Variation Of Transmittance Research Articles

Simultaneous Optical Performance Monitoring and Modulation Format/Bit-Rate Identification Using Principal Component Analysis

We propose a novel technique for simultaneous multi-impairment monitoring and autonomous bit-rate and modulation format identification (BR-MFI) in next-generation heterogeneous fiber-optic communication networks by using principal component analysis-based pattern recognition on asynchronous delay-tap plots. The results of numerical simulations performed for three commonly used modulation formats at two different bit-rates each demonstrate simultaneous and independent monitoring of optical signal-to-noise ratio, chromatic dispersion, and differential group delay with mean errors of 1 dB, 4 ps/nm, and 1.6 ps, respectively, without knowing the signal's bit-rate and modulation format. Similarly, the results for joint BR-MFI validate accurate identification of all the bit-rates and modulation formats despite the presence of various network impairments. The effects of fiber nonli-nearity and transmitter variations on the performance of the proposed technique are also investigated.

Reconstruction of Auto-Tissue-Engineered Lamellar Cornea by Dynamic Culture for Transplantation: A Rabbit Model

To construct an auto-tissue-engineered lamellar cornea (ATELC) for transplantation, based on acellular porcine corneal stroma and autologous corneal limbal explants, a dynamic culture process, which composed of a submersion culture, a perfusion culture and a dynamic air-liquid interface culture, was performed using appropriate parameters. The results showed that the ATELC-Dynamic possessed histological structure and DNA content that were similar to native lamellar cornea (NLC, p>0.05). Compared to NLC, the protein contents of zonula occludens-1, desmocollin-2 and integrin β4 in ATELC-Dynamic reached 93%, 89% and 73%, respectively. The basal cells of ATELC-Dynamic showed a better differentiation phenotype (K3−, P63+, ABCG2+) compared with that of ATELC in static air-lift culture (ATELC-Static, K3+, P63−, ABCG2−). Accordingly, the cell-cloning efficiency of ATELC-Dynamic (9.72±3.5%) was significantly higher than that of ATELC-Static (2.13±1.46%, p<0.05). The levels of trans-epithelial electrical resistance, light transmittance and areal modulus variation in ATELC-Dynamic all reached those of NLC (p>0.05). Rabbit lamellar keratoplasty showed that the barrier function of ATELC-Dynamic was intact, and there were no signs of epithelial shedding or neovascularization. Furthermore, the ATELC-Dynamic group had similar optical properties and wound healing processes compared with the NLC group. Thus, the sequential dynamic culture process that was designed according to corneal physiological characteristics could successfully reconstruct an auto-lamellar cornea with favorable morphological characteristics and satisfactory physiological function.

Note: Limitations of the optoelectronic control for carbon nanoparticles synthesis via arc-discharge in solution

Submerged electric arc discharge in liquids has shown to be a promising method for synthesizing a wide variety of nanomaterials. However, it requires an accurate current stability control to ensure the desired purity and structure of the products. The discharge stability control through light emission has been previously studied, but still requires further investigation to clarify the influence of some parameters. The present work has studied the solution's transmittance variation over time, the correlation between the arc light emission and the arc current, and the feasibility of controlling the arc current by using a specific wavelength of the arc light spectrum. Several limitations of the optoelectronic control were found at low currents (I < 50 A).

Electrorheological response of the interfacial layer between a liquid crystal and a polymer alignment sublayer

The interfacial layer between a liquid crystal (LC) and a polymer alignment sublayer was investigated using the quartz crystal microbalance (QCM) method. The time variations in the optical transmittance through the LC cells and the interfacial viscoelasticity were monitored simultaneously using the QCM to provide a comprehensive picture of the interfacial phenomena associated with the motion of LC molecules both in the bulk and in the interfacial layer. The response time of shift in the resonant resistance associated with the director orientation in the interfacial layer was about 90ms, while that in the LC bulk was about 5ms. This indicates that the reorientation of the LC molecules in the vicinity of the interface is much slower than in the bulk. The response time for the changes in thickness of the adsorbed layer, as estimated from the QCM results, was found to be about 1000ms. These results indicate that the electrorheological response, or the viscoelasticity, in the vicinity of the interface between the LC and the polymer should be taken into account for the development of LC devices.

