Open Aperture Research Articles

Ambient Synthesis of Vanadium-Based Prussian Blue Analogues Nanocubes for High-Performance and Durable Aqueous Zinc-Ion Batteries with Eutectic Electrolytes.

Prussian blue analogues (PBAs) have been widely studied in aqueous zinc-ion batteries (AZIBs) due to the characteristics of large specific surface area, open aperture, and straightforward synthesis. In this work, vanadium-based PBA nanocubes were firstly prepared using a mild in situ conversion strategy at room temperature without the protection of noble gas. Benefiting from the multiple-redox active sites of V3+/V4+, V4+/V5+, and Fe2+/Fe3+, the cathode exhibited an excellent discharge specific capacity of 200 mAh g-1 in AZIBs, which is much higher than those of other metal-based PBAs nanocubes. To further improve the long-term cycling stability of the V-PBA cathode, a high concentration water-in-salt electrolyte (4.5 M ZnSO4+3 M Zn(OTf)2), and a water-based eutectic electrolyte (5.55 M glucose+3 M Zn(OTf)2) were designed to successfully inhibit the dissolution of vanadium and improve the deposition of Zn2+ onto the zinc anode. More importantly, the assembled AZIBs maintained 55 % of their highest discharge specific capacity even after 10000 cycles at 10 A g-1 with superior rate capability. This study provides a new strategy for the preparation of pure PBA nanostructures and a new direction for enhancing the long-term cycling stability of PBA-based AZIBs at high current densities for industrialization prospects.

Nonlinear Optical Properties of La3+-Doped Tellurite-Zinc Glasses: Impact of Chemical Bonding and Physical Properties via Raman and XPS

Understanding the connection between the local environments of lanthanum ions in tellurite glasses and their nonlinear optical (NLO) properties is essential for various technological applications. Rare earth ions can serve as probes for the local environments of the host material if the structure-property correlations are well understood. In this study, we investigated glasses with compositions 70TeO2 - (30-x)ZnO - (x)La2O3 (mol%) (x = 0, 5, 7, 9) fabricated by the melt-quenching technique. The capabilities of combined Raman and X-ray photoemission (XPS) spectroscopy were used to identify these glasses and define spectral deconvolution for distinguishing them in the formation of bridging oxygens (BO) and non-bridging oxygens (NBO). NLO properties were evaluated using open-aperture (OA) and closed-aperture (CA) Z-scan measurements with femtosecond (fs) laser pulses (∼220 fs, 750 Hz) at wavelengths ranging from 600 to 1500 nm. Raman spectra revealed a shift to higher frequencies from 731 to 746 cm-1, with increasing of La3+ ions, indicating the conversion of TeO4 polyhedra to TeO3 structural units, affecting the Te-O- Zn2+ or Te=O bonds and resulting in a variation of the polarizability. Besides the conventional analysis of oxidation state and chemical shifts of the core-level peaks, XPS spectroscopy included a careful analysis of the type oxygen bridges and metal-oxygen bond length to distinguish otherwise similar spectral contributions of different TZL glasses. Glasses with a high fraction of Zn2⁺ ions bonded with oxygen form NBO and modify the local structure of the glass network, while La³⁺ ions coordinate with oxygen atoms or interact with the lone pairs of tellurium atoms. By analyzing the correlation in different concentrations of La3+ ions, the Te-O bonds and NBO/(BO+NBO) ratio were clearly demonstrated. These findings suggest charge compensation between the Zn2⁺ and La³⁺ ions, for maintaining structural stability within the glass network. This study also reveals an enhancement of NLO properties as a function of La3+ ions concentration in TZL glasses under fs laser excitation due to resonant nonlinearity. The third-order optical nonlinearities showed an increase in the two-photon absorption coefficient (β) from 0.26×10-2 cm GW-1 (TZL5) to 0.62×10-2 cm GW-1 (TZL9), along with an increase in the nonlinear refractive index (n2) from 0.32×10-18 m2 W-1 to 0.65×10-18 m2 W-1. This enhancement is attributed to the increased number of NBOs and the high polarizability of La3+ ions. For all-optical switching (AOS) applications, two figures of merit were applied using the n2, α0, and β coefficients. The results suggest that the TZL glasses studied are potential candidates for AOS devices. Thus, this work not only elucidates the factors underlying the NLO properties but also highlights the promising potential of these glasses for use in AOS devices.

