Combined Optical Methods Research Articles

Diverse and controllable soliton molecules in a fiber laser based on PbBi4Te7 saturable absorber

With the advancement of optical communication, optical encoding, and optical storage technologies, the demand for tunable mode-locked fiber lasers (MLFL) with soliton molecules is continuously increasing. The novel ternary two-dimensional topological insulator PbBi4Te7 provides an effective pathway for realizing tunable soliton molecules in MLFL. This study employs a combined liquid phase exfoliation (LPE) and optical deposition methods (ODMs) to prepare PbBi4Te7 saturable absorbers (SAs). In the same MLFL, conventional soliton (CS), controllable soliton molecules with adjustable soliton numbers and intervals, as well as multi-soliton complexes are obtained. Among them, a fundamental frequency CS pulse at 22.778 MHz with a signal-to-noise ratio (SNR) of up to 71 dB is achieved. By adjusting the pump power, 2nd-, 3rd-, 4th-, 9th-, and 11th-order soliton molecules were obtained. By tuning the polarization controller (PC), switching of the soliton interval for 2nd-, 3rd-, and 4th-order soliton molecules was achieved. Additionally, we obtained three unequally spaced multi-soliton complexes: 2 + 1 soliton molecule, 2 + 2 soliton molecule complex and 2 + 2 + 1 soliton molecule complex. The results indicate that PbBi4Te7-SA exhibits outstanding nonlinear optical performance.

Statistical distributions for modeling mineral liberation

Using the algorithm and the results of laboratory studies on grinding of loparite ores from the Lovozero deposit in a ball and rod mill, simulation grinding models were designed based on the transformation of a discrete function of the density distribution of outputs of mineral particle size classes. The model’s adequacy was quantitatively analysed carried out by calculating the determination coefficient without taking into account the constant component of the distribution; for a qualitative assessment of the result the authors used the Cheddock scale. The authors studied the minerals disintegration at ball and rod grinding with the following verification of the proposed algorithm. To identify the distribution of loparite by size classes in the initial ore samples and in the samples obtained in the disintegration taking place at different productivity, the X-ray diffraction analysis and the combined (weight, optical and geometric) methods were used.

Nanoelectrochemistry Concepts in Desalination Energy Harvesting and Analysis

This talk will provide an overview of the research in GWang’s group at Georgia State centered around the electrochemical processes at the nanometer scale. Three examples will be discussed in two research topics. The first is the development of new analytical method/toolbox for actively controlled nucleation and crystal growth. By controlling charge transport through a single nanopore, a single crystal is synthesized while the whole process is monitored by combined electroanalytical and optical methods. In the second topic, ion transport through a single asymmetric nanopipette is studied by experiments and simulation. The solution-substrate interface confined inside the conical nanopore is viewed as structurally-defined unit elements in ensemble porous membrane/electrode/materials. The surface electric field direction is separated from the through-transport ion flux which affects both the structure and dynamics of the electrical double layer (EDL). Selective and efficient transport of ions is the fundamental process in 1. the desalination with energy input; and a retrospective process of 2. energy harvesting from salinity when fresh and brackish/sea water mix. Novel time-dependent current-potential features are captured in electrochemical experiments due to the polarization of the nanoscale EDL or selective transport of ions. Characteristic signatures include a non-zero cross point in I-V curves separating pinched hysteresis loops. Finite element simulations by solving the Poisson, Nernst-Planck and Navier-Stokes equations reveal the respective transport of cations and anions driven by migration, diffusion and electroosmotic flow. The transport selectivity and efficiency under time- and space- confined conditions provide fundamental insights to better transport related applications such as desalination separation and energy harvesting from salinity gradients. Financial supports from NSF (CHE-1610616) and DOE (DE-SC0019043) are acknowledged.

Assessment of cardiac-driven liver movements with filtered harmonic phase image representation, optical flow quantification, and motion amplification.