Infrared measurements and simulations of metal meshes in a focused beam

Infrared transmittance measurements of quasioptical filters are often restricted to a focused beam due to the optical design of the spectrometer. In contrast, numerical simulations assume an incident plane wave, which makes it difficult to compare theory with experimental data. We compare transmittance measurements with numerical simulations of square arrays of circular holes in 3-μm thick Cu sheets at angles of incidence from 0° to 20° for both s and p polarizations. These simple structures allow detailed tests of our electromagnetic simulation methods and show excellent agreement between theory and measurement. Measurements in a focused beam are accurately simulated by combining plane wave calculations over a range of angles that correspond to the focal ratio of the incident beam. Similar screens have been used as components of narrow bandpass filters for far-infrared astronomy, but these results show that the transmittance variations with angle of incidence and polarization limit their use to collimated beams at near normal incidence. The simulations are accurate enough to eliminate a costly trial-and-error approach to the design of more complex and useful quasioptical infrared filters and to predict their in-band performance and out-of-band blocking in focused beams.

Green Li+- and Er3+-doped poly(ε-caprolactone)/siloxane biohybrid electrolytes for smart electrochromic windows

Novel electrolytes composed of a sol–gel derived di-urethane cross-linked poly(ε-caprolactone) (d-PCL(530))/siloxane (where 530 is the average molecular weight in gmol−1) biohybrid network doped with a 50:50molar mixture of lithium and erbium triflates were prepared in the light of the “mixed cation effect”. These environmentally friendly electrolytes, which are multi-wavelength emitters from the UV/VIS to the NIR spectral regions, are attractive candidates for electrochromic devices. Prototype devices based on a glass/ITO/WO3/electrolyte/ITO/glass layered configuration exhibited fast switching speed, high electrochromic reversibility and cyclic stability, along with good coloration efficiency and open circuit memory. The visible average transmittance variation and the optical density change attained were 41.6% and 0.39, respectively. The combined use of these electrolytes with transparent conducting oxides in the VIS and NIR spectral regions opens exciting new prospects for the fabrication of electrochromic windows exhibiting NIR emission and improved performance in terms of energy efficiency in buildings. In addition, these electrolytes offer new possibilities for the production of dual light emitting and electrochromic windows.

Electrochromic and optical properties of tungsten oxide films deposited with DC sputtering by introducing hydrogen

Research was undertaken to investigate the electrochromic and optical properties of tungsten oxide (WO3) films deposited by introducing hydrogen with a direct current (DC) and pulsed DC sputtering. The results show that WO3 films have optimum electrochromic properties at a hydrogen flow of 4 and 3 sccm for DC and pulsed DC, respectively. In the Raman spectra, the peak intensity increased with the increase of hydrogen flow at both 770 cm1 and 950 cm(-1) peaks, which resulted in bonds of W(6+)-O and W(6+)=O, respectively. Simultaneously, the transmittance (ΔT550 nm) variations were 65.6% and 64.4%, and the average transmittance (ΔT400-500 nm) variations were 56.7% and 56.4% for DC and pulsed DC, respectively. The bleached/colored ability of the cyclic voltammograms (CVs) was DC>pulsed DC, and the resistances of AC impedance were pulsed DC>DC.

Single basin double slope solar still: Year round performance prediction for local climatic conditions at Southern India

In this work, performance of a single basin double slope solar still has been studied theoretically and experimentally. The theoretical model is used to predict the year round performance of the still at the local climatic conditions for the year 2008. Average values of maximum and minimum atmospheric temperatures, wind velocities were taken from meteorological data for last five years. Radiation models were used to predict the global and diffused irradiances on the inclined covers. The time to time variations in transmittance of the cover were considered. The rate of production variation and the total production for first day of the every month had been calculated. The overall production of the still was higher during March, April, August, November and December and it is around 4 liters/day. The average production of the still was 2.1 liters/day/m2. The economy of the still was also studied and the payback period of the still was three years.