General theory of diaphragm rupture in a shock tunnel

As the flow field starting device is in a shock tunnel, the rupture performance of the diaphragm directly influences the successful formation of the shock wave. The general theory of diaphragm rupture in shock tunnels is proposed first in this paper. The reasons for diaphragm rupture are explained fundamentally. The existing ideologies on diaphragm rupture are unified, and two hypotheses with corresponding methods are introduced. In the ideal diaphragm, diaphragm rupture pressure or rupture time can be predicted by considering the diaphragm opening as a throat through a diaphragm opening aperture. In the non-ideal diaphragm, the control of diaphragm rupture pressure can be realized by considering nominal rupture stress and grooved thickness. The correctness of the general theory of diaphragm rupture is proved through argumentation and based on experimental results of the literature. The general theory of diaphragm rupture can be used to predict the diaphragm rupture behavior of any shock tunnel worldwide and avoid the risk of shearing of petals on the diaphragm caused by the impact load. A new system of diaphragm rupture theory is constituted, and it is of significant importance for the efficient operation of shock tunnel equipment.

High contrast computational imaging with vortex phase diversity

Abstract Optical imaging systems employing spatially incoherent illumination are widely used in routine imaging applications like photography and bright-field microscopy. We describe an incoherent computational imaging system that uses an open aperture as well as a vortex phase aperture for recording the same scene. The two raw recorded images provide a diversity of information that can be effectively combined using the generalized Wiener filter. For the specific choice of aperture functions used here, the two corresponding generalized Wiener filters have nearly opposing polarity. This property leads to an effective computational PSF whose central lobe is $0.6$ times smaller compared to the diffraction-limited PSF and has a super-oscillatory character with side-lobes. The resultant computational imaging system provides images with significantly improved contrast. While our methodology requires two image records, the enhanced point spread function (PSF) with super-oscillatory character is obtained by employing bulk off-the-shelf optical elements instead of sub-wavelength structured masks. The vortex phase diversity concept along with computational image reconstructions are illustrated with both simulation and experimental data. The proposed imaging methodology may be used to improve imaging performance for wide ranging imaging systems without changing their form factor.

Study of Solvent Dependent on Third-Order Nonlinear Optical and Thermo-Optic Coefficient of Malachite Green Dye.

This study reveals the solvent dependent third-order nonlinear optical (NLO) features of malachite green (MG) dye using Z-scan technique. MG dye is dissolved in polar solvents, including DMF, DMSO, ethanol, acetone, methanol, and 1-propanol. The study employs the Z-scan instrument, using a continuous wave (CW) laser as the excitation source, operating at a wavelength of 650nm. The closed aperture (CA) and open aperture (OA) Z-scan techniques are used to assess the nonlinear indices of refraction (n2) and nonlinear coefficient of absorption (β) of MG dye. MG dye demonstrates both saturable absorption (SA) and reverse saturable absorption (RSA) in the OA Z-scan results, due to negative and positive NLO absorption coefficients. MG dye proves a self-defocusing NLO refractive index while operating under low-power conditions. The third-order NLO susceptibility (χ3) of MG dye in various liquids are calculated to be the order of 10-6 esu. Multilinear regression fit is applied here to investigate the various intermolecular interactions between the solute and solvent. MG dye exhibited large thermo-optic coefficient of the order of 10- 3 K- 1 is observed. The results give important new information about the characteristics of MG dye and indicate potential sources of material for NLO applications in future.

Optical sensing and nonlinear optical properties of Cr-doped MoO3/PEDOT:PSS Nanocomposites

In this study, we observed a negative UV photoresponse that switched to a positive photoresponse in Cr-doped MoO3/PEDOT:PSS nanocomposite films(NCF) prepared via drop-casting. MoO3 and Cr-doped MoO3 were synthesized using a hot oil bath co-precipitation method, combined with PEDOT:PSS (poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate)), and coated onto flexible OHP sheets. The open aperture z-scan method investigated the nonlinear optical properties of NCF on the glass substrate. The films were characterized by X-ray diffraction, scanning electron microscopic (SEM), UV–Vis spectroscopy, and Fourier Transformed Infrared (FTIR). Chromium doping caused minor changes in lattice parameters, crystalline size, and microstrain. UV spectroscopy revealed an increase in bandgap with higher Cr–MoO3 concentrations. The photoresponse of different Cr–MoO3 concentrations showed an initial current decrease under UV light, but the photoresponse became positive beyond a threshold and continued to improve. Nonlinear optical studies indicated saturable absorption in the nanocomposite. This work enhances our understanding of Cr-doped MoO3/PEDOT:PSS nanocomposites, contributing to advancements in flexible UV photodetectors and nonlinear optical applications.

