1
|
Myers TL, Bernacki BE, Wilhelm MJ, Jensen KL, Johnson TJ, Primera-Pedrozo OM, Tonkyn RG, Smith SC, Burton SD, Bradley AM. Influence of intermolecular interactions on the infrared complex indices of refraction for binary liquid mixtures. Phys Chem Chem Phys 2022; 24:22206-22221. [PMID: 36097852 DOI: 10.1039/d2cp02920k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This paper investigates the accuracy of deriving the composite optical constants of binary mixtures from only the complex indices of refraction of the neat materials. These optical constants enable the reflectance spectra of the binary mixtures to be modeled for multiple scenarios (e.g., different substrates, thicknesses, volume ratios), which is important for contact and standoff chemical detection. Using volume fractions, each mixture's complex index of refraction was approximated via three different mixing rules. To explore the impact of intermolecular interactions, these predictions are tested by experimental measurements for two representative sets of binary mixtures: (1) tributyl phosphate combined with n-dodecane, a non-polar medium, to represent mixtures which primarily interact via dispersion forces and (2) tributyl phosphate and 1-butanol to represent mixtures with polar functional groups that can also interact via dipole-dipole interactions, including hydrogen bonding. The residuals and the root-mean-square error between the experimental and calculated index values are computed and demonstrate that for miscible liquids in which the average geometry of the cross-interactions can be considered isotropic (e.g., dispersion), the refractive indices of the mixtures can be modeled using composite n and k values derived from volume fractions of the neat liquids. Conversely, in spectral regions where the geometry of the cross-interactions is more restricted and anisotropic (e.g., hydrogen bonding), the calculated n and k values vary from the measured values. The impact of these interactions on the reflectance spectra are then compared by modeling a thin film of the binary mixtures on an aluminum substrate using both the measured and the mathematically computed indices of refraction.
Collapse
Affiliation(s)
- Tanya L Myers
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
| | - Bruce E Bernacki
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
| | - Michael J Wilhelm
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
| | - Karissa L Jensen
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
| | - Timothy J Johnson
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
| | | | - Russell G Tonkyn
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
| | - Steven C Smith
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
| | - Sarah D Burton
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
| | - Ashley M Bradley
- Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
| |
Collapse
|
2
|
Kautz EJ, Yeak J, Bernacki BE, Phillips MC, Harilal SS. Expansion dynamics and chemistry evolution in ultrafast laser filament produced plasmas. Phys Chem Chem Phys 2020; 22:8304-8314. [PMID: 32202277 DOI: 10.1039/d0cp00078g] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Laser ablation in conjunction with optical emission spectroscopy is a potential non-contact, stand-off detection method for all elements in the periodic table and certain isotopes such as radionuclides. Currently, significant development efforts are on-going to use ultrafast laser filaments for remote detection of materials. The application of filaments is of particular interest in extending the range of stand-off capability associated with elemental and isotopic detection via laser-induced breakdown spectroscopy. In this study, we characterize the expansion dynamics and chemical evolution of filament-produced uranium (U) plasmas. Laser filaments are generated in the laboratory by loosely focusing 35 femtosecond (fs), 6 milli Joule (mJ) pulses in air. Time-resolved, two-dimensional plume and spectral imaging was performed to study hydrodynamics and evolution of U atomic and UO molecular emission in filament-produced U plasmas. Our results highlight that filament ablation of U plasmas gives a cylindrical plume morphology with an appearance of plume splitting into slow and fast moving components at later times of its evolution. Emission from the slow-moving component shows no distinct spectral features (i.e. broadband-like) and is contributed in part by nanoparticles generated during ultrafast laser ablation. Additionally, we find U atoms and U oxide molecules (i.e. UO, UxOy) co-exist in the filament produced plasma, which can be attributed to the generation of low-temperature plasma conditions during filament ablation.