Slow-Light and Enhanced Sensitivity in a Displacement Sensor Using a Lossy Fiber-Based Ring Resonator

Along the last years, much debate has been done on the efficiency of slow-light phenomena in order to enhance light-matter interactions, especially for sensing purposes. This improvement could be key to develop more compact and sensitive devices. In this work we develop an all-fiber sub-micrometric displacement sensor using slow-light sensitivity enhancement in a lossy ring resonator. In the proposed structure the losses produced by the displacement of a mechanic transducer can be translated into strong variations of group index and therefore strong transmittance variations. We show that this effect is strictly related to slow light, and not related to confinement effects or any other.

Analysis of radiative signals from normal and malignant human skins subjected to a short-pulse laser

Responses from a normal skin and a malignant human skin subjected to a low power short-pulse laser are studied. Temporal variations of transmittance and reflectance that carry the signature of the skin conditions are analyzed. The normal skin is modeled based on the anatomical details available in the literature. The malignant skin represents commonly found skin lesions, viz., non-melanoma and cutaneous melanoma. Optical properties of the skin such as the absorption and the scattering coefficients cover various lesions, and they are within the therapeutic optical window of 600–1300nm wavelength. Scattering is modeled using Henyey–Greenstein phase function. The transient radiative heat transfer equation is solved using the modified discrete ordinate method.

NIR cutoff filter for true color imaging sensors

Abstract The function of a near-infrared (NIR) cutoff filter for imaging sensors is being described. The main purpose of the NIR cut filter is to obtain correct color recognition; therefore, the NIR filter is made of an absorbing filter glass and an interference coating. The absorbing filter glass is needed to minimize multiple reflections inside the lens system, which are the cause for ghost images. An additional interference coating enhances the function of the filter. Coating and filter glass are strongly dependent on each other. This requires high reproducibility and low tolerances of the filter glass and interference coating. In addition, features like inner quality – especially striae – and stability of the refractive index are important. A NIR cut filter may be designed as a flat plate or as a lens. Our analysis provides an estimation about striae level and variation of transmittance and their effect on image quality and color recognition. Furthermore, the use of an absorption filter glass as a lens (shrinking down the overall size) is discussed in terms of the influence on transmission and striae.

Spectrometric Characteristic of Superficial &lt;i&gt;Chlorella&lt;/i&gt; Sp. Grown in Photo-Bioreactor under Different Flow Rates

In this study, photo-bioreactor designed with 4 L of volume to cultivate Chlorella sp. was conducted for comparing the differences of biomass increase among three gas flow rates. All experiments were controlled at light reaction of 12 hrs. with 1,700 lux. The organic fluorescence of algae, expressed in excitation emission fluorescent matrix (EEFM), was obtained from algal solution deducted from EEFM of the filtrate obtained from the filtration of algal solution using 0.2 μm membrane filter. Also, the surface charge and functional group for Chlorella sp. were respectively measured by zeta meter and Fourier transform infrared spectroscopy (FTIR). Biomass was measured by absorbance wavelength of 683 nm or dried biomass. Current results reveal that high flow rate produced more biomass than low flow rate did. Regarding to the fluorescent characteristic derived from Chlorella sp., two peaks were appeared in both wavelengths of excitation and Emission (EX/EM) respectively located at 280/330 nm (protein-like) and 440-480/680 nm (pigment). For the variation of autofluorescent intensities during algal incubation, algal image captured by epofluorescent microscope equipped with CCD (Charge-Coupled Device) could be further dealt using image software, showing that there were divergences of fluorescent intensities derived from varied amount of protein-like substance or pigment. Functional group of Chlorella sp. analyzed by FTIR, hydroxyl, peptidic bond, carboxylic acids and polysaccharide were existed with variations of transmittance (%) while gas flow rate was changed.