Third-order non-linear optical switching and threshold limiting of NiO thin films

This study discusses the nonlinear optical properties of as-grown and annealed NiO thin films using the Z-scan technique utilizing the femtosecond laser pulses at a repetition rate of 100 kHz of wavelength 1030 nm with a pulse duration of 370 fs. In open aperture measurements, pristine reveal saturable absorption (SA) with a negative sign of nonlinearity, while annealed samples exhibit reverse saturable absorption (RSA) with a positive sign of nonlinearity. In closed aperture conditions, all samples show prefocal minima and postfocal maxima, indicating self-focusing behavior. The observed RSA phenomena are attributed to the indirect two-photon absorption (TPA) process. The influence of surface plasmon resonance on nonlinear absorption is successfully ruled out due to insufficient excitation energy (1.20 eV) to induce resonance in the samples. The increase in bandgap with annealing temperature, associated with indirect TPA, is elucidated with the shifting of Ni-dx2-y2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d_{x^2-y^2}$$\\end{document} and Ni-dz2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d_{z^2}$$\\end{document} orbitals in the conduction band, under the framework of Density Functional Theory (DFT). The DFT results are correlated with the observed nonlinear SA and RSA processes. The Ni d-d and Ni-d to O-p transitions contribute to the modulation of nonlinearity in the indirect TPA process. The study suggests that the sample annealed at 400 °C exhibits superior optical limiting properties with the highest nonlinear absorption coefficients compared to the other annealed sample, while the as-grown sample is suitable for passive Q-switching applications.

Effect of morphology on the optical limiting of BiVO4 films

Precise control over the morphology and crystal structure of semiconductor-based optical materials is essential for optimizing their nonlinear optical properties. Morphological factors significantly affect the material’s interaction with light, influencing nonlinear absorption, harmonic generation, and optical confinement. In this study, the nonlinear optical (NLO) properties and optical limiting (OL) performance of bismuth vanadate (BiVO4) films depending on precursor solution pH condition, powder morphology and weight percentage of the BiVO4 powders in PMMA (10–30 wt.%) were investigated. The BiVO4 powders were synthesized via the hydrothermal method and the effect of precursor solution pH (pH of 1, 7.5 and 12) was investigated on the size and morphology of the BiVO4 powders. BiVO4 films were prepared using the spin coating method utilizing the BiVO4 powders and PMMA. The bandgap values of films were found to change from 3.39 to 3.56 eV depending on the BiVO4 growth solution pH. The nonlinear absorption coefficients (βeff), saturation intensity thresholds (ISAT) and optical limiting (OL) threshold were obtained using the open aperture (OA) Z-scan experiment. It has been observed that the nonlinear absorption and optical limitation performance of the BiVO4 films can be altered by changing the powder morphology and BiVO4 weight concentration. BiVO4 thin films fabricated using a precursor solution pH 12 and weight concentration of 30 wt.% showed the best performance among all fabricated films with the highest nonlinear absorption coefficient (βeff), saturation density threshold (ISAT) and lowest OL threshold value.

Power dependent tunable optical nonlinearity in Iron oxide/Borophene core-shell nanoparticles under ultrashort laser excitation