To characterize cardiac-driven liver movements using a harmonic phase image representation (HARP) with an optical flow quantification and motion amplification method. The method was applied to define the cardiac trigger delay providing minimal signal losses in liver DWI images. The 16-s breath-hold balanced-SSFP time resolved 20 images/s were acquired at 3T in coronal and sagittal orientations. A peripheral pulse unit signal was recorded. Cardiac-triggered DWI images were acquired after different peripheral pulse unit delays. A steerable pyramid decomposition with multiple orientations and spatial frequencies was applied. The liver motion field-map was derived from temporal variations of the HARP representation filtered around the cardiac frequency. Liver displacements were quantified with an optical flow method; moreover the right liver motion was amplified. The largest displacements were observed in the left liver (feet-head:3.70 ± 1.06 mm; anterior-posterior: 2.35 ± 0.51 mm). Displacements were statistically significantly weaker in the middle right liver (0.47 ± 0.11 mm; P = 0.0156). The average error was 0.013 ± 0.022 mm (coronal plane) and 0.021 ± 0.041 mm (sagittal plane). The velocity field demonstrated opposing movements of the right liver extremities during the cardiac cycle. DWI signal loss was minimized in regions and instants of smallest amplitude of both velocity and velocity gradient. Cardiac-driven liver movements were quantified with combined cardiac frequency-filtered HARP and optical flow methods. A motion phase opposition between right liver extremities was demonstrated. Displacement amplitude and velocity were larger in the left liver especially along the vertical direction. Motion amplification visually emphasized cardiac-driven right liver displacements. The optimal cardiac timing minimizing signal loss in liver DWI images was derived.

Dark Field Scattering Spectroelectrochemistry of Single Au Nanoparticles at Transparent Planar and Micro-Sized Electrodes

Boron dipyrromethene (BODIPY) molecules with donor-acceptor configurations are of great interests for harvesting and converting solar energy in a solar cell. Au nanoparticles have been applied to enhance solar energy harvesting and conversion efficiency of organic solar cells because of their surface plasmon properties for increasing light absorption cross-section of an organic dye. Electrochemical properties of single BODIPY dyes and plasmonic Au nanoparticles (NPs) are studied using combined optical and electrochemical methods to reveal their structure-function relationship at the nanometer scale. Our study shows a heterogeneous half redox potential distribution for the BODIPY molecules embedded in polystyrene film because of the heterogeneity in their charge transfer rates. Single molecules adsorbed onto a TiO2 surface with ordered nanostructures show surprising fluorescence blinking activity with the shortest ON duration time in comparison to bare glass and indium-doped tin oxide (ITO) surfaces. Dark field scattering (DFS), photoluminescence (PL), and electrogenerated chemiluminescence (ECL) are used to probe local redox reactions of single Au nanoparticles at transparent planar and micro-sized electrode. Our study shows that these optical responses at individual plasmonic NPs are strongly dependent on particle size, and are affected by the local chemical and charge transfer environment of the NPs.

Electrochemical Spectroscopic Methods for the Fine Band Gap Electronic Structure Mapping in Organic Semiconductors

Functionality of organic photonic devices is markedly influenced by the electronic band structure of the used materials. An easy and quick determination of the density of states function (DOS) in the whole energy range from HOMO to LUMO, including the presence of defect states in the band gap, is a prerequisite to a successful design of photonic devices. In this study we present the fine band gap electronic structure mapping in P3HT with two electrochemical spectroscopic methods: the energy-resolved electrochemical impedance spectroscopy (ER-EIS) and the kinetic sensitive voltcoulometry (VCM). We showed that the P3HT exposition to air results in the change of light-induced polaron states in the band gap. The electrochemically measured data are compared with those from the literature, obtained with combined optical spectroscopic methods, electrical methods, or first-principles calculations. The ER-EIS method has been shown as capable of providing valuable information on the DOS in the whole energy range fr...

Comparative analysis of combined spectral and optical tomography methods for detection of skin and lung cancers.

Malignant skin tumors of different types were studied in vivo using optical coherence tomography (OCT), backscattering (BS), and Raman spectroscopy (RS). A multimodal method is proposed for early cancer detection based on complex analysis of OCT images by their relative alteration of scattered-radiation spectral intensities between malignant and healthy tissues. An increase in average accuracy of diagnosis was observed for a variety of cancer types (9% sensitivity, 8% specificity) by a multimodal RS-BS-OCT system in comparison with any of the three methods used separately. The proposed approach equalizes the processing rates for all methods and allows for simultaneous imaging and classification of tumors.

Optical Study of Nanotube and Coronene Composites

A novel nanomaterial, graphene nanoribbons encapsulated inside single-walled carbon nanotubes (GNR@SWNT), was studied by combined optical methods. This nanomaterial was found to have a bright photo ...

