Search NASA⌕ Search

SEARCH · Search NASA

Results for “Fourier Transform Spectrometer”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Integrated Silicon Fourier Transform Spectrometer with Broad Bandwidth and Ultra‐High Resolution

An ultra-high resolution Fourier transform spectrometer (FTS) realized in silicon photonic platform that can operate with broad band, narrow band as well as a combination of broad band and narrow band signals is reported. The ultra-high resolution of the spectrometer is achieved by exploiting multiple techniques: a Michelson interferometer (MI) structure to increase the optical path delay (OPD), a hybrid waveguide design to reduce insertion loss, an optimized heater and air trenches to achieve higher thermal efficiency. Here, to further increase the OPD of the spectrometer to increase its resolution, a novel multiple interferometers approach is employed which combines balanced MI with N statically imbalanced MIs, thereby increasing the OPD of a single MI by factor of N + 1. An FTS spectrometer consisting of N = 2 such MIs is fabricated and experimentally characterized using unknown broad bandwidth input signal spectra of about 180 nm centered around 1550 nm, a narrow line laser input signal, and a combination of broad and narrow band signals demonstrating spectral resolution of about 0.16 nm.

Li, Ang↗
DOE OSTI2019

Compact millimeter-wavelength Fourier-transform spectrometer

Here, we have constructed a Fourier-transform spectrometer (FTS) operating between 50 GHz and 330 GHz with minimum volume (355×260×64 mm) and weight (5.9 kg) while maximizing optical throughput (100 mm 2 sr) and optimizing the spectral resolution (4 GHz). This FTS is designed as a polarizing Martin–Puplett interferometer with unobstructed input and output in which both input polarizations undergo interference. The instrument construction is simple with mirrors milled on the box walls and one motorized stage as the single moving element. We characterize the performance of the FTS, compare the measurements to an optical simulation, and discuss features that relate to details of the FTS design. The simulation is also used to determine the tolerance of optical alignments for the required specifications. We detail the FTS mechanical design and provide the control software as well as the analysis code online.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

The POLARBEAR Fourier transform spectrometer calibrator and spectroscopic characterization of the POLARBEAR instrument

Here we describe the Fourier Transform Spectrometer (FTS) used for in-field testing of the POLARBEAR receiver, an experiment located in the Atacama Desert of Chile which measures the cosmic microwave background (CMB) polarization. The POLARBEAR-FTS (PB-FTS) is a Martin-Puplett interferometer designed to couple to the Huan Tran Telescope (HTT) on which the POLARBEAR receiver is installed. The PB-FTS measured the spectral response of the POLARBEAR receiver with signal-to-noise ratio >20 for ~69% of the focal plane detectors due to three features: a high throughput of 15.1 sr cm 2 , optimized optical coupling to the POLARBEAR optics using a custom designed output parabolic mirror, and a continuously modulated output polarizer. The PB-FTS parabolic mirror is designed to mimic the shape of the 2.5 m-diameter HTT primary reflector, which allows for optimum optical coupling to the POLARBEAR receiver, reducing aberrations and systematics. One polarizing grid is placed at the output of the PB-FTS and modulated via continuous rotation. This modulation allows for decomposition of the signal into different harmonics that can be used to probe potentially pernicious sources of systematic error in a polarization-sensitive instrument. The high throughput and continuous output polarizer modulation features are unique compared to other FTS calibrators used in the CMB field. In-field characterization of the POLARBEAR receiver was accomplished using the PB-FTS in April 2014. We discuss the design, construction, and operation of the PB-FTS and present the spectral characterization of the POLARBEAR receiver. We introduce future applications for the PB-FTS in the next-generation CMB experiment, the Simons Array.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Stacked Average Far-infrared Spectrum of Dusty Star-forming Galaxies from the Herschel/SPIRE Fourier Transform Spectrometer

