Near-infrared Range Of Spectrum Research Articles

Lithography-free polarization insensitive and wide-angle solar absorber operating in wide spectrum

The largest source of renewable energy on Earth is Sun. Metamaterial can convert solar radiation into useful thermal energy. Therefore, it would be valuable for use in several practical applications, such as thermal photovoltaics, sensing, and heat generation. This work investigates a wideband solar absorber using the lithography-free approach to attain high absorption efficiency when operating in the visible and near-infrared spectrum range. The proposed unit cell comprises a stacking layer structure made of MXene/SiO2. As a results, an average absorptivity of 90 % is depicted within the 400-200 nm. Further, the lithography-free planar layered design shows insensitivity to polarized waves and stability to the wide obliquity of the incidence wave. This work shows its potential for utilizing it in light-to-thermal conversion and thermal imaging-based applications.

Computational search for efficient single-photon emitters among the substitutional doping defects in two-dimensional GaSe

Single photon emitters (SPE) in the near-infrared (NIR) spectrum range are critical elements in quantum communication technology. We apply here computational methods to reveal local defects in the GaSe monolayer with properties favorable for such SPEs. Based on an educated guess, we selected twelve defects YX in GaSe, where the Y dopant substitutes the X host atom, X = Ga or Se, and Y = C, Si, Ge, N, P, or As. Our calculations show that two defects, NGa, and PGa, are dynamically unstable. For the remaining defects, we apply the linear response GW method and Bethe-Salpeter equation (BSE) to calculate the electronic structure and optical excitation spectra. Some defects are found to have two sharp peaks (occupied and unoccupied) of the density of the electronic states within the band gap. The NSe-, PSe-, and AsSe-defects have intense sharp an optical excitation peak at energies around 0.8 eV (λ = 1550 nm). Analysis of the formation of the BSE eigenstates associated with these peaks suggests that these excitations can cause a narrow zero-phonon line emission. We thus propose the NSe-, PSe-, and AsSe-defects in the GaSe monolayer as promising SPE in NIR region.

Effect of vacuum annealing on the optical properties of tungsten oxide films

• Annealing of WO 3– x films in vacuum initiates their coloration in blue. • Colored film absorption band is adequately described by the Breit-Wigner distribution. • Annealing temperature rise nonlinearly increases the absorption band intensity. • Decrease in the spectral line width is saturated when annealing temperature increases. • Asymptote of refractive index dispersion decreases in proportion to the temperature. In this work, the thermochromic properties of tungsten oxide films are studied. The goal of this work is to study the influence of vacuum annealing on optical properties of amorphous WO 3– x films deposited on silica glass substrates. These dependences of the absorption index were approximated using the Breit-Wigner distribution. An increase in the annealing temperature led to an increase in the intensity and a decrease in the width of the absorption band in the near infrared range of the film transmission spectrum. This changed the dispersion of absorption and refractive indices.

A GGA + vdW study on electronic properties and optoelectronic functionality of Cd-doped tetragonal CH3NH3PbI3 for photovoltaics

The electronic properties and optoelectronic functionalities of tetragonal CH 3 NH 3 PbI 3 doped with different concentrations (6.25%, 12.5% and 25%) of Cd have been investigated using the the generalized gradient approximation with the correction of van der Waals interactions (GGA + vdW). First, we examine the dependence of band gap on the Cd doping concentration, and find that the increased Cd content narrows the band gap up to 1.41 eV, extending the photoabsorption wavelength of CH 3 NH 3 PbI 3 into the range of near-infrared spectrum. Furthermore, the electron mobility is found to be enhanced by 28%, which is beneficial for separating and collecting the photo-excited carriers. The effects of band-gap reduction and electron-mobility enhancement jointly contribute to the promotion in optoelectronics of CH 3 NH 3 PbI 3 . The detailed analyses on the thermodynamic stabilities of doped structures have been made through examining their phonon dispersions and decomposition energies. This work has implications in offering guidance for broadening the photovoltaic applications of CH 3 NH 3 PbI 3 .

Aluminum Doping Effect on Surface Structure of Silver Ultrathin Films.

