Light Gathering Research Articles

A Search for Suitable Water-Splitting Electrodes Using SEAL and Harpoon

The search for suitable electrodes for photoelectrochemical water splitting extends across the periodic table. While III-V semiconductors exhibit superior light gathering properties, metal oxide semiconductors generally cost less and are more robust.The Solar Energy Activity Laboratory (SEAL) 1 and the Heterogeneous Anodes Rapidly Perused for Oxygen Overpotential Neutralization (HARPOON)2 are simple experiments that can quickly scan for suitable oxide semiconductors. The SEAL experiment measures photocurrent and the HARPOON experiment measures oxygen production efficiency.Electrodes made of oxides of Fe, Pd, In, Ni, Zn, Cd, Ga, and W were produced in our laboratory and evaluated using the SEAL and HARPOON experiments. The relative performance of these oxides and their mixtures were evaluated.REFERENCES J. R. McKone et al., “The Solar Army: A Case Study in Outreach Based on Solar Photoelectrochemistry, “ Rev. Adv. Sci. Eng. 3, 288 (2014).S. E. Shaner et al., “Discovering Inexpensive, Effective Catalysts for Solar Energy Conversion: An Authentic Research Laboratory Experience,” J. Chem. Educ. 93, 650 (2016).

LightFormer: Light-Oriented Global Neural Rendering in Dynamic Scene

The generation of global illumination in real time has been a long-standing challenge in the graphics community, particularly in dynamic scenes with complex illumination. Recent neural rendering techniques have shown great promise by utilizing neural networks to represent the illumination of scenes and then decoding the final radiance. However, incorporating object parameters into the representation may limit their effectiveness in handling fully dynamic scenes. This work presents a neural rendering approach, dubbed LightFormer , that can generate realistic global illumination for fully dynamic scenes, including dynamic lighting, materials, cameras, and animated objects, in real time. Inspired by classic many-lights methods, the proposed approach focuses on the neural representation of light sources in the scene rather than the entire scene, leading to the overall better generalizability. The neural prediction is achieved by leveraging the virtual point lights and shading clues for each light. Specifically, two stages are explored. In the light encoding stage, each light generates a set of virtual point lights in the scene, which are then encoded into an implicit neural light representation, along with screen-space shading clues like visibility. In the light gathering stage, a pixel-light attention mechanism composites all light representations for each shading point. Given the geometry and material representation, in tandem with the composed light representations of all lights, a lightweight neural network predicts the final radiance. Experimental results demonstrate that the proposed LightFormer can yield reasonable and realistic global illumination in fully dynamic scenes with real-time performance.

Schottky-junction plasmonic nanocomposite: A non-hazardous excellent visible light photocatalyst for industrial waste management

A bio-compatible nanocomposite “Ag/Ag doped TiO2” with UV–Visible-NIR light gathering quality was synthesized by solvothermal method, followed by green synthesis method. Insertion of Ag+ ions into Ti2+ lattice sites in Ag doped TiO2 alters the n-type TiO2 semiconductor to p-type. Nanostructured doped TiO2 suffers high charge recombination loss in presence of trapped states, resulting 35 % photocatalytic efficiency. Ag decoration on p-type Ag doped TiO2 forms a Schottky barrier at metal-semiconductor junction, which reduces charge recombination loss by separating the photogenerated electron-hole (e-h) in two materials of the nanocomposite. These photogenerated charges create oxide and hydroxide super radicals in the aqueous system of photocatalyst, ensuing 80% degradation of SO dye under 50 min white light illumination. The nanocomposite also demonstrated good performance in degradation of industrial dyes like 50% Mordant Orange (MO) and 15% Direct Blue (DB) under 50 min white light irradiation. DFT analysis of the heterosystems supports absorptivity tuning of experimentally obtained nanocomposite. Moreover, the nanocomposite proved its non-toxicity to human cells, as it reveals <20% cell death with maximum dose (250 µg/ml) of the nanocomposite in cytotoxicity test. Hence, proper designing and synthesizing the nanocomposite explored an eco-friendly solar photocatalyst for industrial waste management.

