarization filter can be effectively tuned in terms of the central wavelength, crosstalk, and bandwidth by adjusting the thickness of the gold film. The proposed PCF polarization filter with t = 22.5 nm has achieved a wide bandwidth of 1850 nm across wavelengths ranging from 1.2 to 3.05 μm for a fiber length of 50 μm, achieving a high value of polarization loss ratio (PLR) of 28,717 at λ = 1.31 μm with losses of 1723 dB/cm for y-polarization and 0.06 dB/cm for x-polarization. The y-polarized core mode in this design with t = 10 nm is rapidly attenuated, experiencing losses larger than 1340 dB/cm over wavelengths ranging from 1.9 to 3.0 μm; it also exhibits a bandwidth of 2200 nm with crosstalk greater than 20 dB when using a fiber length of 50 μm at wavelengths above 1.5 μm. Furthermore, a temperature sensor that utilizes toluene as its core material exhibits a consistent average sensitivity of 6.68 nm/°C for y-polarization and can detect temperatures ranging from − 10 to 40 °C. The sensor maintains stable sensitivity within ± 1

In this paper, a polarization beam splitter(PBS) based on double nested dual-core negative-curvature fiber (DNHC-NCF) is designed. Two hollow cores are constructed by eight double nested cladding tubes arranged at certain angles. The influences of structural parameters on the performances of the DNHC-NCF PBS have been studied by using the finite element method (FEM). According to the simulation results, the structure of the proposed DNHC-NCF PBS is optimized. The final results indicate that the length of the proposed DNHC-NCF PBS is 1.38 cm and the extinction ratio (ER) is less than -20 dB in the wavelength range of 1.48-1.80 mu m (320 nm, covers S + C + L + U bands). Besides, the higher order mode extinction ratio (HOMER) in the wavelength range of 1.3-1.71 mu m is greater than 100, showing good single -mode characteristic as well. It is believed that the proposed double nested dual-core negative curvature fiber polarization beam splitter will have important applications in the fields of optical communication system.

In the study we proposed a novel approach is called a Customized Convolutional Neural Network (CCNN) to innovate in the field of art creation, particularly in composite material paintings. This research harnesses the power of image processing technology to analyze and synthesize various artistic elements, thereby facilitating the creation of composite material paintings. The core of the study revolves around the development of a unique algorithm that enables the integration of diverse materials and textures into a cohesive artistic expression. The Customized CNN is trained on a vast dataset of images, encompassing a wide spectrum of textures, colors, and patterns, representative of different materials commonly used in art. The network learns to identify and replicate the aesthetic qualities of these materials, thereby empowering artists to explore new realms of creativity. The algorithm not only recognizes the distinct characteristics of each material but also understands how to blend them effectively, maintaining artistic coherence. The results are evaluated to prove proposed performance.

A portable small wireless remote-control quadcopter is designed and realized in this paper. The main control module is designed by the microcontrollers based on the STM32s, and by using automatic control and digital wave filtering technologies. The wireless remote-control function is realized through the wireless radio frequency module. The motor control is realized by the motor drive circuit based on the MOSFETs, through our improved quaternion posture solution algorithm. The sensor circuit, composed of MPU6050 and BMP280, realizes more accurate posture and height control. The user operation control and data acquisition/processing are realized by the analog-digital (A/D) conversion module on the microcontrollers. After debugging and testing, the system finally realizes the flight function, it includes wireless remote control, two-way data interaction, front and rear, left and right movements, and speed control. It has the advantages of small size, light weight, and low cost. It is suitable for outdoor flight operation environment.

