Standard Wavelength Research Articles

Bassoite, SrV3O7·4H2O, a new mineral from Molinello mine, Val Graveglia, eastern Liguria, Italy

AbstractBassoite, ideally SrV3O7·4H2O, is a new mineral from the Molinello manganese mine, Val Graveglia. eastern Liguria, northern Apennines, Italy. It occurs as black euhedral to subhedral grains up to 400 urn across, closely associated with rhodonite, quartz and braunite. Bassoite is opaque with a sub-metallic lustre and a black streak. It is brittle and neither fracture nor cleavage was observed; the Vickers micro-hardness (VHN100) is 150 kg/mm (range 142—165; corresponding to a Mohs hardness of 4—41/2). The calculated density is 2.940 g/cm3 (on the basis of the empirical formula and X-ray single-crystal data). Bassoite is weakly bireflectant and very weakly pleochroic from grey to a dark green. Internal reflections are absent. The mineral is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) for the four standard COM wavelengths are 18.5%, 19.0% (471.1 nm); 17.2%, 17.8% (548.3 nm); 16.8%, 17.5% (586.6 nm) and 16.2%, 16.8% (652.3 nm), respectively.Bassoite is monoclinic, space group P21/m, with unit-cell parameters: a = 5.313(3) Å, b = 10.495(3) Å, c = 8.568(4) Å, β = 91.14(5)°, V= 477.7(4) Å3, a:b:c = 0.506:1:0.816, and Z = 2. The crystal structure was refined to R1 = 0.0209 for 1148 reflections with Fo > 4σ(Fo) and it consists of layers of VO5 pyramids (with vanadium in the tetravalent state) pointing up and down alternately with Sr between the layers (in nine-fold coordination). The nine most intense X-ray powder-diffraction lines [d in Å (I/I0) (hkt)] are: 8.5663 (100) (001); 6.6363 (14) (011); 3.4399 (14) (1̄21); 3.4049 (17) (121); 2.8339 (15) (1̄22); 2.7949 (11) (122); 2.6550 (15) (200); 2.6237 (11) (040) and 1.8666 (15) (240). Electron microprobe analyses produce a chemical formula (Sr0.97Ca0.02Na0.01)V3.00O74H20, on the basis of 2(Sr+Ca+Na) = 1, taking the results of the structure refinement into account. The presence of water molecules was confirmed by micro-Raman spectroscopy. The name honours Riccardo Basso (b. 1947), full professor of Mineralogy and Crystallography at the University of Genova. The new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA (2011-028).

Understanding the behaviour of X-shooter via the application of a physical model

We show how traditional instrument quality control trending can be augmented by the use of a physical instrument model. The ESO VLT archive contains a detailed record of instrument diagnostics and calibration parameters while ESO quality control monitors changes in critical parameters. The physical model allows changes in positions, orientations and other physical properties of a spectrograph to be determined from standard wavelength calibration exposures via an optimisation process that seeks the physical model parameters that best reproduce the calibration features in the data. We introduce physical model parameters to the quality control monitoring. When applying this technique to archived calibration exposures, we find that the results are sensitive to the combination of parameters open to the optimisation process. Therefore we determine the most favourable set of physical parameters to optimise for each arm. We then show correlations between several physical parameters and instrument temperature sensor readings and epoch. In addition we find clear discontinuities in some physical parameter values that correspond to known maintenance events.

