Visible Infrared Region Research Articles

Dual-mode optical thermometer and spectral conversion for c-Si solar cells in Ag clusters and Yb3+ co-doped borate glasses

Borate glasses doped with Ag clusters and Yb3+ were prepared using the conventional melt-quenching method. Fluorescence spectra and decay curve measurements confirmed that energy transfer (ET) occurred from the Ag clusters to Yb3+. The fluorescent glasses can convert ultraviolet light to visible-infrared region which matches well with the spectral response of c-Si solar cells to improve the conversion efficiency. The lifetimes of Ag clusters decreased in Ag clusters mono-doped and Ag clusters/Yb3+ co-doped glasses as the temperature increased. Sensitivity values based on the fluorescence lifetime (FL) were calculated. Furthermore, a high optical sensitivity based on the fluorescence intensity ratio (FIR) technology and the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) were 4.79 % K−1 and 0.97 % K−1, respectively. Temperature cycling tests demonstrated the repeatability of the luminescence. These results indicate that this fluorescent glass can serve as an excellent temperature sensing material.

Broadband Room-Temperature Photodetection via InBiTe3 Nanosheet.

Broadband room-temperature photodetection has become a pressing need as application requirements for communication, imaging, spectroscopy, and sensing have evolved. Topological insulators (TIs) have narrow bandgap structures with a wide absorption spectral response range, which should meet the requirements of broadband detection. However, owing to their high carrier concentration and low carrier mobility resulting in poor noise equivalent power (NEP), they are generally considered unsuitable for photodetection. Here, InBiTe3 alloy nanosheet formed by doping In2Te3 into Bi2Te3(≈ 1:1) is utilized, effectively improving carrier mobility by over ten times while maintaining a narrow bandgap structure, to fabricate a broadband photodetector covering a wide response range from visible to millimeter wave (MMW). Under the synergistic multi-mechanism of the photoelectric effect in the visible-infrared region and the electromagnetic-induced potential well (EIW) effect in Terahertz band, the performance of NEP=75pWHz-1/2 and response time τ ≈100µs in visible to infrared band and the performance of NEP=6.7×10-3pWHz-1/2, τ ≈8µs in Terahertz region are achieved. The results demonstrate the promising prospects of topological insulator alloy (like InBiTe3) nanosheet in optoelectronic detection applications and provide a direction for the research into high-performance broadband photoelectric detectors via TIs.

Deep-subwavelength multilayered meta-coatings for visible-infrared compatible camouflage

Abstract Camouflage is a common technique in nature, enabling organisms to protect themselves from predators. The development of novel camouflage technologies, not only in fundamental science, but also in the fields of military and civilian applications, is of great significance. In this study, we propose a new type of deep-subwavelength four-layered meta-coating consisting of Si, Bi, Si, and Cr from top to bottom with total thickness of only ∼355 nm for visible-infrared compatible camouflage. The visible color and the infrared emission properties of the meta-coating can be independently adjusted. Colorful meta-coating for visible camouflage can be obtained by changing the thickness of top Si layer, while the selective high emissivity in non-atmospheric window for infrared camouflage remains. Due to the deep-subwavelength properties, the meta-coating shows high angle tolerance in both visible and infrared regions. The compatible camouflage capability of our proposed meta-coating in the visible-infrared region is validated under different environments. The deep-subwavelength, angular insensitivity, visible-infrared compatibility and large-area fabrication feasibility promise the meta-coating an effective solution for camouflage in various applications such as military weapons and anti-counterfeiting.

Role of Native Defects in Fe-Doped β-Ga2O3.

