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In this work, zinc oxide (ZnO) nanorods structure in the form of thin film have been grown on soda-lime glass (SLG) substrate incorporating two simple steps. Firstly, ZnO seed layer was pre-deposited onto the SLG substrate by the thermal evaporation method. During this process, the oxidation temperatures were varied in the range of 450 oC to 650 oC annealed for 3 hours. Then, the nanorods structure were grown on the surface of the seed layer by sol-gel immersion method with the use of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and hexamethylenetetramine (HMT) in deionized (DI) water. The optical, structural and morphological properties at different oxidation temperatures were studied using UV-Vis-NIR spectroscopy, X-ray diffraction (XRD) and Field-enhanced Scanning Electron Microscopy (FeSEM). The surface morphology results revealed the formation of hexagonal shaped ZnO on top of the seed layer as a result of heterogeneous nucleation. X-ray diffraction results show that the c-axis orientation became more prominent while the optical band gap of ZnO thin films decreases from 3.31 eV to 3.14 eV as the annealing temperature increased respectively. It is shown that the size and alignment of ZnO NRs are greatly affected by the pre-deposition annealed temperature of the ZnO seed layer on the surface of SLG substrate.

Owing to the fast responsive fiber optic pH sensing, silica nanomatrix (SNM) and titania nanomatrix (TNM) are synthesized by the sol–gel method at low temperatures. Cresol red (CR) is immobilized within SNM and TNM for sensing evaluation. Crack-free, crystallinity and porous surfaces with an average particle size of CR-SNM ~45 ± 0.4 nm and CR-TNM ~24 ± 0.4 nm are observed through microscopic analysis. The is observed in CR immobilized matrices. The CR-SNM shows lower roughness ~7 nm, a large surface area ~380 m2/g, thermal stability at ≤400 °C, and a refractive index 1.47. Whereas, CR-TNM revealed high roughness 48 nm, surface area 211 m2/g, and refractive index 1.76. The sensitivity of the CR-SNM coated fiber is estimated at around 52.8 counts/pH which is greater than CR-TNM coated fiber sensitivity 14.53 counts/pH. Moreover, CR-SNM shows response time 0.17 s at pH 12 which is faster than CR-TNM time response 0.48 s.

Studies of comparing the performance of photoelectrode for dye-sensitized solar cells (DSSCs) continue to be carried out and developed. The ZnO nanorods as an electrode for DSSCs have been shown to have high electron collection due to the capability of electron photoexcitation and increased electron transport. Various methods of making ZnO nanorods have been studied and developed. However, the method requires controlled conditions under high temperature and pressure, thus limiting the commercialization of ZnO nanorods. Therefore, the seed solution-based hydrothermal method was chosen in the ZnO nanorod deposition process because it is an effective method, low-cost and easier fabrication process. The method of growing ZnO nanorod was carried out with three times of growing for 6 hours. ZnO nanorod was synthesized using different seed solutions, namely sample 1 and sample 2 by using methoxy and isopropanol, respectively. In this work, the SEM image shows the growth of ZnO nanorods vertically aligned on the FTO substrate and resulted in a smaller diameter for the isopropanol seed solution. The smaller diameter of the ZnO nanorod provides a larger surface area then increasing the total amount of dye attached to the ZnO nanorod and improve the photovoltaic performance. DOI: 10.17977/um024v6i22021p077

Tapered single-mode fibre (SMF) immobilized with glucose oxidase enzyme (GOD) and gold nanoparticles (AuNP) for the recognition of glucose and sucrose elements have been proposed. A tapered fibre was fabricated using a flame heating technique to improve the sensitivity of the fibre-based sensor. By taking advantage of amine groups in 3-aminopropyl triethoxysilane (APTES), GOD and AuNP are functionalized onto the tapered region of SMF through covalent interaction. The developments of the immobilized tapered fibre sensor for the analysis of glucose and sucrose concentration in different concentrations of the solution and types of carrots extracts were discussed in this paper. The solution concentrations of 0.1, 0.2, and 0.3 g/ml of glucose and sucrose were used to analyze the sensitivity of the fibre sensor. The extracts of baby carrots, imported carrots, and organic carrots were used to determine the existence of glucose and sucrose in these carrots. We demonstrated the sensitivities of GOD-immobilized fibre for 0.00672, 0.00722, 0.00902, and 0.00921 a.u/nm in terms of their glucose solutions, baby carrots, imported carrots, and organic carrots, respectively. Meanwhile, the sensitivities of AuNP-immobilized fibre were found to be 0.000030, 0.000026, 0.000012, and 0.000024 a.u/nm, respectively.

A sensitive tapered optical fiber sensor incorporating graphene oxide (GO) and polyvinyl alcohol (PVA) composite film for the rapid measurement of changes in relative humidity was proposed and experimentally demonstrated. The sensing principle was based on the intensity modulation of the transmitted light induced by the refractive index changes of the sensitive coatings. The sensing region was obtained by tapering a section of single-mode optical fiber (SMF) from its original 125 µm diameter down to 9.03 µm. The tapered structure was then modified through deposition of GO/PVA nanocomposites by using the dip-coating technique. The field emission scanning electron microscope (FESEM) and Raman spectroscopy were used to characterize the structure of the composite film. As evidenced by a Fourier transform infrared spectroscopy (FTIR) analysis, the presence of oxygen functional groups (such as −OH and COOH) on the GO structure enabled the attachment of PVA molecules through hydrogen bonding and strong adhesion between GO/PVA layers. The performance of the sensor was tested over a wide range (20%RH to 99.9%RH) of relative humidity. The sensor showed a good response with its signal increasing linearly with the surrounding humidity. The tapered optical fiber sensor with the coating of GO/0.3g PVA achieved the highest sensitivity [0.5290RH (%)]. The stability, repeatability, reversibility, as well as response time of the designated sensor were also measured and analyzed.

