Optical Analysis Research Articles

Analysis of vapor bubble diameter, departure frequency and dynamics in a single cavity

The ongoing quest for methods that enhance the efficiency of heat transfer processes, particularly those involving phase change, underscores the importance of comprehending the dynamics of vapor bubbles during boiling. This study investigates heat transfer mechanisms and the dynamics of vapor bubbles within the nucleate boiling regime. Experimental tests were conducted on a flat copper surface featuring a single cavity, focusing on analyzing vapor bubble growth and departure stages. The working fluid examined was HFE-7100 under saturated conditions. The formation and growth aspects of vapor bubbles, including their diameter (Dd) and departure frequency (f), were investigated through experimental data obtained by two different techniques: by an optical sensor of variable resistance capable of generating an analog signal from a voltage change and by a high-speed camera that captures images immediately after the instant that the bubble detached from the surface. Both techniques provide visual insights into the boiling phenomenon. An escalation in heat flux and, consequently, wall superheat resulted in an increased bubble departure frequency. Furthermore, the optical flow analysis successfully identified velocity and vorticity fields induced by micro convection, the prevailing heat transfer mode in nucleated boiling. A slight horizontal displacement trend over time was observed, which may be caused by the asymmetry in the velocity profile, confirmed by velocity peaks tending toward one direction. Vortex analysis reveals rotational motion concentrated in specific regions, with noticeable deformation near the bottom of the bubble and asymmetric movement contributing to vorticity. These findings provide insights into the vapor bubble dynamics, which is important for understanding the cavity rewetting phenomena.

Na2Zn0.5Co0.5P2O7 diphosphate: Sol-gel synthesis, physico-chemical studies, and prospects as a novel supercapacitor electrode material

For the first time, a mixed-metal diphosphate Na2Zn0.5Co0.5P2O7 has been successfully synthesized via the sol-gel method. The sample was characterized by means of XRD, DTA/TGA, SEM/EDX, UV–vis, Raman, IR and color measurements (CIE-L*a*b*). Its structure was determined through X-ray powder diffraction, in tetragonal system, with space group P42/mnm. The 3D structure of the material consists of infinite chains formed by [Zn/CoO4] tetrahedra and [P2O7] diphosphate units sharing corners. Sodium cations occupy two types of interstitial positions between the infinite chains [Zn/CoP2O7]2-. Raman and Infrared spectra of the studied phosphate have been investigated. A factor group analysis leads to determination of internal modes of the P2O74− anion. Tetrahedral environment of Co2+ ions was confirmed by mean of optical analysis, in which numerous bands in the region 475–675 nm, assigned to the forbidden and allowed d–d transitions of Co2+ are detected and the gap energy is extracted from Tauc and Kubelka-Munk plots. The prepared Na2Zn0.5Co0.5P2O7 diphosphate was extensively investigated for its potential use as an electrode material for supercapacitors. The electrode was prepared by depositing the active material on a conductive substrate (nickel foam) and demonstrated significant electrochemical performance with a specific capacitance of 277 F.g-1 at a scan rate of 5 mV.s-1. This outstanding performance underlines its relevance for supercapacitor applications.

Study of temperature-dependent copper iodide thin film by thermal evaporation system

The development of heterostructure devices has gained significant attention towards scientific communities in the present time. This article reports on the effective use of the horizontal thermal evaporation (TE) method to successfully fabricate copper iodide (CuI) films on silicon (Si) substrates. By using the TE technique, CuI-based heterojunctions have been fabricated in this research . CuI exhibits semiconductor qualities of the p-type, making it a promising option for optoelectronic devices in the future. The temperature was varied from room temperature (RT) to 230 °C to synthesise the CuI/Si heterojunction. The structural, morphological, optical, and electrical analyses have been carried out with various substrate temperatures. The x-ray diffraction (XRD) data shows that the CuI films have demonstrated a polycrystalline character and have lattice parameters of 6.03 Å. The Raman spectroscopy study shows the microstructural analysis of CuI films. The field emission scanning electron microscopy (FESEM) study reveals the variation of grain size and shape with synthesis temperature. The atomic force microscope (AFM) was used to estimate the surface roughness. The CuI films were found to be p-type by the Hall effect measurement. The sample synthesised at 130 °C shows the highest mobility of 83.12 cm2 V−1 s−1 with a carrier concentration of 1019 cm−3. The UV-visible (UV–vis) spectroscopy measurements show good absorption of UV light by the CuI thin films. The CuI/Si heterojunctions are rectifying, as demonstrated by the I-V measurements, and those respond well to UV light irradiation.