Application of Optical Methods in Blood Studies upon Evaluation of Severity Rate of Diffuse Liver Pathology

Possible early diagnostic application of optical methods (dielectrophoresis, spectral and imaging ellipsometry, Fourier-transform infrared spectroscopy, Raman spectroscopy) in studies of red blood cells and serum of patients with diffuse liver disease with varying degrees of fibrosis has been evaluated. Application of combined optical methods was confirmed to significantly improve the performance of sensitivity, specificity, and accuracy index as well as to achieve the reliable results in diagnosis of both severe fibrosis and slight ulterior liver fibrosis. Identified diagnostic potential of optical methods can be effectively utilized in noninvasive screening evaluation of stages of diffuse liver disease of various geneses.

Physical Properties, Chemical Composition, and Cloud Forming Potential of Particulate Emissions from a Marine Diesel Engine at Various Load Conditions

Particulate matter (PM) emissions from one serial 4-stroke medium-speed marine diesel engine were measured for load conditions from 10% to 110% in test rig studies using heavy fuel oil (HFO). Testing the engine across its entire load range permitted the scaling of exhaust PM properties with load. Emission factors for particle number, particle mass, and chemical compounds were determined. The potential of particles to form cloud droplets (cloud condensation nuclei, CCN) was calculated from chemical composition and particle size. Number emission factors are (3.43 +/- 1.26) x 10(16) (kg fuel)(-1) at 85-110% load and (1.06 +/- 0.10) x 10(16) (kg fuel)(-1) at 10% load. CCN emission factors of 1-6 x 10(14) (kg fuel)(-1) are at the lower bound of data reported in the literature. From combined thermal and optical methods, black carbon (BC) emission factors of 40-60 mg/(kg fuel) were determined for 85-100% load and 370 mg/(kg fuel) for 10% load. The engine load dependence of the conversion efficiency for fuel sulfur into sulfate of (1.08 +/- 0.15)% at engine idle to (3.85 +/- 0.41)% at cruise may serve as input to global emission calculations for various load conditions.

High-Resolution Facies Analyses of Mudstones: Implications for Paleoenvironmental and Sequence Stratigraphic Interpretations of Offshore Ancient Mud-Dominated Successions

Abstract The extent of lithofacies variability in fine-grained sedimentary rocks is very poorly known in comparison to that present in coarser grained clastic and carbonate successions. The absence of this information means that sediments present on continental shelves are rarely considered as integrated systems because fine-grained facies (such as shales) are mostly excluded from sophisticated, regional facies models. To shed light upon lithofacies and grain size in shale-dominated successions, so that they can be incorporated into shelf-wide depositional models, the Blackhawk Formation of the Mancos Shale (Campanian age), exposed in the Book Cliffs, Utah was investigated using combined field, whole-rock geochemical, optical, and electron optical methods. These sediments show systematic grain-size variations, are intensely bioturbated, and composed predominantly of detrital clays (mainly dioctahedral micas), quartz, and feldspar with minor pyrite and organic matter. They are organized into very thin (< 10 mm), upward-fining, genetic beds; they exhibit both systematic lateral (103 m scale), and vertical (10−2 to 100 m scales) lithofacies variability. Preferentially cemented units occur close to sequence boundaries (unconformities). These cemented units typically contain a very different detrital assemblage (including significant quantities of chlorite) from the rest of the succession and are located close to levels where there are marked stacking-pattern discontinuities. Overall, lithofacies variability is interpreted in terms of deposition occurring on an oxic continental shelf, with the coarser-grained facies being deposited in proximal settings (offshore-transition zone), in contrast to the finer-grained units that were deposited in more distal environments (offshore zone). Storms are interpreted to have been the dominant mechanism dispersing the sediment. Once deposited, the surface layers of the sediment were intensely reworked by burrowing organisms. Preferential preservation of ichnogenera from mid- and lower tiers suggest that the depositional environment was energetic and erosion commonly removed the surface sediment layers, prior to deposition of thin (10−2 m) storm beds. The larger scale (100 m) upward-coarsening units that are composed of stacked beds, are interpreted to be parasequences. Preferential cementation, at levels where large-scale stacking patterns change, is interpreted to occur at horizons where there were breaks in sediment accumulation, and bacterial metabolic processes were able to supply sufficient solutes to fill uncompacted pore space with cement. The presence of a very different detrital assemblage in these units suggests that winnowing occurred. Despite their relatively innocuous appearance in the field, these surfaces are likely to be significant bypass surfaces, over which sediment was delivered to the deeper parts of the basin during times of relative lowstand of sea level.

