Enhancement Of Light Intensity Research Articles

Features of anthocyanin biosynthesis in pap1-D and wild-type Arabidopsis thaliana plants grown in different light intensity and culture media conditions

The number of different anthocyanin molecules potentially produced by Arabidopsis thaliana and which anthocyanin molecule is the first product of anthocyanidin modification remain unknown. To accelerate the understanding of these questions, we investigated anthocyanin biosynthesis in rosette leaves of both pap1-D and wild-type (WT) A. thaliana plants grown in nine growth conditions, which were composed of three light intensities (low light, middle light, and high light) and three media derived from MS medium (medium-1, 2, and 3). These nine growth conditions differentially affected the levels of anthocyanins and pigmentation patterns of rosette leaves, which were closely related to the diversification levels of cyanin structures. The combined growth conditions of high light and either medium-2 or medium-1 induced the most molecular diversity of anthocyanin structures in rosette leaves of pap1-D plants. Twenty cyanin molecules, including five that were previously unknown, were characterized by HPLC-ESI-MS and HPLC-TOF-MS analyses. We detected that the A. thaliana anthocyanin molecule A11 was most likely the first cyanin derived from the multiple modification steps of cyanidin. In addition, in the same growth condition, rosette leaves of pap1-D plants produced much higher levels and more diverse molecular profiling of cyanins than those of WT plants. The transcript levels of PAP1, PAL1, CHS, DFR, and ANS cDNAs were much higher in pap1-D rosette leaves than in WT ones. Furthermore, on the same agar-solidified medium, an enhancement of light intensity increased levels and molecular diversity of cyanins in both pap1-D and WT rosette leaves. In the same light intensity condition, the responses of anthocyanin levels and profiling to medium alternation were different between pap1-D and WT plants.

Increased light gathering capacity of sub-wavelength conical metallic apertures

We study light transmission through individual and arrays of sub-wavelength metallic apertures of conical shape as a function of their taper angle. With a fixed aperture size at the substrate, there is a dramatic increase in light throughput with increasing taper angle. Similar behaviors hold when considering the intensity enhancement inside the aperture near the substrate interface, where more than four-fold increase can be obtained. When arranged in regular arrays, apertures can interact via surface waves, creating distinct minima and maxima in light transmission and intensity enhancement. The effect of aperture taper is also to dramatically increase light transmission and intra-aperture intensity, but with a red shift in the maxima and negligible shift in the minima. The use of conical apertures should improve the efficiency of nonlinear optical processes as well as applications of light harvesting, such as biomolecule detection.

Stimulated emission on two-dimensional distributed feedback scheme in triangular GaN nanocolumn arrays

Triangular GaN nanocolumn arrays, in which InGaN/GaN multiple quantum wells were integrated at the top region of each nanocolumn, were grown by Ti-mask selective-area growth of RF-plasma-assisted molecular beam epitaxy. In the nanocolumn arrays, a strong enhancement in light intensity at the specific wavelength of 479.4 nm was observed under low optical excitation, and then optically pumped stimulated emission occurred at near the specific wavelength (476.3 nm) under high optical excitation with a threshold excitation density of 400 kW/cm2. The light response of the nanocolumn array was numerically analysed by two-dimensional (2D) finite-difference time-domain and 2D plane-wave expansion methods, proving that the stimulated emission occurred in the 2D distributed feedback scheme.

Numerical simulation of light intensity distribution in the vicinity of three-dimensional Hertzian conical scratch on fused silica subsurface

The main factor of laser induced damage is the modulation caused by the scratch in the subsurface of the fused silica. The three-dimensional Hertzian conical scratch (HCS) model on the exit surface is establised in this article. Three-dimensional finite-difference time-domain method is used to calculate and simulate the electric field intensity distribution in the vicinity of HCS. The effects of depth, radius and gradient angle of the HCS on incident light field modulation are analyzed, respectively. The results show that the electric field enhancement in the center of HCS is the largest. This area is apt to be damaged. The maximal electric field intensity in the fused silica will be enhanced as the depth of the HCS changes from λ to 19λ/2. The fused silica is liable to be damaged while the radius of HCS is below 15λ. When the radius is larger than 175λ, the maximal electric fields in the fused silica tend to be 2.5 V/m. And the maximal electric fields are independent on the radius. The effect of light intensity enhancement is more obviously when total internal reflection occurs between internal interface of HCS and the rear surface of fused silica.