Quantitative phenotyping of crop roots with spectral electrical impedance tomography: a rhizotron study with optimized measurement design

BackgroundRoot systems are key contributors to plant health, resilience, and, ultimately, yield of agricultural crops. To optimize plant performance, phenotyping trials are conducted to breed plants with diverse root traits. However, traditional analysis methods are often labour-intensive and invasive to the root system, therefore limiting high-throughput phenotyping. Spectral electrical impedance tomography (sEIT) could help as a non-invasive and cost-efficient alternative to optical root analysis, potentially providing 2D or 3D spatio-temporal information on root development and activity. Although impedance measurements have been shown to be sensitive to root biomass, nutrient status, and diurnal activity, only few attempts have been made to employ tomographic algorithms to recover spatially resolved information on root systems. In this study, we aim to establish relationships between tomographic electrical polarization signatures and root traits of different fine root systems (maize, pinto bean, black bean, and soy bean) under hydroponic conditions.ResultsOur results show that, with the use of an optimized data acquisition scheme, sEIT is capable of providing spatially resolved information on root biomass and root surface area for all investigated root systems. We found strong correlations between the total polarization strength and the root biomass (R2=0.82\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R^2 = 0.82$$\\end{document}) and root surface area (R2=0.8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R^2 = 0.8$$\\end{document}). Our findings suggest that the captured polarization signature is dominated by cell-scale polarization processes. Additionally, we demonstrate that the resolution characteristics of the measurement scheme can have a significant impact on the tomographic reconstruction of root traits.ConclusionOur findings showcase that sEIT is a promising tool for the tomographic reconstruction of root traits in high-throughput root phenotyping trials and should be evaluated as a substitute for traditional, often time-consuming, root characterization methods.

Optical analysis and design of a novel solar beam down concentrator for indoor cooking

This investigation provides the design and optical analysis of an innovative solar beam-down configuration, which can be a promising passive solution for indoor solar-based cooking, offering an eco-friendly and sustainable approach. The system uses a beam-down parabolic dish concentrator to concentrate the solar radiation onto a ground-mounted receiver module, which has a secondary optical module consisting of a secondary reflector-light pipe system. The receiver module is a well-insulated tank consisting of a receiver in contact with a primary heat transfer fluid. The thermal energy stored in the receiver module is transported via a secondary heat transfer fluid to and from the cooktop via a tube-in-tube arrangement, which induces a thermosyphon effect. A multi-variable optical analysis through an efficient ray tracing methodology has been adopted to identify optimal design values of optical components such as parabolic dish concentrators, secondary reflectors, and light pipe-receiver assemblies. The optimal optical design parameters and their corresponding ray trace analysis results are elaborated. It was found that the designed beam-down parabolic dish concentrator system provides an ideal thermal energy of 10.3 kWh per day at an average DNI of 650 W/m2. Further, this investigation provides a design for a beam-down parabolic dish concentrating system that may be used for efficient and sustainable solar energy solutions.