Rare earth ions-doped oxide glasses with improved traits are needed for sundry applications. Based on this fact, physiochemical and magnetic characteristics of Er3+ -doped lead–tellurite glasses embedded with gold nanoshapes (Au-NSPs) were customized via preparation and characterization. Glasses of composition 78.95TeO2–15PbO–5PbCl2–1Er2O3–0.05AuCl3 were made using conventional melt-quenching techniques at varying (1, 6, 16, and 24 h) heat treatment durations (HTDs) to optimize their morphology, structure, chemical, and magnetic properties. Structure analysis verified the amorphous nature of the as-quenched samples and the homogeneous distribution of Au-NSPs within a network matrix with an average diameter ranged from 1.32 to 7.12 nm. Significant chemical functional groups of the glasses were detected at 360 and 598 cm‒1, attributed to the number of non-bridging oxygen (NBO) in glass and the conversion of TeO4 tbp into TeO3 polyhedra through TeO3+1. The magnetic behavior of the glasses was due to the diffusion-limited growth of Au-NSPs as evidenced from the ESR and VSM results. Saturation magnetization and magnetic coercivity were in the range of 4.61 × 10–2 to 10.614 × 102 emu/g) and 1441.60 to 1992.20 Oe, respectively. The variations of g-factor, resonant magnetic field, and peak-to-peak line-width of the glasses were established to be promising for various functional applications especially for biomedical devices as antiviral screen protectors.

Herein, sol-gel based synthesis of poly ethanol glycol assisted gold nanodendrites (AuNDs) is reported at low-temperature. Taking advantage of its facile synthesis, phenolphthalein (phph) is encapsulated/immobilized in AuNDs for the assay of fiber optic pH sensing. Hierarchical structure is observed by FE-SEM analysis before and after phph encapsulation. EDX analysis confirms the uniform distribution of elements with smooth morphology. AFM analysis shows that phph encapsulated AuNDs have low average roughness (2 nm) and less thickness ~20 nm. The chemical bonding between phph species and Au molecules are explored by FTIR analysis. The polycrystalline nature of AuNDs matrix before and after encapsulation is confirmed by XRD. HR-TEM analysis exhibited preferential growth of dendrites structure before and after encapsulation along (111) direction. UV–Vis analysis shows that AuNDs has refractive index 1.24 at 550 nm, which reduces down to 1.18 at 550 nm after phph encapsulation. 30 cm coated middle segment of plastic clad silica fiber (PCS) is used as sensor. Variations in output intensities in terms of transmission are used to characterize the sensor response. A fast response ~0.87 s, repeatability/reproducibility and linear response (R2 = 0.8912) is obtained at 440 nm. Acidity of rainwater (pH 6) is determined by prepared sensor for validity purpose and practical applications.

Unique nonlinear optics (NLO) properties i.e. intensity-dependent nonlinear absorption and refraction of carmoisine (food dye) is studied using a single beam z-scan technique. A switchover behavior from a saturable absorption (SA) to reverse saturable absorption (RSA) is observed by increasing concentration of carmoisine dye. The flip in the absorption response is attributed to the aggregated dye molecules under intense laser beam, which induces the formation of carmoisine dimers. In the UV–Vis absorption analysis, the appearance of two bands at higher concentration confirms the formation of carmoisine dimers. Fourier transform infrared spectroscopy (FTIR) suggests the intermolecular charge transfer (ICT) within the naphtyl-azo bonds. Huge magnitude of χ(3) is calculated in the order of 10−5 esu due to ICT process within the dye molecules. Optical limiting (OL) behavior is observed with low OL action threshold ∼0.01 kW/cm2 under continuous wave laser beam. The experimental findings shows that carmoisine dye has potential as an optical material for photonics applications such as an optical limiter under low-powered continuous wave laser.

Thermally stable surfactant modified silica nano-matrix is synthesized by the sol–gel method at low temperature. The surfactant such as cetyltrimethylammonium bromide (CTAB) assisted silica matrix is encapsulated with bromophenol blue (BPB) for sensing activities. Prepared nano-matrix consists of numerous morphological structures such as a pseudo-spherical, hierarchal and islands. The morphology of mesoporous high surface area matrices is strongly affected by CTAB, BPB dye and the aging conditions that determine the transformation from disordered silica nano-matrix morphologies to ordered encapsulated structures. Furthermore, smooth surface matrices with low surface roughness 1.2 nm, low refractive index 1.36, large pores and small dimensions of heteroatoms contribute to the stable sensing activities. The response of coated fiber optic is determined at dynamic pH range 1–12. The prepared sensor has reversibility/repeatability, stability and fast response time of approximately 0.25 s in basic media. The accuracy of sensing device measurements in household ammonia solution and the borax solution suggested that prepared device has clear potential for daily life usage. Keywords: Silica nano-matrix, Bromophenol blue dye, Mesoporous structure, Optical properties, Evanescent field optical fiber sensors, Sensitivity

Silica–titania (ST) nanohybrid and bromophenol blue (BPB) immobilized ST nanohybrid matrix are synthesized by low-temperature sol–gel route. The influence of BPB on the structural, morphological, and nonlinear optical properties of silica–titania nanohybrid was investigated by fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), atomic force microscopy (AFM), and z-scan technique. FTIR analysis confirms the chemical bonding between hydrophobic BPB dye species and hydrophilic type ST nanohybrid matrix. TEM and AFM analysis shows that the synthesized immobilized nanohybrid has inter-dispersed structure with average particle size of 0.8 ± 0.3 nm, smooth morphology, and low average surface roughness ~4.57 nm. The immobilization of BPB greatly improves the nonlinear refraction response and the nonlinear refractive index increases from 4.8 × 10–9 cm2/W to 451.9 × 10–9 cm2/W. Reverse saturable absorption is observed in both BPB and BPB/ST nanohybrid. However, the magnitude of nonlinear absorption coefficient in BPB/ST is lower than the BPB dye due to the occurrence of saturable absorption of the ST matrix. The optical limiting (OL) behavior of the BPB/ST nanohybrid reveals the low OL threshold at 0.33 kW/cm2. The synthesized BPB/ST nanohybrid has potential as an optical limiters for safety of photonic and optoelectronic devices under low-powered CW laser.