Focus on lasers and imaging

Focus on lasers and imaging

Icosahedrite, Al63Cu24Fe13, the first natural quasicrystal

Icosahedrite, ideally Al63Cu24Fe13, is a new mineral from the Khatyrka River, southeastern Chukhotka, Russia. It occurs as dark gray-black anhedral to subhedral grains up to 100 µm across, closely associated with spinel, diopside, forsterite, nepheline, sodalite, corundum, stishovite, khatyrkite, cupalite, and an unnamed phase of composition AlCuFe. Icosahedrite is opaque with a metallic luster, possesses a gray streak, and is brittle with an uneven fracture. The density could not be determined. For quasicrystals, by definition, the structure is not reducible to a single three-dimensional unit cell, so neither cell parameters nor Z can be given. In plane-polarized incident light, icosahedrite exhibits neither bireflectance nor pleochroism. Between crossed polars, it is isotropic. Reflectance percentages (Rmin = Rmax) for the four standard COM wavelengths are 62.3 (471.1 nm), 60.6 (548.3 nm), 58.1 (586.6 nm), and 56.0 (652.3 nm), respectively. The X-ray powder pattern was indexed on the basis of six integer indices, as conventionally used with quasicrystals, where the lattice parameter (in six-dimensional notation) is measured to be a6D = 12.64 A, with probable space group Fm3 5. The four strongest X-ray powder-diffraction lines [d in A (I/I0) (n1,n2,n3,n4,n5,n6)] are: 2.006 (100) (420 042), 2.108 (90) (422 222), 1.238 (30) (604 064), and 3.41 (25) (311 111). Average results of 34 electron-microprobe analyses gave, on the basis of total atoms = 100, the formula Al63.11Cu24.02Fe12.78Si0.03Co0.01Ca0.01Zn0.01Cr0.02Cl0.01. The simplified formula is Al63Cu24Fe13, which requires the mass fractions Al 43.02, Cu 38.60, Fe 18.38, total 100.00 wt%. The new mineral is named for the icosahedral symmetry of its internal atomic structure, as observed in its diffraction pattern. Both the new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA (2010-042).

A New Approach to Quantify Na-Fluorescein (Uranine) in Acid Mine Waters

Sodium fluorescein (uranine) is one of the most popular fluorescent dyes for tracer experiments due to its chemical properties, low detection limits and low costs. As a limiting factor, it is generally assumed that Na-fluorescein cannot be properly detected under acid conditions because of weak fluorescence intensities at the standard excitation wavelength (490 nm). This laboratory study introduces a method to quantify Na-fluorescein in low pH waters without having to raise pH to alkaline conditions, which spares the time- and cost-intensive filtration of hydroxide precipitates prior to analysis. It was applied for recovery tests in water samples from five mining sites in Germany. These were buffered to pH 1.5 where Na-fluorescein shows a second fluorescence intensity maximum at an excitation wavelength of 438 nm. The method had satisfying recovery rates although, as expected, a higher detection limit compared to standard wavelength and pH. High Fe contents in the waters are a limiting factor—the impact of increasing Fe concentrations at a constant dye spike was evaluated and yielded a distinct negative trend between Fe and detected Na-fluorescein, probably due to Fe-fluorescein complexation. However, good recovery can be expected in mine waters with up to ≈100 mg L−1 Fe. The method of standard addition offers a potential calculative solution for higher Fe concentrations, resulting in significantly better Na-fluorescein recovery rates, compared to direct measurements. The method introduced here represents a promising approach for improving Na-fluorescein applicability in acid environments.

Split Bull’s Eye Shaped Aluminum Antenna for Plasmon-Enhanced Nanometer Scale Germanium Photodetector

Bull's eye antennas are capable of efficiently collecting and concentrating optical signals into an ultrasmall area, offering an excellent solution to break the bottleneck between speed and photoresponse in subwavelength photodetectors. Here, we exploit the idea of split bull's eye antenna for a nanometer germanium photodetector operating at a standard communication wavelength of 1310 nm. The nontraditional plasmonic metal aluminum has been implemented in the resonant antenna structure fabricated by standard complementary metal-oxide-semiconductor (CMOS) processing. A significant enhancement in photoresponse could be achieved over the conventional bull's eye scheme due to an increased optical near-field in the active region. Moreover, with this novel antenna design the effective grating area could be significantly reduced without sacrificing device performance. This work paves the way for the future development of low-cost, high-density, and high-speed CMOS-compatible germanium-based optoelectronic devices.