We present stacked average far-infrared spectra of a sample of 197 dusty star-forming galaxies (DSFGs) at 0.005<z<4 using about 90% of the Herschel Space Observatory SPIRE Fourier Transform Spectrometer (FTS) extragalactic data archive based on 3.5 years of science operations. These spectra explore an observed-frame 447–1568 GHz frequency range, allowing us to observe the main atomic and molecular lines emitted by gas in the interstellar medium. The sample is subdivided into redshift bins, and a subset of the bins are stacked by infrared luminosity as well. These stacked spectra are used to determine the average gas density and radiation field strength in the photodissociation regions (PDRs) of DSFGs. For the low-redshift sample, we present the average spectral line energy distributions of CO and H{sub 2}O rotational transitions and consider PDR conditions based on observed [C i] 370 and 609 μm, and CO (7-6) lines. For the high-z (0.8<z<4) sample, PDR models suggest a molecular gas distribution in the presence of a radiation field that is at least a factor of 10{sup 3} larger than the Milky Way and with a neutral gas density of roughly 10{sup 4.5}–10{sup 5.5} cm{sup −3}. The corresponding PDR models for the low-z sample suggest a UV radiation field and gas density comparable to those at high-z. Given the challenges in obtaining adequate far-infrared observations, the stacked average spectra we present here will remain the measurements with the highest signal-to-noise ratio for at least a decade and a half until the launch of the next far-infrared facility.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Design and performance of a multi-terahertz Fourier transform spectrometer for axion dark matter experiments

Dedicated spectrometers for terahertz radiation with [0.3, 30] THz frequencies using traditional optomechanical interferometry are substantially less common than their infrared and microwave counterparts. This paper presents the design and initial performance measurements of a tabletop Fourier transform spectrometer (FTS) for multi-terahertz radiation using infrared optics in a Michelson arrangement. This is coupled to a broadband pyroelectric photodetector designed for [0.1, 30] THz frequencies. We measure spectra of narrowband and broadband input radiation to characterize the performance of this instrument above 10 THz, where signal-to-noise is high. This paves the groundwork for planned upgrades to extend below 10 THz. We also briefly discuss potential astroparticle physics applications of such FTS instruments to broadband axion dark matter searches, whose signature comprises low-rate monochromatic photons with unknown frequency.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Two-dimensional fourier transform spectrometer

The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

An On-Chip Superconducting Kinetic Inductance Fourier Transform Spectrometer for Millimeter-Wave Astronomy

An on-chip FTS consists of two waveguides coupled to long superconducting transmission lines (STLs) (similar to 620 mm) using two coupling probes. The signal propagating on one of the STLs is phase-shifted with respect to the other line with a bias current that affects the nonlinear dependence of kinetic inductance, Lk(I)of the STL material. Here we describe the design and simulation of a superconducting on-chip FTS coupled to a dual polarization W-band (90-110 GHz) waveguide. These devices have applications in ground-based and space-based millimeter-wave spectral surveys.

Fourier transform spectrometer↗
DOE OSTI2016

Supercontinuum Fourier transform spectrometry with balanced detection on a single photodiode

We demonstrate a method of combining a supercontinuum light source with a commercial Fourier transform spectrometer, using a novel approach to dual-beam balanced detection, implemented with phase-sensitive detection on a single light detector. A 40 dB reduction in the relative intensity noise is achieved for broadband light, analogous to conventional balanced detection methods using two matched photodetectors. Unlike conventional balanced detection, however, this method exploits the time structure of the broadband source to interleave signal and reference pulse trains in the time domain, recording the broadband differential signal at the fundamental pulse repetition frequency of the supercontinuum. The method is capable of real-time correction for instability in the supercontinuum spectral structure over a broad range of wavelengths and is compatible with commercially designed spectrometers. A proof-of-principle experimental setup is demonstrated for weak absorption in the 1500-1600 nm region.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Early Stage Detection of Stress Due to Copper on Maize (Zea mays L.) by Laser-Induced Fluorescence and Infrared Spectroscopy