Abstract. Considering the low loss transmission and commercialization of hollow core fiber, negative curvature hollow core fiber (NC-HCF) has become a research hotspot in recent years. We report an innovative NC-HCF with an antiresonant layer inside the cladding tubes based on semi-ellipse and semi-circle structures. Based on the COMSOL simulation, it exhibits an ultralow loss from 0.6 to 1.6μm transmission band. On the one hand, as for semi-ellipse and semi-circle with antiresonant layer structure, the fiber lowest confinement loss (CL) of LP01 mode reaches a lowest value of 7.608  ×  10  −  4  dB  /  km at 0.78  μm, and the high-order mode suppression ratio (HOMER) value can reach 4069. On the other hand, the semi-circle and semi-ellipse with antiresonant layer fiber structure shows the lowest CL of 1.675  ×  10  −  4  dB  /  km at 0.79  μm, and the value of HOMER is 1776. Moreover, based on the fabrication tolerance analysis, the hollow core fibers proposed indicate better performance.

We numerically investigated a novel refractive index (RI) sensor based on a liquid-filled and Au -coated hollow-core negative-curvature fiber (HC-NCF). In the design, the cladding area of the HC-NCF was composed of only one ring of six silica tubes, all the air holes in the fiber were filled with analytic liquids. The fiber bent in either the x or y-axis direction and Au-coated inside the single cladding tube in the corresponding bending direction. The influences of Au-coated HC-NCF structure parameters on the propagation characteristics under different bending directions were investigated using the finite element method (FEM). Moreover, the sensing performances in the RI range of 1.30-1.35 were evaluated through analyzing the position of the confinement loss peak. The simulation results showed that the HC-NCF RI sensor in the y-axis bending direction showed higher sensitivity, and the maximum sensitivity was 6.974 mu m/RIU. The sensor shows high sensitivity and provides an effective method for measuring the RI of liquids.

A systematic analysis of the dependence of the confinement loss of an anti-resonant capillary on the curvature of the core surround is presented. The core boundary is described by circular arcs and the construction allows for a wide range of core shapes to be considered. It is found that both negative and positive curvatures substantially reduce the confinement loss relative to that of a circular anti-resonant capillary and that this effect is insensitive to the size of the core relative to the wavelength and to the properties of the glass capillary wall. In contrast, for a solid core surround there is a small increase in the confinement loss with curvature. Results of scalar and vector calculations are shown to be similar. A qualitative explanation of the results is proposed based on azimuthal confinement of the wave fields generated by the curved boundaries.

We numerically investigated a novel temperature sensor, which utilized a liquid-filled and Aucoated hollow-core negative-curvature fiber. All the air holes in the fiber were filled with a temperature-sensitive liquid, while two cladding tubes were coated with Au films. As the temperature increased, the coupling wavelength between the core mode and surface plasmon polariton mode supported by the Au layer shifted. The temperature sensitivity was 2.860 nm/degrees C in the range of 20-40 degrees C, and the inner wall of double-sided cladding tubes were deposited with a 30 nm Au layer. The designed sensor shows a high sensitivity, which is suitable for temperature detection in industrial and biomedical applications.

Two ultra-broadband polarization filters based on Structure 1 and Structure 2 are reported and characterized in terms of attenuation, crosstalk, bandwidth, and polarization filtering properties by the finite element method. Structure 1 is formed by introducing partial elliptical air holes in the first layer of the square-lattice gold-filled photonic crystal fiber. Based on the design solution of Structure 1, Structure 2 is arranged by using circular air holes with the changed transverse pitch to replace elliptical ones. Numerical results show that high resonance intensities of 2265.07 and 1831.83 dB/cm for y polarization, together with the corresponding x polarization losses of 0.50 and 0.18 dB/cm at respective communication wavelengths of 1.55 and 1.31 mu m can be achieved by varying the gold film thickness for Structure 1.Moreover, the design of Structure 2 with all circle holes can also realize a high resonance loss of 1942.54 dB/cm for y polarization with a low loss of 0.43 dB/cm for x polarization at 1.55 mu m. Structure 1 and Structure 2 with the fixed fiber length of 300 mu m can obtain the crosstalk values of -590.09 and -506.07 dB at 1.55 mu m, together with the bandwidths of 1500 and 900 nm, respectively. Additionally, two types of designs represent good produce tolerances. These results show a high potential of the suggested fiber for application in polarization-dependent filtering and other polarizing devices.