Iron impurities are believed to act as deep acceptors that can compensate for the n-type conductivity in as-grown Ga2O3, but several scientific issues, such as the site occupation of the Fe heteroatom and the complexes of Fe-doped β-Ga2O3 with native defects, are still lacking. In this paper, based on first-principle density functional theory calculations with the generalized gradient approximation approach, the controversy regarding the preferential Fe incorporation on the Ga site in the β-Ga2O3 crystal has been addressed, and our result demonstrates that Fe dopant is energetically favored on the octahedrally coordinated Ga site. The structural stabilities are confirmed by the formation energy calculations, the phonon dispersion relationships, and the strain-dependent analyses. The thermodynamic transition level Fe3+/Fe2+ is located at 0.52 eV below the conduction band minimum, which is consistent with Ingebrigtsen's theoretical conclusion, but slightly smaller than some experimental values between 0.78 eV and 1.2 eV. In order to provide direct guidance for material synthesis and property design in Fe-doped β-Ga2O3, the defect formation energies, charge transitional levels, and optical properties of the defective complexes with different kinds of native defects are investigated. Our results show that VGa and Oi can be easily formed for the Fe-doped β-Ga2O3 crystals under O-rich conditions, where the +3 charge state FeGaGai and -2 charge state FeGaOi are energetically favorable when the Fermi level approaches the valence and conduction band edges, respectively. Optical absorption shows that the complexes of FeGaGai and FeGaVGa can significantly enhance the optical absorption in the visible-infrared region, while the energy-loss function in the β-Ga2O3 material is almost negligible after the extra introduction of various intrinsic defects.

Proximal remote sensing and gross primary productivity in a temperate salt marsh

Salt marshes are highly productive ecosystems relevant for Blue Carbon assessments, but information for estimating gross primary productivity (GPP) from proximal remote sensing (PRS) is limited. Temperate salt marshes have seasonal canopy structure and metabolism changes, defining different canopy phenological phases, GPP rates, and spectral reflectance. We combined multi-annual PRS data (i.e., PhenoCam, discrete hyperspectral measurements, and automated spectral reflectance sensors) with GPP derived from eddy covariance. We tested the performance of empirical models to predict GPP from 12 common vegetation indices (VIs; e.g., NDVI, EVI, PSRI, GCC), Sun-Induced Fluorescence (SIF), and reflectance from different areas of the electromagnetic spectrum (i.e., VIS-IR, RedEdge, IR, and SIF) across the annual cycle and canopy phenological phases (i.e., Greenup, Maturity, Senescence, and Dormancy). Plant Senescence Reflectance Index (PSRI) from hyperspectral data and the Greenness Index (GCC) from PhenoCam, showed the strongest relationship with daily GPP across the annual cycle and within phenological phases (r2=0.30–0.92). Information from the visible-infrared electromagnetic region (VIS-IR) coupled with a partial least square approach (PLSR) showed the highest data-model agreement with GPP, mainly because of its relevance to respond to physiological and structural changes in the canopy, compared with indices (e.g., GCC) that particularly react to changes in the greenness of the canopy. The most relevant electromagnetic regions to model GPP were ∼550 nm and ∼710 nm. Canopy phenological phases impose challenges for modeling GPP with VIs and the PLSR approach, particularly during Maturity, Senescence, and Dormancy. As more eddy covariance sites are established in salt marshes, the application of PRS can be widely tested. Our results highlight the potential to use canopy reflectance from the visible spectrum region for modeling annual GPP in salt marshes as an example of advances within the AmeriFlux network.

Intense Hydrochromic Photon Upconversion from Lead-Free 0D Metal Halides For Water Detection and Information Encryption.

Hydrochromic materials that change their luminescence color upon exposure to moisture have attracted considerable attention owing to their applications in sensing and information encryption. However, the existing materials lack high hydrochromic response and color tunability. This study reports the development of a new and bright 0D Cs3 GdCl6 metal halide as the host for hydrochromic photon upconversion in the form of polycrystals (PCs) and nanocrystals. Lanthanides co-doped cesium gadolinium chloride metal halides exhibit upconversion luminescence (UCL) in the visible-infrared region upon 980nm laser excitation. In particular, PCs co-doped with Yb3+ and Er3+ exhibit hydrochromic UCL color change from green to red. These hydrochromic properties are quantitatively confirmed through the sensitive detection of water in tetrahydrofuran solvent via UCL color changes. This water-sensing probe exhibits excellent repeatability and is particularly suitable for real-time and long-term water monitoring. Furthermore, the hydrochromic UCL property is exploited for stimuli-responsive information encryption via cyphertexts. These findings will pave the way for the development of new hydrochromic upconverting materials for emerging applications, such as noncontact sensors, anti-counterfeiting, and information encryption.