Structured light field three-dimensional measurement based on equivalent camera array model for highly reflective surfaces

Light-field cameras are gaining attention for their unique light gathering and post-capture processing capabilities. In our previous work, we combined light-field imaging with structured light technology to realize three-dimensional (3D) reconstruction for highly reflective surface. However, due to the lack of effective calibration of the light-field camera and reconstruction systems, it cannot meet the requirements of precise 3D measurement. A universal sub-aperture image extraction algorithm for the light-field camera with hexagonal microlens is presented to accurately extract the multidirectional images. Then, we explore the spatial relationship in equivalent camera array (ECA) of focused light-field camera according to the perspective variation of sub-aperture images. After that, an accurate 3D measurement system based on ECA model is proposed to achieve 3D measurement for highly reflective surface. To test the system’s practical performance, a precision analysis is conducted for a standard gauge block with ground truth. By comparing the reconstruction result of traditional method and ours, we demonstrated the validity of the proposed method to perform 3D measurement for highly reflective surface.

Nano-silver incorporated amine functionalized graphene oxide titania nanotube composite: a promising DSSC photoanode

BackgroundIn dye-sensitized solar cell (DSSC), the semiconductor photoanode plays a vital role in gathering photo-excited electrons from the sensitizer. Generally, the photoconversion efficiency of photoanode is hampered by electron-hole recombination. To circumvent this, modification of TiO2 nanotubes with amine functionalized graphene oxide (GO) has been attempted. MethodsNanocomposites consisting of ethylenediamine functionalized graphene oxide (GO/NH2) and titania nanotubes (TiO2 NTs) are prepared by hydrothermal method and are incorporated with 3 wt% of Ag nanoparticles. The nanocomposites are studied using diffuse reflectance spectroscopy, Raman spectroscopy, XRD, TEM and XPS techniques. Significant FindingsThe GO surface acquire defect structure and disorder after amine functionalization which occurs via reactive oxygen groups to form C−N bond. The nano-silver incorporated amine functionalized GO modified TiO2 nanotubes (TiO2 NTs-GO/NH2/Ag) exhibit high dye adsorption capacity and leads to more light gathering. The DSSC fabricated with TiO2 NTs-GO/NH2/Ag photoanode exhibits very good photo-conversion efficiency (8.18%). Significant light-to-electrical energy conversion efficiency of the TiO2 NTs-GO/NH2/Ag photoanode DSSC is due to the efficient charge transport at the interfaces, high dye loading and broad absorption by the sensitizer adsorbed TiO2 NTs-GO/NH2/Ag thin-film.

Ultrafast charge dynamics in molecular thin films

Conjugated molecular thin films have potential for novel optoelectronic devices such as flexible solar cells and display devices. However, a detailed understanding of their excited state dynamics is crucial for their technological applications. Tetrapyrrole complexes are an important class of conjugated organic molecules for optoelectronic applications due to their high light gathering ability and thermal stability. In this review, we summarize excited state dynamics of porphyrin and phthalocyanine molecular thin films investigated by pump–probe techniques. The relaxation dynamics for metallo-phthalocyanine molecules are observed to be ultrafast in nature and are in femtosecond time scale while that for metal free phthalocyanine are moderately fast. In case of metallo-phthalocyanines exciton lifetime is much longer than for metal free phthalocyanines. The central metal atom plays an important role in the excited state dynamics of porphyrin molecular thin films thus providing additional excitation channels. Time-resolved photoemission spectroscopy reveals about the evolution of charge transfer excitons at donor–acceptor interfaces and their dissociation mechanism. In case of metallo-phthalocyanines the exciton transport is dominated by hopping mechanism rather than spatial coherent length of excitons. The pump–probe studies provide a basis for appropriate selection of molecules for technological applications.

The power of large-scale community science in addressing anthropogenic change.