Tunable optofluidic microlens through active pressure control of an air–liquid interface

We demonstrate a tunable in-plane optofluidic microlens with a 9× light intensity enhancement at the focal point. The microlens is formed by a combination of a tunable divergent air–liquid interface and a static polydimethylsiloxane lens, and is fabricated using standard soft lithography procedures. When liquid flows through a straight channel with a side opening (air reservoir) on the sidewall, the sealed air in the side opening bends into the liquid, forming an air–liquid interface. The curvature of this air–liquid interface can be conveniently and predictably controlled by adjusting the flow rate of the liquid stream in the straight channel. This change in the interface curvature generates a tunable divergence in the incident light beam, in turn tuning the overall focal length of the microlens. The tunability and performance of the lens are experimentally examined, and the experimental data match well with the results from a ray-tracing simulation. Our method features simple fabrication, easy operation, continuous and rapid tuning, and a large tunable range, making it an attractive option for use in lab-on-a-chip devices, particularly in microscopic imaging, cell sorting, and optical trapping/manipulating of microparticles.

Synthesis, characterization and UV curing kinetics of hyperbranched polysiloxysilanes from A2 and CB2 type monomers

A controllable approach to synthesize UV curable hyperbranched polysiloxysilanes from A2 (1,1,3,3-tetramethyldisiloxane) and CB2 type monomers (methyl(vinyl)silanediylbis(oxy)bis(ethane-2,1-diyl) diacrylate and methyl(vinyl) silanediylbis(oxy)bis(ethane-2,1-diyl)bis(2-methylacrylate)) was developed in the presented paper. The polymerization was monitored using FTIR, where a two-step polyaddition mode was observed. Vinyl silane group preferentially reacted with hydride silane, resulting in the formation of AB2 type intermediates containing one hydride silane and two acrylate (or methacrylate) groups, at the same time, there may be low quantity of B4 type intermediates. The intermediates further polymerized to form hyperbranched polymers. The UV curing kinetics of the hyperbranched polymers, especially the effects of atmosphere, content of photoinitiator and light intensity on UV curing behavior were studied in detail. The results indicated that the hyperbranched polymers could be cured rapidly under UV irradiation. The curing rates increased with the enhancement of light intensity, and the inhibition effect of oxygen could be restrained by increasing light intensity.

Light intensity enhancement by diffracting structures in solar cells

A simplified three-dimensional study is presented of the light confinement, that is, of the enhancement of the Poynting vector of the electromagnetic radiation of the light inside a solar cell absorbing the light weakly when diffracting structures are used. The model is based on the theory of periodic radiation arrays and is easily applied to one- and two-dimensional diffraction gratings. Realistically wide illumination bundles are considered. The extended nature of illumination severely limits the enhancement capabilities of diffraction structures. Results are compared to those of the more widely used Lambertian light confinement.

Characteristics of light intensity enhancement of a silver nanoprism with rounded corners

We have fabricated silver nanoprisms of 100-600 nm side length by focussed ion beam lithography and measured the light intensity scattering spectra using dark-field microscopy. Two resonance peaks due to localized surface plasmon excitation were observed in the spectra and their central frequency shown to depend on the prism size. The near-field electromagnetic intensity distribution with TE-polarized light at the vacuum wavelength of 632.8 nm was measured. We have obtained a much lower light intensity enhancement than previously numerically predicated. However, scattering spectra obtained numerically, taking into account roundness of the prism corners, agree well with experimental ones. At the same time, the numerically determined field distribution was different to the near-field intensity obtained experimentally. Our results suggest the particular shape of the corner region of the prism is a key factor for obtaining a large light intensity enhancement and shaping the local field distribution.

Enhancement of Light Output Intensity by Integrating ZnO Nanorod Arrays on GaN-Based LLO Vertical LEDs

Enhancement of light output intensity for GaN-based vertical light-emitting diodes (LEDs), combining wafer bonding and the laser lift-off (LLO) process, employing an omnidirectional extraction surface with synthesized single-crystal ZnO nanorod arrays in aqueous solution at room temperature is presented. The light output intensity and wall-plug efficiency of the GaN-based LLO vertical LED with the omnidirectional extraction surface by ZnO nanorod arrays shows 38.9 and 41.2% increases, respectively, at 200 mA current injections compared to that of a vertical LED without ZnO nanorod arrays. The ZnO nanorod arrays not only support a current spreading layer but enhance the probability of photon escape through the omnidirectional extraction surface.