Collapse
Affiliation(s)
| | | | | | - Mark C Phillips
- Opticslah, LLC, Albuquerque, NM 87106, USA and James C. Wyant College of Optical Sciences, University of Arizona Tucson, AZ 85721, USA
| | | |
Collapse
|
3
|
Phillips MC, Bernacki BE, Harilal SS, Yeak J, Jones RJ. Standoff chemical plume detection in turbulent atmospheric conditions with a swept-wavelength external cavity quantum cascade laser. Opt Express 2020; 28:7408-7424. [PMID: 32225970 DOI: 10.1364/oe.385850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/13/2020] [Indexed: 06/10/2023]
Abstract
Rapid and sensitive standoff measurement techniques are needed for detection of trace chemicals in outdoor plume releases, for example from industrial emissions, unintended chemical leaks or spills, burning of biomass materials, or chemical warfare attacks. Here, we present results from 235 m standoff detection of transient plumes for 5 gas-phase chemicals: Freon 152a (1,1-difluoroethane), Freon 134a (1,1,1,2-tetrafluoroethane), methanol (CH3OH), nitrous oxide (N2O), and ammonia (NH3). A swept-wavelength external cavity quantum cascade laser (ECQCL) measures infrared absorption spectra over the range 955-1195 cm-1 (8.37- 10.47 µm), from which chemical concentrations are determined via spectral fits. The fast 400 Hz scan rate of the swept-ECQCL enables measurement above the turbulence time-scales, reducing noise and allowing plume fluctuations to be measured. For high-speed plume detection, noise-equivalent column densities of 1-2 ppm*m are demonstrated with 2.5 ms time resolution, improving to 100-400 ppb*m with 100 ms averaging.
Collapse
|
4
|
Harilal SS, Kautz EJ, Bernacki BE, Phillips MC, Skrodzki PJ, Burger M, Jovanovic I. Physical conditions for UO formation in laser-produced uranium plumes. Phys Chem Chem Phys 2019; 21:16161-16169. [PMID: 31294428 DOI: 10.1039/c9cp02250c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We investigate the oxidation of uranium (U) species, the physical conditions leading to uranium monoxide (UO) formation and the interplay between plume hydrodynamics and plasma chemistry in a laser-produced U plasma. Plasmas are produced by ablation of metallic U using nanosecond laser pulses. An ambient gas environment with varying oxygen partial pressures in 100 Torr inert Ar gas is used for controlling the plasma oxidation chemistry. Optical emission spectroscopic analysis of U atomic and monoxide species shows a reduction in the emission intensity and persistence with increasing oxygen partial pressure. Spectral modelling is used for identifying the physical conditions in the plasma that favor UO formation. The optimal temperature for UO formation is found to be in the temperature range of ∼1500-5000 K. The spectrally integrated and spectrally filtered (monochromatic) imaging of U atomic and molecular species reveals the evolutionary paths of various species in the plasma. Our results also highlight that oxidation in U plasmas predominantly occurs at the cooler periphery and is delayed with respect to plasma formation, and the dissipation of molecular species strongly depends on oxygen partial pressure.
Collapse
Affiliation(s)
- S S Harilal
- Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - E J Kautz
- Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - B E Bernacki
- Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - M C Phillips
- Pacific Northwest National Laboratory, Richland, WA 99352, USA. and Optics Science Center, University of Arizona, Tucson, AZ 85721, USA and Opticslah, LLC, 2350 Alamo Ave. SE, Albuquerque, NM 87106, USA
| | - P J Skrodzki
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, MI 48109, USA and Center for Ultrafast Optical Science, University of Michigan, MI 48109, USA
| | - M Burger
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, MI 48109, USA and Center for Ultrafast Optical Science, University of Michigan, MI 48109, USA
| | - I Jovanovic
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, MI 48109, USA and Center for Ultrafast Optical Science, University of Michigan, MI 48109, USA
| |
Collapse
|
5
|
DeVetter BM, Bernacki BE, Alvine KJ. Disordered spontaneously buckled optical gratings for improved lighting applications. Opt Lett 2018; 43:4895-4898. [PMID: 30320777 DOI: 10.1364/ol.43.004895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 08/30/2018] [Indexed: 06/08/2023]
Abstract
Technologies for directing daylight deeper within a building space are highly sought after for energy efficiency applications in order to offset artificial lighting costs and to improve workplace productivity via the use of natural light. Vertical window coatings that can perform this task by redistributing sunlight deeper into a space are especially attractive as they are significantly more straightforward to incorporate into a wide variety of architectures as well as to retrofit into existing facades as compared to roof-based skylights or bulky horizontal daylight shelf-type options. The potential energy savings are even greater when one takes into account the fact that such technologies would mitigate harsh glare, allowing window shades to be open for longer portions of the day. However, low-cost and readily scalable techniques are essential for widespread adoption of these window coating technologies. Here, we describe a potentially low-cost method to create a window coating that could enhance daylight penetration, requiring only a thin film of polymeric material deposited on an elastomeric substrate. The resulting structure is a disordered, spontaneously buckled optical grating that spreads incident light without noticeable chromatic dispersion due to its stochastic patterning. The described method has the potential to improve energy efficiency while maintaining acceptable optical clarity.