Laser-induced fluorescence (LIF) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy has been applied for the nondestructive, label free, and rapid analyses of the impact of copper (25, 50, and 75 μM) on maize seedlings at an early stage before the changes appear visually on the plant. The LIF measurement has been used to detect the signs of stress in the photosynthetic pigment. The integrated areal intensity and increasing fluorescence intensity ratios indicate decrease in the photosynthetic pigments in the leaves of maize plants stressed with copper. The ATR-FTIR technique has been utilized to estimate the changes arising in the cell wall polysaccharides, amino acid, secondary structure of protein and lipid content of the leaves of control and copper-treated maize seedlings. The second derivative and curve fitting analyses have been applied for the enhancement of the spectral variations and quantitative estimation of the changes arising in the biochemical profile. The result shows an increase in the pectin, lignin, amino acid, and protein content and reduction in the amount of cellulose and lipid in the leaves of maize seedlings due to the treatment of copper. This study indicates the toxic response of copper by hampering the growth and reduction in the photosynthetic pigments and biochemical content of the maize seedlings. This study also demonstrates the feasibility of the spectroscopic techniques (LIF and ATRFTIR) as a rapid, label free, and nondestructive probe for the assessment of stress and monitoring of crops.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Photoluminescent and Thermoluminescent Studies of Dy{sup 3+} and Eu{sup 3+} Doped Y{sub 2}O{sub 3} Phosphors

Eu{sup 3+} doped and Dy{sup 3+} codoped yttrium oxide (Y{sub 2}O{sub 3}) phosphors have been prepared using solid-state reaction technique (SSR). The prepared phosphors were characterized by X-ray diffractometer (XRD), energy dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR) techniques. Photoluminescence (PL) and Thermoluminescence (TL) properties were studied in detail. PL emission spectra were recorded for prepared phosphors under excitation wavelength 254 nm, which show a high intense peak at 613 nm for Y{sub 2}O{sub 3}:Dy{sup 3+}, Eu{sup 3+} (1:1.5 mol %) phosphor. The correlated color temperature (CCT) and CIE analysis have been performed for the synthesized phosphors. TL glow curves were recorded for Eu{sup 3+}doped and Dy{sup 3+}codoped phosphors to study the heating rate effect and dose response. The kinetic parameters were calculated using peak shape method for UV and γ exposures through computerized glow curve deconvolution (CGCD) technique. The phosphors show second order kinetics and activation energies varying from 5.823 × 10{sup − 1} to 18.608 × 10{sup − 1} eV.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Polyaniline-Modified TiO{sub 2}, a Highly Effective Photo-catalyst for Solid-Phase Photocatalytic Degradation of PVC

A series of polyaniline-modified TiO{sub 2} photo-catalysts (TiO{sub 2}@PANI) were prepared via an in-situ polymerization of aniline onto TiO{sub 2} nanoparticles. The Fourier-transform infrared spectroscopy (FT-IR) and thermogravimetric analyses (TGA) confirmed that the polyaniline (PANI) successfully grafted on the TiO{sub 2} NPs. The X-ray diffraction (XRD) patterns showed that the crystalline structure of the TiO{sub 2} did not change during the preparation of PANI. Photodegradable nanocomposites were prepared by embedding the photocatalysts into the commercial poly(vinyl chloride) (PVC) samples. The nanocomposite films were compared against pure PVC and PVC-TiO{sub 2} films for their photodegradation performances. The photocatalytic activity of the TiO{sub 2}@PANI catalysts improved with an increase in the inorganic/organic molar ratio. With the TiO{sub 2} aniline molar ratio of 10, the PVC-TiO{sub 2}@PANI nanocomposite film lost about 67% of its weight after 720 h irradiation under UV. Meanwhile, the pure PVC and PVC-TiO{sub 2} control films lost about 12 and 45% of their initial weights, respectively. Results showed that the rate at which the PVC is photodegraded can be controlled by the amount of the TiO{sub 2} NPs as well as the initial TiO{sub 2} aniline molar ratio. The SEM micrograms indicated a rougher and more porous surface for the irradiated PVC-TiO{sub 2}@PANI compared with controls. .