High-Sensitivity and Large-Range Displacement Sensor Based on a Balloon-Shaped Optical Fiber and Machine Learning Analysis

High-Sensitivity and Large-Range Displacement Sensor Based on a Balloon-Shaped Optical Fiber and Machine Learning Analysis

The effect of platelet-rich plasma and sodium alginate hydrogel on corneal wound healing after corneal alkali burns in rats with computer-assisted anterior segment optical coherence tomography image analysis

Our objective was to determine the effect of a semi-synthetic sodium alginate hydrogel and its combination with platelet-rich plasma (PRP) on histopathological, biochemical, clinical, and anterior segment optical coherence tomography (AS-OCT) data. Alkali chemical burn of the cornea was induced. Injured rats were randomly divided into five equal groups and topically treated with phosphate-buffered saline (sham), platelet-rich plasma (PRP), 0.5% sodium citrate, a semi-synthetic sodium alginate hydrogel, or a combination of PRP and hydrogel (combined group) three times daily. The degree of corneal opacity (CO), corneal epithelial staining (CES), percentage of corneal epithelial defects (CEDP), degree of ciliary hyperemia (CH), neovascularization size (NVS), and extent of neovascularization (NVE) were evaluated. AS-OCT was performed at nine days, and then rats were sacrificed. Histological examination and enzyme-linked immunosorbent assays were performed to detect the concentrations of IL-1β and MMP-9 in the cornea. There were no significant differences between the groups regarding CEDP, CO, CES, CH, NVS, or NVE on the first day after corneal alkali burn injury (p > 0,05). At the last examination, CO was significantly lower in the PRP group than in the sham group (p = 0,044), while the CO concentrations were similar in terms of NVS (p > 0,05). Similarly, in terms of tissue MMP-9 levels, there were no significant differences between groups (p > 0,05). However, there was a significant difference in tissue IL-1β levels between the groups (p < 0,001). In the PRP and combined groups, the level of IL-1β was significantly lower than that in the sham group (p = 0,043 and p = 0,036, respectively). There was a significant difference in epithelial necrosis between the PRP, and it was the lowest in the combined group (p = 0,003). Epithelial thickness was highest in the combined group (p = 0,002). CEDP was significantly different at the last visit between the groups (p = 0.042). The fastest epithelial closing rate was observed for the combined group (p = 0,026). There was a significant negative correlation between tissue MMP-9 levels and corneal solidity and between tissue MMP-9 levels and the corneal area according to the AS-OCT measurements (p = 0,012 and p = 0,027, respectively). When used alone, topical hydrogel application did not significantly enhance the healing of corneal wounds. However, when combined with PRP, it leads to an increased rate of epithelial closure and neovascularization. This combination did not exacerbate inflammation or corneal opacity compared to PRP alone. The anticoagulant citrate solution in the PRP tube did not prove effective. The synergistic use of PRP and hydrogel could enhance epithelial thickness and reduce epithelial necrosis. The use of new parameters for corneal wound healing assessment was facilitated through AS-OCT image processing.

Jailed Balloon Technique Versus Jailed Wire Technique for Side Branch Ostium Protection in Bifurcation Lesions: Evidence from Three-dimensional Optical Coherence Tomography Analysis.

There is controversy regarding the effectiveness the of jailed wire technique (JWT) and jailed balloon technique (JBT) in preserving the side branch (SB) during treatment. This study compares the protective effect of JBT versus JWT on the SB ostium area in coronary bifurcation lesions using three-dimensional optical coherence tomography (3D-OCT). We obtained data from coronary heart disease patients who received OCT-guided percutaneous coronary intervention (PCI) for bifurcation lesions. The SB protection strategies were divided into JWT and JBT, with the latter further subdivided into active JBT (A-JBT) and conventional JBT (C-JBT). The primary endpoint was the SB ostium area difference measured by 3D-OCT before and after PCI. Partial correlation analysis and propensity score matching (PSM) was used to mitigate confounding biases. A total of 207 bifurcation lesions from 191 patients were analyzed, including 136 lesions treated with JWT and 71 lesions treated with JBT. The SB ostium area was significantly greater in the JBT group compared to the JWT group (0.41 1.22 mm2 vs. -0.25 1.40 mm2, p = 0.001). Following 1:1 PSM to adjust for 60 pairs, the difference between groups was not statistically significant (0.28 1.06 mm2 vs. -0.02 1.29 mm2, p = 0.165). Subgroup analysis revealed that A-JBT provided superior protection in both true (0.47 1.22 mm2 vs. -0.10 1.10 mm2, p = 0.011) and non-true bifurcation lesions (0.56 1.43 mm2 vs. -0.38 1.62 mm2, p = 0.030) over JWT, while C-JBT provided protection similar to JWT. A positive partial correlation was observed between the diameter of the jailed balloon and the increase in SB ostium area (r = 0.296, p = 0.013). Overall, A-JBT, but not C-JBT, provided better protection in bifurcation lesions compared to JWT. The larger diameter of the jailed balloon, rather than the application of higher pressure, enhanced the SB protection.

