Wavelength Range Research Articles

Modification of the Spectral Absorption Characteristics of ZnGeP2 in the THz and IR Wavelength Ranges Due to Diffusion Doping with Impurity Atoms of Mg, Se, Sn, and Pb

This study demonstrates that diffusion doping of ZGP single crystals with impurity atoms (Mg, Se, Sn, Pb) leads to a decrease in the specific conductivity of the samples. Consequently, this results in reduced absorption in the terahertz frequency range (150–1000 μm). It has been shown that doping ZGP samples with selenium (Se) and lead (Pb) atoms reduces absorption in the infrared region from 0.3–0.6 cm−1 to 0.06–0.09 cm−1. Doping with tin (Sn) leads to a decrease in absorption only in the wavelength region near 2.1 μm from 0.2 cm−1 to 0.05 cm−1. The proposed mechanism for the decrease in infrared absorption is a reduction in zinc vacancies due to doping with impurity atoms. This research lays the groundwork for a technology that produces ZGP crystals with minimal absorption within the 2–8 μm wavelength range, eliminating the need for fast electron beam irradiation technology. This advancement will facilitate the fabrication of ZGP crystals with arbitrary apertures.

Waveguide adapter with contactless flange for operation in the millimeter wavelength range

Waveguide adapter with contactless flange for operation in the millimeter wavelength range

Preparation of Panchromatic Silver Halide Emulsion to Fabricate High Efficiency Multiplexed Volume Phase Holograms for Solar Concentration Application

Volume Phase Gratings (VPG) are often recorded using holographic emulsions such as photopolymer, Dichromated Gelatin (DCG), and silver halide. We employed silver halide emulsion to record the VPG in monochromatic red wavelength for solar concentration purposes. According to the Braggs condition, the recorded VPG's diffraction efficiency reaches its peak at the recorded angle and wavelength. For solar applications, we needed high diffraction efficiency over a wide angle and wavelength range. So, we captured multiplexed single VPG in our own panchromatic silver halide emulsion. The procedure of making panchromatic silver halide emulsion is described in depth. This technique is unique in that it achieves peak diffraction efficiency at broad wavelength and wide angle in a single multiplexed VPG. The panchromatic multiplexed VPG produced a high diffraction efficiency in wide-angle response with overall visible wavelengths. This study describes the high diffraction efficiency multiplexed VPG in its own manufactured panchromatic silver halide emulsion for solar concentrating applications.

Enhanced solar hydrogen evolution by laminated integration of n+p-SiIP/TiO2/Pt inverted pyramid black Si photocathode

The nano/microstructuring of silicon (Si) via chemical methods has garnered significant attention due to its excellent light-trapping capabilities across a wide spectral range. Current research has predominantly focused on the synthesis of pyramidal-shaped microtextures, which enable two reflections on the surface, while largely overlooking the superior light-trapping potential of inverted pyramid silicon (SiIP) microtextures, which theoretically allow for three reflections. Moreover, there has been limited investigation into the application of inverted pyramid black silicon for solar-driven hydrogen evolution. This study reports the synthesis of uniformly arranged inverted pyramid-textured black silicon using the copper-assisted chemical etching (Cu-ACE) method to enhance the efficiency of solar-driven water splitting for hydrogen production. The formation mechanism and the influence of copper-localized surface plasmon resonance (Cu-LSPR) from Cu nanoparticle (NP) byproducts on photoelectrochemical (PEC) activity were systematically analyzed. To reduce sidewall defects and minimize photogenerated carrier recombination, the surface of the SiIP was treated with tetramethylammonium hydroxide (TMAH). A vertical PN junction was developed through ion implantation to reduce the external bias of the SiIP. Additionally, a uniform TiO₂ antireflective layer was deposited via atomic layer deposition (ALD), reducing the average reflectance of the SiIP-T4 to 5.78 % over the 300–1100 nm wavelength range. MoSₓ and Pt NPs were electrodeposited to improve the fill factor and enhance HER kinetics. With optimized catalyst loading, the n+p-SiIP-T4/TiO₂/Pt 80 mC electrode achieved a photocurrent density of 8.0 mA cm−2 at 0 V vs. RHE, an applied bias photon-to-current efficiency (ABPE) of 0.93 % at 0.24 V vs. RHE, and a double-layer capacitance (Cdl) of 91 μF cm−2. The onset potential (Von) was positively shifted by ∼1.13 V to 0.49 V vs. RHE compared to a SiIP photocathode, and the photocathode operated continuously at 0 V vs. RHE for 27 h in an acidic electrolyte. These results demonstrate that SiIP has significant potential for PEC hydrogen evolution, with further performance optimization achievable through structural and surface engineering.