Ultrathin silver films with low loss in the visible and near-infrared spectrum range have been widely used in the fields of metamaterials and optoelectronics. In this study, Al-doped silver films were prepared by the magnetron sputtering method and were characterized by surface morphology, electrical conductivity, and light transmittance analyses. Molecular dynamics simulations and first-principles density functional theory calculations were applied to study the surface morphologies and migration pathway for the formation mechanisms in Al-doped silver films. The results indicate that the migration barrier of silver on a pristine silver surface is commonly lower than that of an Al-doped surface, revealing that the aluminum atoms in the doping site decrease the surface mobility and are conducive to the formation of small islands of silver. When the islands are dense, they coalesce into a single layer, leading to a smoother surface. This might be the reason for the observably lower 3D growth mode of silver on an Al-doped silver surface. Our results with electronic structure insights on the mechanism of the Al dopants on surface morphologies might benefit the quality control of the silver thin films.

Assessment of cerebral circulation through an intact skull using imaging photoplethysmography

The feasibility of assessing the parameters of cerebral hemodynamics without skull trepanation using imaging photoplethysmography with illumination in the near-infrared spectrum range was demonstrated for the first time. The results were obtained when studying changes in blood flow in the rat brain in response to short-term respiratory failure (apnea test). Translation of the results into clinical practice will be useful for the development of a method for non-invasive assessment of cerebral blood flow in patients with cerebrovascular diseases.

High selectivity color filters based on bismuth enhanced plasmonic nanorods

In view of the low intensity of surface plasmon resonance in nanorod-array based color filters, we propose a Bi-SiO2-Ag nanorod array color filter, which takes advantage of the perfect absorption of the incident light by bismuth and the enhancement effect of metal–insulator–metal (MIM) cavity on localized surface plasmon resonance. By changing the thickness of silicon dioxide in the middle layer to adjust the resonance wavelength and using the COMSOL Multiphysics software to study and verify, we show that the proposed device can achieve filtering effect in the visible and near-infrared spectrum range, leading to up to 95% reflectivity in a specific wavelength range. In addition, the full width at half maximum (FWHM) of the device is considerably lower than that of traditional metallic materials, significantly reducing color crosstalk. Therefore, it can be used as a reflective color filter. The proposed structure has many potential applications in the fields of photoelectric detection, image sensing and display.

Microstructure and Photothermal Conversion Performance of Ti/(Mo-TiAlN)/(Mo-TiAlON)/Al2O3 Selective Absorbing Film for Non-Vacuum High-Temperature Applications

This paper aims to clarify the phase composition in each sub-layer of tandem absorber TiMoAlON film and verify its thermal stability. The deposited multilayer Ti/(Mo-TiAlN)/(Mo-TiAlON)/Al2O3 films include an infrared reflectance layer, light interference absorptive layers with different metal doping amounts, and an anti-reflectance layer. The layer thicknesses of Ti, Mo-TiAlN, Mo-TiAlON, and Al2O3 are 100, 300, 200, and 80 nm, respectively. Al content increases to 12 at.% and the ratio of N/O is nearly 0.1, which means nitride continuously changes to oxide. According to X-ray Diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) results, the diffraction peak that appears at 2θ = 40° demonstrates that Mo element aggregates in the substitutional solid solution (Ti,Al)(O,N) columnar grain. TiMoAlON films have low reflectivity in the spectrum range of 300–900 nm. When Al content is more than 10 at.%, absorptivity is almost in the spectrum range from visible to infrared, but absorptivity decreases in the ultraviolet spectrum range. When Al content is increased to 12 at.%, absorptivity α decreases by 0.05 in the experimental conditions. After baking in atmosphere at 500 °C for 8 h, the film has the highest absorptivity when doped with 2 at.% Mo. In the visible-light range, α = 0.97, and in the whole ultraviolet-visible-light near-infrared spectrum range, α = 0.94, and emissivity ε = 0.02 at room temperature and ε = 0.10 at 500 °C.

Single Bi2S3/Bi2S3-xOx nanowire photodetector with broadband response from ultraviolet to near-infrared range

Abstract Constructing heterojunction in single nanowire (NW) can improve the band alignments of heterogeneous interface to promote the optoelectronic performance of materials. In this paper, Bi2S3/Bi2S3-xOx heterojunction NWs are in situ constructed by surface oxidation technique to fill the vacancies of sulfur with oxygen atoms into Bi2S3 NWs. According to the first principle calculation, Bi2S3-xOx shell possesses a narrower band gap of 1.32 eV than that of Bi2S3 core, which aids NW further to enlarge the response range of near infrared spectrum. Moreover, n-type Bi2S3 converts to p-type Bi2S3-xOx owing to the incorporation of oxygen atoms in the surface of the NWs based on the calculated electronic structures. The band alignment of Bi2S3/Bi2S3-xOx heterojunction contributes to transform the carriers between the interface of Bi2S3 and Bi2S3-xOx. As a result, the single Bi2S3 NW based photodetector presents a broadband response from ultraviolet light of 325 to near-infrared light of 1064 nm. Moreover, the detectivity of photodetector is up to 1011 Jones for the visible light of 405, 442 and 642 nm. This investigation demonstrates an efficient broadband photodetector based on Bi2S3/Bi2S3-xOx NWs, in which provides an effective route to develop the high performance of optoelectronic devices for the other NWs.

