Spectral Optical Properties Research Articles

Synthesis, spectral and third-order nonlinear optical properties of terpyridine Zn(II) complexes based on carbazole derivative with polyether group

Four novel Zn(II) terpyridine complexes (ZnLCl2, ZnLBr2, ZnLI2, ZnL(SCN)2) based on carbazole derivative group were designed, synthesized and fully characterized. Their photophysical properties including absorption and one-photon excited fluorescence, two-photon absorption (TPA) and optical power limiting (OPL) were further investigated systematically and interpreted on the basis of theoretical calculations (TD-DFT). The influences of different solvents on the absorption and One-Photon Excited Fluorescence (OPEF) spectral behavior, quantum yields and the lifetime of the chromophores have been investigated in detail. The third-order nonlinear optical (NLO) properties were investigated by open/closed aperture Z-scan measurements using femtosecond pulse laser in the range from 680 to 1080nm. These results revealed that ZnLCl2 and ZnLBr2 exhibited strong two-photon absorption and ZnLCl2 showed superior optical power limiting property.

Studies on the growth, structural, spectral and third-order nonlinear optical properties of Ammonium 3-carboxy-4-hydroxy benzenesulfonate monohydrate single crystal

An organic nonlinear optical bulk single crystal, Ammonium 3-carboxy-4-hydroxy benzenesulfonate monohydrate (ACHBS) was successfully grown by solution growth technique. Single crystal X-ray diffraction study confirms that, the grown crystal belongs to P21/c space group. Powder X-ray diffraction and high resolution X-ray diffraction analyses revealed the crystallinity of the grown crystal. Infrared spectral analysis showed the vibrational behavior of chemical bonds and its functional groups. The thermal stability and decomposition stages of the grown crystal were studied by TG-DTA analysis. UV–Visible transmittance studies showed the transparency region and cut-off wavelength of the grown crystal. The third-order nonlinear optical susceptibility of the grown crystal was estimated by Z-scan technique using HeNe laser source. The mechanical property of the grown crystal was studied by using Vicker’s microhardness test.

Radiation Models and Radiation Transfer in Hypersonics

The paper presents radiation models developed to investigate radiation in entry in Earth, Mars and Jupiter atmospheres. The capacity of ASTEROID computing code to simulate elementary radiative processes, calculate spectral and groups optical properties, and also solve simple radiative heat transfer problems is presented for Earth entry. The large number of radiative processes involved in the radiative flux is put forward. The contributions of the different radiative processes encountered in Mars entry are studied using the HTGR spectroscopic database. The validity of this database with respect to diatomic molecules systems and CO2 infrared radiation is illustrated through experimental validations. The accuracy of statistical narrow-band model to predict radiative flux is illustrated for an afterbody. Finally recent improvements of the model developed for the calculation of radiative properties of high-temperature H2/He mixtures representative of Jupiter atmosphere is presented. The model takes into account the most important radiative processes.

Arrangement of fibril side chains studied by molecular dynamics and simulated infrared and vibrational circular dichroism spectra.

Highly ordered assemblies of β-sheet-forming peptide and protein fibrils have been the focus of much attention because of their multiple and partially unknown biological functions, in particular as related to degenerative neuronal disorders. Recently, vibrational circular dichroism (VCD) spectra have been shown to provide a unique means of detection for such extended structures utilizing modes of the peptide main chain backbone. In the case of poly-glutamic acid, surprising VCD responses were also found for side chain modes. In this study, in an attempt to explain this latter observation and obtain a link between fibrillar structure and its optical spectral properties, molecular dynamics (MD) methods are used to model the geometry and dynamics of assemblies containing repeating β-strands of Glu(n). A crystal-like model was adopted for the MD structure simulations. Infrared and VCD spectra for segments of MD modeled fibrillar geometries were first calculated using density functional theory (DFT), and then, those parameters were applied to larger structures by means of Cartesian coordinate transfer (CCT) of atomic tensors from the segments. The computations suggest the side chains exhibit residual conformational constraints, resulting in local coupling giving rise to non-negligible VCD intensity, albeit with an overall broad distribution. Calculated spectral distributions are qualitatively consistent with the experimental results but do differ in magnitude. The possibility of realistic modeling of vibrational spectra significantly broadens the potential for application of optical spectroscopies in structural studies of these aggregated biopolymers.