Collapse
|
6
|
Myers TL, Tonkyn RG, Danby TO, Taubman MS, Bernacki BE, Birnbaum JC, Sharpe SW, Johnson TJ. Accurate Measurement of the Optical Constants n and k for a Series of 57 Inorganic and Organic Liquids for Optical Modeling and Detection. Appl Spectrosc 2018; 72:535-550. [PMID: 29286824 DOI: 10.1177/0003702817742848] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
For optical modeling and other purposes, we have created a library of 57 liquids for which we have measured the complex optical constants n and k. These liquids vary in their nature, ranging in properties that include chemical structure, optical band strength, volatility, and viscosity. By obtaining the optical constants, one can model most optical phenomena in media and at interfaces including reflection, refraction, and dispersion. Based on the works of others, we have developed improved protocols using multiple path lengths to determine the optical constants n/k for dozens of liquids, including inorganic, organic, and organophosphorus compounds. Detailed descriptions of the measurement and data reduction protocols are discussed; agreement of the derived optical constant n and k values with literature values are presented. We also present results using the n/k values as applied to an optical modeling scenario whereby the derived data are presented and tested for models of 1 µm and 100 µm layers for dimethyl methylphosphonate (DMMP) on both metal (aluminum) and dielectric (soda lime glass) substrates to show substantial differences between the reflected signal from highly reflective substrates and less-reflective substrates.
Collapse
Affiliation(s)
- Tanya L Myers
- Pacific Northwest National Laboratory, Richland, WA, USA
| | | | - Tyler O Danby
- Pacific Northwest National Laboratory, Richland, WA, USA
| | | | | | | | | | | |
Collapse
|
7
|
Blake TA, Johnson TJ, Tonkyn RG, Forland BM, Myers TL, Brauer CS, Su YF, Bernacki BE, Hanssen L, Gonzalez G. Methods for quantitative infrared directional-hemispherical and diffuse reflectance measurements using an FTIR and a commercial integrating sphere. Appl Opt 2018; 57:432-446. [PMID: 29400793 PMCID: PMC6193458 DOI: 10.1364/ao.57.000432] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 12/07/2017] [Indexed: 06/07/2023]
Abstract
We have developed methods to measure the directional-hemispherical (ρ) and diffuse (ρd) reflectances of powders, liquids, and disks of powders and solid materials using a commercially available, matte gold-coated integrating sphere and Fourier transform infrared spectrometer. To determine how well the sphere and protocols produce quantitative reflectance data, measurements were made of three diffuse and two specular standards prepared by the National Institute of Standards and Technology (NIST), LabSphere Infragold and Spectralon standards, hand-loaded sulfur and talc powder samples, and water. Relative to the NIST measurements of the NIST standards, our directional hemispherical reflectance values are within ±4% for four of the standards and within ±7% for a low reflectance diffuse standard. For the three diffuse reflectance NIST standards, our diffuse reflectance values are within ±5% of the NIST values. For the two specular NIST standards, our diffuse reflectance values are an order of magnitude larger than those of NIST, pointing to a systematic error in the manner in which diffuse reflectance measurements are made for specular samples using our methods and sphere. Sources of uncertainty are discussed in the paper.