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Effect of Alkali Treatment on Mechanical and Morphological Properties of Pineapple Leaf Fibre/Polyester Composites

In this study, our aim is to analyze the influence of fibre treatments and different fibre loading on mechanical, physical and chemical properties of pineapple leaf fibre reinforced polyester composites (PALF/PE). Fibre treatments were carried out with 1 N NaOH and KOH for 1 h. The untreated and treated PALF/PE composites were fabricated with 25 wt%, 35 wt% and 45 wt% fibre loadings by compression molding technique. Fourier Transform Infrared Spectroscopy (FTIR) was used to understand the effects of chemical treatment on PALF mechanical test results revealed that 45 wt% of PALF/PE composites treated with NaOH showed a 35% increase in tensile strength compared to untreated PALF/PE composites. The tensile modulus and the flexural module are also the highest at 45 wt% of KOH treated composites. The highest impact strength of 70 J/m was obtained for PALF/PE composites with NaOH treated fibres at 25% fibre loading. The results show that the fibre treatments in terms of the flexural and inter-laminar shear strength of composites were not effective. SEM of the tensile fractured specimen of PALF/PE composites revealed the changes in fibre characteristics due to the alkali treatment and less fibre pull-out at higher fibre loading. Overall we conclude that 1 N NaOH, 45 wt% treated PALF/PE composites satisfactorily and effectively improved both the mechanical and morphological properties. Obtained composites would be promising for construction materials, furniture and automotive components due to their superior strength and modulus at higher fibre loading.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Novel Biocide Based on Cationic Derivative of Psyllium: Surface Modification and Antibacterial Activity

To circumvent the problems (such as volatilization, photolytic decomposition, chemical instability, easy permeability through the skin) associated with low molecular weight antimicrobial agents, our strategy employed graft copolymerization of cationic monomer with the polymeric substrate viz. psyllium husk. The surface graft concentration of quaternary ammonium ion on psyllium was optimized by measuring the extent of grafting in the microwave-induced process. The surface modification of graft copolymers was evident by different physico–chemical techniques like {sup 13}C nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffractometer (XRD), differential scanning calorimetry (DSC), Thermo gravimeteric analysis (TGA), and viscometric study. The synthesized water soluble product resulted good antibacterial activity against Gram positive Staphylococcus aureus and Bacillus anthracis but failed to produce any antibacterial activity against Gram negative Salmonella typhi and Escherichia coli. The reason to failure has been explained on the basis of differences in the electrokinetic property between Gram-positive and Gram-negative bacteria. Optimum minimum inhibitory concentration (MIC) for the polymeric grade which showed good biocidal effect evaluated by both zone of inhibition and absorbance is found at 1000 µg/ml.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Adsorption of Iron(III) and Copper(II) by Bacterial Cellulose from Rhodococcus sp. MI 2

Modified cellulose from the pellicle produced by Rhodococcus sp. MI 2 was more efficient at removing Fe(III) and Cu(II) from aqueous solution than similarly modified cellulose from Komagataeibar xylinus TISTR 998. This study first describes the modification of the cellulose to produce mercerized bacterial cellulose (MBC), phosphorylated bacterial cellulose (PBC), acid–base cellulose and diethylenetriamine bacterial cellulose (EABC). Their efficacy as adsorbents to adsorb Fe(III) and Cu(II) was then determined. In aqueous solution at pH 4 at initial Fe(III) concentration of 20 mg/L, PBC reached adsorption equilibrium within 195 min. At pH 5 in an initial Cu(II) concentration of 75 mg/L, EABC reached adsorption equilibrium within 210 min. Molecular structures and chemical bonds were examined by Fourier transform infrared spectroscopy (FT-IR) and physical morphologies by scanning electron microscopy. The adsorption kinetics of MBC, PBC and EABC showed good agreement with the proposed pseudo-second order model and the adsorption isotherm was best described by the Freundlich model. Our study determined optimal conditions, molecular structures, physical morphologies and adsorption kinetics. The cellulose produced by the new strain Rhodococcus sp. MI 2 was highly efficient at adsorbing and removing metal ions from aqueous solution.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Nanoclay Addition on the Biodegradability and Performance of Starch-Based Nanocomposites as Mulch Films

