Efficient Illumination Research Articles

Demonstration of a simplified optical mouse lighting module by integrating the non-Lambertian LED chip and the free-form surface

A cost-effective, high-throughput, and high-yield method for the efficiency enhancement of an optical mouse lighting module is proposed. We integrated imprinting technology and free-form surface design to obtain a lighting module with high illumination efficiency and uniform intensity distribution. The imprinting technique can increase the light extraction efficiency and modulate the intensity distribution of light-emitting diodes. A modulated light source was utilized to add a compact free-form surface element to create a lighting module with 95% uniformity and 80% optical efficiency.

Ethanol partial photoxidation on Pt/TiO2 catalysts as green route for acetaldehyde synthesis

Heterogeneous photocatalytic partial oxidation of ethanol was studied over different Pt/TiO2 as an alternative green process for acetaldehyde production.The catalysts were synthesized through the photodeposition of Pt over sol–gel TiO2 with platinum loads of 0.5 and 1wt.%. The effect of some experimental conditions during photodeposition, such as deposition time and Pt loading, was investigated. A short deposition time at 0.5wt.% Pt nominal loading led to small average particle size of platinum (2–3nm) homogeneously distributed all over the TiO2 surface.Ethanol partial oxidation was tested in a gas–solid photocatalytic fluidized bed reactor at high illumination efficiency, using different reaction temperatures. Activity results have been correlated with characterization results of the different samples. Platinized samples prepared with short deposition times showed high conversion levels and high selectivity to acetaldehyde. Materials prepared at longer times, 120min, showed selectivities >98%, although with lower ethanol conversion.Sample with 1wt.% Pt loading prepared with 15min deposition time combined a good compromise between a relevant ethanol conversion and a very high selectivity to acetaldehyde at a selected reaction temperature of 80°C, with an acetaldehyde yield higher than 80%, which make of this catalyst a good candidate for acetaldehyde production by photocatalysis.

Characterization of fast microchannel plate photomultipliers for the ITER core LIDAR Thomson scattering system

In the new ITER core LIDAR Thomson scattering system under development, detectors with pulse response as low as 330 ps and 10 mm diameter active area, covering with good sensitivity the spectral range 380–1100 nm will be necessary. For the visible region 400–750 nm, fast microchannel plate photomultipliers with a GaAsP photocathode that fulfill the characteristics of speed, sensitivity and active area are already commercially available and have been recently characterized for operation in the JET edge LIDAR Thomson scattering system. In this paper we present a further characterization of these devices to evaluate their usefulness in the more demanding operating conditions of the ITER core LIDAR Thomson scattering system. The characteristics of these detectors with regard to linearity, gain recovery time, pulse repetition rate, quantum efficiency and response time for large F-number illumination, have been measured. Linearity and recovery time data have been interpreted according to a new, time dependent, microchannel plate operational model. The results show that these detectors are suitable also for use in ITER.

Slab waveguide photobioreactors for microalgae based biofuel production

Microalgae are a promising feedstock for sustainable biofuel production. At present, however, there are a number of challenges that limit the economic viability of the process. Two of the major challenges are the non-uniform distribution of light in photobioreactors and the inefficiencies associated with traditional biomass processing. To address the latter limitation, a number of studies have demonstrated organisms that directly secrete fuels without requiring organism harvesting. In this paper, we demonstrate a novel optofluidic photobioreactor that can help address the light distribution challenge while being compatible with these chemical secreting organisms. Our approach is based on light delivery to surface bound photosynthetic organisms through the evanescent field of an optically excited slab waveguide. In addition to characterizing organism growth-rates in the system, we also show here, for the first time, that the photon usage efficiency of evanescent field illumination is comparable to the direct illumination used in traditional photobioreactors. We also show that the stackable nature of the slab waveguide approach could yield a 12-fold improvement in the volumetric productivity.

The Research on the Application of Two Kinds of Light Sources in the Training Venue for Physical Education of Universities

The energy efficiency experiment of electric light is implemented according to the lighting design of the physical training venues. In the experiment, the corresponding illumination, power and energy efficiency ratio of the commonly used high pressure sodium lamp and metal halide lamp which work under the voltage ranging from 187V to 234V are experimentally measured and the lighting effect characteristics of the two kinds of electric light sources compared, proving that the high pressure sodium light source should be employed in the training venue for physical education of universities.