The human imprint on the global environment has become so pervasive that it rivals the forces of nature in its impact on ecosystem function. We are now living in the Anthropocene with increased air, light, noise, and heavy metal pollution (Foley et al., 2005). Understanding the link between anthropogenic stressors and functional trait characteristics will be vital to predict species response and adaptability to environmental change. Especially as urban areas increase, where anthropogenic changes are highly concentrated and overlapping, investigating how multiple stressors interact to affect individuals and populations is a current research priority. Wilson et al. (this issue) levy the power of human interest in wildlife to study the effects of human-generated pollution (2021). The authors provide a timely and novel continent-level study that addresses the interaction of light and noise pollution on species abundance and response using community science.

Characteristics of Compact Spectrometers with Diffraction Gratings of Different Types

Modern small-sized spectrometers are mainly designed by the Czerny–Turner scheme with a flat diffraction grating or, if the goal is to obtain the maximum aperture at the expense of resolution, by the scheme with a concave diffraction grating. In such spectrometers, the spectrum is registered by photodiode array. In this work, we provide an overview of characteristics of the compact spectrometers developed by our group. These spectrometers use caseless linear photodiode arrays for spectrum registration that eliminates the reflection of radiation from the cover glass of the photodiode array and reduces stray light. The tightness of the housing of spectrometers prolongs their service life. The parameters of the spectrometer modifications designed according to the Czerny–Turner scheme are given. The main advantage of the spectrometer of this type is the low stray light inside the device and the same spectral resolution throughout the spectral range. Aberrations limit the working aperture in the Czerny–Turner scheme to 1/6. The scheme with a flat field allows operation with a larger working aperture. Three modifications of the spectrometer have been developed according to this scheme; a description of their main parameters is given. The results of experimental comparison of the light gathering power and spectral resolution of spectrometers with different optical schemes, as well as the examples of their application, are presented. Devices designed according to the Czerny–Turner scheme are used in atomic emission and atomic absorption spectral analysis and in spectrophotometry for registration of absorption spectra of condensed media. The spectrometers with flat field are used for recording luminescence and Raman spectra of minerals. The developed compact spectrometers can work in a spectral range of 190–1100 nm with the width of the recorded spectral range from 70 to 1000 nm; the best spectral resolution is 0.1 nm, the stray light level is less than 0.05%, and the maximum measured optical density exceeds 3. Owing to a large working aperture of 1 : 2.1, the flat field spectrometers have an increased light gathering power.

Hybrid porous core photonic crystal fiber sensor for monitoring nitrous oxide gas

This paper presents the design and simulation of hybrid porous core photonic crystal fiber (HPC-PCF) for monitoring nitrous oxide (N2O) gas. The design, numerical simulation and optimization process have been accomplished by utilizing COMSOL Multiphysics software and finite element method. The simulation results show the relative sensitivity of 27% and confinement loss of 0.0034 dB/m at λ = 5 μm absorption wavelength of N2O gas. In this design, we consider a spectral band of wavelength from 4.6 μm to 5.6 μm because the absorption wavelength of N2O gas having the value of 5 μm is suitably matched to this range. In addition, highly birefringent HPC-PCF design is more capable for separating the light polarizations and its high numerical aperture allows strong gathering of light into the core, which further reduces the confinement loss.

Lens eyes in protists.

Eyes are not unique to animals. As described by Nilsson and Marshall, prominent eyes, complete with retina and lens, have unexpectedly evolved in single cell dinoflagellates.

Handheld multi-frame super-resolution

Compared to DSLR cameras, smartphone cameras have smaller sensors, which limits their spatial resolution; smaller apertures, which limits their light gathering ability; and smaller pixels, which reduces their signal-to-noise ratio. The use of color filter arrays (CFAs) requires demosaicing, which further degrades resolution. In this paper, we supplant the use of traditional demosaicing in single-frame and burst photography pipelines with a multiframe super-resolution algorithm that creates a complete RGB image directly from a burst of CFA raw images. We harness natural hand tremor, typical in handheld photography, to acquire a burst of raw frames with small offsets. These frames are then aligned and merged to form a single image with red, green, and blue values at every pixel site. This approach, which includes no explicit demosaicing step, serves to both increase image resolution and boost signal to noise ratio. Our algorithm is robust to challenging scene conditions: local motion, occlusion, or scene changes. It runs at 100 milliseconds per 12-megapixel RAW input burst frame on mass-produced mobile phones. Specifically, the algorithm is the basis of the Super-Res Zoom feature, as well as the default merge method in Night Sight mode (whether zooming or not) on Google's flagship phone.