Owing to the pH sensing applications, a mixture of four pH dyes (phenol red, bromophenol blue, creosol red, and phenolphthalein) is encapsulated in mesoporous silica aerogel by sol-gel method. FE-SEM analysis shows that dyes have great influence on the morphology of silica matrix. After encapsulation, silica aerogel matrix has low surface roughness ∼ 1.76 nm, ultra-thin layer 8.26 nm, high surface area of 433 m2/g, high optical transparency 77%, low refractive index ∼1.37 at 550 nm and thermally stable. The sensor response is optimized at pH 1–12 with the high value of pKa ∼8.35 at 565 nm without any leaching traces. The fast response time 0.71s in acidic medium (pH 1) and 0.36 s in basic medium (pH 12) is observed. From experimental findings, it can be concluded that fusion of sol-gel and nano-technologies can thus open a new way to synthesize thermally stable, high quality nano-porous optical material for sensing applications at dynamic pH range.

We propose a new concept of the nonlinear effect called the Kerr-Vernier effect by using cascaded Si-ChG microring circuits. The circuit is simulated for two materials of different refractive indices which results in phase difference in propagating light and hence observed in the output signal. By varying the input power into the system, the Vernier effects in terms of the Kerr-Vernier effects are seen. In application, the comparative results of the two-channel outputs are used to form the phase sensors, while the self-calibration between the two-channel outputs can be performed. The change in wavelength at the whispering gallery mode of 8 nm is achieved when the applied input power was fixed at 10 mW. A sensitivity of ∼120 µm W-1 is obtained for this proposed sensor.

Two new anthracenyl chalcone isomers namely (E)-1-(anthracen-9-yl)-3-(2,4-dichlorophenyl)prop-2-en-1-one and (E)-1-(anhracen-9-yl)-3(2,6-dichlorophenyl)prop-2-en-1-one were successfully synthesized using Claisen Schmidt condensation method. The compounds were then characterized by using IR, 1H and 13C NMR and UV–Vis methods. The dichloro anthracene chalcone isomers have been solved and refined using X-ray single crystal diffraction data and optimized at the ground state using density functional theory (DFT) method with B3LYP/6-311G++(d,p) level. The experimental spectroscopic data were compared with the calculated TD-DFT spectra, where the values are in good agreement. The most stable conformer of the chalcones is identified from the computational results. Both compounds also show a good HOMO-LUMO energy gap values of 2.96 and 3.14 eV. The dipole moment at the different ortho-para and ortho-ortho position are 2.71D and 4.58D, respectively. The difference in orientation of the ortho-para and ortho- ortho position results affect the dipole moments and NLO properties response of the compounds. The analyses of nonlinear optical (NLO) properties were performed by calculating the third-order nonlinear polarizabilities. Both compounds show reasonably good NLO responds with the magnitude and sign of the third order optical susceptibility was determined. Based on the measured nonlinear susceptibility χ3 both structures offers great potential in applications such as optical switching and other optoelectronics devices.

© 2018 The Authors We propose a new variant of electro-optic multiplexing scheme using the boxcar filter arrangement. The circuits consist of multistage add-drop multiplexers that can offer external input-output connections. Input from a single light source can be fed into the system through the input port or through the free-space from light fidelity (LiFi) node. The light signal is fed into boxcar filters and the roll-off bands are obtained. The output of the circuits is formed at the drop, through and the whispering gallery mode (WGM) node of the circuit output. By using the electro-optic conversion in Si-Graphene-Au layer stack, time division (TDM), wavelength division (WDM), frequency division multiplexing (FDM) can be performed. The simulations have shown that a combination of 7 roll-off bands with the maximum spectral widths or bandwidths of ∼6.09 µm or ∼7.63 THz can be obtained.

The on-chip scale microring circuit is proposed to numerically investigate the supercontinuum (SC) generation of light power. The device is formed by the chalcogenide Panda-ring resonator with the nanoscale planar waveguide using Ge11.5As24Se64.5 chalcogenide glass channel waveguide, air-clad and MgF2 glass for lower cladding. The waveguide is designed to exhibit normal dispersion along with a low-energy pumped at 1.55 μm using a short pulse, which has the duration of 50 fs and peak power ranging from 1 W to 100 W. The numerical result obtained has shown a good-quality SC generation of both the spectral bandwidth and high output peak power. All SC spectral extended to more than 13 μm by cumulative Kerr nonlinearities. The obtained results can be useful for developing new experimental work in the important area of SC generation on compact chip broadband sources, which can be used in both infrared and radio wave applications. Keywords: Supercontinuum, Panda-ring resonator, Cumulative nonlinearities, Chalcogenide waveguide, ChG, Split-step fouriermethod (SSFM), Generalized nonlinear Schrodinger equation (GNLS), Group-velocity dispersion (GVD)

This research work is concerned with the synthesis of cetyl trimethylammonium bromide (CTAB) assisted silica nanomatrix and creosol red (CR) immobilization in silica nanomatrix. The synthesized nanomatrices are systematically characterized by FESEM/EDS analysis, AFM, FTIR, TGA, BET and UV–vis spectroscopy. FESEM analysis suggests the porous structure network of CTAB assisted silica occupied by CR species after immobilization. Silicon and oxygen signals along with CTAB and CR species by EDS spectra confirm a strong interaction with each other. AFM analysis exhibited the crack-free smooth surface with low average surface roughness ∼2.25 nm which decreased down to ∼1.98 nm. The thickness ∼12 nm is calculated after CR immobilization. FTIR spectroscopy confirmed the presence of silica molecules and CR species bonding after immobilization in silica matrix. BET analysis confirmed the mesoporosity of synthesized matrices with surface area of 458 m2/g, after immobilization. TGA and UV–vis analysis show that thermally stable CR immobilized matrix is 82% transparent and has low refractive index ∼1.38. The proposed sensing device has linear sensitivity ∼90 (a.u.)/pH unit with coefficient of determination (R2) ∼0.98 within pH 1–9. Fast response has been observed at 0.2 s in pH 9 with color change behavior and 98% repeatability identify that the coated matrix has potential in opto-chemical sensing device.

