Optical Materials最新文献

In recent years, metamaterials have emerged as a crucial technology for designing sub-wavelength thick optical components capable of performing various optical functions. Among the others, these nanostructures could be employed to tune the refractive index, making them useful in various fields (from optoelectronic applications to gravitational wave detectors). In this work, nanostratified structures composed of alternating layers of silica (SiO₂) and titania (TiO₂) were proposed and fabricated using plasma-assisted electron beam deposition. The quality of the deposition was demonstrated using Scanning Transmission Electron Microscopy (STEM), revealing 38 titania/silica doublets with a total thickness compatible with the nominal one of 125.4 nm. X-ray Reflectivity (XRR) and Spectroscopic Ellipsometry (SE) confirmed that the average thicknesses of the titania and silica layers are in good agreement with the expected nominal values even after annealing at 500 °C. Finally, Atomic Force Microscopy (AFM) revealed a very flat surface, both in the as-deposited sample and in the thermally processed one.

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.

The paper studies the reflectivity and radiation resistance of calcium carbonate, which is often an accompanying component of wollastonite, a promising material as a pigment for spacecraft thermal control coatings. Synthetic calcium carbonate of the calcite modification was obtained in an aqueous medium, its phase composition, morphology and particle size were investigated. The study was carried out on a facility simulating outer space conditions, under irradiation of CaCO₃ powders with accelerated electrons with an energy of 30 keV and a fluence of 1·10¹⁶, 2·10¹⁶ and 3· 10¹⁶ cm⁻². The spectra recording before and after the irradiation periods was conducted in vacuum in situ, which allows avoiding the interaction of irradiation-induced defects with atmospheric gases. A negligible optical degradation of calcite in the wavelength region of 250 and 600 nm is observed during irradiation, while the structure of CaCO₃ does not undergo noticeable degradation according to IR spectroscopy.

The role of tin oxide (SnO₂) on the structure-optical features of borate glasses containing low cobalt oxide impurities was studied. The study was carried out on a glass system [x ${\text{SnO}}_2$ – (80-x) $B_2{O}_3$ – 19.5 ${\text{Na}}_{2}O$ – 0.5 CoO]; x = 0.0, 0.5, 1.0, 2.0 and 3.0 mol%. Glass synthesis was carried out by the melt-quench technique. Structure and optical absorption spectroscopy were carried out to explore the optical transitions of Co cations inside the present glass matrix. The obtained results indicate that, with the further addition of ${\text{SnO}}_2$ content, the molar volume decreased from 31.675 ${\text{cm}}^3/\text{mol}$ to 29.147 ${\text{cm}}^3/\text{mol.}$ FTIR studies indicated the basic structural units of trigonal BO₃ units and BO₄ tetrahedra. Herein also, additional contents of tin oxide increased the nonbridging oxygen contents. The reason behind such increment is attributed to the existence of ${\text{Sn}}^{4+}$ ions in octahedral coordination acting as network modifiers. Optical absorption spectra indicated the existence of Co ions in both Co²⁺ and Co³⁺ oxidation states. Moreover, the existence of significant SnO₂ concurred with the significant blue shift in the visible absorption bands and red shift in near infrared absorption bands. The positions absorption bands of Co ions were analyzed in the context of ligand field parameters determinations. The obtained data of the crystal field splitting parameter (10Dq_t) showed decreased values from 3451 cm⁻¹ to 3364 cm⁻¹ with more SnO₂ addition. While Racah parameter B values were also, attained showing increased values from 967 cm⁻¹ to 985 cm⁻¹ when additional SnO₂ is added. Further, the impacted role of SnO₂ addition on the structural and optical properties of the present glasses was finally estimated.

A straightforward hydrothermal method was employed to fabricate WO₃/MoO₃ composites, with the addition of ascorbic acid (Vc) for modification, resulting in WO₃/MoO₃ composites with oxygen defects (WO₃/MoO_3-x). WO₃/MoO_3-x exhibits exceptional adsorption-photocatalytic properties, demonstrating strong adsorption capability for dyes achieved through hydrogen bonding and electrostatic interactions. For all products, adsorption rates for methylene blue (MB) exceeded 95 % when reaching adsorption equilibrium. Moreover, an increase in molybdenum (Mo) content endows the samples with enhanced adsorption capacity for methyl orange (MO) and improved photocatalytic performance. Dynamic fitting of the samples revealed that when the W/Mo molar ratios is 2:8, the product W2Mo8-Vc, exhibits the highest photocatalytic activity. After 3 h of illumination, W2Mo8-Vc achieves a remarkable photocatalytic efficiency of 98 % for dyes. This research not only successfully recycles W–Mo alloy scrap but also yields WO₃/MoO_3-x composites with adsorption-photocatalytic properties, offering a novel approach for the recycling of W–Mo secondary resource.

The emission of InAs quantum dots (QDs) grown on Al_0.30 Ga_0.70As/GaAs heterostructures and integrated into additional capping/buffer quantum wells (QW), known as dot-in-a-well (DWELL) structures, has been investigated. Two different AlGaInAs confining barriers (CBs) and buffer layers (BLs) are compared. The first QD structure includes the Al_0.30 Ga_0.70As CB (#1) and the In_0.15Ga_0.85As BL. The second QD structure consists of the Al_0.40Ga_0.45In_0.15As CB (#2) and the In_0.25Ga_0.75As BL. Comparison of photoluminescence (PL) spectra has revealed that the ground state (GS) emission band in the structure #2 with Al_0.40Ga_0.45In_0.15As CB is characterized by the lower peak energy, smaller PL linewidth (more homogeneous QD sizes) and higher GS emission intensity compared to that parameters in the structure #1 with Al_0.30 Ga_0.70As CB. The smaller potential barriers at the Al_0.40Ga_0.45In_0.15As CB/QD interfaces in #2 lead to faster thermal decrease in the GS PL intensity at high temperatures compared with that in #1. High-resolution X-ray diffraction (HR-XRD) method was used for the study of the QD structures with the aim of monitoring the sizes and compositions of QDs and QWs. Numerical simulation of HR-XRD scans has shown that the material compositions of QDs and QW in #2 with Al_0.40Ga_0.45In_0.15As CB has not changed in the process of QD structure growth at high temperatures compared to those in #1. The obtained results are interesting for further improvement of InAs/GaAs QD structures for telecommunication technology and optoelectronic applications.