Photocurrent Enhancement in Polythiophene-Based Photoelectrodes through Electrochemical Anodic Halogenation

In this work we demonstrate for the first time an efficient donor-acceptor effect in polythiophene-based photovoltaic materials prepared by post-polymerization electrochemical anodic halogenation of the polymers. Electrochemical, photoelectrochemical and Mott-Schottky measurements showed that the halogenated polythiophenes acted as efficient acceptor moieties and were able to facilitate the separation of primary photoexcitons generated in non-modified parent polymers. As a result, such halogenated photoelectrodes produced photocurrents in solution reaching 1.8 mA cm−2 at 88 mW cm−2 405-nm monochromatic illumination and external quantum efficiency exceeding 8% at 480 nm. Working solid-state photovoltaic device prototypes were also fabricated that also showed a dramatic enhancement in photoefficiency upon halogenation. At the same time, it was also found that the materials prepared by electrochemical halogenation were susceptible to photoinduced cathodic dehalogenation, which gave rise to a relatively rapid decline in the photocurrent. Nevertheless, our results show that halogenated polythiophenes can act as efficient electron acceptors in donor-acceptor organic solar cells.

Photocatalytic Ethanol Oxidative Dehydrogenation over Pt/TiO2: Effect of the Addition of Blue Phosphors

Ethanol oxidative dehydrogenation over Pt/TiO2photocatalyst, in the presence and absence of blue phosphors, was performed. The catalyst was prepared by photodeposition of Pt on sulphated TiO2. This material was tested in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency. The effect of the addition of blue phosphors into the fluidized bed has been evaluated. The synthesized catalysts were extensively characterized by different techniques. Pt/TiO2with a loading of 0.5 wt% of Pt appeared to be an active photocatalyst in the selective partial oxidation of ethanol to acetaldehyde improving its activity and selectivity compared to pure TiO2. In the same way, a notable enhancement of ethanol conversion in the presence of the blue phosphors has been obtained. The blue phosphors produced an increase in the level of ethanol conversion over the Pt/TiO2catalyst, keeping at the same time the high selectivity to acetaldehyde.

In‐Situ Partial Sintering of Gold‐Nanoparticle Sheets for SERS Applications

A new, versatile substrate design for surface-enhanced Raman spectroscopy (SERS) is introduced that provides better illumination and collection efficiency than other solid substrates. It uses sheets of 5 nm diameter gold nanoparticles that are draped by drying-mediated self-assembly onto 100 nm thick silicon nitride membranes. During laser illumination, partial in-situ sintering of the nanoparticles into larger structures with tiny gaps (≈2 nm) greatly increases the SERS enhancement factor. The detection of 1 pM of p-mercaptoaniline and 1 fg of 2,4-dinitrotoluene is demonstrated. The use of self-assembled nanoparticle sheets furthermore makes it possible to perform SERS detection in situ on top of a probe solution droplet.

Current sensitivity and efficiency of a CdO-pCdTe-Mo structure at low light levels

It is shown that the CdO-pCdTe-Mo structure established on the basis of large-block p-type films has a spectral range of photosensitivity of Δλ = 480–830 nm, which fully covers the visible area of solar radiation. It was found that the CdO-pCdTe-Mo structure has a high integral sensitivity of Sint = 430–520 mA/lm and a high efficiency of illumination by light of E = 10–100 lx. The anomalous behavior of Sint and the efficiency of this structure are explained by an increase in the photocurrent due to redistribution of the potential between the barrier and the series resistance of the structure as a result of illumination.

Automated optimization of an aspheric light-emitting diode lens for uniform illumination

In this paper, an automated optimization method in the sequential mode of ZEMAX is proposed in the design of an aspheric lens with uniform illuminance for an LED source. A feedback modification is introduced in the design for the LED extended source. The user-defined merit function is written out by using ZEMAX programming language macros language and, as an example, optimum parameters of an aspheric lens are obtained via running an optimization. The optical simulation results show that the illumination efficiency and uniformity can reach 83% and 90%, respectively, on a target surface of 40 mm diameter and at 60 mm away for a 1×1 mm LED source.

Gridded Vivaldi Antenna Feed System for the Northern Cross Radio Telescope

The design of a broadband antenna feed system for the cylindrical offset parabolic reflector of the Italian Northern Cross radio telescope is described. Its operative frequency band spans from the Low Frequency Array (LOFAR) upper band, i.e. 120-240 MHz, to the present telescope operative band centered at 408 MHz. The proposed configuration consists of a linear array of gridded Vivaldi (tapered slot) radiators inside a wired subreflector. Numerical simulations have been carried out using both commercial software and a specialized Method-of-Moments approach. They show that the designed feed system provides both a good impedance matching and an efficient illumination of the main reflector in the overall frequency band.