This work presents an optical switching model that the tweezer probe uses for manually switching the controlled by an external switch, in which the upward and downward switching can be operated and simultaneously switched. By using the microring resonator incorporated with the two non-linear phase modulators, the optical tweezer can be generated and the switching probes controlled. The switching time with the table force of ~2 fs is obtained. The tweezer force and torque are calculated and interpreted for molecule trapping and injecting from and to the trapping and the target surfaces. The relative forces and torques are calculated and plotted. In applications, the specific forces and torques can be controlled to perform the appropriate trapping and injecting. The switching time depends on the external switching module, which may be electronically controlled.

We have proposed the simple method of the squeezed light generation in the modified microring resonator, which is known as the microring conjugate mirror (MCM). When the monochromatic light is input into the MCM, the general form of the squeezed coherent states for a quantum harmonic oscillator can be generated by controlling the additional two side rings, which are the phase modulators. By using the graphical method called the Optiwave program, the coherent squeezed states of coherent light within an MCM can be obtained and interpreted as the amplitude, phase, quadrature and photon number-squeezed states. This method has shown potentials for microring related device design, which can be used before practical applications.

Phenol red dye (PR) functionalized mesoporous silica matrix nano-structures/ nano-tubes (MSNs) are synthesized by sol-gel method for pH sensing. FE-SEM analysis revealed formation of different nano-objects (i.e. nano-clusters and nano-tubes) with defined pores, which are arranged into bunch of nanotubes after PR encapsulation. AFM analysis shows the crack-free dense matrices films with low average surface roughness and thickness. XRD and FT IR exhibited the interaction/bonding of phenolic anchoring groups of PR with silica. HRTEM analysis confirms the formation of crystalline nano-tubes after PR encapsulation within silica matrix. TGA/DTA analysis shows PR dye interacts efficiently within the silica matrix species from 300 °C - 1000 °C. N2 adsorption isotherms confirms the meso-porous nature of the PR encapsulated silica matrix have high surface area value of 434 m2/g with a pore volume of 0.96 cm3/g. UV–vis analysis exhibited that silica matrix has transmission of 84% at 550 nm and 1.36 refractive index. However, transmission is reduced to 79% whilst refractive index increased to 1.37 at 550 nm after PR encapsulation. Coated fiber optic displayed dynamic range of 1–10 pH with fast response time (

We propose the remote charger model using the light fidelity (LiFi) transmission and integrate microring resonator circuit. It consists of the stacked layers of silicon-graphene-gold materials known as a plasmonic island placed at the center of the modified add-drop filter. The input light power from the remote LiFi can enter into the island via a silicon waveguide. The optimized input power is obtained by the coupled micro-lens on the silicon surface. The induced electron mobility generated in the gold layer by the interfacing layer between silicon-graphene. This is the reversed interaction of the whispering gallery mode light power of the microring system, in which the generated power is fed back into the microring circuit. The electron mobility is the required output and obtained at the device ports and characterized for the remote current source applications. The obtained calculation results have shown that the output current of ∼2.5 × 10−11 AW−1, with the gold height of 1.0 µm and the input power of 5.0 W is obtained at the output port, which is shown the potential application for a short range free pace remote charger.

This letter presents the use of a plasmonic sensing transducer on an embedded Mach–Zehnder interferometer (MZI) arm, allowing the sensing transducer to be formed through the stacked layers of the silicon–graphene–gold materials and embedded on an MZI arm with a gripping force to allow it to be used in sensing applications. The transduction process introduces an energy conversion between the input light and the excited electron mobility within the silicon and graphene layers. That way the electron drift velocity within the gold layer can drive the plasmonic wave group velocity induced through the interaction with the graphene layers, and consequently, the electron mobility in the gold layer increases. The driven electron mobility in the gold layer, caused by the plasmonic waves from graphene in the embedded sensing layers, will affect the electron output mobility, where the relative change in the phase of the light in the silicon can be seen at the output port of the MZI. To optimize the key parameters of such a system (especially input optical power and dimensions of the gold layer), simulations are performed at various input optical powers and the results are graphically represented. A maximum sensitivity of ~ $2\times {10}^{-14}$ mV−1s−1 in electron mobility sensing is obtained through these simulations, designed to optimize the performance characteristics of the proposed sensor.

A conventional Michelson interferometer is modified and used to form the various types of interferometers. The basic system consists of a conventional Michelson interferometer with silicon-graphene-gold embedded between layers on the ports. When light from the monochromatic source is input into the system via the input port (silicon waveguide), the change in optical path difference (OPD) of light traveling in the stacked layers introduces the change in the optical phase, which affects to the electron mean free path within the gold layer, induces the change in the overall electron mobility can be seen by the interferometer output visibility. Further plasmonic waves are introduced on the graphene thin film and the electron mobility occurred within the gold layer, in which the light-electron energy conversion in terms of the electron mobility can be observed, the gold layer length is 100 nm. The measurement resolution in terms of the OPD of ∼50 nm is achieved. In applications, the outputs of the drop port device of the modified Michelson interferometer can be arranged by the different detectors, where the polarized light outputs, the photon outputs, the electron spin outputs can be obtained by the interference fringe visibility, mobility visibility and the spin up-down splitting output energies. The modified Michelson interferometer theory and the detection schemes are given in details.