High-power hybrid GaN-based green laser diodes with ITO cladding layer

Green laser diodes (LDs) still perform worst among the visible and near-infrared spectrum range, which is called the “green gap.” Poor performance of green LDs is mainly related to the p-type AlGaN cladding layer, which on one hand imposes large thermal budget on InGaN quantum wells (QWs) during epitaxial growth, and on the other hand has poor electrical property especially when low growth temperature has to be used. We demonstrate in this work that a hybrid LD structure with an indium tin oxide (ITO) p-cladding layer can achieve threshold current density as low as 1.6 kA / cm 2 , which is only one third of that of the conventional LD structure. The improvement is attributed to two benefits that are enabled by the ITO cladding layer. One is the reduced thermal budget imposed on QWs by reducing p-AlGaN layer thickness, and the other is the increasing hole concentration since a low Al content p-AlGaN cladding layer can be used in hybrid LD structures. Moreover, the slope efficiency is increased by 25% and the operation voltage is reduced by 0.6 V for hybrid green LDs. As a result, a 400 mW high-power green LD has been obtained. These results indicate that a hybrid LD structure can pave the way toward high-performance green LDs.

Investigating extraordinary optical transmission and sensing performance through periodic bilayer magneto-plasmonic structure

This paper proposes the phenomenon of extraordinary optical transmission via a magneto-plasmonic nanostructure, which combines magnetic and plasmonic functionalities. The structure includes an active magnetic film magnetized perpendicular to its surface and a plasmonic metal film, perforated with subwavelength circular annular arrays, with a ring placed in the middle of each annular circle. We use the finite element method and the finite-difference time-domain method for simulation of the structure. Numerical analysis shows an improvement in the Faraday rotation and optical transmission, simultaneously, in a magneto-plasmonic structure based on a silver- and bismuth-substituted ferrite garnet. Simultaneous improvement is achieved by coupling the TE and TM waveguide-plasmon modes. The amount of enhancement is adjusted by changing the dimensions, the periodicity of the hole arrays, and the refractive index of the materials filled in the holes. The influence of excitation of the two kinds of plasmon modes and the application of the external magnetic field are used to enhance the optical response. The resulting investigation shows two resonance peaks in the near-infrared range of the Faraday effect spectrum. Because of the strong Faraday rotation coinciding with the dual-band transmission of approximately 90%, the maximum figure of merit can also be obtained. Finally, this structure is investigated as a sensor in different reflective indexes from 1 to 1.5 RIU, and sensitivity of 45.97 nm/RIU was achieved. The potential applications of these nanostructures include, for example, subwavelength optics, optoelectronic devices, biosensing devices, and magneto-optical devices.

Plasmonic Pixel Biosensor Based on Grazing Angle Illumination and Computational Imaging

Surface plasmon resonance (SPR) has been adapted for analyzing biomolecular interactions in real time as a label-free technology. However, SPR instruments, which are usually bulky and expensive, require specialized optical components for exciting surface plasmons and detecting spectral signals, and the technique has yet to evolve into a more affordable and accessible analytic tool. In this paper, we demonstrate a plasmonic sensing device integrated with plasmonic pixels for exciting surface plasmons and displaying spectral information. The plasmonic pixels based on continuous nanostructured metallic thin films establish a direct relationship between nanostructure patterns and plasmon resonances in the visible and near-infrared spectrum range. Steep dispersion of Fano resonances induced by incident light from a grazing angle transduces plasmonic spectral responses into a unique two-dimensional image. Spectral information extracted from the plasmonic pixels exhibits an asymmetric Fano resonance behavior with sharp intensity peaks and the full width half maxima (FWHM) down to 10 nm. The relative brightness of the plasmonic pixels allows naked human eyes to detect the formation of a biomolecule monolayer. Most importantly, subnanometer spectral information can be extracted from the plasmonic pixel images and computed to analyze dynamics of chemical and biomolecular binding events in real time. We envision that these nanostructure plasmonic pixel biosensors can provide a compact and low-cost analytic platform to meet the emerging demands, particularly in portable, mobile, and wearable devices for label-free detection and point-of-care diagnostics.