High temperature oxides for selective absorption of thermal radiation

Most high melting temperature oxides are translucent in the visible-infrared region characteristic of the blackbody thermal radiation at high temperatures. Consequently, over this broad-band spectral region, the “thermal radiation window”, they do not absorb thermal radiation. Translucent oxides, such as the zirconates, can be extensively doped with rare-earth (RE) ions (Nd, Sm, Er, Dy, Yb) to achieve selective spectral absorption, and the doped oxides exhibit low thermal conductivity. The optical absorption bands are due to electronic transitions between electronic states associated with the rare-earth ions and are relatively insensitive to other rare-earth ions within the same compound. Therefore, mixed rare-earth compounds exhibit optical absorption characteristic of the sum of the individual ions’ absorptions. By contrast, the thermal conductivity of the RE zirconates is shown to be relatively independent of composition suggesting that their optical properties in the thermal radiation window regions can be modified without affecting their thermal conduction properties.

Effects of Cu, Zn Doping on the Structural, Electronic, and Optical Properties of α-Ga2O3: First-Principles Calculations.

The intrinsic n-type conduction in Gallium oxides (Ga2O3) seriously hinders its potential optoelectronic applications. Pursuing p-type conductivity is of longstanding research interest for Ga2O3, where the Cu- and Zn-dopants serve as promising candidates in monoclinic β-Ga2O3. However, the theoretical band structure calculations of Cu- and Zn-doped in the allotrope α-Ga2O3 phase are rare, which is of focus in the present study based on first-principles density functional theory calculations with the Perdew-Burke-Ernzerhof functional under the generalized gradient approximation. Our results unfold the predominant Cu1+ and Zn2+ oxidation states as well as the type and locations of impurity bands that promote the p-type conductivity therein. Furthermore, the optical calculations of absorption coefficients demonstrate that foreign Cu and Zn dopants induce the migration of ultraviolet light to the visible-infrared region, which can be associated with the induced impurity 3d orbitals of Cu- and Zn-doped α-Ga2O3 near the Fermi level observed from electronic structure. Our work may provide theoretical guidance for designing p-type conductivity and innovative α-Ga2O3-based optoelectronic devices.

TiO2 Nanowires on TiO2 Nanotubes Arrays (TNWs/TNAs) Decorated with Au Nanoparticles and Au Nanorods for Efficient Photoelectrochemical Water Splitting and Photocatalytic Degradation of Methylene Blue

In this study, TiO2 nanowires on TiO2 nanotubes arrays (TNWs/TNAs) and Au-decorated TNWs/TNAs nanostructures are designed and fabricated as a new type of photoanode for photoelectrochemical (PEC) water splitting. The TNWs/TNAs were fabricated on Ti folds by anodization using an aqueous NH4F/ethylene glycol solution, while Au nanoparticles (NPs) and Au nanorods (NRs) were synthesized by Turkevich methods. We studied the crystal structure, morphology, and PEC activity of four types of nanomaterial photoanodes, including TNWs/TNAs, Au NPs- TNWs/TNAs, Au NRs-TNWs/TNAs, and Au NPs-NRs-TNWs/TNAs. The TiO2 and Au-TiO2 samples exhibited pure anatase phase of TiO2 with (0 0 4), (1 0 1), and (1 0 5) preferred orientations, while Au-TiO2 presented a tiny XRD peak of Au (111) due to a small Au decorated content of 0.7 ± 0.2 at.%. In addition, the samples obtained a well-defined and uniformed structure of TNAs/TNWs; Au NPs (size of 19.0 ± 1.9 nm) and Au NRs (width of 14.8 ± 1.3 nm and length of 99.8 ± 15.1 nm) were primarily deposited on TNWs top layer; sharp Au/TiO2 interfaces were observed from HRTEM images. The photocurrent density (J) of the photoanode nanomaterials was in the range of 0.24–0.4 mA/cm2. Specifically, Au NPs-NRs- decorated TNWs/TNAs attained the highest J value of 0.4 mA/cm2 because the decoration of Au NPs and Au NRs mixture onto TNWs/TNAs improved the light harvesting capability and the light absorption in the visible-infrared region, enhanced photogenerated carriers’ density, and increased electrons’ injection efficiency via the localized surface plasmon resonance (LSPR) effect occurring at the Au nanostructures. Furthermore, amongst the investigated nanophotocatalysts, the Au NPs-NRs TNWs/TNAs exhibited the highest photocatalytic activity in the degradation of methylene blue with a high reaction rate constant of 0.7 ± 0.07 h−1, which was 2.5 times higher than that of the pristine TNWs/TNAs.