Quantification of dsDNA using the Hitachi F-7000 Fluorescence Spectrophotometer and PicoGreen Dye

Quantification of DNA, especially in small concentrations, is an important task with a wide range of biological applications including standard molecular biology assays such as synthesis and purification of DNA, diagnostic applications such as quantification of DNA amplification products, and detection of DNA molecules in drug preparations. During this video we will demonstrate the capability of the Hitachi F-7000 Fluorescence Spectrophotometer equipped with a Micro Plate Reader accessory to perform dsDNA quantification using Molecular Probes Quant-it PicoGreen dye reagent kit. The F-7000 Fluorescence Spectrophotometer offers high sensitivity and high speed measurements. It is a highly flexible system capable of measuring fluorescence, luminescence, and phosphorescence. Several measuring modes are available, including wavelength scan, time scan, photometry and 3-D scan measurement. The spectrophotometer has sensitivity in the range of 50 picomoles of fluorescein when using a 300 μL sample volume in the microplate, and is capable of measuring scan speeds of 60,000 nm/minute. It also has a wide dynamic range of up to 5 orders of magnitude which allows for the use of calibration curves over a wide range of concentrations. The optical system uses all reflective optics for maximum energy and sensitivity. The standard wavelength range is 200 to 750 nm, and can be extended to 900 nm when using one of the optional near infrared photomultipliers. The system allows optional temperature control for the plate reader from 5 to 60 degrees Celsius using an optional external temperature controlled liquid circulator. The microplate reader allows for the use of 96 well microplates, and the measuring speed for 96 wells is less than 60 seconds when using the kinetics mode. Software controls for the F-7000 and Microplate Reader are also highly flexible. Samples may be set in either column or row formats, and any combination of wells may be chosen for sample measurements. This allows for optimal utilization of the microplate. Additionally, the software allows importing micro plate sample configurations created in Excel and saved in comma separated values, or "csv" format. Microplate measuring configurations can be saved and recalled by the software for convenience and increased productivity. Data results can be output to a standard report, to Excel, or to an optional Report Generator Program.

Quantification of dsDNA using the Hitachi F-7000 Fluorescence Spectrophotometer and PicoGreen Dye

Quantification of DNA, especially in small concentrations, is an important task with a wide range of biological applications including standard molecular biology assays such as synthesis and purification of DNA, diagnostic applications such as quantification of DNA amplification products, and detection of DNA molecules in drug preparations. During this video we will demonstrate the capability of the Hitachi F-7000 Fluorescence Spectrophotometer equipped with a Micro Plate Reader accessory to perform dsDNA quantification using Molecular Probes Quant-it PicoGreen dye reagent kit. The F-7000 Fluorescence Spectrophotometer offers high sensitivity and high speed measurements. It is a highly flexible system capable of measuring fluorescence, luminescence, and phosphorescence. Several measuring modes are available, including wavelength scan, time scan, photometry and 3-D scan measurement. The spectrophotometer has sensitivity in the range of 50 picomoles of fluorescein when using a 300 μL sample volume in the microplate, and is capable of measuring scan speeds of 60,000 nm/minute. It also has a wide dynamic range of up to 5 orders of magnitude which allows for the use of calibration curves over a wide range of concentrations. The optical system uses all reflective optics for maximum energy and sensitivity. The standard wavelength range is 200 to 750 nm, and can be extended to 900 nm when using one of the optional near infrared photomultipliers. The system allows optional temperature control for the plate reader from 5 to 60 degrees Celsius using an optional external temperature controlled liquid circulator. The microplate reader allows for the use of 96 well microplates, and the measuring speed for 96 wells is less than 60 seconds when using the kinetics mode. Software controls for the F-7000 and Microplate Reader are also highly flexible. Samples may be set in either column or row formats, and any combination of wells may be chosen for sample measurements. This allows for optimal utilization of the microplate. Additionally, the software allows importing micro plate sample configurations created in Excel and saved in comma separated values, or "csv" format. Microplate measuring configurations can be saved and recalled by the software for convenience and increased productivity. Data results can be output to a standard report, to Excel, or to an optional Report Generator Program.