Progress of diagnosis and treatment of light chain amyloidosis

Systemic amyloidosis is caused by misfolding of heavy or light chain in immune globulin and extracellular deposition of proteins as amyloid fibrils. The most common form is light chain amyloidosis,which results in dysfunction of vital organs. Specific biomarkers and amyloid imaging can prompt organ dysfunction at early diagnosis and prevent the organ failure at end stage. Combination therapy is the direction of light chain amyloidosis therapy in the future. The studies on the target therapy concerning clone light chain and amyloid deposition, and new drugs that can control light chain gathering and hydrolysis are under exploration. This paper reviews the treatment progress of light chain amyloidosis. Key words: Amyloidosis; Diagnosis; Treatment

A new imaging model of Lytro light field camera and its calibration

Abstract Due to the unique light gathering and post-capture processing, light field cameras with microlens array are being paid more and more attention. Especially, commercial light field cameras, such as Lytro and Raytrix, have been released. But calibrating light field cameras is still an open and challenging problem. In this paper, we present a new imaging model and a calibration method for Lytro camera, which makes its imaging process be easy to understand. Firstly, according to the image formation for pinhole camera and the theory of light propagation, we model the imaging process of Lytro light field camera, and drive a homogenous intrinsic matrix, which represents the relationship between each pixel on the image plane and its corresponding light field. Then, based on the derived intrinsic matrix, a calibration algorithm using the checkerboard grid for Lytro light field camera is proposed. At last, extensive experimental results have demonstrated the correctness of our imaging model of Lytro light field camera and the effectiveness of our calibration algorithm.

Micro-lensed polymeric optical fiber by CO2 laser cutting

Thin polymeric optical fiber (POF) with good illumination is appreciated when POF is utilized as the luminous element in fabric structure. The CO2 laser cutting is employed to create a micro-lens in POF end to optimize the light gathering or light distribution in textile fields. The image analysis implies that the end shape varies from a polynomial to a lens with increasing laser energy, and meanwhile, the POF axis shifts gradually away from the central axis, which could be optimized by fiber rotation. A ball lens of POF end could be obtained at 1 μs mark speed and 850 rpm rotation speed.

Using SEAL and Harpoon to Search for Suitable Water-Splitting Electrodes

The search for suitable electrodes for photoelectrochemical water splitting extends across the periodic table. While III-V semiconductors exhibit superior light gathering properties, metal oxide semiconductors generally cost less and are more robust. The Solar Energy Activity Laboratory (SEAL) 1 and the Heterogeneous Anodes Rapidly Perused for Oxygen Overpotential Neutralization (HARPOON)2 are simple experiments that can quickly scan for suitable oxide semiconductors. The SEAL experiment measures photocurrent and the HARPOON experiment measures oxygen production efficiency. In addition, an electroplating and lithography technique3 can produce nanowires of nearly any composition that can increase the achievable current density at the electrode surface. Electrodes made of oxides of Fe, Cr, Zn, Al, Bi, Co, and Ni were produced in our laboratory and evaluated using the SEAL and HARPOON experiments. Promising candidates were made into nanowires for additional study. This presentation will communicate the preliminary results. REFERENCES J. R. McKone et al., “The Solar Army: A Case Study in Outreach Based on Solar Photoelectrochemistry, “ Rev. Adv. Sci. Eng. 3, 288 (2014).S. E. Shaner et al., “Discovering Inexpensive, Effective Catalysts for Solar Energy Conversion: An Authentic Research Laboratory Experience,” J. Chem. Educ. 93, 650 (2016).http://www.unitedsci.com/product-catalog/making-wire-lithograph-pressure-sensor-nanotechnology-stem-kit