Enhancing power conversion efficiency of polycrystalline silicon photovoltaic cells using yttrium oxide anti-reflective coating via electro-spraying method

The achievement of optimal performance is a crucial aspect of renewable energy resources. The study attempts to boost the power conversion efficiency of polycrystalline silicon (Si) photovoltaic cells by the application of anti-reflective coating (ARC). The solgel method is employed to synthesize yttrium oxide (Y2O3). The electro spraying method was utilized to apply the ARC on photovoltaic cells. The effect of coating on PV cells were determined through the structural, electrical, optical and thermal analysis. The antireflective material was uniformly applied over the coated substrate for 45 min (Y-I), 90 min (Y-II), 135 min (Y-III), and 180 min (Y-IV). The sample coated for 135 min showed an optimal power conversion efficiency (PCE) of 21.65 % and 20.09 % in the presence of neodymium light and direct sunlight, respectively, and a minimum electrical resistivity of 3.96 × 10−3 Ω-cm. In addition, Y-III coated cells exhibit a maximum absorbance of 94 %. The Y-III coated photovoltaic cells demonstrated the lowest temperature of 34.6 °C when exposed to an open environment and 40.6 °C when exposed to a controlled environment. The results from numerous studies demonstrated that Y2O3 can be a suitable ARC, which effectively improved the efficiency of photovoltaic cells.

Fringe pattern normalization using conditional Generative Adversarial Networks

Fringe pattern normalization is an important pre-processing operation in optical fringe analysis, and is usually required as the initial step for several phase retrieval methods. However, noise and rapid amplitude fluctuations in the fringe pattern pose significant challenges for fringe pattern normalization. In this paper, we propose a robust approach for fringe normalization using conditional Generative Adversarial Network, which works on the principle of image-to-image translation with conditioning on input images. The performance of the proposed method under different noise conditions and amplitude variations is demonstrated using numerical simulations. Further, the practical applicability of the proposed method is also tested with experimental data obtained in digital holographic interferometry.

Exploring the structural and optical properties of lithium-chromium phosphate Li3Cr2(PO3)4

The Lithium-chromium phosphate Li3Cr2(PO3)4 sample was synthesized via the solid-state reaction method. The morphological integrity and chemical homogeneity were verified by energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM). Infrared and Raman patterns were also analyzed. Optical absorption spectrum analysis, conducted within the range of 10000 cm−1 to 30000 cm−1 at room temperature, yielded some optical parameters (Eg, Eu, δ, k, n). The Neuhauser model is used to interpret the interference dip which was on the absorption spectrum of Li3Cr2(PO3)4. The Fourier transform of the autocorrelation function leads to the Zero Phonon Lines of the observed absorption energies. The electronic structure of Cr3+ (3d (Huang et al., 2009) 33) ions in Li3Cr2(PO3)4 was calculated using Racah method, which allowed for precise calculations of Racah and crystal-field parameters. The results showed good agreement between the theoretical and experimental energy levels.