MOSEL Survey: Spatially Offset Lyman-continuum Emission in a New Emitter at z = 3.088 Can Explain the Low Number Density of Observed LyC Leakers

We present the discovery of a unique Lyman-continuum (LyC) emitter at z = 3.088. The LyC emission was detected using the Hubble Space Telescope WFC3/UVIS F336W filter, covering a rest-frame wavelength range of 760–900 Å. The peak signal-to-noise ratio of LyC emission is 3.9 in an r = 0.″24 aperture and is spatially offset by 0.″29 ± 0.″04 (∼2.2 ± 0.3 kpc) from the peak of rest-UV emission (F606W). By combining imaging and spectroscopic data from the James Webb Space Telescope (JWST) JADES, FRESCO, and JEMS surveys, along with VLT/MUSE data from the MXDF survey, we estimate that the probability of random alignment with an interloper galaxy causing the LyC emission is less than 6 × 10−5. The interstellar medium (ISM) conditions in the galaxy are similar to those in other LyC emitters at high redshift ( 12+log(O/H)=7.79−0.05+0.06 , logU=−3.27−0.12+0.14 , O32 = 0.63 ± 0.03), although the single-peaked Lyα profile and lack of rest-UV emission lines suggest an optically thick ISM. Our observations indicate that LyC photons are leaking through a narrow cone of optically thin neutral ISM, most likely created by a past merger (as evidenced by medium-band F210M and F182M images). Using the constraints on escape fraction from individual leakers and a simple model, we estimate that the opening half-angle of ionization cones can be as small as 16° (2% ionized fraction) to reproduce some of the theoretical constraints on the average escape fraction for galaxies. The narrow opening angle required can explain the low number density of confirmed LyC leakers.

BaMoO4:Nd3+-Yb3+ upconverting phosphors for NIR to NIR contactless temperature reading out

BaMoO4:Nd3+–Yb3+ phosphors have been synthesized by using conventional solid state reaction synthesis technique. Frequency up-conversion (UC) emission studies have been performed under 980 nm excitation. The developed UC phosphors show multicolor upconverted emission bands in the 400–900 nm wavelength range and assigned via the radiative transitions of Nd3+ ion. FIR technique based on frequency upconversion has been applied for the 4F7/2→4I9/2 and 4F5/2→4I9/2 transitions of Nd3+ ion in the NIR (750–804 nm) region arising from the two thermally coupled energy states. The energy gap (ΔE) between the upper and lower excited levels (4F7/2 and 4F5/2) was found to be ∼ 800 cm−1. The maximum sensor sensitivity ∼ 23.2 × 10−4 K−1 at 306 K (operating temperature range 306–483 K) under 980 nm NIR laser irradiation for BaMoO4:Nd3+-Yb3+ phosphors is reported. The prepared phosphors have proven their utility as a novel upconverting material for NIR to NIR contactless temperature reading out.

Advancing CubeSats Capabilities: Ground-Based Calibration of Uvsq-Sat NG Satellite’s NIR Spectrometer and Determination of the Extraterrestrial Solar Spectrum