Two-dimensional (2D) nanomaterials find immense applications in ultrafast photonics and optical switching systems due to their fascinating nonlinear optical (NLO) characteristics. This work presents a systematic investigation of laser power-dependent nonlinear optical characteristics of borophene nanosheets in a core-shell nanostructure. For this purpose, we have synthesized Borophene encapsulated Iron oxide (Fe3O4) core-shell nanoparticles (Fe3O4/Borophene CSNPs). The CSNPs were synthesized by mixing and annealing sodium borohydride (NaBH4) as a boron precursor with iron oxide nanoparticles (Fe3O4 NPs) in a controlled environment using chemical vapor deposition technique (CVD) followed by characterization using XRD, FTIR Spectroscopy, UV–vis absorption spectroscopy, TEM, SEM, and EDX techniques. Magnetic properties were analyzed by a vibrating sample magnetometer (VSM) which shows that the saturation magnetization of Fe3O4 NPs increases after being encapsulated in borophene nanosheets. The role of borophene in modifying the NLO characteristics of Fe3O4/Borophene CSNPs was studied using a power-dependent Z-scan technique utilizing ultrashort (femtosecond) laser pulses at a wavelength of 800 nm in both open and close aperture configuration. It was found that borophene-coated Fe3O4 NPs reveal tunable NLO properties that resemble the NLO characteristics of borophene nanosheets with enhanced features. This provides insights into an interaction between materials in NLO phenomena and illustrates the distinctive performance of the core-shell nanostructure. The tunable NLO properties of Fe3O4/Borophene CSNPs offer an innovative approach for developing optoelectronics and ultrafast nonlinear photonic devices.

A solar air receiver with porous ceramic structures for process heat at above 1000 °C – Heat transfer analysis

Abstract Concentrated solar energy can be used as the source of heat at above 1000 °C for driving key energy-intensive industrial processes, such as cement manufacturing and metallurgical extraction, contributing to their decarbonization. The cornerstone technology is the solar receiver mounted on top of the solar tower, which absorbs the incident high-flux radiation and heats a heat transfer fluid. The proposed high-temperature solar receiver concept consists of a cavity containing a reticulated porous ceramic (RPC) structure for volumetric absorption of concentrated solar radiation entering through an open (windowless) aperture, which also serves for the access of ambient air used as the heat transfer fluid flowing across the RPC structure. A heat transfer analysis of the solar receiver is performed by means of two coupled models: a Monte Carlo (MC) ray-tracing model to solve the 3D radiative exchange and a computational fluid dynamics (CFD) model to solve the 2D convective and conductive heat transfer. Temperature distributions computed by the iteratively coupled models were compared with experimental data obtained by testing a lab-scale 5 kW receiver prototype with a silicon carbide RPC structure exposed to 3230 suns flux irradiation. The receiver model is applied to optimize its dimensions for maximum efficiency and to scale up for a 5 MW solar tower.

Analysis on optical, thermal and third-order nonlinear properties of L-histidine hydrochloride monohydrate single crystal

This research contributes valuable insights into the understanding of third-order nonlinear optical effects in L-histidine hydrochloride monohydrate (LHHC) single crystal, offering a foundation for future work in optimizing its properties for practical applications in the field of nonlinear optics. It presents a systematic analysis into the LHHC crystal properties harvested by slow evaporation solution (SEST) method. Originally, structure of the compound was confirmed through single crystal x-ray diffraction and powder x-ray diffraction analysis. FTIR analysis was performed to get information about molecular composition of the compound. The assessment of the optical quality of LHHC single crystal was done by UV–Visible and photoluminescence spectroscopies. TG-DTA was employed to assess the stability of the single crystal under different temperature conditions. Z-scan technique, with an open aperture (OA) & closed aperture (CA) configuration, was employed to comprehensively explore the third-order nonlinear response of LHHC single crystal. The nonlinear absorption coefficient β is determined to be 5.32 × 10−10 cm W−1. The NLR index (n2) is calculated as −2.72 × 10−15 cm2 W−1.

Investigation of Nonlinear Optical Properties of NiO Nanoparticles using the Z-Scan Technique

In this research, linear and nonlinear optical properties of NiO nanoparticles (NPs) dissolved in ethanol were investigated. Linear optical characteristics of NiO NPs were studied using a UV-Vis spectrophotometer. The linear absorption coefficient (α0) was 0.88 and 0.57 cm-1 at 405 and 532 nm wavelengths, respectively. The band gap energy rose from 3.56 eV for a sample with a 10-7 g/ml concentration to 3.92 eV for the 10-3 g/ml concentration sample. Using the Z-scan technique, the nonlinear optical characteristics of the NPs were investigated. Two continuous wave laser diodes with 405 and 532 nm wavelengths and different powers were used. The Z-scan system with a closed aperture revealed that NiO NPs have a negative n2 (self-defocusing effect) at various laser powers. n2 increases as the power of the laser increases. The value of n2 was found to be 0.51×10-4 cm2/mW at a wavelength of 405 nm and a power of 0.33 mW. It improved as the laser power increased, reaching a maximum of 0.64×10-4 cm2/mW at a laser power of 1.51 mW. For the laser with a wavelength of 532 nm, the n2 value was 0.27×10-4 cm2/mW for a laser power of 1.01 mW. This value increased to 0.76×10-4 cm2/mW when the laser power increased to 6.2 mW. As measured by the Z-scan system with an open aperture, NiO NPs have a nonlinear absorption coefficient and display a two-photon absorption behavior.