Comment on “Enhanced optical field intensity distribution in organic photovoltaic devices using external coatings” [Appl. Phys. Lett. 89, 233502 (2006)

O’Connor et al.1 reported the enhancement of light intensity at a donor-acceptor (D-A) interface in organic solar cells, in which an external coating of an aluminum hydroxiquinoline (Alq3) cap layer was used. Since the enhancement of light intensity at the D-A interface is periodic with the thickness of Alq3 and the lifetime of an organic solar cell based on copper phthalocyanine (CuPc)–C60 is sensitive to air,2,3 the suggestion of protecting the cells by external coating of Alq3 seems like a great idea that not only improves the cell photocurrent but also protects the cells from the ambient, particularly with the use of thick Alq3. However, as the discussion in this letter later, this may be not true.

Experimental Study of the Photocatalytic Degradation of Formaldehyde in Indoor Air using a Nano-particulate Titanium Dioxide Photocatalyst

Formaldehyde in the indoor environment may be degraded using nano-particulate titanium dioxide (TiO2) photocatalysis to improve air quality. In the work described, a polytetrafluoroethylene filter is employed as the substrate for a nano-particulate TiO2 coating. This is mounted in an experimental setup developed for the tests, similar to an actual air purification system, which are conducted at room temperature. The effects on the formaldehyde photocatalytic degradation rate of some key factors are investigated, including initial concentration, stream flow rate, reaction temperature, light source intensity, and relative humidity. Within the experimental ranges studied, the degradation rate increases with the enhancement of initial concentration and light intensity. The stream flow rate and reaction temperature have dual effects on the degradation rate. It is shown that the degradation rate is relatively high under low relative humidity.

Electric Field Enhancement of Nano Gap of Silver Prisms

Using numerical calculation, we examine the effects of gap distance ofa pair of nano gap silver prisms with rounded corners on the locallight intensity enhancement. Two peaks due to localized surface plasmon(LSP) excitation are observed in a wavelength range from 900 nm to300 nm. The results demonstrate that peaks at a longer and a shorterwavelength corresponded to dipole-like and quadrupole-like LSPresonances, respectively. It is found that a gap distance up to 20 nmprovides larger light intensity enhancement than that of a singlesilver nano prism with rounded corners. Furthermore, nano gap silverprisms are fabricated by direct focused ion beam processing, and wemeasure the scattering light spectrum of a pair of nano prisms by aconfocal optical system. However, the two LSP peaks are not observed invisible range because the sizes of the nano gap and prisms are toolarge.

Schematic design of a complex thin-film luminescent screen usable for vacuum fluorescent and field emission display

Based on the facts related to solid-state cathodoluminescence, mixed excitation, and serial excitation recently discovered in our laboratory, a fundamental schematic design and a series of different schematic elaborated designs are proposed for protection from electron accumulation, reasonable use of a luminescent screen, and enhancement of light intensity.

A general combustion approach to multipod ZnO and its characterization

By a general approach of combustion oxidation at high temperature, multipod ZnO was synthesized without any catalysts or additives. The morphology and optical properties of the multipod ZnO were studied in detail. The growth mechanism was discussed preliminarily. An ultraviolet (UV) emission peak at 374 nm and a broad green emission peak centered at 502 nm are observed in photoluminescence spectrum of the multipod ZnO. The multipod structure exhibits significant enhancement of UV emission intensity and green light emission intensity compared with the tetrapod structure, which are attributed to less structural defects and increased surface area respectively. Furthermore, compared with nano-particle and micro-particle ZnO, UV emission peak of multipod ZnO appears a slight blue shift. Due to slim tips of the legs, quantum size effect cause a slight blue shift of UV emission peak. We believe that these optical properties of the multipod structure have extensive applications in nanoscale optical devices.