Structural, electrical, magnetic & optical properties of Nickel, cobalt doped and Co-doped wurtzite GaN: A first-principle investigation

The structural, electronic, magnetic, and optical properties of Co (6.25%) and Ni (6.25%) monodoped and co-doped GaN were calculated by the DFT+U method using a 2 × 2 × 2 supercell of a total of 32 atoms. The formation energy was negative under both Ga-rich and N-rich conditions for all structures. N-rich condition is found to be favorable for GaN growth. The electronic and magnetic properties changed after doping due to the transition of the 3 d states of Ni, Co and hybridization of 2p of N. Hence monodoped GaN is ferromagnetic whereas the co-doped one is ferrimagnetic due to partial cancellation by the opposite spin of Ni and Co. The doped and co-doped absorption peaks are blue-shifted in the ultraviolet (UV) and redshifted in the visible-infrared (VIS-IR) region from the peaks of pure GaN. A pronounced absorption of VIS-IR is observed in monodoped structures. Both dielectric constant and refractive index increased due to co-doping whereas monodoping had enhanced the properties significantly. This theoretical study suggests the potential application of the Co, Ni monodoped in VIS- IR photonic and co-doped GaN in spintronic devices.

Plasmonic colloidal Nb-doped TiO2 nanocrystals with improved electrochromism in visible-infrared region

Dual-band electrochromic materials can achieve separate modulate of visible and near-infrared (NIR) transmittance, which are important components of smart windows. A promising colloidal Nb-doped TiO2 anatase nanocrystals (NCs) was prepared via the fluoride-assisted synthesis technique. The dual-band electrochromic properties of the NCs are closely related to the localized surface plasmon resonance (LSPR) absorption intensity. With the assistance of fluoride anions, TiO2 NCs can be easily doped with Nb, which is an important discovery. The product is a highly uniform Nb-doped TiO2 colloidal solution. Spectral analysis clarified that the Nb5+ replaced Ti4+, resulting in free carrier generation in the TiO2 conduction band, thereby exciting LSPR. Moreover, Nb-doped TiO2 NCs exhibited outstanding dual-band electrochromic properties including a wide modulation range for visible and NIR region (92.8 % at 620 nm and 75.2 % at 1800 nm) and a high electrochemical cycling stability (83.1 % at 620 nm and 70.3 % at 1800 nm after 1800 cycles). As a novel kind of electrochromic materials, the Nb-doped TiO2 NCs have great potential application for the smart windows.

Quasi-epitaxial growth of BaTiS3 films

Perovskite chalcogenides have emerged as a new class of semiconductors with tunable band gap in the visible-infrared region. High quality thin films are critical to understand the fundamental properties and realize the potential applications based on these materials. We report growth of quasi-epitaxial thin films of quasi one-dimensional (quasi-1D) hexagonal chalcogenide BaTiS$_3$ by pulsed laser deposition. We identified the optimal growth conditions by varying the growth parameters such as the substrate temperature and H2S partial pressure and examined their effects on the thin film structure. High resolution thin film X-Ray diffraction shows strong texture in the out-of-plane direction, whereas no evidence of in-plane relationship between the film and the substrate is observed. Grazing incidence wide-angle X-ray scattering and scanning transmission electron microscopy studies reveal the presence of weak epitaxial relationships of the film and the substrate, despite a defective interface. Our study opens up a pathway to realize quasi-1D hexagonal chalcogenide thin films and their heterostructures with perovskite chalcogenides.