Uvsq-Sat NG is a French 6U CubeSat (10 × 20 × 30 cm) of the International Satellite Program in Research and Education (INSPIRE) designed primarily for observing greenhouse gases (GHG) such as CO2 and CH4, measuring the Earth’s radiation budget (ERB), and monitoring solar spectral irradiance (SSI) at the top-of-atmosphere (TOA). It epitomizes an advancement in CubeSat technology, showcasing its enhanced capabilities for comprehensive Earth observation. Scheduled for launch in 2025, the satellite carries a compact and miniaturized near-infrared (NIR) spectrometer capable of performing observations in both nadir and solar directions within the wavelength range of 1100 to 2000 nm, with a spectral resolution of 7 nm and a 0.15° field of view. This study outlines the preflight calibration process of the Uvsq-Sat NG NIR spectrometer (UNIS), with a focus on the spectral response function and the absolute calibration of the instrument. The absolute scale of the UNIS spectrometer was accurately calibrated with a quartz-halogen lamp featuring a coiled-coil tungsten filament, certified by the National Institute of Standards and Technology (NIST) as a standard of spectral irradiance. Furthermore, this study details the ground-based measurements of direct SSI through atmospheric NIR windows conducted with the UNIS spectrometer. The measurements were obtained at the Pommier site (45.54°N, 0.83°W) in Charentes–Maritimes (France) on 9 May 2024. The objective of these measurements was to verify the absolute calibration of the UNIS spectrometer conducted in the laboratory and to provide an extraterrestrial solar spectrum using the Langley-plot technique. By extrapolating the data to AirMass Zero (AM0), we obtained high-precision results that show excellent agreement with SOLAR-HRS and TSIS-1 HSRS solar spectra. At 1.6 μm, the SSI was determined to be 238.59 ± 3.39 mW.m−2.nm−1 (k = 2). These results demonstrate the accuracy and reliability of the UNIS spectrometer for both SSI observations and GHG measurements, providing a solid foundation for future orbital data collection and analysis.

Phase-field modeling of peritectic coupled growth in the TRIS–NPG model system

Microstructures forming during the directional solidification of the hypo-peritectic TRIS–NPG model alloy were studied by phase-field simulations. Steady state growth forms could be obtained under conditions similar to those in recent space experiments. In two dimensions, the wavelength range of stable lamellar structures has been determined as function of the temperature gradient and the melt composition. Front temperatures extracted from simulations were compared to the predictions of the modified Jackson–Hunt theory. In three dimensions, structures and phenomena known from eutectic systems were reproduced. Transitions between lamellar and rod structures were induced by slowly changing the melt composition. The regularizing effect of tilting the temperature gradient, transforming a random labyrinth pattern to an ordered one, has also been demonstrated. These simulations show the universality of the basic governing mechanism — that is, the competition of solute diffusion with capillary effects — in the pattern formation of these multi-phase systems.

Efficient Near-Infrared Quantum Cutting in Y2O3 co-doped with Ho3+, Yb3+ Phosphor for the Application in Solar Cell

Abstract: An efficient Near-Infrared Quantum Cutting has been demonstrated in Ho3+ and Yb3+ co-activated Y2O3 sample, synthesized by a complex based precursor solution method. The phosphors have been characterized by X-ray diffraction (XRD), Crystal structure photoluminescence (PL) and CIE Chromaticity analysis. The phosphor materials give efficient emission in the green region both through UC and PL, while efficient NIR emission is observed through the QC process. The Photoluminescence emission (PL) spectra of Y2O3 doped 1% Ho3+ x% Yb3+ (x= 0, 5, 10, 20, 30, and 50) samples, The cooperative energy transfers from one Ho3+ to two Yb3+, an intense NIR emission around 549 nm of Yb3+ 2F5/2 - 2F7/2 transition was obtained under 449 nm excitation. Near infrared photons (wavelength range 549 nm) emitted by an Yb3+ ion pair. The Properties of Y2O3 doped with Ho3+ and Yb3+ quantum-cutting phosphors are dependent on various factors such as dopant concentration, crystallinity, homogeneity, particle size. Effective control of the above parameters the quantum-cutting ability of the phosphor material. Small particle size of the quantum-cutting phosphor Y2O3:Ho3+, Yb3+ make it a suitable candidate for its application in solar cells.

Utilizing bypass cement dust in the production of radiation shielding bismuth borate glass