High-resolution spectrally-resolved fiber optic sensor interrogation system based on a standard DWDM laser module

This paper presents a spectrally-resolved integration system suitable for the reading of Bragg grating, all-fiber Fabry-Perot, and similar spectrally-resolved fiber-optic sensors. This system is based on a standard telecommunication dense wavelength division multiplexing transmission module that contains a distributed feedback laser diode and a wavelength locker. Besides the transmission module, only a few additional opto-electronic components were needed to build an experimental interrogation system that demonstrated over a 2 nm wide wavelength interrogation range, and a 1 pm wavelength resolution. When the system was combined with a typical Bragg grating sensor, a strain resolution of 1 με and temperature resolution of 0.1 °C were demonstrated experimentally. The proposed interrogation system relies entirely on Telecordia standard compliant photonic components and can thus be straightforwardly qualified for use within the range of demanding applications.

A novel laser wavelength meter based on the measurement of synthetic wavelength

The accuracy of the current wavelength meter using optical interferometry is limited by the numbers of fringe counted. To solve this problem, a novel laser wavelength meter based on the measurement of synthetic wavelength is proposed. The unknown wavelength is obtained by measuring the value of synthetic wavelength produced by the unknown and reference wavelengths, and half of this value corresponds to 2π variation of the phase difference between the interference signals of the unknown and reference wavelengths. The optical configuration of the wavelength meter is designed and the measurement principle is analyzed theoretically. To verify its feasibility, three helium-neon lasers' wavelengths were determined experimentally, and a relative uncertainty on the unknown wavelength of the order of 10(-8) was realized. Accuracy analysis shows that this wavelength meter has the advantage of high accuracy when the unknown wavelength is around the standard laser wavelength recommended by CIPM.

Assessing the optical changes in dissolved organic matter in humic lakes by spectral slope distributions

The impact of photodegradation and mixing processes on the optical properties of dissolved organic matter (DOM) was examined using a distribution of absorption spectral slopes and fluorescence measurements in two Argentine lakes. By examining the variability of the absorption spectral slopes throughout the ultraviolet and visible wavelengths, it was possible to determine which wavelength intervals were most sensitive to dominant loss processes. For DOM photodegradation, results show that increases in the absorption spectral slope between 265 and 305 nm were highly sensitive to increased exposure to solar ultraviolet radiation. A slightly larger wavelength range (265–340 nm) was found to be influenced when both mixing and photodegradation processes were considered, in terms DOM residence time, DOM absorption and UV diffuse attenuation coefficients. This same interval of spectral slopes (265–340 nm) was found to highly correlate with changes in fluorescence emission/excitation in wavelengths that are typically associated with terrestrial humic-like DOM. The identification of specific wavelength intervals, rather than the use of standard wavelength intervals or ratios, improved our ability to identify the dominant dissolved organic matter (humic-like) and major loss mechanisms (photodegradation) in these lakes.

Entirely passive reach extended GPON using Raman amplification

In previous investigation of extended GPON system, we employed 1240 nm and 1427 nm dual pumps within optical line terminal (OLT) equipments at central office (CO) to provide distributed Raman gains of upstream 1310 nm and downstream 1490 nm signals. These pump wavelengths were selected to ensure compatibility with the standard GPON wavelengths and reduce the unwanted pump-to-signal interactions. In this paper, we propose a new system scheme for an entirely-passive extended reach GPON to further enhance the system performance by eliminating the pump-to-signal interactions. In this scheme, a 1240 nm laser is employed to provide counter-pumping distributed Raman amplification of the upstream 1310 nm signal, and a discrete Raman amplifier is integrated with the 1490 nm transmitter to booster the downstream signal power and to improve the link loss budget. An operation over 60-km of zero-water-peak Allwave® fiber with a 1:128 way splitter is experimentally demonstrated at 2.5 Gbit/s. The system performance of such purely passive GPON extender is investigated in the paper. The system transmission limitation of upstream signal due to Raman ASE noises is discussed, and the non-linear impairment on downstream signal due to high launch power into feeder fiber is also examined.

Chemical Distinction by Nuclear Spin Optical Rotation

Nuclear spin optical rotation (NSOR) arising from the Faraday effect constitutes a novel, advantageous method for detection of nuclear magnetic resonance, provided that a distinction is seen between different chemical surroundings of magnetic nuclei. Efficient first-principles calculations for isolated water, ethanol, nitromethane, and urea molecules at standard laser wavelengths reveal a range of NSOR for different molecules and inequivalent nuclei, indicating the existence of an optical chemical shift. 1H results for H2O(l) are in excellent agreement with recent pioneering experiments. We also evaluate, for the same systems, the Verdet constants of Faraday rotation due to an external magnetic field. Calculations of NSOR in ethanol and a 11-cis-retinal protonated Schiff base imply an enhanced chemical distinction between chromophores at laser wavelengths approaching optical resonance.