Surface plasmon resonance and oxygen vacancy on Bi/BiO1−y ClxBr1−x synergistically boost high-efficiently photodegradation acetaminophen in waste water

Novel surface plasmon resonance (SPR) and oxygen vacancy-promoted three-dimensional bismuth oxyhalides (Bi/3D-BiO1−yClxBr1−x) were fabricated through solvothermal in-situ chemical reduction method in the presence of PVP assisted with prior introduction of N2. Density functional theory (DFT) calculations and electrochemical analysis revealed that hot electrons were transferred from Bi-NPs to 3D-BiO1−yClxBr1−x via the Bi/3D-BiO1−yClxBr1−x interface. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) confirmed the presence of oxygen vacancy in Bi/3D-BiO1−yClxBr1−x. The SPR effect of Bi nanoparticles(Bi-NPs) improved the visible light utilization of 3D-BiOClxBr1−x and increased the oxygen vacancy (OVs) effects induced by impurity energy level. The Bi/3D-BiO1−yClxBr1−x showed excellent performance in adsorption and degradation of acetaminophen from pharmaceutical industry wastewater. The excellent photocatalytic performance can be ascribed to the synergistic effect of the SPR of Bi-NPs and the reactive centers of surface OVs defects, which extended the photoresponse to visible-infrared light region and favored the spatial separation and transfer of photogenerated charge carriers.

Photocatalytic and tunable optical absorption properties of sandwich-like p-n type LaBO3/KNbO3 (B = Al, Ga) heterostructures

Photocatalytic efficiency enhancement through the construction of heterostructure interface in traditional materials is remain a significant challenge. In this paper, the photocatalytic properties of LaBO3/KNbO3 (B = Al, Ga，abbreviated as LBO/KNO) interfaces were investigated by building sandwich-like p-n type KNO/LBO/KNO heterostructures. Through the analyses of band alignment, the LaBO3/KNbO3 heterostructures with KO–KO, KO–NbO2, NbO2–KO and NbO2–NbO2 terminal can all be promised as photocatalysts for reduction reactions. Compared with the KO–NbO2 and NbO2–KO terminal, the absorption spectra of KO–KO terminal and NbO2–NbO2 terminal show obvious absorption peaks in visible-infrared region for LaBO3/KNbO3 heterostructures. With increasing the number of KNbO3 layers, the width of the pseudo band gap gradually decreases leading to a bathochromic shift of absorption peak. The absorption band eventually moves from ultraviolet to visible and infrared regions, which accounts for 92% of the total solar energy. Benefited from the construction of p-n heterojunction with special sandwich-like structure, the absorption photon achieves the energy interval modulation. Moreover, the unique LaBO3/KNbO3 interfaces enhance the absorption bandwidth and efficiency of solar energy, which may provide a novel pathway for design high-performance photocatalytic materials.

Occurrence of secondary minerals at Tharsis Montes of Mars: A critical assessment

Identification of phyllosilicates on Mars suggests the existence of an aqueous environment, indicating an active period in its evolutionary history. This study analysed the surface mineralogy of caldera and flank regions of Tharsis Montes using remote spectral analysis. Though a thick layer of dust obscures the surface of Tharsis volcanic province, relatively lesser dust regions provide a unique window for exploration. The reflectance data obtained from CRISM onboard Mars Reconnaissance Orbiter in the visible-infrared region is used for the mineralogical study. Spectral parameter indices were used to identify the distribution of minerals over the caldera and flank regions of Tharsis Montes. The spectral characterisation indicates the well-distributed presence of mafic minerals such as olivine with low-calcium pyroxene and plagioclase with the sparse presence of high-calcium pyroxene in the region. The dusty region, typically with a high TES DCI index and low thermal inertia values in the Tharsis Montes, shows a high concentration of olivine. Few regions identified as comparatively dust-free at the caldera and flank show the presence of secondary mafic minerals like FeMg bearing phyllosilicates. Our spectral analysis using nonlinear mixing models with the MICA spectral library indicates the occurrence of absorption features characteristic of hydrated minerals. The occurrence of the secondary mafic minerals, especially the phyllosilicates on Tharsis Montes suggest active weathering or hydrothermal alteration from episodic volcanic activity over time.