Enhancement of photothermal conversion performance using nanofluids based on bimetallic Ag-Au alloys in nitrogen-doped graphitic polyhedrons

The working fluids with higher solar thermal conversion performance within broadband spectrum ranges are of great concern for direct absorption solar collectors (DASCs). Both metal nanoparticles with localized surface plasmon resonance (LSPR) effects and carbon nanomaterials have unique spectral absorption behaviors and have shown better photothermal performance in DASCs. In this paper, we attempted to prepare composite nanofluids including plasmonic bimetallic alloy and carbon nanomaterials to realize enhanced solar absorption and photothermal conversion performance. By taking ZIF-8-derived nitrogen-doped graphitic polyhedrons (ZNGs) as carrier, plasmonic bimetallic Ag-Au alloy nanoparticles were loaded on them by an impregnation-reduction method successfully. Ag-Au/ZNGs ethylene glycol nanofluids showed significant broadband absorption in the visible and near-infrared spectrum range at a lower concentration. Comparing to ethylene glycol, the photothermal conversion effeiency of all ZNGs nanofluids increased remarkablely. Plasmonic bimetallic Ag-Au alloy nanoparticles further improved the photothermal conversion efficiency, which was up to 74.35% for Ag-Au ZNGs nanofluids compared with 72.41%, 70.35% for Au/ZNGs, Ag/ZNGs respectively. This work presents a new way to enhance solar energy absorption and improve solar thermal conversion efficiency of nanofluids for DASCs.

The Photobiomodulation of Vital Parameters of the Cancer Cell Culture by Low Dose of Near-IR Laser Irradiation

The mechanisms underlining the cell adaptive and/or activating oxidative stress, called low level light or photobiomodulation therapies (PBMT), still remain unclear for the near-infrared spectrum range (750–3000 nm), especially for the 1265–1270 nm range (highest absorption by molecular oxygen). It is most probable that the mitochondria may also appear to be the main target for these wavelengths. It is known that mitochondria can generate ROS under visible and 800–1060 nm spectrum range irradiation, which in turn control voltage-dependent anion channels (VDAC). Here we investigated cellular damage regarding VDAC activity, level of oxidative stress, malondialdehyde content, cell viability, mitochondrial potential and mass, GSH level, mitochondrial and nuclear DNA damage in the cancer cell culture exposed to low-level laser irradiation at 1265 nm. We used a continuous wave laser with output power 4 mW; the energy densities employed were 0.3–9.45 J/cm 2. We observed that the laser radiation at 1265 nm can induce the oxidative stress, enhance apoptosis, and disturb mitochondrial functioning at the energy density of 9.54 J/cm2. In addition, inhibition of VDAC enhances the observed effects. It has been shown that the laser irradiation at 1265 nm damages mitochondrial DNA but does not affect the nuclear DNA. The performed experiments bring us to the conclusion that the laser irradiation at 1265 nm can affect cells through mitochondrial damage and the inhibition of VDAC enhances effects of PBMT.

Optical properties of woodpile structures for application on the surface of photonic devices

The paper brings new concept and useful technique, how to modify diffraction and optical properties of different optical and optoelectronical devices by application of three dimensional (3D) photonic crystal structures made of polymer in the surface of photonic devices. This paper is focused on the design, fabrication and characterization of woodpile structures based on IP-Dip polymer for application on the output aperture of optical fiber. The woodpile structures with different periods were fabricated by 3D laser lithography using direct laser writing process based on two-photon absorption mechanism. Effect of woodpile structures on diffraction properties was investigated using of light emitting diode by measurement of radiation patterns in wide range of visible and near infrared spectrum. Also the photonic band gap was simulated and revealed in woodpile structure.

Changes of transmission characteristics for different optic radiation incidence angles in filters protecting against hazardous infrared radiation

AbstractThe paper presents the fundamental information concerning the types of protective optical filters used for protection against hazardous radiation within the visible and near-infrared spectrum range. The changes of transmission characteristics for different optic radiation angles of incidence with metallic reflective filters and interference filters have been analyzed. The results demonstrate that such changes exert no effect on the level of protection provided by the filters.