Influence of the spectral solar radiation on the air flow and temperature distributions in a passenger compartment

The present study aims to investigate spectral solar radiation effect on the air flow and temperature distributions in a passenger compartment. For achieving this goal, transmittance and reflectance for different glass types were measured to analyze the spectral characteristics of windshield by using a spectrophotometer. Using the measurement data, extensive CFD simulations were conducted for three different cases by using the commercial CFD software (ANSYS Fluent 13.0) based on the discrete ordinates method in solving radiative energy transfer equation. It was found that 99% of solar energy intensively existed in the wavelength range between 280 nm and 2500 nm on the basis of the standard solar spectrum (ASTM G173). In particular, strong deflection of air flows were observed near the front seat and it could generate higher mixing region due to the complex vortical flows. Considering the spectral effect, the predicted temperature in the compartment increased by approximately 3 °C, resulting from spectral variation of transmittance and reflectance. Therefore, the spectral solar radiation effect should be considered for more accurate prediction of air flow and thermal fields in the compartment.

Terahertz-Pulse Radiation Properties of Oxygen-Deficient YBa2Cu3O7−δ Thin Films

By measuring the detailed characteristics of terahertz-pulse (THz-pulse) radiation and applying THz time-domain spectroscopy, we investigate the generation mechanism of THz-pulse radiation from biased YBa2Cu3O7−δ (YBCO) thin films with various carrier concentrations. To vary the carrier concentration, the oxygen deficiency of the YBCO samples was systematically varied. With decreasing carrier concentration, the THz-pulse width increases and the response speed of supercarriers to illumination by femtosecond optical pulses tends to decrease. By examining the radiated waveforms, we clarify the influence of carrier doping not only on the relaxation process of quasiparticles but also on the excitation process. A suitably underdoped YBCO film results in maximum efficiency for generating THz radiation. This tendency is difficult to explain if we only consider the variation in transmittance, which has been the approach till now. Instead, we suggest that a variation in quasiparticle excitation efficiency due to carrier doping should also be considered.

Hydrothermal-synthesized mesoporous nickel oxide nanowall arrays with enhanced electrochromic application

Mesoporous NiO nanowall arrays are prepared by a facile hydrothermal synthesis method in combination with a following annealing process. The as-prepared NiO nanowalls have average diameters of ∼10nm and composed of interconnected nanoparticles ranging from 5 to 30nm. The NiO nanowall arrays show a hierarchical porous structure from mesopores of 5–20nm to macropores of 30–200nm. The electrochromic performances of the NiO nanowall arrays are characterized by means of UV–vis spectroscopy and cyclic voltammetry (CV) measurements. The mesoporous NiO nanowall arrays exhibit much better electrochromic performance with faster switching speed and higher color contrast than the dense NiO film. The mesoporous NiO nanowall arrays show a transmittance variation with 77% at 550nm, and the coloration and bleaching times are 2s and 2.5s, respectively. The improved electrochromic performances are due to the porous morphological characteristics, which provide fast ion and electron transfer resulting in fast reaction kinetics and high color contrast.

Highly flexible, conductive and transparent MoO3/Ag/MoO3 multilayer electrode for organic photovoltaic cells

MoO3/Ag/MoO3(MAM) multilayer structures were deposited by vacuum evaporation on polyethylene terephthalate (PET) substrate. We demonstrate that, as in the case of glass substrate, the sheet resistance of such structures depends significantly on the Ag film deposition rate. When it is deposited between 0.2 and 0.4nm/s, an Ag thickness of 11nm allows achieving sheet resistance of 13Ω/sq and an averaged transmission of 74%. A study of the influence of the PET substrate on the optimum MoO3 thicknesses was done. A good qualitative agreement between the theoretical calculations of the variation of the optical transmittance of the MoO3/Ag/MoO3 structures is obtained. The optimum MAM structures MoO3 (17.5nm)/Ag (11nm)/MoO3 (35nm) has a factor of merit FM=4.21 10−3 (Ω/sq)−1. Proven by the scotch test the MAM structures exhibit a good adhesion to the PET substrates. The MAM structures were also submitted to bending tests. For outer bending, the samples exhibit no variation of their resistance value, while for inner bending there is a small increase of the resistance of the MAM structures. However this increasing is smaller than that exhibited by Indium Tin Oxide. When the PET/MAM structures are used as anode in organic photovoltaic cells, it is shown that the need to use thicker Ag films inside the multilayer and to cover the MAM with Au to obtain promising Current density vs Voltage characteristics is due to the heating of the PET substrate during the deposition process.