Highly Efficient, Ultrabroad PdSe2 Phototransistors from Visible to Terahertz Driven by Mutiphysical Mechanism.

The noble transition metal dichalcogenide palladium diselenide (PdSe2) is an ideal candidate material for broad-spectrum photodetection owing to the large bandgap tunability, high mobility, low thermal conductivity, and large Seebeck coefficient. In this study, self-powered ultrabroadband PdSe2 photodetectors from the visible-infrared to terahertz (THz) region driven by a mutiphysical mechanism are reported. In the visible-infrared region, the photogenerated electron-hole pairs in the PdSe2 body are quickly separated by the built-in electric field at the metal-semiconductor interface and achieve a photoresponsivity of 28 A·W-1 at 405 nm and 0.4 A·W-1 at 1850 nm. In the THz region, PdSe2 photodetectors display a room-temperature responsivity of 20 mA·W-1 at 0.10 THz and 5 mA·W-1 at 0.24 THz based on efficient production of hot carriers in an antenna-assisted structure. Owing to the fast response speed of ∼7.5 μs and low noise equivalent power of ∼900 pW·Hz-1/2, high-resolution transmission THz imaging is demonstrated under an ambient environment at room temperature. Our research validates the great potential of PdSe2 for broadband photodetection and provides a possibility for future optoelectronic applications.

High performance electrochromic supercapacitors powered by perovskite-solar-cell for real-time light energy flow control

Electrochromic devices (ECDs) can alter their optical transmittances under external electrical power but are unable to spontaneously modulate the light flow in real-time along with the intensity change of surrounding light. To address this problem, a module of smart perovskite solar cell (PSC)-powered all-in-one gel ECDs was reported. The PSC-powered ECDs could modulate their transmittance swiftly in visible-infrared regions, hence regulating the photo energy flow in real time according to the surrounding light intensity. The ECD based on 4, 4′-(thiophene- 2, 5-diyl)bis(1-ethylpyridin-1-ium) diiodide (TEV) showed large optical contrast (79.7% at 570 nm, 64.9% at 908 nm), excellent coloration efficiency (231.2 cm2/C), and outstanding stability (only 1.1% ΔT change after 60,000 cycles). The PSC-powered ECDs showed fast response time (≤5 s) and high stability (negligible degradation after 5000 s consecutive switching between bright and dark conditions in air). Meanwhile, the stored power accompanied with the electrochromic process could drive a red LED with high cyclic stability (95.6% of areal capacitance maintained after 10,000 charging-discharging cycles), indicating that ECDs can serve as ideal electrochromic supercapacitors (ECSs). In addition, the fabricated ECD with large area (5.0 cm × 5.4 cm) showed excellent thermal regulation (7 °C of temperature difference between colored and bleached states). We expect this work would pave a new way to save energy and improve energy efficiency in modern buildings and automobiles.

Estimating heavy metal concentrations in Technosols with reflectance spectroscopy