Refractive Index Estimation of Nanoporous Silicon in Visible and Near-Infrared Spectrum Range

In this paper, we use Bruggeman model to calculate refractive index of nanoporous silicon, which was fabricated by electrochemical etching. The calculated result shows that the refractive index of the nanoporous silicon decreases linearly with increasing porosity and etching current density. In addition, the refractive index of nanoporous silicon was also measured by spectroscopic ellipsometry in the visible light spectrum range. The measured refractive index and extinction coefficient were in agreement with the calculated data, after being modified by the refractive index modified model of heavily doped silicon. In particular, we estimate the refractive index at the optical wavelengths in visible and near-infrared spectrum ranges, which may be widely used in various types of optical sensors and optoelectronic devices for optical communication systems.

PIXEL VS OBJECT-BASED IMAGE CLASSIFICATION TECHNIQUES FOR LIDAR INTENSITY DATA

Abstract. Light Detection and Ranging (LiDAR) systems are remote sensing techniques used mainly for terrain surface modelling. LiDAR sensors record the distance between the sensor and the targets (range data) with a capability to record the strength of the backscatter energy reflected from the targets (intensity data). The LiDAR sensors use the near-infrared spectrum range which provides high separability in the reflected energy by the target. This phenomenon is investigated to use the LiDAR intensity data for land-cover classification. The goal of this paper is to investigate and evaluates the use of different image classification techniques applied on LiDAR intensity data for land cover classification. The two techniques proposed are: a) Maximum likelihood classifier used as pixel- based classification technique; and b) Image segmentation used as object-based classification technique. A study area covers an urban district in Burnaby, British Colombia, Canada, is selected to test the different classification techniques for extracting four feature classes: buildings, roads and parking areas, trees, and low vegetation (grass) areas, from the LiDAR intensity data. Generally, the results show that LiDAR intensity data can be used for land cover classification. An overall accuracy of 63.5% can be achieved using the pixel-based classification technique. The overall accuracy of the results is improved to 68% using the object- based classification technique. Further research is underway to investigate different criteria for segmentation process and to refine the design of the object-based classification algorithm.

Measurement and Analysis of near Infrared Spectrum of Gasoline Vapor

In the fiber-sensing gas detection system, characteristic of near infrared absorption spectrum of the detected gas is greatly significant. The volatilized gasoline vapor is a mixture rich in various components, of which near infrared absorption spectrum shall be determined by means of experimental measurement. In this paper, an experimental platform is constructed by analyzing absorption characteristic of liquid composition in gasoline within the range of near infrared spectrum, which achieves measurement of the volatilized gasoline vapor with different concentration. In addition, reliability of this measurement method is inspected, a comparison between features of absorption spectrograms of liquid and gas is made, and linear relation of absorbance and concentration of gasoline vapor is verified. The result shows that the experimental data is acceptable and may be used as the basis of further analysis and for design of the online detecting system of gasoline vapor concentration in the hazardous environment.

LAND COVER INFORMATION EXTRACTION USING LIDAR DATA

Abstract. Light Detection and Ranging (LiDAR) systems are used intensively in terrain surface modelling based on the range data determined by the LiDAR sensors. LiDAR sensors record the distance between the sensor and the targets (range data) with a capability to record the strength of the backscatter energy reflected from the targets (intensity data). The LiDAR sensors use the near-infrared spectrum range which has high separability in the reflected energy from different targets. This characteristic is investigated to implement the LiDAR intensity data in land-cover classification. The goal of this paper is to investigate and evaluates the use of LiDAR data only (range and intensity data) to extract land cover information. Different bands generated from the LiDAR data (Normal Heights, Intensity Texture, Surfaces Slopes, and PCA) are combined with the original data to study the influence of including these layers on the classification accuracy. The Maximum likelihood classifier is used to conduct the classification process for the LiDAR Data as one of the best classification techniques from literature. A study area covering an urban district in Burnaby, British Colombia, Canada, is selected to test the different band combinations to extract four information classes: buildings, roads and parking areas, trees, and low vegetation (grass) areas. The results show that an overall accuracy of more than 70% can be achieved using the intensity data, and other auxiliary data generated from the range and intensity data. Bands of the Principle Component Analysis (PCA) are also created from the LiDAR original and auxiliary data. Similar overall accuracy of the results can be achieved using the four bands extracted from the Principal Component Analysis (PCA).