Iron modified structural and optical spectral properties of bismuth silicate glasses

Iron bismuth silicate glasses have been successfully synthesized by melt quenching technique. The amorphous nature of the glass samples is ascertained by the XRD patterns. The values of density, molar volume and crystalline volume have been measured and are found to decrease with increase in iron content. The glass transition temperature measured using Differential Scanning Calorimetry (DSC) also varies with increase in Fe2O3 content. The Raman and FTIR spectra of the studied glass system taken at room temperature suggests that Fe2O3 modifies the structure of bismuth silicate glasses and it acts as both network modifier as well as network former. Bismuth also plays the role of both network modifier (BiO6 octahedra) as well as network former (BiO3 pyramids) and SiO2 exists in SiO4 tetrahedral structural units with two non-bridging oxygens. The Hydrogenic excitonic model is found to be applicable to the studied glass compositions. The variation in Urbach energy value observed for the studied glass samples suggests the possibility of increase in the number of glass defects. The metallization criterion for the synthesized glass samples is determined and found to be in the range 0.30–0.38.

Theoretical investigations into spectral and non-linear optical properties of brucine and strychnine using density functional theory

The density functional theoretical (DFT) computations were performed at the B3LYP/6-311G++(d, p) level to calculate the equilibrium geometry, vibrational wave numbers, intensities, and various other molecular properties of brucine and strychnine, which were found in satisfactory agreement with the experimental data. The out-of-phase stretching modes of aromatic rings and carbonyl stretching modes in combination with CH stretching modes at stereogenic centers generate VCD signals, which are remarkably efficient configuration markers for these chiral molecular systems. NBOs analysis reveals that the large values of second order perturbation energy (47.24kcal/mol for brucine and 46.93kcal/mol for strychnine) confirms strong hyperconjugative interaction between the orbital containing the lone pair of electron of nitrogen and the neighboring CO antibonding orbital. The molecular electrostatic potential map of strychnine molecule, with no polar groups other than the lone keto group, shows less polarization, which accounts for its lower susceptibility towards electrophilic attack as compared to brucine.

Spectral optical properties and thermodynamic performance of reflective coatings in a mild climate zone

Abstract The article deals with optical properties and thermodynamic performance of reflective coatings applied on the vertical non-transparent external building surfaces. The starting point of this study comes from the fact, that there are various modifications of coatings, that their guaranteed properties can reduce heating and cooling loads with their application on external building surfaces. The paper presents the results of a comparative nature investigating the optical properties and thermodynamic performance of coatings containing hollow microspheres, as regards their impact upon the thermal properties of buildings envelope walls. The spectral laboratory and full scale outdoor testing methods were used and finally confronted in an experimental study. The tested samples were monitored by dynamic outdoor testing especially under clear sky in daytime and nocturnal conditions. Hollow microspheres coating and standard facing coating of acrylic base as a reference were analyzed primarily and confronted with materials of low-emissivity functions. As a result, the measured data demonstrate no differences in thermodynamic performance of the studied coating due to reducing heating loads especially for nocturnal conditions as well as their thermal emissivity parameters in comparison with the standard facade coating. On the other hand, coatings of hollow microspheres can contribute to the thermodynamic performance up to 5% in daytime conditions of predominantly insolated and weakly isolated walls due to reducing cooling loads in comparison with the standard facade coatings of an identical color shade.

Spectral Light Transmission Measure of Metal Screens for Glass Façades and Assessment of their Shading Potential

Metal mesh grids and perforated screens are used in new and renovated buildings as an external second skin for the building envelope; to enhance architecture design, to filter daylight and to reduce solar gains. Their effectiveness as shading devices depends on their geometry, texture and application.In the first part of the paper six types of shadings with similar transparencies, depending on geometry and openness factor of metal mesh grid and perforated screen, were investigated. Integrating sphere measurements were collected to obtain spectral optical properties of the shading devices. The optical properties were measured for incidence angles between normal and 60°with a step of 15°. The data collected were integrated to obtain visible and solar transmittance values in accordance with ISO 9050.In the second part of the paper a parametric study on spacing and thread dimension of metal mesh grids was done using Window 6.2 models to evaluate their shading potential, defining annual different shading profiles depending on shading geometry, latitude and orientation.A conventional office unit with a curtain wall façade with a metal mesh grid shading system was modeled in TRNSYS to evaluate the solar gain profiles and their effects on the energy balance of the office unit, under different weather conditions.