Radiation‐induced defects in chalcogenide glasses characterized by combined optical spectroscopy, XPS and PALS methods

AbstractTemperature‐dependent optical absorption spectroscopy, high‐resolution X‐ray photoelectron spectroscopy and positron annihilation lifetimes spectroscopy are utilized to understand radiation‐induced changes in Ge–Sb–S chalcogenide glasses. Theoretically predicted topological scheme of γ‐induced coordination defect formation in stoichiometric Ge23.5Sb11.8S64.7 glass composition is supported by these measurements. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Polymer thin film photodegradation and photochemical crosslinking: FT-IR imaging, evanescent waveguide spectroscopy, and QCM investigations

Photodegradation and photocrosslinking of benzophenone blended polystyrene (PS) thin films were investigated primarily using Fourier transform infrared (FT-IR) imaging, evanescent waveguide spectroscopy (WS), and quartz crystal microbalance (QCM) methods. The main objective is to observe the changes (spectral and chemical) indicative of these competitive processes in an ultrathin polymer film. This also serves as a model study in the application of combined spectroscopic, optical, and acoustic methods towards understanding crosslinking and degradation phenomena within the same time frame of observation. To induce photocrosslinking, 1,12-dodecanediylbis(oxy-4,1-phenylene)] [bis[phenylmethanone] (2BP12), a small molecule with two benzophenone groups, was blended with PS in solution, spincast onto glass and silicon substrates, and irradiated with ultraviolet light. Photodegradation and benzophenone-mediated crosslinking were observed both directly via functional group spectroscopies and indirectly via their effects on thin film surface properties and morphologies. Atomic force microscopy (AFM) and QCM were used to elucidate local morphology change and mass-uptake kinetics in the presence of O 2 in air, respectively. All results correlated well with the two photoprocesses occurring simultaneously and competitively on these films with the refractive index, thickness, and mass change differing with the presence of 2BP12. Crosslinking was observed to cause an increase in thickness while photodegradation gave a decrease. Both processes resulted in an increase in the refractive index and mass. While various methods have separately identified these observations, this is the first instance that the in situ chemical, optical, and structural dimensionality of the photodegradation and photocrosslinking phenomena in a thin polymer film is correlated within the same time frame of observation.

Some observations on the effect of the trivalent counterion Al3+ to the self-assembly of sodium dodecyl sulphate in water

The phase behavior and phase structure of the SDS (sodium dodecyl sulfate)–Al(NO3)3–H2O system have been studied by combined NMR, SAXS, cryo-TEM and optical polarization microscopy methods at 298K (25°C) and 311K (38°C). At 298K, the micellar solution phase of the binary system SDS–water is not capable of solubilising substantial amount of Al(NO3)3 salt, and at a certain substoichiometric molar ratio Al(NO3)3/SDS, the solution phase coexists with a precipitate. When the concentration of the salt exceeds 5wt.%, the precipitate is completely solubilised giving rise to a concentrated micellar phase that dominates the phase diagram. At high concentration of Al(NO3)3 (30–40wt.%), a vesicle phase is formed at low (maximum 10wt.%) SDS content. On warming to 311K, the vesicle region expanded, by converting the hydrated surfactant crystals to a lamellar liquid crystalline phase, around the concentrated micellar phase, with a narrow width towards the SDS–H2O axis (up to 43.5wt.% SDS and 3wt.% Al(NO3)3). The lamellar phase coexists with both hexagonal and micellar phases with appropriate multiphase regions. The optical- and cryo-transmission electron microscopy images show the presence of unilamellar vesicles and the liquid crystalline phases are characterized by 2H NMR quadrupolar splitting and following the liquid crystalline texture by optical microscopy techniques. The NMR self-diffusion measurements, together with the cryo-TEM micrographs, identified the long worm-like micelles in the redissolution area.