A free space cross-connection of the optical signals using an optical micro/nano-electro-mechanical system(OMEMS/ONEMS) is designed and simulated using the commercial software called MATLAB and OPTI-WAVE programs, in which a nonlinear micro-ring device known as a Panda-ring resonator is used to form the cross connection of two different sources, the whispering gallery modes (WGM) of those two wavelengths are multiplexed, where bandwidth capacity of the dense wavelength multiplexing can reach the Big data link criteria, in which the capacity link is up 40 PB (Petra bytes). The design device material is the AlGaAsP/InP, from which the WGM beams of the cross connection is generated within each center ring device by controlling the two coupled nonlinear side ring parameters. The cross connection of the multi-light nodes are generated and the cross-connection performed. The triple Panda-ring is embedded by the light photo-detector and source, from which the ring three input signals are modulated and input into the system and multiplexed with the previous cross connection sources. The cross-connection among the input signals via the WGMs and input signals from ring three can emerge, where finally, the cross-connected signals of them can be generated and seen at the center rings, i.e. WGM nodes and the output ports, which is allowed to have the high capacity transmission, where the use of the internet of things (IoT) is plausible.

The electro-optic power pumping system model using the inline successive technique within the modified add-drop filter is proposed. A pumping system consists of a closed loop Panda ring resonator, from which the optical power is coupled inline into the system. By controlling the two side phase modulators, the whispering gallery mode (WGM) is generated by the amplitude-squeezed light within the modified add-drop filter. By using the proposed circuits, the low current can be applied into the system via a gold layer connection, from which the amplified output current can be obtained at the throughput port, which can be functioned as the electronic operational amplifier (op-amp). In application, the WGM output is the amplified signal that can be used for the up (down) link in free space communication network called light fidelity (LiFi). The electro-optic signals conversion can be performed by the stacked layers of silicon–graphene–gold materials. The results obtained have shown that large gain is obtained at the WGM output, which is ~ 5 × $$10^{ - 6}\; {\text{cm}}^{2} \;({\text{V}}\;{\text{sW}})^{ - 1}$$ , when the pumping saturation time is ~ 2 fs. It concludes the suitability of our proposed model for light fidelity, LiFi up-down link conversion.

In this article, we have proposed the plasmonic interferometry concept and analytical details given. By using the conventional optical interferometry, which can be simply calculated by using the relationship between the electric field and electron mobility, the interference mobility visibility (fringe visibility) can be observed. The surface plasmons in the sensing arm of the Michelson interferometer is constructed by the stacked layers of the silicon-graphene-gold, allows to characterize the spatial resolution of light beams in terms of the electron mobility down to 100-nm scales, with measured coherence lengths as low as ∼100 nm for an incident wavelength of 1550 nm. We have demonstrated a compact plasmonic interferometer that can apply to the electron mean free paths measurement, from which the precise determination can be used for the high-resolution mean free path measurement and sensing applications. This system provides the practical simulation device parameters that can be fabricated and tested by the experimental platform.

Some new types of Rose Bengal dye-encapsulated cinnamon nanoparticles (RB-CNPs) were prepared via the laser ablation in liquid (PLAL) method at various laser fluences (LFs) and characterized. The influence of different LF (1.7–14.2 Jcm−2) on the absorption, fluorescence and color chromaticity properties of these RB-CNPs was evaluated. Both fluorescence and absorption spectra of the RB-CNPs displayed two prominent peaks at approximately 439 nm and 571 nm, and 267 nm and 546 nm, respectively due to the presence of phenolic acids in CNPs and structural units in RB dye. The fluorescence lifetime and quantum yield were in the range of 6.12–6.911 ns and 0.341–0.61%. Furthermore, these RB-CNPs coated fiber-optic sensor showed very fast response when exposed to ethylene glycol medium. It is established that the proposed optically active and stable RB-CNPs can be advantageous designing low-cost fiber-optic sensors useful for environmental tracers and optical probes.

A micro-conjugate mirror (MCC) is designed and modified using a nonlinear microring resonator system, a system consists of a nonlinear microring resonator known as a Panda ring resonator. An MCC can be formed by adjusting the reflected light power from the Throughput and Add ports, from which the outputs can be detected by the Drop port output and 3D image construction can be performed. The short distance naked-eye 3D imaging transmission is accomplished, which can be confirmed by the four-wave mixing outputs, which is useful for 3D image transmission, bio-sensors and medical imaging and diagnostic applications.

A micro-current source using the drive electron mobility model is proposed by using the non-linear micro-ring resonator. The system consists of a nonlinear microring resonator known as Panda ring resonator made of InGaAsP/InP. The stacked waveguide (plasmonic island) of silicon-graphene-gold is formed at the center of the Panda ring, through which the whispering gallery mode (WGM) of light can be controlled and generated by the central ring it allows the driven electron mobility within the gold layer that can increase WGM beam acceleration and device current density with respect to the input optical power and ring parameters. The simulation results are obtained using the Opti-wave and MATLAB software programs. Results have shown that the relationship between the input of optical power and driven output current density can be obtained.

Mesoporous hematite nanoparticles (HNPs) encapsulated SiO2–TiO2 nanocomposites (STNC) are synthesized and heat-treated at low-temperature 50 °C for 1h (STNC/1h) and 2h (STNC/2h) by sol-gel process for hydrocarbons chemical sensing. Microscopic analysis revealed the thermally stable hierarchical structure of HNPs, which changed into aggregated porous spherical morphology after encapsulation in STNC and heat treatment. The low surface area of HNPs ~55 m2/g which is increased up to 289 m2/g for H-STNC/2h, is advantageous to enhance sensing device activity. Magnetic properties exhibited the superparamagnetic behavior of H-STNC/2h. The H-STNC/2h coated fiber optic chemical sensor revealed a linear response towards the higher carbon chains, sensitivity is calculated as 5.3 counts per unit variations in the carbon chain at 515 nm with R2 ~ 0.98. The proposed magnetic sensing device has good reversibility, stability, and validity without any leaching traces.