Nonlinear optical properties of laser synthesized Pt nanoparticles: saturable and reverse saturable absorption

In this paper, the spectral and nonlinear optical properties of a colloidal solution of platinum nanoparticles (Pt NPs) in water are presented. The Pt NPs were prepared by laser ablation of a Pt metallic target in distilled water using a 1064 nm high frequency Nd:YAG laser. The intensity-dependent nonlinear optical absorption and nonlinear refraction behaviors of the sample exposed to the 532 nm nanosecond laser pulses were investigated by applying the Z-scan technique. The saturated nonlinear absorption coefficient 5.4 × 10−7 cm W−1 was obtained in a saturation intensity of 1.8 × 107 W cm−2. The saturable absorption response of the Pt NPs was switched to the reverse saturable absorption in the higher laser intensities. The nonlinear refractive index that has a negative value was increased from −3.5 × 10−13 cm2 W−1 up to −15 × 10−13 cm2 W−1 by increasing the laser intensity.

Stretchable optical device with electrically tunable absorbance and fluorescence

We report the first proof-of-principle demonstration of a quantum dot (QD) doped dielectric elastomer actuator as a new stretchable optical device with electrically tunable optical absorbance and fluorescence. A polyacrylate dielectric elastomer film with carbon grease electrodes was loaded with organic-phase CdSe/CdS luminescent QDs. This study moved from the working hypothesis that electrical actuation of the QD doped elastomer varies the distances among each QD and its neighbours in the structure, modifying the volume and/or surface density of QDs, and thus leading to variable interactions among them, therefore changing the optical spectral properties of the QDs in the elastomer matrix. Experiments revealed that applied voltages increased the UV–vis absorbance, and decreased the photoluminescence (fluorescence) intensity and lifetimes. The former effect proved the working hypothesis, while the latter was not expected. The drop in photoluminescence intensity was found to be caused by the high fringe electric field generated by the actuator. The paper presents characterizations and discusses results, highlighting potentials and challenges of such systems.

The incidence of obscuration in active galactic nuclei

We study the incidence of nuclear obscuration on a complete sample of 1310 AGN selected on the basis of their rest-frame 2-10 keV X-ray flux from the XMM-COSMOS survey, in the redshift range 0.3<z<3.5. We classify the AGN as obscured or un-obscured on the basis of either the optical spectral properties and the overall SED or the shape of the X-ray spectrum. The two classifications agree in about 70% of the objects, and the remaining 30% can be further subdivided into two distinct classes: at low luminosities X-ray un-obscured AGN do not always show signs of broad lines or blue/UV continuum emission in their optical spectra, most likely due to galaxy dilution effects; at high luminosities broad line AGN may have absorbed X-ray spectra, which hints at an increased incidence of small-scale (sub-parsec) dust-free obscuration. We confirm that the fraction of obscured AGN is a decreasing function of the intrinsic X-ray luminosity, while the incidence of absorption shows significant evolution only for the most luminous AGN, which appear to be more commonly obscured at higher redshift. We find no significant difference between the mean stellar masses and star formation rates of obscured and un-obscured AGN hosts. We conclude that the physical state of the medium responsible for obscuration in AGN is complex, and mainly determined by the radiation environment (nuclear luminosity) in a small region enclosed within the gravitational sphere of influence of the central black hole, but is largely insensitive to the wider scale galactic conditions.

Relating aerosol absorption due to soot, organic carbon, and dust to emission sources determined from in-situ chemical measurements

Abstract. Estimating the aerosol contribution to the global or regional radiative forcing can take advantage of the relationship between the spectral aerosol optical properties and the size and chemical composition of aerosol. Long term global optical measurements from observational networks or satellites can be used in such studies. Using in-situ chemical mixing state measurements can help us to constrain the limitations of such estimates. In this study, the Absorption Ångström Exponent (AAE) and the Scattering Ångström Exponent (SAE) derived from 10 operational AERONET sites in California are combined for deducing chemical speciation based on wavelength dependence of the optical properties. In addition, in-situ optical properties and single particle chemical composition measured during three aircraft field campaigns in California between 2010 and 2011 are combined in order to validate the methodology used for the estimates of aerosol chemistry using spectral optical properties. Results from this study indicate a dominance of mixed types in the classification leading to an underestimation of the primary sources, however secondary sources are better classified. The distinction between carbonaceous aerosols from fossil fuel and biomass burning origins is not clear, since their optical properties are similar. On the other hand, knowledge of the aerosol sources in California from chemical studies help to identify other misclassification such as the dust contribution.