Energetic budget on an evaporating monodisperse droplet stream using combined optical methods: Evaluation of the convective heat transfer

Aerothermal properties in a fuel spray is a central problem in the field of the design of the combustion chambers of automotive engines, turbojets or rocket engines. Heat and mass transfer models are necessary in the predictive calculation schemes used by the motorists. Reliable experimental data must be obtained for both the validation and development of new physical models linked to heat transfer and evaporation in sprays, where aerodynamic interactions have a key role. This paper proposes an experimental study of the energetic budget of a monodisperse ethanol droplet stream, injected in the thermal boundary layer of a vertical heated plate. The droplet size reduction is measured using a light scattering technique (interferential method) in order to characterize the evaporation, as the droplet mean temperature is monitored using the two colors laser-induced fluorescence technique. The convection heat transfer coefficient and the Nusselt number are inferred from the overall energetic budget, as a function of the inter-droplet distance, characterizing the interaction regime. The results are compared to physical models combined with numerical simulations available in the literature, for moving, evaporating isolated droplets and for three droplets arrangement in linear stream.

Mass transfer properties in a grid generated turbulent flow: some experimental investigations about the concept of turbulent diffusivity

This paper is devoted to the analysis of the mass transfer properties in a grid generated turbulent flow. The closure of the transport equation of the turbulent mass flux has been experimentally investigated. Two combined optical non-intrusive methods, the laser-induced fluorescence and the laser Doppler velocimetry have been used in order to measure simultaneously and instantaneously the concentration of a passive contaminant and the velocity of the flow. It has been demonstrated that the approximation production = pressure scrambling is valid over the major part of the flowfield. A model for the pressure scrambling term has been analysed in order to define a turbulent diffusivity concept.

Experimental investigation of mass transfer in a grid-generated turbulent flow using combined optical methods

The aim of this paper is to provide some significant experimental results for the mass diffusion process from a point source in a quasi-isotropic homogeneous turbulent field generated by means of a grid. Experimental data for the mean, the fluctuating concentration fields, and the turbulent mass flux, which is the cross-correlation between concentration and velocity, are provided. Two combined optical non-intrusive methods, laser-induced fluorescence and laser Doppler velocimetry, have been used to measure simultaneously and instantaneously the concentration of the passive contaminant and the velocity of the flow. The experimental results are compared with a theoretical development, including the concept of turbulent diffusivity. An experimental determination of the turbulent diffusivity is also performed.

On-line remote prediction of gasoline properties by combined optical methods

On-line prediction of 10 gasoline properties, such as research and motor octane numbers, vapor pressure, API gravity, aromatic contents, etc., are carried out on-line by a remotely operated detector coupled to the main control unit by communication optical fibers. This information is of considerable importance since it is needed for process monitoring and for the preparation of final petrochemical products of well defined properties. The currently available spectroscopic methods for predicting gasoline properties, which are based on near infrared (NIR) (and recently on Fourier transform infrared (FTIR) spectrometry) coupled with chemometric algorithms, provide limited performance (e.g. 0.4 standard error of prediction (SEP), for octane number). We propose an improvement of the performance by applying combined optical methods. In this study we combine on-line information from a short-wave NIR photodiode array spectrometer (700–1000 nm) with laser induced fluorescence (LIF) spectra obtained with a PC-plugged in linear CCD spectrometer. UV excitation is performed by harmonics of a compact and low-cost Nd:YAG laser, and the system is remotely operated through optical fibers. A comparison between the octane number predictions by NIR spectrometry and by LIF from third and fourth harmonics, is provided. It is shown that the addition of the fluorescence information improves octane number prediction (<0.2 SEP). These two setups (NIR and LIF) can be combined into one integrated system, based on common optical fibers and detector.

Heat Transfer in Excimer Laser Melting of Thin Polysilicon Layers

A pulsed KrF excimer laser with nanosecond pulse duration is used for surface melting of thin polycrystalline silicon films. The velocity of the moving phase boundary during melting and solidification, the maximum melting depth, as well as the melting duration are experimentally determined by combined optical and electrical methods. A melting interface tracking model is used to calculate the melt front propagation and the transient temperature field in the semiconductor. A phase-change model, which allows the occurrence of melting and solidification at temperatures other than the equilibrium melting temperature, is employed in the numerical calculation. The effect of interfacial superheating/undercooling is discussed.