Highly Sensitive Extrinsic X-Ray Polymer Optical Fiber Sensors Based on Fiber Tip Modification

An extrinsic X-ray fiber sensor with improved sensitivity is presented. The developed device is based on an inorganic scintillator (terbium-doped gadolinium oxysulfide) attached to a polymer fiber tip. Sensitivity improvement has been accomplished by modifying the fiber tip in two ways: by thermomechanical tapering and by chemical etching. Thus, the useful surface in contact with the scintillator increases, and so the fluorescence light gathering capability. All the fabricated devices have been tested under X-ray irradiation from a Linac at a dose rate of 300 monitor units/min, with a readout every 100 ms. The obtained results shown a signal improvement of up to 43 times when compared with previous reported proposals using inorganic scintillators and polymer fibers. Moreover, the recorded signal under the same measurement conditions can be further improved if the inorganic scintillator is used in powder format instead into an epoxy matrix.

Improved extrinsic polymer optical fiber sensors for gamma-ray monitoring in radioprotection applications

Gamma radiation detection in the range of 662keV, the reference for environmental protection, is done through extrinsic optical fiber sensors. The fluorescence rendered by an inorganic scintillator when irradiated with such gamma rays is gathered by a modified polymer optical fiber tip. This modification increases the recorded signal when compared with plain unaltered fiber. Two fiber tip modification are then compared in terms of light gathering capability. A chemically etched fiber, in which the cladding and part of the core are removed, and a tapered fiber in which the core-cladding structure is kept. Both structures are comparable in length and final diameter, and show linear response in the tested range up to 2Gy/h air Kerma rate. The etched fiber shows a higher slope than the tapered one, although both improve the signal gathered by a plain fiber tip. The easy fabrication and handling of the reported transducers, together with the improved signal gathering, allow to reduce the overall system budget with the use of low-cost optoelectronics in the detection stage. This offers a significant improvement for surveillance systems in radioprotection applications, in which presence of gamma radiation coming out accidental leakage or spurious sources activity is the main target.

Sunlight All the Way into the Basement

AbstractInterior rooms, illuminated by daylight are considered ideal in contemporary architecture. Actual results have been less than perfect as of yet. Light gathering optics and quartz glass fibers make it achievable for the first time.

A Global Prospective of the Indian Optical and Near-Infrared Observational Facilities in the Field of Astronomy and Astrophysics: A Review

A review of modernization and growth of ground based optical and near-infrared astrophysical observational facilities in the globe attributed to the recent technological developments in optomechanical, electronics and computer science areas is presented. Hubble Space Telescope (HST) and speckle and adaptive ground based imaging have obtained images better than 0.1 arc sec angular resolution bringing the celestial objects closer to us at least by a factor of 10 during the last two decades. From the light gathering point of view, building of large size (more than 5 meter aperture) ground based optical and nearinfrared telescopes based on latest technology have become economical in recent years. Consequently, in the world, a few 8-10 meter size ground-based optical and near-infrared telescopes are being used for observations of the celestial objects, three 25-40 meter size are under design stage and making of a ~ 100 meter size telescope is under planning stage. In India, the largest sized optical and near-infrared telescope is the modern 3.6-meter located at Devasthal, Nainital. However, the existing Indian moderate size telescopes equipped with modern backend instruments have global importance due to their geographical location. Recently, participation of India in the Thirty Meter Telescope (TMT) project has been approved by the Government of India.

Decoding and calibration method on focused plenoptic camera

The ability of light gathering of plenoptic camera opens up new opportunities for a wide range of computer vision applications. An efficient and accurate method to calibrate plenoptic camera is crucial for its development. This paper describes a 10-intrinsic-parameter model for focused plenoptic camera with misalignment. By exploiting the relationship between the raw image features and the depth–scale information in the scene, we propose to estimate the intrinsic parameters from raw images directly, with a parallel biplanar board which provides depth prior. The proposed method enables an accurate decoding of light field on both angular and positional information, and guarantees a unique solution for the 10 intrinsic parameters in geometry. Experiments on both simulation and real scene data validate the performance of the proposed calibration method.