The biodegradation and performance of potential agricultural mulch films prepared from native and oxidized corn starch nanocomposites with chitosan-modified bentonite were studied under simulated soil test conditions. Samples were removed at different times and their wet and dry weights were registered. A photographic register of films appearance was also included. Bio-physicochemical changes along biodegradation progress were followed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TG). Results indicate that all samples degraded in a three step process and that they almost fully degrade by 100 days of testing. The chemical modification of starch and the addition of fillers did not produce significant differences in biodegradation rate. Microbial attack, mainly by fungal microorganisms started at the end of the first week and produced a 50% weight loss in approximately 35 days. Biological assays indicate that germination was negatively affected by proposed starch-based films.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Annealing Temperature on Structural, Morphological, Optical and Magnetic Properties of NiFe{sub 2}O{sub 4} Thin Films

Nickel ferrite (NiFe{sub 2}O{sub 4}) thin films have been deposited on glass substrates by a chemical spray pyrolysis technique at 350 {sup ∘}C substrate temperature. The deposited films were annealed at four different temperatures (400, 450, 500 and 550 {sup ∘}C), and the effect of annealing temperature on the structural, morphological, optical and magnetic properties were studied. The annealed films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), UV-visible spectroscopic analysis and vibrating sample magnetometer (VSM). XRD patterns showed that the NiFe{sub 2}O{sub 4} is oriented along (311) plane, which enhances peak intensity with respect to the annealing temperature. The analysis of XRD pattern revealed the formation of single-phase cubic spinel structure. The FT-IR spectrum of NiFe{sub 2}O{sub 4} thin films showed strong absorption peaks around 616 and 353 cm{sup − 1} which indicates the cubic spinel crystal structure of the films. FE-SEM micrographs show that the grain size increases with an increase in annealing temperature. The grain size varies between ∼ 19 and ∼ 28 nm, confirming the nanocrystalline nature of the prepared thin films. The optical properties of the films were studied by an absorbance spectrum in the range of 300 to 800 nm. The results showed that the energy band gap decreased with the increase of annealing temperature. Magnetic properties of NiFe{sub 2}O{sub 4} thin films exhibit a strong dependence on the annealing temperature. The saturation magnetization increases from ∼ 68.29 to ∼ 205.24 emu/cm{sup 3} with increasing annealing temperature, which is in favour of modern electronic device miniaturization.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Infrared Spectroscopic Study of Magnetic Behavior of Dysprosium Doped Magnetite Nanoparticles

Dysprosium doped magnetite (Fe{sub 3−x}Dy{sub x}O{sub 4} with x = 0.0–0.1) nanoparticles have been synthesized using the co-precipitation method. Magnetic characterization using vibrating sample magnetometer (VSM) has revealed an enhancement in the saturation magnetization with Dy{sup 3+} doping. The occupancy of the dopant ions in magnetite lattice has been probed using Fourier transform infrared spectroscopy (FTIR). The shifting of ν{sub 2} (Fe–O) band at 452 cm{sup − 1} for undoped samples to 443 cm{sup − 1} for dysprosium-doped samples is indicative of occupancy of dysprosium at the octahedral site. X-ray diffraction (XRD) patterns have been used to calculate the strain and lattice constant. The strain is found to increase with doping level and attained a maximum value for the x = 0.03. This increase in the strain can be attributed to occupancy of large diameter Dy{sup 3+} ions at the octahedral site of spinel structure of the magnetite lattice.

77 NANOSCIENCE AND NANOTECHNOLOGY↗