This paper reported the experimental and theoretical analysis of a non-contact fiber optics displacement sensor for the concentration measurement of opaque dye solution. This sensor was able to detect the concentration without having to dilute the opaque solution. Brilliant Blue FCF dye was used to demonstrate the sensor. The displacement curves of dye solutions with various concentrations were taken using a white light source and a spectrometer as the detectors. The cumulative reflected powers (CRP) of the samples at various wavelengths were determined, and the simulated data were also in agreement. A unique transition wavelength was observed at 613.5 nm when the samples’ CRP curve was compared with the water data. The sensing parameter was based on the total positive differences in the CRP results in a highly linear relationship over the dye concentration of 0.01 to 0.1 M. The sensitivity was measured at 4.7 × 10 8 a.u./M and the resolution was 2.0 mM. The proposed sensor had consistent performance, and the results were highly repeatable measurement with small variances.

A passively Q-switched and mode-locked laser was successfully demonstrated, the saturable absorber based on Gadolinium oxide was inserted into the ytterbium-doped fiber laser to generate pulses at the 1.0 µm region. By adjusting the pump power of the laser to 146.46 mW, the laser resonator generates a Q-switched pulse at the center wavelength of 1033.84 nm. The maximum achievable pump power of 175.83 mW has produced a 6.93 µs pulse width, 71.43 kHz repetition rate, and 6.23 nJ pulse energy. Later, the incorporation of a 200 m single-mode fiber has triggered a self-started mode-locked laser. The pulse centered at the peak wavelength of 1033.54 nm. The generated pulse was in the range of 146.46 mW to 183.18 mW with a repetition rate of 0.98 MHz. These results proved an outstanding non-linear optical property of Gadolinium oxide, which offers its compatibility with a near-infrared photonics device.

Multi-walled carbon nanotubes (MWCNTs) were grown on cathode deposit by arc discharge plasma under H2, Ar, and air ambient environment. The influence of ambient gas pressure on the structure and physical properties of carbon nanotube were compared. Herein, we highlight the influence of ambient environment and pressure to grow high quality carbon nanotubes. Field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction were used for structural characterization and yield determination. The result revealed that background gas and pressure were crucial factor for growing highly crystalline and highly graphitic with ID/IG ratio 0.237 obtained for MWCNTs' synthesized in H2 environment with extreme low defects.

A graphene diaphragm integrated silica fiber Bragg grating (FBG) based sensor head was developed for simultaneous determination of water level and temperature. This new design used two FBG sensors with uniform grating made of SMF-28 fiber with 1550 nm of central wavelength, bandwidth of 0.5 nm, 4 mm length and 90% reflectivity. The response of the sensor to water level was monitored in terms of Bragg wavelength shift, which is proportional to the strain. Upon immersing inside the water column, the diaphragm gets deformed due to a strain originated from the water level imposed hydrostatic pressure. A linear response of the sensor head was achieved for water level in the range of 0–100 cm. The FBG based sensor head revealed high detection sensitivity ∼24.84 pm/cm. The temperature measurement sensitivity of the sensor was 13.31 pm/°C in the range of 27–77 °C. The water level detection sensitivity was found to reduce with increasing thickness of the graphene diaphragm.

Colloidal suspension of alloy nanoparticles has been prepared and their third-order nonlinear optical response was investigated by means of the Z-scan technique, employing 532 nm continuous wave laser excitation. Alloys colloidal suspension of industrial grade brass, aluminium, and copper was prepared via laser ablation in liquid technique. FESEM analysis reveals the particles size of less than 102.33 nm on average. The magnitude and sign of the nonlinear refraction, n2 and nonlinear absorption, β were determined. It was observed from the closed aperture Z-scan that all the suspensions exhibited a self-focusing effect with a negative nonlinear refractive index, n2, attributed to thermal lensing effect. Colloids of brass possess highest n2 followed by copper and aluminium suspension, attributed to the thermally agitated process whereby heat is transferred into non-local region of the propagation axis. Open Z-scan results revealed that the brass suspension exhibited saturable absorption (SA) with significant negative β value. Aluminium and copper alloy NPs suspension rather shows reverse saturable absorption with a positive β value. These materials were found to exhibit significant nonlinear refraction and nonlinear absorption behaviour, making them possible candidates for photonic and/or optoelectronic applications, especially with low powered continuous wave laser excitation.

3D metal printing and aerospace industry is an ideal combination where 3D metal printing offers unmatched advantages over the conventional method in terms of its rapid prototyping, rapid tooling, easy maintenance and repairs. With the provision and implementation of 3D metal printing onto aerospace sector, leading manufacturers are now enjoying great benefits as this exciting technology reduces the lead-time, increases production flexibility as well as cost-effective. However, we are now left with a big question: whether or not this 3D metal printing technology has arrived to its maximum capacity where the system operates with no flaw. Previous studies have shown that 3D metal printing is battling with its consistency, repeatability and traceability due to many independent variables that need to be controlled in a single run. Adoption of Artificial Intelligence onto the 3D metal printing has been viewed to be a promising step and therefore, serves as a cornerstone towards a better development of 3D metal printing technology.

Nd3+ with composition of (60 - x) P2O5 - 10ZnO - 30PbF2 - (x) Nd2O3 where (0.0 ≤ x ≤ 2.0 mol %) was prepared using a melt-quenching approach to the development of transparent glasses. These glasses have been confirmed to be an amorphous structure through XRD analysis. The glass density, molar volume and ionic packing density were obtained in the range of 3.978-4.157 g cm−3, 41.949 - 41.073 cm3 mol−1 and 0.614-0.624, respectively. Using Fourier Transform Infrared (FTIR) and Raman Spectroscopy, the chemical functional groups and biomolecules of samples were characterised. The FTIR spectra revealed six main bands assigned to P-O, P-O-P, P=O, (PO3)2- and hydroxyl groups (O-H), while Raman shift detected five symmetric and asymmetric bands attributed to P-O-P bonds in Q1 units, (PO4)3- bonds in Q0 units, (PO3)2- bonds in Q1 units, (PO2)− bonds in Q2 units and P=O bonds in Q3 units. It is believed that the proposed oxyfluoride glasses may be useful and suitable applicant to lasing materials and sensors sensitivity.