Parallel hierarchical radiosity on hybrid platforms

Achieving an efficient realistic illumination is an important aim of research in computer graphics. In this paper a new parallel global illumination method for hybrid systems based on the hierarchical radiosity method is presented. Our solution allows the exploitation of systems that combine independent nodes with multiple cores per node. Thus, multiple nodes work in parallel in the computation of the global illumination for the same scene. Within each node, all the available computational cores are used through a shared-memory multithreading approach. The good results obtained in terms of speedup on several distributed-memory and shared-memory configurations show the versatility of our hybrid proposal.

Intensification of gas-phase photoxidative dehydrogenation of ethanol to acetaldehyde by using phosphors as light carriers

In this work a significant improvement of VO(x)/TiO(2) photocatalytic activity in the selective partial oxidation of ethanol to acetaldehyde was achieved by the simultaneous irradiation with light emitting phosphorescent particles and UVA-LEDs as external light source. Photocatalytic tests were carried out in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency, in which the bed is constituted by VO(x)/TiO(2) photocatalyst at nominal V(2)O(5) content of 5 wt% and suitable selected phosphors, diluted with glass spheres. In this way, phosphors were fluidized together with the catalyst, excited by external UVA-LEDs, emitting their stored energy in close proximity to the catalyst. In the absence of phosphors the ethanol consumption rate initially grows linearly with initial alcohol concentration, then bends towards an asymptotic value for initial ethanol concentration higher than 0.5 vol%. By contrast, when phosphors are present, the ethanol consumption rate increased linearly in the overall range. In all cases acetaldehyde was the main product detected in gas phase with a selectivity of about 97%, ethylene and carbon dioxide the by-products. The results evidenced that the presence of phosphors allowed improved photon transfer, increasing the apparent quantum yield from 2 to 30% together with a high photoreactivity.

Rectangular loop-gap resonator with the light access to the sample

A modified rectangular loop-gap resonator for X-band electron paramagnetic resonance (EPR) studies of aqueous samples, enabling the light access, is described. Changes introduced into rectangular resonator geometry, previously presented in Piasecki et al. (1998) [1], and redesigned coupling structure lead to the better thermal and mechanical stability. The modified structure makes provision for the controlled light access to the sample placed in a flat cell during an EPR experiment. The sensitivity of the resonator for aqueous samples as well as an experimentally tested microwave magnetic field homogeneity are presented. Results of simulations and experimental tests indicate that the presence of light access holes in the resonator’s front side does not disturb the uniformity of microwave magnetic field distribution in the nodal plane. The optimal flat cell thickness for unsaturable and saturable aqueous samples has been calculated for this new structure. A modified rectangular geometry of the loop-gap resonator ensures a good performance for aqueous samples allowing its convenient and efficient light illumination during EPR signal recording .

Effect of Jumbo Compact Fluorescent Lamp on the Electrical Energy Saving and Harmonics Noise

This paper presents the effect of jumbo compact fluorescent lamp (energy saving lamp) on the electrical energy saving and harmonics noise. The test was set to find public favor in marketto test. The power rate of incandescent lamp are 200 watts, ML are 160 watts and 250 watts and compact fluorescent lamps (energy saving lamps type) are 23 watts, 24 watts (small size), 45 watts,65 watts and 85 watts (jumbo size). The effect of the lamps on the illuminance efficiency, electrical performance and harmonics noise are compared to verify the effectiveness of each lamps.

Study of probe-sample distance for biomedical spectra measurement

BackgroundFiber-based optical spectroscopy has been widely used for biomedical applications. However, the effect of probe-sample distance on the collection efficiency has not been well investigated.MethodIn this paper, we presented a theoretical model to maximize the illumination and collection efficiency in designing fiber optic probes for biomedical spectra measurement. This model was in general applicable to probes with single or multiple fibers at an arbitrary incident angle. In order to demonstrate the theory, a fluorescence spectrometer was used to measure the fluorescence of human finger skin at various probe-sample distances. The fluorescence spectrum and the total fluorescence intensity were recorded.ResultsThe theoretical results show that for single fiber probes, contact measurement always provides the best results. While for multi-fiber probes, there is an optimal probe distance. When a 400- μm excitation fiber is used to deliver the light to the skin and another six 400- μm fibers surrounding the excitation fiber are used to collect the fluorescence signal, the experimental results show that human finger skin has very strong fluorescence between 475 nm and 700 nm under 450 nm excitation. The fluorescence intensity is heavily dependent on the probe-sample distance and there is an optimal probe distance.ConclusionsWe investigated a number of probe-sample configurations and found that contact measurement could be the primary choice for single-fiber probes, but was very inefficient for multi-fiber probes. There was an optimal probe-sample distance for multi-fiber probes. By carefully choosing the probe-sample distance, the collection efficiency could be enhanced by 5-10 times. Our experiments demonstrated that the experimental results of the probe-sample distance dependence of collection efficiency in multi-fiber probes were in general agreement with our theory.