A polarization-maintaining hollow-core negative curvature fiber is proposed,which can be used to transmit mid-infrared laser with an operating wavelength of 2. 94 mu m. By adjusting the thickness of the cladding tube in the y-direction and the maximum distance from the nested tube to the inner diameter of the cladding tube,the polarization mode in the y-direction is weakly coupled with the surface mode of the cladding tube. By optimizing the core diameter and the outer diameter of the cladding tube,the y-direction polarization mode is strongly coupled with the cladding tube surface mode,causing the y-direction polarization mode to leak out of the core. The gap between the cladding tubes guides the high-order mode to leak out of the core,while the x-direction polarization mode keeps the low confinement loss due to the coupling suppression effect of the thickness of the cladding tube and the nested tube. Finally,a polarization-maintaining hollow core negative curvature fiber with an operating wavelength of 2. 94 mu m is obtained. The confinement loss of the x-direction polarization mode is 2. 8x10(-2) dB/m,the polarization extinction ratio is greater than 2x10(3), the high-order mode rejection ratio is greater than 100,and the birefringence is1. 4x10(-5). When bending in the y direction with a radius of 25 cm,the bend loss is 0. 62 dB/m.

A hollow-core anti-resonant fiber is proposed with low confinement loss in infrared band. The cladding tube is a semicircular semi-elliptical splicing structure. The full vector finite element method is used for the simulation. The semi-minor axis of the semi-elliptical tube is equal to the radius of the semicircular tube. A semi-circular tube and a semi-elliptical tube are spliced to form a semi-circular semi-elliptical cladding tube. The negative curvature and the positive curvature are changed by improving the structure parameters of the tube. The purpose of this paper is to study the loss characteristics of the positive and negative curvature of the cladding tube, and to design a low loss hollow core anti-resonant fiber applied in the 1.5 similar to 3.0 mu m band. The results show that the effect of limiting loss is better when the negative curvature decreases and the positive curvature increases. The lowest confinement loss is 8.22x10(-2) dB/km at the wavelength of 2.1 mu m when the semi-circular tube is close to the core and the elliptical tube is far away from the core, as well as the circular radius r(y)=25 mu m, the semi-major axis of the ellipse r(x)=65 mu m, the semi-minor axis of the ellipse r(y)=25 mu m.

We use the theory of elasticity and finite element modelling to optimize single coating parameters for microbending loss reduction in hollow-core fibers. We find that stiffer coating materials can offer effective loss reduction.

We report a hollow core Nested Antiresonant Nodeless Fibre (NANF) with a loss of 0.65dB/km across the full C and L telecommunication bands. The fabricated fibre is 1.23km long, it is effectively single moded over sufficiently long lengths, and is able to transmit data.

We propose a nanofilm-modified grating bioscnsor that is able to detect low-concentration antigen biomolecules in order to find a solution for the insensitivity problem of the long-period fiber gratings (LPFGs) when used as refractive index sensors to detect low-concentration solutions. The experimental results show that the sensitivity of this hiosensor is significantly improved. When the concentration of goat anti-rabbit lgG is fixed to 0.01 mg"mL-1, the peak loss of the LPFG of the film indicates a significant response to the increase in rabbit lgG concentrations. Herein, the concentration is defined as a mass concentration. The biosensors successfully achieve concentration sensitivities of 2101. 5, 1306. 5, and 575. 9 dhl " mg-1 " ml, measured at 115, 160, and 500 p.m, respectively. Furthermore, the concentration of the antigen is related to the peak loss of the grating. The lowest detectable concentration of the rabbit lgG is 0. 0003125 mg" m1,-1. Given the high sensitivity, free labeling, high stability, simple structure, and immunity from the electromagnetic interference, the sensor promises an excellent application prospect in the hiosensing field.