Improving the High-Performance Inductively Coupled Plasma Optical Emission Spectrometry Methodology through Exact Matching

Exact matching is investigated as a means of improving high-performance inductively coupled plasma optical emission spectrometry (HP-ICP-OES), a technique developed at the National Institute of Standards and Technology (NIST) to enable elemental determinations with relative expanded uncertainty of approximately 0.2% expressed at 95% confidence. "Exact matching" refers to the very careful matching of analyte mass fractions, internal standard mass fractions, and matrix compositions among the calibration and unknown sample solutions prepared for an analysis. Computer spreadsheet modeling results and laboratory data involving 16 pairs of analyte and internal standard wavelengths show that exact matching of analyte and internal standard mass fractions mitigates imprecision and bias that can be caused by even subtle nonlinearity in the ICP-OES instrument response. Laboratory experiments also demonstrate matrix effects caused by small variations in acid composition and by mass fractions of Na less than 4 mg kg(-1), emphasizing the need for exact matching of matrix compositions. HP-ICP-OES analyses performed at NIST with and without exact matching illustrate that exact matching enables relative expanded uncertainties to be halved to approximately 0.1%.

Long‐term total ozone observations at Arosa (Switzerland) with Dobson and Brewer instruments (1988–2007)

Dobson and Brewer spectrophotometers are the standard instruments for ground‐based total ozone monitoring under the World Meteorological Organization's Global Atmosphere Watch program. Both types of instruments have been simultaneously used at Arosa station (Switzerland) since 1988; presently two Dobson and three Brewer instruments (one of which is type Mark III) are in operation. The large data set of quasi‐simultaneous measurements (defined here as observations performed less than 10 min apart) allows for the determination of both inter‐ and intrainstrumental precision. The results for one standard deviation of total ozone are ±0.5% for Dobson standard wavelength pair observations and ±0.15% for Brewer total ozone measurements. To transform Dobson data into Brewer total ozone observations, empirical transfer functions are used to describe the observed difference in seasonal variations of total ozone data derived from the two types of instruments (amounting to a seasonal amplitude of approximately 2% with maximum deviation in winter). The statistical model (applied to quasi‐simultaneous measurements) includes the ozone effective temperature and the air mass multiplied by total ozone (ozone slant path) as explanatory variables; it removes the seasonal cycle in the difference and it allows the significance of the proxies introduced and systematic errors in the data to be determined. However, even when these transfer functions are applied, a 3% drift over about a 10 year period (1988–1997) between Arosa's Dobson and Brewer derived total ozone data series remains unexplained, adding to the model an aerosol proxy for which only part of the drift can be removed (related to the period 1992–1996).

Observation of Magnetic Dipole Forbidden Transitions in LHD and Its Application to Burning Plasma Diagnostics

Magnetic dipole forbidden (M1) transition was studied in large helical device (LHD) and F-, Si- and Ti-like Ml transitions are successfully observed for highly ionized Ar, Kr, Mo and Xe ions. The wavelengths measured in visible range for the heavy elements, which are carefully determined with extremely small uncertainties of 0.02 ∼ 0.05 Å as a standard wavelength of usual electric dipole (E1) plasma emissions, are compared with theoretical predictions. The result shows a good agreement with recent Hatree-Fock calculation including semi-empirical adjustment. The M1 intensity for the F-like ions is examined by analyzing the intensity ratio of M1 to E1. Density dependence of the ratio is experimentally verified by comparing with collisional- radiative model calculation on level population. The M1/E1 line ratio for the F-like ions is applied to the α (He2+) particle diagnostics in ITER, in which a steady-state operation of burning plasmas based on D-T fusion reaction is expected with α particle heating. Unfortunately, the present estimation suggests a negative result for the α particle measurement because the ratio is largely enhanced by the collisional excitation with bulk ions due to high ion temperature of ITER of 10 keV as assumed and the resultant effect of the collisional excitation with α particles becomes less. Meanwhile, the Ml transition, in particular, Ti-like WLIII (W52+) transition (3627 Å) emitted in visible range, is very useful for diagnostics of the impurity behavior and the core plasma parameters in ITER.