Dissolved oxygen (DO) concentration is the most critical parameter to evaluate water quality, commonly addressed in global freshwater, and seawater aquacultures. Research trends and patterns on optical fibre for environmental DO sensing and monitoring, specifically, photonics, are rising and revolutionilising the current practices. Transition metals have emerged as a promising material for use in determining DO concentration in the water. Their unusual physicochemical and optical properties enable them to be used as an oxygen-sensitive dye and a so-called waveguide in thin-film that can be easily integrated with optical fibre. Thus, the selection of transition metals is important in the early phase of this research to design the optical-based transducers for DO sensing and monitoring. The DO concentration needs to be accurately measured in real-time, as its change is a continuous dynamic process. Gaps were identified utilising various transition metals embedded onto optical fibre for the in-situ determination of DO concentration in the water, contributing new knowledge for future scholarly work. The detection mechanism of DO concentration in the water with various transition metals is briefly outlined and concludes by addressing the real world’s laboratory-scale challenges. In short, we focus on the Stern-Volmer model for mechanistic study on transition metals for DO sensing and monitoring.

Nanocomposites (NCPs) with excellent physical, chemical and optical properties have been broadly used for commercial products and industrial applications. Based on these features of the NCPs, we prepared colloidal gold (Au) and organic cinnamon (Cin) NCPs by laser irradiated Au and Cin targets separately immersed in glass container fulfilled with different pH solutions (5.0 to 8.0). A Q-switched pulse laser ablation in liquid (PLAL) technique was employed to customize morphology, structural and optical characteristics of these grown nanoparticles inside various pH solutions at room temperature. Colloidal solution of gold-cinnamon nanocomposites (Au-Cin NCPs) was characterized via Transmission electron microscopy (TEM), Ultraviolet-visible (UV-Vis) spectrometer and CIE 1931 chromaticity diagram. TEM image and SAED patters revealed spherical shaped Au-Cin NCPs with a particle diameters of 5.19 ± 1.23 nm and a nanocrystalline face centred cubic (FCC) nucleation. These plasmonic Au-Cin NCPs very strong UV-Vis absorbance bands at (270 nm and 522 nm) and CIE color coordinate (color temperature of 6437.001 K and color purity of 11.9130 %). It is established that the PLAL made-up Au-embedded Cin NCPs may be useful for the formulation of nanobiomedicine drugs.

In this research effort, the nonlinear refraction (NLR) and nonlinear absorption (NLA) of Acid Fuchsin dye solution were measured using Z-scan technique. Both properties were measured through the application of open aperture and closed aperture Z-Scan measurements in order to analyse the relationship between different laser input fluences and on four different dye concentrations (0.03 mM, 0.05 mM, 0.10 mM, and 0.20 mM). The results showed that both; NLR, NLA and optical limiting properties were observed starting from 0.05 mM. There is a reduction in terms of its NLR value observed as the concentrations increased with 0.03 mM has the highest value of n2. It is shown that the increment of NLA value is also observed as the concentrations increased. The low optical limiting (OL) threshold is observed around 0.04 W under continuous wave (CW) 532 nm laser beam. This shows that acid fuchsin dye has the capability as an optical limiter in photonics applications.

The pericarp of Garcinia mangostana (mangosteen) contains α -mangostin ( α -MG), which is an essential compound derived from the family of xanthone. This study aimed to determine the nonlinear optical response of the extracted α -MG using Z-scan technique (532 nm, 0.5–1.0 W). A series of characterisations were also done by using 1H & 13C nuclear magnetic resonance (NMR), electron impact mass spectrometry (EIMS), ultraviolet-visible (UV–vis) and Fourier transform infrared (FTIR) to validate the identity of the extracted α -MG. The results showed that only nonlinear refraction (NLR) was successfully captured and measured by the closed-aperture signal. The localized absorption across the media enabled the α -MG to exhibit a self-defocusing effect. The recorded values of the nonlinear refractive index, which were denoted as n2, were then compared with two different theoretical fitting curves, which were Sheikh-Bahae Formalism (SBF) and Thermal Lens Model (TLM). The values of n 2 obtained were in the order of 10−9 and 10-10 for SBF and TLM, respectively. The NLO characteristics of the α -MG were observed at the excitation wavelength of 532 nm.

A passively mode-locked erbium-doped fiber laser (EDFL) was successfully demonstrated by using gold (Au) nanoparticles as saturable absorber (SA). The Au nanoparticles were mixed with Polyvinyl alcohol (PVA) solution and the mixed solution was dripped onto the fiber ferrule and left to dry to form a SA device by connecting with another fresh ferrule. By incorporating the SA into an EDFL cavity, stable passively mode-locked pulse train was realized as the 980 nm pump was set within a pump power range from 45 to 145 mW. The laser operated at 1563 nm with a pulse width of 2.85 ps and repetition rate of 0.99 MHz. A maximum peak power of 9 kW was achieved at a pump power of 145 mW. © 2020 Elsevier GmbH

This study focuses on the design of the new dye of donor-π-acceptor (D−π−A) system of methyl 4-((4-aminophenyl)ethynyl)benzoate (MAPEB) to highlight its structural-property relation through a combined experimental and quantum chemical calculation approaches for optical limiting applications. MAPEB was synthesized via aerobic condition palladium-catalysed Sonogashira cross-coupling reaction with good yield. This molecular structure was confirmed by single crystal X-ray crystallographic analysis and the crystal exhibits monoclinic non-centrosymmetric space group of Pc. The existence of intermolecular interactions was confirmed by Hirshfeld analysis, showing high contribution of C⋯H contact which suggested the high nonlinear optical response of the compound. The experimental spectroscopic data including Fourier Transform Infrared (FT-IR), 1H and 13C Nuclear Magnetic Resonance, electronic absorption spectra, HOMO-LUMO energy gap were compared with Density Functional Theory (DFT) at 6–311++G (d,p) basis set. The experimental results complement the theoretical findings in supporting anticipated electronic properties of the molecule. Additionally, the z-scan analysis unveils an excellent value of χ3 of MAPEB in the order of 10−6 esu which indicate good nonlinear optical material under 532 nm continuous wave laser. Low optical limiting action was measured at 110 kW/cm2 which is suitable for various continuous wave laser applications. These findings prove that MAPEB has the potential to be employed as NLO materials for photonic applications.