Overconstraint Associated With a Modified Lemaire Lateral Extra-Articular Tenodesis Is Decreased by Using an Anterior Femoral Insertion Point in a Cadaveric Model

To investigate tibiofemoral knee kinematics when shifting the femoral insertion point of the modified Lemaire lateral extra-articular tenodesis (LET) anterior to the lateral epicondyle. Six fresh-frozen human knee joints were tested on a test bench in the following states: (1) native, (2) anterolateral insufficient, (3) original Lemaire (oLET; insertion point: 4 mm posterior and 8 mm proximal to the epicondyle), (4) anterior Lemaire (aLET; insertion point: 5 mm anterior and 5 mm proximal to the epicondyle). Internal tibial rotation was statically investigated under an internal tibial torque of 5 Nm in 0°, 30°, 60°, and 90° of flexion. Anterior translation was statically investigated during a simulated Lachman test with an anterior translational force of 98 N. Additionally, the range of internal tibial rotation and anterior translation were dynamically investigated by a simulated pivot-shift test. Tibiofemoral kinematics were measured using an optical 3D motion analysis system. The aLET showed an internal tibial rotation comparable to the native state for all tested flexion angles except 90° (0°: P= .201; 30°: P= .118; 60°: P= .126; 90°: P= .026). The oLET showed an internal tibial rotation below the values of the native state for all tested flexion angles indicating an overconstraint (0°: P= .003; 30°: P= .009; 60°: P= .029; 90°: P= .029). Direct comparisons between aLET and oLET showed a significantly decreased overconstraint at 0° and 30° of flexion (P= .001 and P= .003, respectively) when using the aLET. No differences in anterior translation and internal tibial rotation were found between the oLET and aLET during simulated Lachman andpivot-shift test (P > .05), approximating the native state. An anteriorly shifted LET insertion point restored internal tibial rotation after anterolateral insufficiency to the native state while decreasing the overconstraint of internal tibial rotation induced by an LET using the originally described insertion point for small flexion angles ≤30°. Using an LET insertion point anterior to the epicondyle was recently reported to lower the risk of tunnel interference and has now been shown to restore internal tibial rotation effectively invitro in the course of the present study. Concerns of overconstraining internal tibial rotation are not diminished by this technique, but using an anterior insertion point helps to decrease overconstraint.

A review on green synthesis, biological applications of carbon dots in the field of drug delivery, biosensors, and bioimaging.

Since the beginning of nanoscience and nanotechnology, carbon dots (CDs) have been the foundational idea and have dominated the growth of the nano-field. CDs are an intriguing platform for utilization in biology, technology, catalysis, and other fields thanks to their numerous distinctive structural, physicochemical, and photochemical characteristics. Since several carbon dots have already been created, they have been assessed based on their synthesis process, and luminescence characteristics. Due to their biocompatibility, less toxic effects, and most significantly their fluorescent features in contrast to other carbon nanostructures, CDs have several benefits. This review focuses on the most recent advancements in the characterization, applications, and synthesis techniques used for CDs made from natural sources. It will also direct scientists in the creation of a synthesis technique for adjustable carbon dots that is more practical, effective, and environmentally benign. With low toxicity and low cost, CDs are meeting the new era's requirements for more selectivity and sensitivity in the detection and sensing of various things, such as biomaterial sensing, enzymes, chemical contamination, and temperature sensing. Its variety of properties, such as optical properties, chemiluminescence, and morphological analysis, make it a good option to use in bioimaging, drug delivery, biosensors, and cancer diagnosis.

Structural, electronic, thermoelectric and optical properties of 2D hexagonal beryllium telluride under DFT investigation