Nonlinear optical studies of Bismuth-doped Titanium di-oxide colloids achieved by femtosecond Z-Scan technique

In this paper, we explored the nonlinear optical (NLO) properties of Bismuth (Bi) doped titanium dioxide (TiO2) nanoparticle (NP) colloids in ethanol, with laser pulses of duration ∼ 150 femtoseconds (fs). The Bi-doped TiO2 NPs were synthesized via the chemical route, sol-gel method. The increased photo response of TiO2 upon doping it with metals has become a burning issue to extend the applications of metal-doped TiO2 NPs as integral parts in solar cells, catalysts, phototherapy, etc. The bandgap of anatase TiO2 NPs was observed to be reduced to 2.89 eV upon doping Bi. The modified band structure of the Bi-doped TiO2 NPs demonstrates novel chemical, mechanical, and optical properties. NLO studies were conducted on Bismuth-doped TiO2 NPs submerged in ethanol employing femtosecond laser input pulses with incoming wavelengths 700, 750, 800, 850, 900, and 950 nm. It has been detected that open aperture (OA) studies performed at an input peak intensity of 100 MW/cm2 on Bi-doped TiO2 NPs in ethanol were exhibiting complex NLO behavior, i.e., reverse saturable absorption (RSA) in saturable absorption (SA) and SA in RSA with mostly effective two-photon absorption (1 + 1) coefficients. Particularly, at ∼800 nm, the behavior observed was so complex, i.e., RSA in SA in RSA in SA, with an effective 3 PA (2 + 1) co-efficient (γ) ∼6.5 × 10−24 m3/W2. The closed aperture (CA) studies at ∼37 MW/cm2 exhibited self-defocusing effects, i.e., an intensity-dependent refractive index (n2) with a negative signature.

Material synthesis, crystal structure, Hirshfeld surface and physicochemical characteristics Novel Stilbazolium crystal of 4-(2-(3-ethoxy-4-hydroxy-phenyl)-vinyl)-1-methyl pyridinium iodide (MEMPI) single crystal for NLO activity

In this study, a novel cation donor group 3-ethoxy-4-hydroxy benzaldehyde has been incorporated in the Stilbazolium cation with iodide anion to generate a new NLO activity of a single crystal of 4-(2-(3-ethoxy-4-hydroxy-phenyl)-vinyl)-1-methyl pyridinium iodide (MEMPI). The MEMPI crystal was effectively formed via the solvent evaporation technique. The structure and hydrogen bond interactions found in the molecule were determined by employing single-crystal X-ray diffraction. The compound crystallizes in the space group P21/c and monoclinic crystal pattern. The crystal structures are stabilized via intramolecular, intermolecular hydrogen bond interactions, C‒H···π, cation‒π, anion‒π, π···π stacking and lone pair-π interaction. In addition, a variety of O‒H···O, O‒H···I and C‒H···O interactions are also responsible for crystal packing. The 3D Hirshfeld surface and 2D fingerprint plots were used to examine the nature of intermolecular interaction. The 2D fingerprint maps indicate that the interactions between H···H contribute to 48.9 % of the total crystal stability. The newly synthesized material was characterized by 1H NMR and 13C NMR. In addition, the vibrational study of the synthesized molecule was performed using FTIR analysis. The grown crystal in linear optical characteristics were examined via a UV–Visible-NIR study. The photoluminescence (PL) activity of a MEMPI was studied with respect to the visible area and green colour emission was observed at 536 nm. The estimated CIE coordinates on the RGB colour gamut show the MEMPI crystal's ability to emit green light. The chemical etching approach was used to analyse the etch pit density and the growth habitat of the MEMPI crystal. The closed and open aperture Z-scan tests were carried out to determine the nature of third-order NLO susceptibility of the MEMPI crystal.