Evaluation of optical properties and thermal performances of different greenhouse covering materials

An inverse method was conducted to obtain the spectral optical properties of four greenhouse covering materials, (Low Density Polyethylene (LDPE), Polyolefin (PO), Polyvinylchloride (PVC) and Fused Silica Glass). Diffuse reflectance and transmittance of the covering materials were measured using spectrophotometric method; the complex index of refraction in the range between 0.22 and 25μm was deduced by inverse calculation using Radiative Element Method by Ray Emission Model (REM2). At longwave radiation, the optical constants of opaque glass material were found by utilizing Kramers–Kronig method resulting good correlation with results obtained by other investigations. A rigorous model for radiative heat transfer analysis to an agricultural greenhouse was developed. The greenhouse covering material was analyzed as a non-gray one-dimension plane-parallel medium subjected to solar and thermal irradiation using REM2. Specular reflectance and diffuse incident irradiation were treated at the boundary surfaces and absorption and emission were taken into account. Thermal performance was evaluated for the above mentioned covering materials.

Tubular daylighting devices. Part I: Development of an optical model (1415-RP)

Tubular daylighting devices are systems that collect and channel daylight from building roofs into deep interior spaces. To meet high standards of building energy efficiency and glare-free indoor environments, tubular daylighting device technologies have been rapidly and continuously evolving over the past two decades. However, this pace has been counteracted by a lack of reliable computer design tools. This article presents the development of analytical models to compute the optical characteristics (transmittance, reflectance, and layer absorptances) of various types of complex tubular daylighting devices New metrics for the optical and lighting performance are developed. The optical models are based on the ray-tracing technique, and account for the spectral (monochromatic) or broad-band optical properties of tubular daylighting device glazing panes. Experimental validation of these models is presented in an accompanying paper (Laouadi et al., 2013c).

Stable single-wavelength emission from fully chaotic microcavity lasers

We experimentally and numerically show that single-wavelength emission can be stably observed for a fully chaotic microcavity laser with a stadium shape under continuous wave condition. The emission pattern is asymmetric with respect to the symmetry axes of the laser cavity, and it cannot be explained by a single cavity mode. On the basis of numerical analysis, we interpret such a lasing as the result of frequency-locking interaction among several low-loss cavity modes. Moreover, we experimentally investigate the optical spectral properties of the laser under pulsed-pumping condition, and discuss the pulse-width dependence on the number of lasing modes.

Synthesis of Optically Uniform Glasses Containing Gold Nanoparticles: Spectral and Nonlinear Optical Properties

A method for preparing batches, melting, producing and modifying the structure of phosphate glass on a nanoscale by introducing gold nanoparticles were developed. Samples of glass with different content of phosphorus oxide were synthesized. The samples were heat-treated in a gradient furnace. Their physical, spectral and nonlinear optical properties were studied.

Infrared spectral evolution, elastic, optical and thermodynamic properties study on mechanically milled Ni0.5Zn0.5Fe2O4 spinel ferrite

This communication presents the effect of high energy ball milling induced strain and grain size reduction on Infrared spectral evolution, elastic, optical and thermodynamic properties of un-milled and 3, 6 and 9h. milled samples of spinel ferrite composition, Ni0.5Zn0.5Fe2O4, studied by means of X-ray powder diffractometry and infrared spectroscopy measurements at 300K. A simple approach is used for force constants determination and found to be quite satisfactory. The elastic moduli, elastic wave velocities, Debye temperature, threshold energy, molar heat capacity, refractive index, reflectivity, jump rate of charge carriers for the ferrites have been determined and they are found to vary in accordance with variation of lattice constant and milling induced strain as a function of milling time. No effect on the elastic parameters is observed due to milling induced grain size reduction. Elastic constants calculated using the relation, Ko=(60+490*SN) and heterogeneous metal mixture rule are in agreement with those determined from IR and XRD patterns analysis, validates the applicability of these approaches. The lattice energy for polycrystalline ferrite materials and single crystalline counterpart as well as electronic contribution to molar heat capacity has been calculated.