In this study we have investigated structural, electronic, thermoelectric and optical properties of monolayer beryllium telluride compound in the hexagonal lattice phase (h-BeTe) using first principle calculations under density functional theory (DFT) approach. Using the frequency dependent phonon dispersion curves, we have analyzed the stability of the h-BeTe compound. The investigation of structural properties, including density of states (DOS) and band structure, demonstrates that h-BeTe is a direct bandgap semiconductor material with bandgap value of 3.054 eV. The h-BeTe compound exhibits exceptional thermoelectric behavior for a temperature range of 50–800 K, as confirmed by the calculated thermoelectric parameters, including thermal conductivity, electrical conductivity, Seebeck coefficient and figure of merit (ZT). It is vital that h-BeTe exhibits exceptional thermoelectric properties specifically, the figure of merit (ZT > 0.9) provides the efficiency of h-BeTe compound in temperature range of 300–800 K. The optical properties of h-BeTe are investigated for the first time with its interaction in applied external electric field based on various optical parameters such as real and imaginary dielectric constant, refractive index n(ω), extinction coefficient k(ω), absorption coefficient α(ω) and reflectivity R(ω). The optical properties analysis reveals the monolayer hexagonal beryllium telluride to be mostly active in the visible-UV spectrum. These findings have the potential to foster researchers to explore h-BeTe compound experimentally for possible optoelectronic applications.

Green Preparation of Stachys Eudenia-Derived Carbon Quantum Dots and Their Photocatalytic Applications

In this present work, the composites were obtained from carbon quantum dots and TiOf via green synthesis and the photoactivities of these composite structures were investigated under ultraviolet light. Carbon quantum dot was obtained from Stachys euadenia which is an endemic plant found only in southern Türkiye. Carbon quantum dot-TiO2 nanocomposites were fabricated via facile hydrothermal approach which is an easy and effectual method to obtaining of environmentally friendly, low cost and well crystallized nanoparticles. The structural and morphological characteristics of these nanocomposites were investigated by X-ray diffraction, tunneling electron microscopy and scanning electron microscopy. Also, optical analyses of carbon quantum dots were carried out by absorbance and fluorescence spectroscopy. Photocatalytic activity of TiO2 and carbon quantum dot-TiO2 nanocomposites were investigated under ultraviolet light illumination with the decomposition of methylene blue dye. Carbon quantum dot-TiO2 nanocomposites show a better activity than TiO2.

A DFB-SOA Based Optical Vector Network Analyzer for Characterization of Bandpass Optical Devices

In this paper a novel optical vector network analyzer (OVNA) utilizing a distributed feedback semiconductor optical amplifier (DFB-SOA) is introduced. The proposed OVNA is implemented by converting the transmission response of the optical device under test (ODUT) into the electrical domain. The main principle of the OVNA is predicated on the optical carrier restoration facilitated by the wavelength-selective amplification attribute of the DFB-SOA. The implemented OVNA effectively determined the transmission spectrum of an optical filter possessing a passband of 9-GHz bandwidth, achieving a commendable resolution of 25 MHz in the measurement process. The dynamic range of the OVNA can be broadened by adjust the driven current under the DFB-SOA. Additionally, the detection range of our system can be expanded through the utilization of broadband optoelectronic devices. Furthermore, the OVNA possesses considerable potential for integration onto a single chip.

Instant Synthesis of Cu2O Nanoparticles by a Selective Ionic Exchange in Nanozeolite 4A

This study presents a novel method for synthesizing Cu2O nanoparticles by employing ion exchange within a modified nanozeolite 4A matrix. The nanoparticles had a consistent particle size, predominantly around 6[Formula: see text]nm, with a narrow distribution. Nanosizing of the zeolite was achieved through high-energy milling treatments, thereby enhancing the surface-to-volume ratio. A band close to 700[Formula: see text]cm[Formula: see text] was observed in the FTIR spectrum, potentially indicating that zeolite downsizing was related to symmetric stretching of the Si–O bond postmilling. Furthermore, a distinctive band corresponding to Cu(I)–O stretching vibrations was identified at approximately 600[Formula: see text]cm[Formula: see text]. Additionally, optical absorption analyses of the UV-Vis spectrum revealed two characteristic bands attributable to Cu2O nanoparticles at 370[Formula: see text]nm and 470[Formula: see text]nm. These findings have led to advancements in resource use and promoted sustainable and environmentally friendly production practices.