Using Femtosecond Laser Pulses to Explore the Nonlinear Optical Properties of Ag/Au Alloy Nanoparticles Synthesized by Pulsed Laser Ablation in a Liquid.

Metallic nanoparticles have gained attention in technological fields, particularly photonics. The creation of silver/gold (Ag/Au) alloy NPs upon laser exposure of an assembly of these NPs was described. First, using the Nd: YAG pulsed laser ablation's second harmonic at the same average power and exposure time, Ag and Au NPs in distilled water were created individually. Next, the assembly of Ag and Au NP colloids was exposed again to the pulsed laser, and the effects were examined at different average powers and exposure times. Furthermore, Ag/Au alloy nanoparticles were synthesized with by raising the average power and exposure time. The absorption spectrum, average size, and shape of alloy NPs were obtained by using an ultraviolet-visible (UV-Vis) spectrophotometer and transmission electron microscope instrument. Ag/Au alloy NPs have been obtained in the limit of quantum dots (<10 nm). The optical band gap energies of the Ag/Au alloy colloidal solutions were assessed for different Ag/Au alloy NP concentrations and NP sizes as a function of the exposure time and average power. The experimental data showed a trend toward an increasing bandgap with decreasing nanoparticle size. The nonlinear optical characteristics of Ag/Au NPs were evaluated and measured by the Z-scan technique using high repetition rate (80 MHz), femtosecond (100 fs), and near-infrared (NIR) (750-850 nm) laser pulses. In open aperture (OA) Z-scan measurements, Ag, Au, and Ag/AuNPs present reverse saturation absorption (RSA) behavior, indicating a positive nonlinear absorption (NLA) coefficient. In the close-aperture (CA) measurements, the nonlinear refractive (NLR) indices (n2) of the Ag, Au, and Ag/Au NP samples were ascribed to the self-defocusing effect, indicating an effective negative nonlinearity for the nanoparticles. The NLA and NLR characteristics of the Ag/Au NPs colloids were found to be influenced by the incident power and excitation wavelength. The optical limiting (OL) effects of the Ag/Au alloy solution at various excitation wavelengths were studied. The OL effect of alloy NPs is greater than that of monometallic NPs. The Ag/Au bimetallic nanoparticles were found to be more suitable for optical-limiting applications.

Structural correlation to linear and non-linear optical properties of Bi3+ ion doped Li2O–SrO–B2O3 glasses: Optical switching and limiting applications

A series of bismuth doped lithium strontium borate glasses are synthetized using melt-quench technique. Compositional modification resulted in the maximum refractive index (2.306) and lowest optical bandgap (3.36 eV) for 2 mol% of Bi2O3. Raman as well as FTIR investigations reveal the presence of diborate, dipentaborate and metaborate ring type structural units and structural interconversions occur between diborate and metaborate rings. These structural interconversions are in support of the trends observed in linear and non-linear optical properties. Photoluminescence spectra reveal a prominent emission peak around 572 nm corresponding to the 2P3/2 → 2P1/2 transition. Commission Internationale de I'Eclairage (CIE) and correlated colour temperature (CCT) studies indicate the glasses emit greenish-yellow light around 7172 K. Z-scan approach is utilised to examine non-linear optical properties with a nanosecond pulsed laser operating at 532 nm. Z-scan investigation revealed good optical nonlinearity in all the glasses. Open aperture normalized transmittance spectra is used to evaluate the values of non-linear absorption coefficient (ꞵ) and optical limiting. ꞵ is in the range of 0.42–3.2x10−10 mW−1 and optical limiting values are in the range of 1.642–2.078x1012 Wm−2. Z-scan studies reveal RSA and RSA to SA (W- patterns) which suggests that the investigated glasses show saturable absorption (SA) as well as reverse saturable absorption (RSA) pattern. According to these findings, the glasses under investigation are promising materials for solid state lasers, greenish-yellow LEDs, compositional tuning optical switching and limiting applications.