Fiber Optic Detection of Ammonia Gas

Bathochromic shifts accompanying the formation of several bivalent metallic complexes containing 5-(4’-dimethylaminophenylimino) quinolin-8-one (L1), and 7-chlore-5(4’-diethylamino-2-methylphenylimino) quinolin-8-one (L2) ligands in ethanol solutions were evaluated by VIS-NIR spectroscopy. The [L1-Cu-L1] sulphide complex was selected as a reagent for further tests on optical fibres. Samples of multimode siloxane-clad fused-silica fibre were sensitized by diffusing an ethanol/chloroform solution of the dye into the cladding polymer, and tested by VIS-NIR optical spectroscopy (12 cm long fibre sections), and optical time domain reflectometry (OTDR; 20 ns laser pulses, wavelength 850 nm, 120 m long fibre sensitized within the interval 104–110 m). A well-resolved absorption band of the reagent could be identified in the absorption spectra of the fibres. After exposure to dry ammonia/nitrogen gas with increasing ammonia concentration (0–4000 ppm), the short fibre samples showed subsequent decay of NIR optical absorption; saturation was observed for higher ammonia levels. The concentration resolution r ? 50 ppm and forward response time t90 ? 30 sec were obtained within the interval 0–1000 ppm. The OTDR courses showed an enhancement of the back-scattered light intensity coming from the sensitized region after diffusion of the initial reagent, and decay after exposure to concentrated ammonia/nitrogen gas (10000 ppm).

Fabrication of Hexagonally Arrayed Nanoholes Using Femtosecond Laser Pulse Ablation with Template of Subwavelength Polystyrene Particle Array

We present nanohole array fabrication on a silicon substrate using a femtosecond laser pulse at 820 nm and 100 fs, and a subwavelength polystyrene (PS) particle array as a template. Nanohole array fabrication uses a particle field enhancement effect and two-dimensional (2-D) arrayed PS nanoparticles deposited on a (100) silicon (Si) substrate. PS spheres 200, 450, and 820 nm in diameter are used. The fabricated nanohole profiles in terms of the particle diameter and irradiated laser fluence are investigated. The nanohole diameter and depth become larger and deeper, respectively, as the diameter of the particles used or the irradiated laser fluence is increased. Light intensity enhancement by the particles is obtained experimentally by comparing ablation rates of the Si substrate with and without particles. The enhanced light intensity between a PS particle and a Si substrate is also calculated by the finite difference time domain (FDTD) method. The calculated optical enhancement factor is consistent with the experimental value.

High-performance GaN-based light-emitting diode using high-transparency Ni∕Au∕Al-doped ZnO composite contacts

We report on a high-transparency low-resistance composite contact structure on p-GaN for light-emitting diode applications. The structure consists of a thin Ni(5nm)∕Au(5nm) layer overcoated with a sputtered Al-doped ZnO (170nm) layer. Enhancement in light emission intensity as high as 74% at 40mA and forward operating voltages in the range of 3.36–3.48V at 20mA are obtained for these devices using a two-step thermal annealing process.

Parametric investigation of laser nanoimprinting of hemispherical cavity arrays

A monolayer of self-assembled silica particles can be imprinted into a silicon substrate by laser irradiation (KrF excimer laser, λ=248nm). Periodical hemispherical cavities can be therefore created on the substrate surface. The influences of various particle sizes and laser fluence were investigated. In addition, preheating of the substrate significantly improves the performance. One-dimensional thermal calculation was employed to understand the thermal effect in this process. Three-dimensional optical simulation provided an accurate insight into the light intensity enhancement. Raman spectroscopy was used to examine the stress induced by the laser imprinting process resided in the cavity structures.

Light Intensity Enhancement and Optical Nonlinear Response due to Localized Surface Plasmons in Nanosize Ag Sphere

Field enhancement due to localized surface plasmons excited in nanosize Ag and coated Ag spheres has been numerically studied using the Mie theory. It has been found that light intensity enhancement becomes maximum at an appropriate diameter of spheres. This maximum has been expected to be determined from mediation of a size-dependent light-confinement effect and a size-dependent dielectric constant of Ag spheres. Such field enhancement should play a crucial role in observing strong nonlinear optical effects. For a nanosize metal sphere coated with a Kerr-nonlinear film, we have succeeded in finding optical switching and optical bistability phenomena using the modified Mie theory.

Tunable resonant optical microcavities by self-assembled templating.

Micrometer-scale optical cavities are produced by a combination of template sphere self-assembly and electrochemical growth. Transmission measurements of the tunable microcavities show sharp resonant modes with Q factors of >300 and 25-fold local enhancement of light intensity. The presence of transverse optical modes confirms the lateral confinement of photons. Calculations show that submicrometer mode volumes are feasible. The small mode volumes of these microcavities promise to lead to a wide range of applications. in microlasers, atom optics, quantum information, biophotonics, and single-molecule detection.