Using the melting-quench technique, a new method for removing bypass cement dust (BCD) was developed in this study using an active environmental glassy system with the chemical formula (65–x)B2O3–5Li2O–5CdO–25BCD–xBi2O3, where x varied from 0 to 30 mol%. A glass density of 3.137 g/cm³ is attained without bismuth, while a density of 5.345 g/cm³ is obtained with 30 mol% Bi2O3. The unit peaks BO3 and BO4 in the FTIR spectra signify the presence of the BLCDBi-series structure. Elevated Bi2O3 concentrations augment BO4 units. Defects influence the optical absorbance of glass within the wavelength range of 190–1000 nm. These defects in the glass network are created by silicon electrons, silicon hole centers, and BCD as well as Bi3+ or Bi6+ after the addition of bismuth oxide to the glassy system. Eg values were found to decrease as Bi2O3 concentration increased, whereas EU and n values exhibited the opposite behavior. A gamma spectroscopy system and the Phy-X/PSD software are used to calculate the linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), half-value layer (HVL), tenth-value layer (TVL), effective atomic number (Zeff), and effective electron density (Neff) of samples. In addition, the Phy-X/PSD software demonstrated good agreement between experimental and theoretical interpretations. Overall, the results showed that the BLCDBi-30 sample is suitable for use in radiation protection.

Spectroscopic ellipsometry investigation of a 6H–SiC single crystal plate for potential use in graphene optoelectronic devices

At room temperature, the spectroscopic ellipsometry SE parameters Epsi (ψ) and Delta (Δ) for 6H–SiC crystal substrate were measured in the wavelength range 350–1700 nm at four different angles of incidence, 60°, 65°, 70°, and 75°. An SE model was developed to extract optical consents of 6H–SiC crystal substrate from the experimentally measured SE parameters. In the wavelength range 350–1700 nm, the refractive index of the 6H–SiC crystal substrate was extracted and fitted to two terms of the Sellmeier dispersion function. In the wide spectral range (350–1700 nm), the Wemple-DiDomenico (WDD) dispersion model shows how the real refractive index changes with wavelength. The analysis of refractive index dispersion of the 6H–SiC crystal substrate using Sellmeier dispersion function and WDD optical model allows to extract oscillator strength Nfij, average oscillator energy Eo, dispersion energy of the single oscillator Ed, lattice oscillator strength El, Abbe dispersion number, energy gap Eg, density of valence electrons nv, refractive index at infinite wavelength n∞, lattice dielectric constant εL, the ratio of free carrier density to free carrier effective mass (N/m∗), and plasma frequency ωp. For the 6H–SiC crystal substrate, in the desired spectral range (240–1700 nm), it does not have any depolarization effect on the reflected polarized light.

Why does distilled liquor (Baijiu) have a yellowish color: A comprehensive analysis

Elucidating the mechanisms underlying Baijiu production is a shared aspiration among academic groups specializing in the field of Baijiu research. This study comprehensively examined the mechanisms underlying the yellowish coloration of Baijiu through a synergistic application of chromatographic, spectroscopic, and physical methodologies. Aging of Baijiu in earthenware pots involves the infiltration of mineral ions such as iron, aluminum, and calcium; however, these ions are detected at extremely low concentrations and are therefore not linked to the development of Baijiu's yellowish color. Instead, the yellowish coloration is attributed to the diverse colorants generated during the high-temperature fermentation of small-molecule sugars derived from the saccharification of grain materials. Although these colorants exist in minimal quantities and exhibit spectral absorption peaks ranging from 300 to 450 nm, their overlapping spectra collectively contribute to the light-absorbing properties of Baijiu across a broad wavelength range, ultimately accounting for its characteristic yellowish color.

The influence of Ag2O/NbO2 nanocomposites on the optical properties of PVA/PVP lend in biomedical applications.

To study the optical properties of nanocomposites as well as antibacterial activity. The experimental study was conducted at the University of Babylon, College of Science and College of Education for Pure Sciences, Babylon, Iraq, from September 2021 to February 2022. Impregnation of transparent matrix polyvinyl alcohol and polyvinyl pyrrolidone nanocomposites was done by silver oxide and niobium oxide nanoparticles. The nanostructures were created using different ratios of polymer matrix, silver oxide nanoparticles and niobium oxide nanoparticles. The optical features of these nanocomposites were examined, whereby the latter type of properties was tested within the wavelength range of 220-820nm. The determination of the anti-microbial activity was done by disc diffusion method. The anti-bacterial activity involved gram-positive and gram-negative organisms. Different bacteria were cultured with Muller-Hinton medium. Absorbance, absorption coefficients and optical conductivity of the nanocomposites increased with the increase in nanocomposite concentrations. The energy gap for silver oxide and niobium oxide nanoparticles decreased when the concentrations of the nanoparticles increased. Promising outcomes may be achieved for the nanocomposites in anti-bacterial applications as the inhibition zones increased along with increased ratio of silver oxide and niobium oxide nanoparticles.