High-speed all-in-focus 3D imaging method based on liquid lens focus scanning

A large open aperture in an optical system can capture high-resolution images but yields a shallow depth of field. To overcome this issue, we propose a method for retrofitting microscopy imaging systems by using a variable-focus liquid lens to achieve 3D focus scanning. Specifically, the focal length of the imaging system was changed by controlling the liquid lens, and a sequence of images was captured at different focal planes in milliseconds. The image scale and phase were corrected. Then the in-focus pixels were abstracted by employing the Laplacian operator. These pixels were marked in the index table. According to the index table, the focused parts of multiple images were merged, and an all-in-focus image was generated. At the same time, a depth map was constructed based on the image number in the index table and the extracted depth information. Additionally, we have optimized the image processing flow; the processing speed was improved to around 6.5 fps.

Extensive isolated bilateral Ankyloblepharon Filiforme Adnatum: a case report

We report a case of a rare congenital eyelid abnormality, ankyloblepharon filiforme adnatum, in an otherwise healthy male neonate, bom to healthy parents out of non-consanguineous marriage. This newborn presented with extensive band of tissue connecting upper and lower eyelid of both eyes, resulting in extremely limited palpebral aperture opening. Antenatal history was unremarkable. The parents came to us at the age of one month. The baby was operated on that day at admission under local anesthesia. The eyelid band of both eyes were excised at the level of each lid margin resulting in normal eye opening. Dilated fundoscopic examination was done along wit,h anterior segment examination. No underlying ocular abnormalities were noted. A detail systemic examination by pediatrician failed to reveal any other congenital anomaly. Echocardiography and cerebral echography (both normal) were performed to exclude congenital heart disease and cerebral malformations. The baby was then discharged without complications. Ankyloblepharon filiforme adnatum may be isolated or may present with other congenital anomalies. Therefore, the presence of eyelid bands should alert for complete systemic examination. Prompt treatment is required for proper opening of the eye and to decrease the risk of amblyopia. CME J 2024; 3(2); 47-49

Defect-controlled fabrication of reduced graphene oxide/ZnO/PMMA-based solid-state optical limiting filters with SA/RSA switching property

A solid-state optical limiting filter was fabricated by noncovalently functionalizing a graphene-based nanocomposite with a polymer. Graphene oxide was reduced by varying reducing agent concentration and functionalized with metal oxide nanoparticles to enhance electronic transitions and third-order nonlinear optical characteristics. The nanocomposite was dispersed over the PMMA polymer framework, and thin films with μm-scale thickness were fabricated using the dip coating method. XRD analysis confirmed the wurtzite crystal structure of ZnO nanoparticles and the amorphous nature of PMMA. The carbon structural integrity was analyzed using Raman spectra. Linear optical studies revealed a redshift in the π-π* transition peak in rGO, suggesting enhanced conjugation. Third-order nonlinear refraction and absorption properties were assessed using the Z-scan technique, revealing a switching behavior in nonlinear absorption at different input intensities. An increase in the relative concentration of sp2 domains enhanced the nonlinear absorption. Optical limiting potential, determined using open aperture Z-scan data, yielded a threshold value of 0.066 GW/cm2. This study aims to develop a solid-state optical filter with a high laser damage threshold by adjusting the reduction rate, tuning defect levels, and analyzing its effect on the optical limiting potential.

Tamm plasmon-induced impressive optical nonlinearity of silver@graphite core–shell nanostructures

Abstract We demonstrate the enhancement in the optical nonlinearity of materials when incorporated within a Tamm plasmon cavity (TPC). This study quantitatively investigates the enhanced nonlinear optical effects exhibited by silver@graphite (Ag@C) core–shell nanostructures integrated within a Tamm plasmon cavity. The Ag@C core–shell nanostructures were synthesized by laser ablation. The transmittance characteristics of the TPC are well-matched with those of the simulated spectra. Nonlinear optical studies, conducted using the open aperture Z-scan technique, demonstrated reverse saturable absorption (RSA) behavior in the Tamm plasmon cavity structure, and a profound enhancement in nonlinear absorption compared to that of the bare material film was also observed. The optical limiting threshold value was found to be 2.5 J/cm2 which is indeed a better value when compared to the reported values. Computational simulations illustrated a significantly intensified electric field within the Tamm plasmon cavity, suggesting the creation of enhanced photonic states leading to increased light–matter interactions. These findings underscore the potential of Ag@C core–shell nanostructures within Tamm plasmon cavities for advancing nonlinear optical devices and applications.