Removal of Orange II Dye in Water by Visible Light Assisted Photocatalytic Ozonation Using Bi2O3and Au/Bi2O3Nanorods

This paper presents the results of visible light assisted photocatalytic ozonation and other related oxidation processes for the removal of Orange II dye from water using Bi2O3 and Au/Bi2O3 nanorods prepared using microwave irradiation which was found effective compared to Bi2O3 particles prepared by conventional heat treatment method at 90 °C. Particularly, in the photocatalytic ozonation using Au/Bi2O3 nanorods, a fourfold increase in the rate was observed as compared to that in the absence of Au/Bi2O3. This is because tuning semiconductor materials into nanosize could create high quantum confinement of electron and hole to increase the illumination efficiency. In addition, the deposition of nanomaterial can also be employed to enhance the mechanical strength of devices. That is, deposited Au nanoparticles act as electron traps to impede electron/hole recombination.

Dead zones in colloidal quantum dot photovoltaics: evidence and implications

In order to fabricate photovoltaic (PV) cells incorporating light-trapping electrodes, flexible foil substrates, or more than one junction, illumination through the top-contact (i.e.: non-substrate) side of a photovoltaic device is desirable. We investigate the relative collection efficiency for illumination through the top vs. bottom of PbS colloidal quantum dot (CQD) PV devices. The external quantum efficiency spectra of FTO/TiO₂/PbS CQD/ITO PV devices with various PbS layer thicknesses were measured for illumination through either the top (ITO) or bottom (FTO) contacts. By comparing the relative shapes and intensities of these spectra with those calculated from an estimation of the carrier generation profile and the internal quantum efficiency as a function of distance from the TiO₂ interface in the devices, a substantial dead zone, where carrier extraction is dramatically reduced, is identified near the ITO top contact. The implications for device design, and possible means of avoiding the formation of such a dead zone, are discussed.

Improving the durability of dye-sensitized solar cells through back illumination

Highly efficient and stable back illumination dye-sensitized solar cell (BIL-DSSC) is developed using its Pt-counter electrode (Pt-CE) as the light-irradiating surface. Photovoltaic parameters are measured for DSSCs with Pt-CEs obtained with different sputtering periods of platinum layer. By optimizing the transmittance and catalytic property of the platinum layer on the counter electrode, a light-to-electricity conversion efficiency ( η) of 7.54% is achieved with back illumination at 100 mW cm −2, when the platinum deposition time is 30 s. The effects of platinum layers with different sputtering periods on the photovoltaic characteristics of the respective DSSCs are explained in terms of transmittance and catalytic activity of the layers. A comparative study is also made on the durability of the DSSCs with BIL and front illumination (FIL), in which the respective DSSCs are previously subjected to UV-soaking for different periods of time under simulated conditions of back and front illuminations; at-rest stability tests for such UV-soaked DSSCs carried out through BIL and FIL suggest a far higher stability in favor of the BIL-DSSC, compared to that of the FIL-DSSC. Explanations are substantiated with transmittance spectra, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and absorption spectra.

Integration of Non-Lambertian LED and Reflective Optical Element as Efficient Street Lamp

A cost effective, high throughput, and high yield method for the increase of street lamp potency was proposed in this paper. We integrated the imprinting technology and the reflective optical element to obtain a street lamp with high illumination efficiency and without glare effect. The imprinting technique can increase the light extraction efficiency and modulate the intensity distribution in the chip level. The non-Lambertian light source was achieved by using imprinting technique. The compact reflective optical element was added to efficiently suppress the emitting light intensity with small emitting angle for the uniform of illumination intensity and excluded the light with high emitting angle for the prevention of glare. Compared to the conventional street lamp, the novel design has 40% enhancement in illumination intensity, the uniform illumination and the glare effect elimination.