Near-field enhancement of infrared intensities for f-f transitions in Er3+ ions close to the surface of silicon nanoparticles

Erbium doped waveguide amplifiers can be used in optical integrated circuits to compensate for signal losses. Such amplifiers use stimulated emission from the first excited state ((4) I (13/2)) to the ground state ((4) I (15/2)) of Er(3+) at 1.53 µm, the standard wavelength for optical communication. Since the intra-f transitions are parity forbidden for free Er(3+) ions, the absorption and the emission cross sections are quite small for such doped amplifiers. To enhance the absorption, Si nanoclusters can be embedded in silica matrix. Here we investigate the effect of the Si nanocluster on the Er(3+) emission using ab initio theory for the first time. We combine multi-reference configuration interaction with one-electron spin-orbit Hamiltonian and relativistic effective core potentials. Our calculations show that the presence of a polarizable Be atom at 5Ǻ from the Er(3+) ion in a crystalline environment can lead to an enhancement in the emission by a factor of three. The implications of this effect in designing more efficient optical gain materials are discussed.

Optical Filters Using Optical Multi-Layer Structures for Optical Communication Systems

In this article, light reflection spectrums for different one-dimensional multi-layer structures are obtained. Optical reflectivities for periodic, superperiodic, and quasiperiodic structures have been calculated using the transfer matrix method. PBGs of each structure have been obtained using the optical reflectivity pattern. From a comparison of reflectivity and standard dense wavelength division multiplexing grids, it is demonstrated that narrow and dense band filters can be built from generalized Fibonacci quasiperiodic structures. Reflectivity of these structures contains bands that meet the ITU-T dense wavelength division multiplexing standard. Reflectivity of other multi-layer structures has poor or less potential to be used in dense wavelength division multiplexing systems.

Comparative Study of the Dissociative Ionization of 1,1,1 Trichloroethane Using Nanosecond and Femtosecond Laser Pulses

Changes in the laser induced molecular dissociation of 1,1,1-trichloroethane (TCE) were studied using a range of intensities and standard laser wavelengths with nanosecond and femtosecond pulse durations. TCE contains C-H, C-C and C-Cl bonds and selective bond breakage of one or more of these bonds is of scientific interest. Using laser ionization time of flight mass spectrometry, it was found that considerable variation of fragment ion peak heights as well as changes in relative peak ratios is possible by varying the laser intensity (by attenuation), wavelength and pulse duration using standard laser sources. The nanosecond laser dissociation seems to occur via C-Cl bond breakage, with significant fragmentation and only a few large mass ion peaks observed. In contrast, femtosecond laser dissociative ionization results in many large mass ion peaks. Evidence is found for various competing dissociation and ionization pathways. Variation of the nanosecond laser intensity does not change the fragmentation pattern, while at high femtosecond intensities large changes are observed in relative ion peak sizes. The total ionization yield and fragmentation ratios are presented for a range of wavelengths and intensities, and compared to the changes observed due to a linear chirp variation.

Silicon Raman Amplifiers With Ring-Resonator-Enhanced Pump Power

In this paper, design rules for optimal silicon Raman amplifiers operating at standard telecommunications wavelengths are formulated. For given material and waveguide parameters, and a specified upper pump-power limit, explicit expressions are derived for the optimal length and maximum possible gain of single-pass-pumped amplifiers. For ring-resonator (RR) amplifiers, the optimization problem is reduced to finding a zero of a fifth-order polynomial. Due to resonant pump-power enhancement, RR amplifiers with positive gain can be realized for any pump power, however small it is. Finally, for small pump powers, the maximum possible gain is most effectively increased by reducing the linear waveguide losses as opposed to the effective area or the effective free-carrier lifetime.