(Invited) Development of Fiber-Optic Hydrogen Sensor Using Platinum-Supported Tungsten Trioxide-Silica Composite Film

A fiber-optic hydrogen gas sensor using a platinum-supported tungsten oxide-silica composite film was fabricated. This sensor utilizes the absorption of the evanescent field interaction in the hydrogen sensitive clad which was composed of WO3 and SiO2, coated on a silica core with sol-gel process. As a first step, transmission spectra of sensing film itself were measured. The transmittance of the sensitive film decreased in the range of wavelengths above about 500 nm after exposure to pure hydrogen, and the change in transmittance at 1300 nm was greater than that at 850 nm. Then, fiber optic sensor device was fabricated, and the amount of propagating light was measured. In the case of using the light source with a wavelength of 1300 nm, the sensitivity with respect to the hydrogen response was nearly twice and the response speed was faster, compared with those at 850 nm.

Bi-functional hydrogen tungsten bronze/carbon composite catalysts towards biomass conversion and solar water purification

We presented a novel bi-functional catalyst composed of HxWO3 and carbon composites, which exhibits excellent catalytic activity in biomass conversion and has the ability to effectively purify water via a wide range of wavelengths in the light spectrum. The HxWO3/carbon composites were effectively produced from commercially available monoclinic tungsten trioxide (WO3) and polypropylene (PP) powders to a single-step mechanochemical reaction employing high-energy ball milling. We systemically investigated how different synthesis parameters, such as rotation speed, processing duration, and ball diameter, affect the mechanochemically-induced phase transformation to either tetragonal or cubic HxWO3 during planetary ball milling. The crystal phase of HxWO3 was controllable by altering the total impact energy in the ball milling. In addition, real-time monitoring of the pressure increment inside the pot and evaluation of the evolved gas revealed the degassing behavior through the oxidative degradation of PP assisted by WO3. The CV and Rietveld analysis proved that HxWO3 exhibited significant enhancement by two orders of magnitude in the rate of H+ diffusion compared to monoclinic WO3. This enhancement would be attributed to the expansion of a mechanically-formed tunnel along the a-axis, which facilitates the migration of H+ ions. The HxWO3/carbon composites performed approximately 12-fold higher efficiency in generating soluble solids (glucose and furfural derivatives) compared to untreated WO3 through the catalytic hydrolysis of cellulose, owing to the enhanced Brønsted acidity. Moreover, the composite particles showed broad light absorption in the UV–Vis–NIR range and demonstrated a considerable enhancement of over three orders of magnitude in the photocatalytic degradation of methyl orange pollutants when exposed to NIR and visible light.

Method of Investigation of Soil Contamination with Heavy Metals at the Sites of Explosions

The study evaluates the method of investigation of soil contamination with heavy metals at the sites of explosions. Results of method application were obtained. Soil samples were collected in location selected as the typical place were explosions take place for explosive objects destruction. For the qualitative and quantitative analysis of soil samples, the "KBr tablets" method was used. Obtained pellets were investigated with spectral-analytical installation created on the basis of infrared-spectrometer IKS-21 and thermal imager LAND-814. IR spectrometric research was carried out in the most informative spectral range of wavelengths of 7.5...14 μm. Proposed method of investigation of soil contamination with heavy metals at the sites of explosions allowed to identify presence of such metals as Al, Cu, Fe, Mg, Ni and Zn in soil samples of explosion site. Mg, Ni and Zn show stable presence in the soil of explosion site with low amount. Al, Cu and Fe we have seen sharp decrease of logarithmic transmittance value at the depth of 10…15 cm which means that these elements are accumulated at these depths of soil after explosions.