Reflectance spectroscopy in the visible-infrared and shortwave infrared (450–2500 nm) wavelength region is a rapid, cost-effective and non-destructive method that can be used to monitor heavy metal (PTE, potential toxic elements) contaminated areas. Due to the PTE pollution that has accumulated in the course of wastewater treatment, the existence of Technosols presents an environmental problem, a potential source for PTE uptake by vegetation, or even the release of PTEs into groundwater. In this study, multivariate procedures using Partial Least Squares Regression (PLSR) and Random Forest Regression (RFR) are applied to quantify relationships between soil heavy metal concentration (Cr, Cu, Ni, Zn) and reflectance data of highly contaminated Technosols from a former sewage farm near Berlin, Germany. Laboratory measurements of 110 soil samples in four different preparation steps were acquired with HySpex hyperspectral cameras. The impact of the different preparation steps, namely “oven-dried”, “sieved”, “ground”, “LOI”, was evaluated for its potential to enhance the method performance or to reduce the time-consuming soil sample preparation. Furthermore, different spectral pre-processing methods were evaluated regarding improvements of spectral modelling performance and their ability to minimise noise and multiple scattering effects. Considering the optimal coefficient of determination (R2), PLSR shows an improving performance and accuracy with increasing preparation steps such as ground or LOI for all metals of interest (R2_Cr: 0.52–0.78; R2_Cu: 0.36–0.73; R2_Ni: 0.19–0.42 and R2_Zn: 0.41–0.74). RFR shows a weaker estimation performance for all metals, even when using higher sample preparation levels (R2_Cr: 0.36–0.62; R2_Cu: 0.17–0.72; R2_Ni: 0.20–0.35 and R2_Zn: 0.26–0.67). The results show that an application of methods such as PLSR for the prediction of PTE concentration in Technosols is still a challenge but provides more robust estimations than the user-friendly RFR method. Additionally, this study shows that PTE estimation performance in heterogeneous soil samples can be improved by increased laboratory soil preparation steps and further spectral pre-processing steps.

Optical and upconversion properties of bismuth tellurite glasses Co-doped with Er3+-Yb3+ ions

Heavy glass system (HGS) with batch compositionsTeO2-Bi2O3-Na2O co-doped with rare earth ions Er2O3&Yb2O3 are synthesized by melt- quench and press method. The batch composition is taken (80-x-y)%TeO2-10%Bi2O3-10%Na2O-x%Er2O3-y%Yb2O3 where (x, y) are (0.1, 0) and (0.5, 0.5). Thermal study of the synthesized sample is done by Differential Scanning Calorimetry (DSC). Amorphous nature of samples is characterized by X-Ray diffractogram. Heaviness of the samples justifies by the calculated densities of the glass samples. For the study of optical properties, Refractive index (R.I.), Optical energy gap (Eg), Urbach’s energy (Eu) absorption spectroscopy in ultra violet –visible-Infrared (UV–VIS-IR) region is carried. For upconversion (UC) characteristics photoluminescence spectroscopy studied.

Spectral radiative properties of seawater-in-oil emulsions in visible-infrared region

Optical identification, classification and quantification of different oil slicks play important roles in oil-slick monitoring and detection. Under the actions of wind, waves and other marine forces, oil slicks on the sea surface mix with seawater to form oil-seawater emulsions. Herein, we focus on the spectral radiative properties of seawater-in-oil emulsions in the visible-infrared region. The complex refractive indices of crude oil are precisely measured using the combined ellipsometry-transmission method, after which the radiative properties of seawater droplets embedded in crude oil and seawater-in-oil emulsions obtained using the traditional and improved Lorenz-Mie theory are compared and analyzed to illustrate the effects of the absorption of host medium. The directional-hemispherical emittance and reflectance for seawater-in-oil emulsions are calculated using the Monte Carlo method. Results show that even though the traditional Mie-calculated radiative properties deviate obviously from the improved Lorenz-Mie theory results, directional-hemispherical reflectance and emittance of seawater-in-oil emulsions show relatively small difference. Besides, increasing the droplet volume fraction and film thickness may generally lead to enhanced scattering of seawater droplets, further leading to enhanced light reflection and reduced light emission. With the increase in both droplet size and absorption index of seawater and crude oil, the effects of seawater droplet absorption and oil absorption on overall attenuation of emulsions increase considerably; they may weaken the reflection and strengthen the emission. Obtaining the key radiative parameters of different oil species and oil emulsions will be helpful for promoting the practical application of quantitative optical remote sensing of oil slicks on sea surface.