Geometric changes of TMP fibres due to thermo-hydrolytic disintegration of waste MDF evaluated by three fibre analysers

ABSTRACT Thermo-hydrolytic disintegration of medium-density fibreboard (MDF) is a promising method for recovering fibres. This process, however, may affect the geometry and size distribution of the applied fibres initially obtained by thermomechanical pulping (TMP), and thus, the properties of MDF produced thereof. Optical methods based on image acquisition are increasingly common for geometrical characterisation to assess fibre quality. In this study, we analysed the size distribution of recovered fibres (RF) obtained by thermo-hydrolytic disintegration of urea–formaldehyde-bonded waste MDF and subsequent hammer-milling by using three optical fibre analysers, FibreShape Pro, QICPIC and Valmet FS5, while comparing them to virgin fibres (VF). The analysers use different evaluation methods and therefore gave different absolute values. Thus, size distributions could not be directly compared. Nevertheless, the results provided an indication of the changes that occurred during the manufacturing and recycling process. The RF displayed a similar fibre geometry to the VF, in spite of process-related shortening. Mean fibre length and length-based distribution of the VF were always greater than those of the RF, while fibre width of the hammer-milled RF was slightly greater than that of the VF. The analysers, however, provided substantially different results, especially between FibreShape Pro and QICPIC, although the general tendencies observed for the process-related changes were consistent. It can be concluded that the thermo-hydrolytic disintegration applied to the UF-bonded MDF did not cause any substantial changes in fibre geometry (i.e. fibre shortening). All fibre analysers are capable of detecting these changes, but the absolute values provided can vary widely between the instruments.

Microscopic Temperature Sensor Based on End-Face Fiber-Optic Fabry–Perot Interferometer

This work proposes a simple and affordable technology for the manufacturing of a miniature end-face fiber-optic temperature sensor based on a Fabry–Perot interferometer formed from a transparent UV-curable resin. For the manufactured working prototype of the sensor, the sensitivity and operating temperature range were determined, and the methods for their enhancement were proposed. Due to its small size, the proposed type of sensor can be used in high-precision and minimally invasive temperature measurements, in biology for microscale sample monitoring, and in medicine during operations using high-power lasers. A microwave photonic method is proposed that enables the interrogation of the sensor without using an optical spectrum analyzer.

Nucleation, crystal growth, XRD, optical, electrical, PC, SEM, SHG and Z-scan analysis of LHPP for NLO and optical limiting application

High-quality organic L-histidinium 4-nitrophenolate 4-nitrophenol (LHPP) single crystals were grown using an aqueous solution. The crystals were grown using slow evaporation solution technique (SEST) at a temperature of 40°C using a constant temperature bath (CTB). Nucleation growth rates were monitored for various durations using an optical microscope. The crystalline perfection was confirmed through sharp, high-intensity diffraction peaks observed in the theoretical and experimental powder X-ray diffraction (PXRD) analysis, which also confirmed the monoclinic crystal structure with the noncentrosymmetric P21 space group. The crystallite size and strain were calculated using Williamson–Hall coefficient. Vibrational frequency assignments of LHPP were determined using FTIR spectroscopic analysis. Optical properties were studied using UV–Vis NIR spectroscopic studies, which showed that the crystals have very low absorption and high transmittance in the entire visible region. Additionally, the optical energy bandgap (Eg) was calculated and found to be 6.15[Formula: see text]eV. Luminescence properties were studied using fluorescence (FL) analysis. Dielectric investigations were subjected to varying frequencies to study the suitability of the crystal for transistor application. The positive photoconductive (PC) nature of the crystal was confirmed using photoconductivity studies to confirm suitability for photodetector devices that measure the intensity of light rays. Etching studies revealed the growth pattern and the formation of different kinds of etch pits. The surface morphology was studied using scanning electron microscopy (SEM) and electrochemical studies were also carried out. The relative second harmonic generation (SHG) efficiency of the material was also examined and found to be 1.34 times that of standard KDP. The optical limiting and higher-order nonlinear optical (NLO) properties of the grown crystals were studied by the [Formula: see text]-scan method using a Nd: YAG laser functioning at 532[Formula: see text]nm.