A non-adiabatic tapered fiber sensor coated with humidity-sensitive graphene oxide (GO)/Poly (vinyl) alcohol (PVA) nanocomposite film for humidity sensing application was proposed. GO/PVA film was deposited onto the tapered region by dip-coating technique. The surface morphology of the coating film was characterized through Field Emission Scanning Electron Microscope (FESEM). When exposed to percent relative humidity (RH) ranging from 20 to 99.9 % RH, the sensor exhibited sensitivity for both untapered and tapered fibers at −0.00132 ± 0.00043 a. u (%)−1 and 0.00106 ± 0.00008 a. u (%)−1, respectively. The contribution of GO/PVA composite film in enhancing sensor sensitivity was proven, which was 0.00624 ± 0.00033 a. u (%)−1 with percentage of sensitivity boosting up to 15.86 % when compare to the uncoated ones.

Every single day, a large amount of fish dies from infection such as hyperoxia-induced gas bubble disease consequences by unusual dissolved oxygen (DO) level due to the natural occurrences and human-caused processes of supersaturated water. We are concentrating on the issue of sustainability – an issue of great importance and where this interdisciplinary area has the potential to make a profound impact. We need to step up our game by introducing DO sensing and monitoring at a large scale to overcome this global environmental issue. DO is known as oxygen saturation, one of the most critical parameters in accessing water quality, and necessary to be kept at a sufficient level for the survival of many forms of aquatic biodiversity. Hence, this review article mainly focuses on the potential of optical glass micro-fibre transducers for DO sensing and monitoring, and its contribution toward water security impacts - as part of the Sustainable Goals Development blueprint. The growing body of literature associated with five main work packages i) research motivation of water security, ii) research market analysis discussing the perspective on size, share, growth, trends, and forecast, iii) typical approach on characterising DO level as compared to the optical glass micro-fibre based transducers, iv) conventional design of the optical glass micro-fibre based transducers and v) mechanism of light modulation characteristic in the optical glass micro-fibre based transducers, are highlighted in order to gain a better understanding on the development and progress of optical glass micro-fibre as a transducer for DO sensing and monitoring that can change our life for the better. Finally, several recommendations for future work are presented at the end of this study for the reference of future readers.

Tapered optical fiber (TOF) sensor based on localized surface plasmon resonance is demonstrated for refractive index sensing application. The single-mode fiber (G652D) with 10/125 µm of core/core-cladding diameter was tapered by flame brushing method and achieved a waist diameter of approximately 15µm. Mercapto group (-SH) of 3-mercatoptopropyltrimethoxysilane (MPTMS) was utilized for immobilization of gold nanoparticles (AuNPs) by self-assemble monolayer (SAM) method on fiber surface. Evanescent field at the TOF sensing region excites the localized surface plasmons of AuNPs, with average mean diameter 15 ± 2 nm as evidence by scanning electron microscopy (SEM). The effect on deposition time was examined on three different samples; S1, S2 and S3 with 24h, 48h and 72h of coating time respectively. TOF sensor performance was evaluated with surrounding refractive indices ranges from 1.3324 to 1.4254. The sensing mechanism is based on the modulation of output light signal that represent by transmission shifting spectra. The optimum sensitivity was obtained for S2 at 18 nm/RIU with good repeatability, reversibility and stability.

Discovery of materials which exhibit large real third-order optical nonlinearities have recently become the topic of a broad scientific interest, due to its potential applications in many areas especially in the field of all-optical signal-processing. Here in this work, we report a preliminary investigation on the third-order nonlinear optical (NLO) response of different type of trace metal ions in nitric acid standard solution. A facile and rapid single beam z-scan technique incorporating 532nm diode pump solid state laser was employed to study the response of Lead (Pb), Cadmium (Cd), Mercury (Hg), Zinc (Zn), Aluminum (Al) ions towards NLO properties. Nonlinear refraction (NLR) response of the heavy metal samples were recorded from closed-aperture output and the maximum values of nonlinear refractive index, n 2 for all Pb, Cd, Hg, Zn, Al were recorded at 1.96355×10−9, 3.38228×10−9, 9.36907×10−9, 8.67559×10−10,3.28211×10−9 cm2W−1 respectively. Based on the experimental findings, the negative sign of the nonlinear refractive index values successfully indicates that the samples exhibit nonlinear self-defocusing effect, which is further expected to have potential applications in all-optical devices.

We have proposed the convincing electro-optic circuit for long life-time electron mobility emission. Light a monochromatic source is utilized as input into the circuit via the input port and trapped within the plasmonic island. It is a formed-like capacitor structure formed by the silicon-graphene-gold materials which are stacked layers. All circuit port ends have added the TiO2 to form the reflectors. By selecting the suitable parameters, the fraction of the output power emission can be controlled at the add port, from which it can be successively pumping and trapped(stored) within the plasmonic island. The system energy saturation can be released by squeezing light behavior, therefore, the system is always balanced due to the successive pumping process. The results obtained of the single cell(circuit) have shown that the charging time and discharging times of the nano-capacitor-like of ∼2 to 3 s and 1000 h are achieved. This can be applied to long life mobility emission(discharge) of the capacity-like device. The mobility storage time within the island is 14,000 h, with the electron mobility of ∼3.0 × 10−7 cm2 Vs−1 is obtained.