Monitoring spinach shelf-life with hyperspectral image through packaging films

Different procedures for monitoring the evolution of leafy vegetables, under plastic covers during cold storage, have been studied. Fifteen spinach leaves were put inside Petri dishes covered with three different plastic films and stored at 4°C for 21days. Hyperspectral images were taken during this storage. A radiometric correction is proposed in order to avoid the variation in transmittance of the plastic films during time in the hyperspectral images. Afterwards, three spectral pre-processing procedures (no pre-process, Savitsky–Golay and Standard Normal Variate, combined with Principal Component Analysis) were applied to obtain different models. The corresponding artificial images of scores were studied by means of Analysis of Variance to compare their ability to sense the aging of the leaves. All models were able to monitor the aging through storage. Radiometric correction seemed to work properly and could allow the supervision of shelf-life in leafy vegetables through commercial transparent films.

Sub-15 nm linewidth gratings using roll-to-roll nanoimprinting and plasma trimming to fabricate flexible wire-grid polarizers with low colour shift

Sub-15 nm-wide gratings with a high aspect ratio of up to 16:1 were fabricated using roll-to-roll nanoimprinting and plasma trimming to achieve high optical performance (up to 12 000:1 extinction ratio with an average transmittance of 82%) and low colour shift (transmittance variation less than 3%) flexible wire-grid polarizers for display applications. We applied two imprint platforms onto glass and plastic substrates to identify the optical properties and characteristics of each fabrication process. To enhance the tolerance, reproducibility, and optical performance of the process, the grating profile symmetry and varying residual layer thicknesses were precisely simulated and controlled to achieve the design targets.

Formulation of chemically reduced graphene oxide assembly with poly(4‐vinyl pyridine) through noncovalent interaction

ABSTRACTSoluble chemically reduced graphene oxide (RGO)/poly(4‐vinyl pyridine) (P4VP) assembly was attempted by totally noncovalent approach. Chemical reduction of P4VP/GO mixture by hydrazine produced soluble RGO/P4VP assembly with long term stability. Prepared RGO/P4VP assembly showed pH‐dependent variation of optical transmittance. Transmittance of RGO/P4VP assembly solution at pH 2.0 dramatically increased more than 200% of transmittance of assembly at pH 6. This optical transmittance change was fully reversible. The detailed morphological features of assemble was evaluated by dynamic light scattering (DLS) and atomic force microscopy (AFM). It is estimated that RGO/P4VP assemblies were well separated each other at pH 6, enabling much higher optical absorption of RGO plates. At pH 2, protonation of pyridine ring occurs and this might hamper effective noncovalent interaction between RGO plate and protonated P4VP chains, forming bigger aggregates having less chance for optical absorption. This pH‐dependent optical modulation of RGO/P4VP assembly can be useful for the designing of pH‐sensor, removable nanocatalyst, and targeted drug delivery, etc. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2538–2543, 2013

Highly porous nickel oxide thin films prepared by a hydrothermal synthesis method for electrochromic application

We report NiO nanowall thin films prepared by a facile hydrothermal synthesis method and their electrochromic application. The as-prepared porous nanowall NiO thin films show a highly porous structure built up by many interconnected nanoflakes with a thickness of about 30nm. The electrochromic performances of the NiO films are characterized by means of UV–vis spectroscopy and cyclic voltammetry (CV) measurements. The effect of the annealing temperature on electrochromic properties is discussed. The NiO nanowall film annealed at 300°C exhibits much better electrochromic performance than those counterparts annealed at higher temperature. The film annealed at 300°C exhibits a noticeable electrochromism with reversible color changes from transparent to brown dark and presents a transmittance variation with 77% at 550nm. The NiO nanowall film also shows good reaction kinetics with fast switching speed, and the coloration and bleaching times are 3s and 4s, respectively. The improved electrochromic performances are due to the porous morphological characteristics with fast ion and electron transfer resulting in fast reaction kinetics and high color contrast.