Giant infrared bulk photovoltaic effect in tellurene for broad-spectrum neuromodulation

Given the surpassing of the Shockley-Quiesser efficiency limit in conventional p-n junction photovoltaic effect, bulk photovoltaic effect (BPVE) has garnered significant research interest. However, the BPVE primarily focuses on a narrow wavelength range, limiting its potential applications. Here we report a giant infrared bulk photovoltaic effect in tellurene (Te) for broad-spectrum neuromodulation. The generated photocurrent in uniformly illuminated Te excludes other photoelectric effects and is attributed to the BPVE. The bulk photovoltaic wavelength in Te spans a wide range from the ultraviolet (390 nm) to the mid-infrared (3.8 µm). Moreover, the photocurrent density of 70.4 A cm−2 under infrared light simulation outperforms that in previous ultraviolet and visible semiconductors as well as infrared semimetals. Te attached to the dendrites or somata of the cortical neurons successfully elicit action potentials under broad-spectrum light irradiation. This work lays the foundation for the further development of infrared BPVE in narrow bandgap materials.

Metasurface-enabled broadband multidimensional photodetectors

Light encodes multidimensional information, such as intensity, polarization, and spectrum. Traditional extraction of this light information requires discrete optical components by subdividing the detection area into many “one-to-one” functional pixels. The broadband photodetection of high-dimensional optical information with a single integrated on-chip detector is highly sought after, yet it poses significant challenges. In this study, we employ a metasurface-assisted graphene photodetector, enabling to simultaneously detect and differentiate various polarization states and wavelengths of broadband light (1-8 μm) at the wavelength prediction accuracy of 0.5 μm. The bipolar polarizability empowered by this design allows to decouple multidimensional information (encompassing polarization and wavelength), which can be achieved by encoding vectorial photocurrents with varying polarities and amplitudes. Furthermore, cooperative multiport metasurfaces are adopted and boosted by machine learning techniques. It enables precise spin-wavelength differentiation over an extremely broad wavelength range (1-8 μm). Our innovation offers a recipe for highly compact and high-dimensional spectral-polarization co-detection.

Exploration of Volatileomics and Optical Properties of Fusarium graminearum-Contaminated Maize: An Application Basis for Low-Cost and Non-Destructive Detection.

Fusarium graminearum (F. graminearum) in maize poses a threat to grain security. Current non-destructive detection methods face limited practical applications in grain quality detection. This study aims to understand the optical properties and volatileomics of F. graminearum-contaminated maize. Specifically, the transmission and reflection spectra (wavelength range of 200-1100 nm) were used to explore the optical properties of F. graminearum-contaminated maize. Volatile organic compounds (VOCs) of F. graminearum-contaminated maize were determined by headspace solid phase micro-extraction with gas chromatography-tandem mass spectrometry. The VOCs of normal maize were mainly alcohols and ketones, while the VOCs of severely contaminated maize became organic acids and alcohols. The ultraviolet excitation spectrum of maize showed a peak redshift as fungi grew, and the intensity decreased in the 400-600 nm band. Peak redshift and intensity changes were observed in the visible/near-infrared reflectance and transmission spectra of F. graminearum-contaminated maize. Remarkably, optical imaging platforms based on optical properties were developed to ensure high-throughput detection for single-kernel maize. The developed imaging platform could achieve more than 80% classification accuracy, whereas asymmetric polarization imaging achieved more than 93% prediction accuracy. Overall, these results can provide theoretical support for the cost-effective preparation of low-cost gas sensors and high-prediction sorting equipment for maize quality detection.

Preparation of Multi-colored Binary Silica Supraballs and Color Fine-tuning Based on Color Mixing

Structural colors are highly valued for their eco-friendliness and long-term color stability, deriving from the interaction of structural units with incident light. However, traditional methods for adjusting structural colors typically involve altering the size of structural units, a labor-intensive process necessitating specific diameters for each desired color. Moreover, colors exhibited by photonic crystal materials are monochromatic colors with a narrow wavelength range, failing to exhibit polychromatic colors. This restricts their practical applications, as they do not accurately represent the actual color of objects themselves. Hence, this study focuses on fabricating binary supraballs can display polychromatic colors. These supraballs consist of two types of structural units with distinct diameter differences. By adjusting the mass ratio between these units within the supraballs, fine color tuning is achievable. Utilizing three different diameters of silica nanospheres, this method enables the fabrication of supraballs with a diverse range of colors spanning nearly the entire visible spectrum. The adjustable colors of these binary supraballs not only enhance their ability to replicate the colors of objects, but also reduce the significant workload involved in preparing the original structural units. The synthesized supraballs are in powder form, directly applicable as coatings, inks, and other materials.