Strong thermal optical nonlinearity caused by CdSe nanoparticles synthesised in smectic ionic liquid crystal

Spectral and nonlinear optical properties of cadmium octanoate composites containing CdSe nanoparticles (NPs) have been studied by using optical absorption spectroscopy and laser scanning technique (Z-scan). CdSe NPs are chemically synthesised in thermotropic ionic liquid crystal (ILC) phase of cadmium octanoate which is used as nanoreactor. Anisotropic glassy nanocomposites are obtained by the rapid cooling of the ILC phase of nanocomposites to room temperature. The sizes of the CdSe NPs are determined from the absorption spectra. The thermo-optical nonlinearity of the new nanocomposites is characterised by extremely large value of the nonlinear refractive index, n2, under relatively low-powered CW laser irradiation. This nonlinearity is caused by (1) the efficient light-induced heating due to the CdSe NPs strong exciton absorption, and (2) consequent thermal dissipation, which in turn, produces the photoelastic tensions in the glassy smectic matrix.

Measurement of Solar Radiance Profiles With the Sun and Aureole Measurement System

Due to forward scattering of direct sunlight in the atmosphere, the circumsolar region closely surrounding the solar disk looks very bright. The radiation coming from this region, the circumsolar radiation, is in large part included in common direct normal irradiance (DNI) measurements, but only partially intercepted by the receivers of focusing collectors. This effect has to be considered in the performance analysis of concentrating collectors in order to avoid overestimation of the intercepted irradiance. At times, the overestimation reaches more than 10% for highly concentrating systems even for sky conditions with relevant DNI above 200 W/m2. The amount of circumsolar radiation varies strongly with time, location and sky conditions. However, no representative sunshape measurements exist for locations that are now of particular interest for concentrating solar power (CSP) or concentrating photovoltaics (CPV). A new sunshape measurement system is developed and analyzed in this study. The system consists of the sun and aureole measurement instrument (SAM), an AERONET sun photometer and postprocessing software. A measurement network is being created with the presented system. The uncertainty of this system is significantly lower than what was obtained with previous devices. In addition, the spectral optical properties of circumsolar radiation are determined. As a result, the necessary information for CSP and CPV systems, and a basis for the development of modeling methods for circumsolar radiation, can now be achieved.

Ultraviolet and infrared absorption spectra of Cr2O3 doped – Sodium metaphosphate, lead metaphosphate and zinc metaphosphate glasses and effects of gamma irradiation: A comparative study

The effects of gamma irradiation on spectral properties of Cr2O3-doped phosphate glasses of three varieties, namely sodium metaphosphate, lead metaphosphate and zinc metaphosphate have been investigated. Optical spectra of the undoped samples reveal strong UV absorption bands which are attributed to the presence of trace iron impurities in both the sodium and zinc phosphate glasses while the lead phosphate glass exhibits broad UV near visible bands due to combined absorption of both trace iron impurities and divalent lead ions. The effect of chromium oxide content has been investigated. The three different Cr2O3-doped phosphate glasses reveal spectral visible bands varying in their position and intensity and splitting due to the different field strengths of the Na+, Pb2+, Zn2+ cations, together with the way they are housed in the network and their effects on the polarisability of neighboring oxygens ligands. The effects of gamma irradiation on the optical spectral properties of the various glasses have been compared. The different effects for lead and zinc phosphate are related to the ability of Pb2+, and Zn2+ to form additional structural units causing stability of the network towards gamma irradiation. Also, the introduction of the transition metal chromium ions reveals some shielding behavior towards irradiation. Infrared absorption spectra of the three different base phosphate glasses show characteristic vibrations due to various phosphate groups depending on the type of glass and Cr2O3 is observed to slightly affect the IR spectra. Gamma irradiation causes minor variations in some of the intensities of the IR spectra but the main characteristic bands due to phosphate groups remain in their number and position.