Chemicals like acetone, ethanol, hexane, isopropanol, and hexanol are essential components of our daily routines, serving critical functions in various industries and medical settings. Therefore, it is essential to perform thorough examinations to identify any contamination in these substances, which is crucial for preserving their high quality and confirming their appropriateness for different uses. The detection of these chemicals is done using a novel approach utilizing ultra-short pulses passed through Hollow-Core-Photonic Crystal Fiber based sensor. The fiber characteristics including the non-linear and dispersion parameters are used to sense the change in shape of the ultra-short pulse as the pulse travels through the HC-PCF. By implementing this approach, we've attained distinctive levels of compression sensitivity and power upsurge for the samples tailored to each specific input setup. A minimum compression sensitivity has been recorded as 24.5 % when the input power was 600W, resulting in an outstanding power upsurge of 719 W.

This study investigates the crystallization behavior and optical properties of the 2BaF₂·Al₂O₃·B₂O₃ oxyfluoride glass in the presence of SiO₂ and Er₂O₃ compositions. Samples were synthesized using the melt-quenching method. The amorphous nature of the prepared samples was characterized through X-ray diffraction (XRD) analysis. Differential thermal analysis (DTA) was subsequently employed to determine the glass transition temperature (T_g) and crystallization temperature (T_c). The presence of SiO₂ and Er₂O₃ was found to enhance the glass forming ability and the crystallization temperature of the system. The optical bandgap was calculated by drawing Tauc plots from UV–Vis spectra. Notably, the presence of SiO₂ caused a red-shift in the UV-absorbance edge of the glass, and resulting in a decrease in the optical bandgap. Molecular structure was further studied by Raman and FTIR analysis. Based on the DTA curves, glasses were heat-treated and the resulting glass-ceramics were analyzed using XRD, Photoluminescence and field emission scanning electron microscopy (FESEM). XRD analysis confirmed the crystallization of the BaAlBO₃F₂ crystalline phase within the glass matrix. Furthermore, the recorded down-shifted and upconversion photoluminescence spectra indicated that the Er³⁺ doped glass-ceramics have stronger emissions compared to glasses.

Traditional multi-layer anti-reflection films often encounter phase-matching issues in the infrared spectrum. Furthermore, they exhibit increased sensitivity to incident angles, particularly at large angles. While moth-eye structures can reduce angle dependency, achieving ultra-wide angle and broadband anti-reflection requires high aspect ratios, which present significant fabrication challenges. In this research, a hybrid anti-reflection micro-nanostructure is designed for broadband and ultra-wide angle applications, utilizing thin film interference theory and the effective medium approximation. Through comprehensive analysis of various parameters including periodicity, height, top diameter, and bottom diameter of the moth-eye structure, we have effectively attained a low aspect ratio of approximately 3.18. This achievement effectively addresses the challenges associated with fabricating high aspect ratio structures. Compared to traditional multilayer films, the hybrid micro-nanostructure presents a significant advantage by substantially reducing reflectivity over a wide spectrum (3–5 μm) and at wide angles (0–60°). The hybrid structure exhibits reflectivity below 6 % within the 60–75° range, with an average of 6.9 % at an incidence angle of 80°. Therefore, this hybrid structure can be widely applied in optical components such as infrared lenses, sensors, and windows. By efficiently reducing light reflection losses, it possesses the potential to augment the sensitivity and resolution of these optical elements.

This study presents a cost-effective method for fabricating surface-enhanced Raman spectroscopy (SERS) substrates using Ag-nanospheres (AgNS) capped with Poly (diallyldimethylammonium chloride) (PDADMAC) and poly (styrene sulfonate) (PSS). AgNS synthesis involves immersing Ag-nanocrystals in a nonaqueous solution, mixed with polyelectrolytes (PEs) in an aqueous solution via ultrasonic disturbance. Resulting aggregates form stable spherical assemblies with diameters ranging from 150 nm to 450 nm, and various characterization techniques, including scanning electron microscopy with energy-dispersive X-ray, UV–visible spectrophotometry, dynamic light scattering, and zeta potential analysis, were employed to analyze their fundamental chemical and physical properties. These qualified AgNSs serve as SERS substrates for sensitive and selective identification of charged organic dye contaminants, such as rhodamine 6G (R6G) and rose bengal (RB). Sensitivity assessments with the optimized quantities of either PDADMAC or PSS-capped AgNSs demonstrate successful detection down to concentrations of 10⁻¹⁴ M for RB and 4 × 10⁻¹³ M for R6G. The same SERS substrates also enable electrostatically driven selective detection even in analyte mixtures, and an additional variation of the SERS substrate comprising a complex of PDADMAC-capped and PSS-capped AgNSs exhibited distinct SERS spectra influenced by both positively and negatively charged analytes. Finally, successful detection of two oppositely charged pesticides was achieved through electrostatic attraction, so theses PEs capped AgNS-based SERS substrate presents a promising avenue for efficiently and selectively detecting charged organic contaminants.