Collapse
Affiliation(s)
- Thomas A. Blake
- Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99354, USA
| | - Timothy J. Johnson
- Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99354, USA
| | - Russell G. Tonkyn
- Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99354, USA
| | - Brenda M. Forland
- Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99354, USA
- Current address: Red Rocks Community College, 13300 West 6th Avenue, Lakewood, Colorado 80228, USA
| | - Tanya L. Myers
- Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99354, USA
| | - Carolyn S. Brauer
- Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99354, USA
| | - Yin-Fong Su
- Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99354, USA
| | - Bruce E. Bernacki
- Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99354, USA
| | - Leonard Hanssen
- Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Gerardo Gonzalez
- Alecam FTIR Services and Consulting, The Woodlands, Texas 77381, USA
| |
Collapse
|
8
|
DeVetter BM, Bernacki BE, Bennett WD, Schemer-Kohrn A, Alvine KJ. Fabrication of Periodic Gold Nanocup Arrays Using Colloidal Lithography. J Vis Exp 2017. [PMID: 28892029 DOI: 10.3791/56204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing in combination with new nanofabrication techniques. A plasmon is a quantum of charge density oscillation that lends nanoscale metals such as gold and silver unique optical properties. In particular, gold and silver nanoparticles exhibit localized surface plasmon resonances-collective charge density oscillations on the surface of the nanoparticle-in the visible spectrum. Here, we focus on the fabrication of periodic arrays of anisotropic plasmonic nanostructures. These half-shell (or nanocup) structures can exhibit additional unique light-bending and polarization-dependent optical properties that simple isotropic nanostructures cannot. Researchers are interested in the fabrication of periodic arrays of nanocups for a wide variety of applications such as low-cost optical devices, surface-enhanced Raman scattering, and tamper indication. We present a scalable technique based on colloidal lithography in which it is possible to easily fabricate large periodic arrays of nanocups using spin-coating and self-assembled commercially available polymeric nanospheres. Electron microscopy and optical spectroscopy from the visible to near-infrared (near-IR) was performed to confirm successful nanocup fabrication. We conclude with a demonstration of the transfer of nanocups to a flexible, conformal adhesive film.
Collapse
Affiliation(s)
- Brent M DeVetter
- Pacific Northwest National Laboratory, Energy and Environment Directorate
| | - Bruce E Bernacki
- Pacific Northwest National Laboratory, Energy and Environment Directorate
| | - Wendy D Bennett
- Pacific Northwest National Laboratory, Energy and Environment Directorate
| | - Alan Schemer-Kohrn
- Pacific Northwest National Laboratory, Energy and Environment Directorate
| | - Kyle J Alvine
- Pacific Northwest National Laboratory, Energy and Environment Directorate;
| |
Collapse
|
9
|
Huang Q, Devetter BM, Roosendaal T, LaBerge M, Bernacki BE, Alvine KJ. Fabrication of large area flexible nanoplasmonic templates with flow coating. Rev Sci Instrum 2017; 88:073104. [PMID: 28764523 DOI: 10.1063/1.4994737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We describe the development of a custom-built two-axis flow coater for the deposition of polymeric nanosphere monolayers that could be used in the fabrication of large area nanoplasmonic films. The technique described here has the capability of depositing large areas (up to 7 in. × 10 in.) of self-assembled monolayers of polymeric nanospheres onto polyethylene terephthalate (PET) films. Here, three sets of films consisting of different diameters (ranging from 100 to 300 nm) of polymeric nanospheres were used to demonstrate the capabilities of this instrument. To improve the surface wettability of the PET substrates during wet-deposition, we enhanced the wettability by using a forced air blown-arc plasma treatment system. Both the local microstructure, as confirmed by scanning electron microscopy, describing monolayer and multilayer coverage, and the overall macroscopic uniformity of the resultant nanostructured film were optimized by controlling the relative stage to blade speed and nanosphere concentration. We also show using a smaller nanoparticle template that such monolayers can be used to form nanoplasmonic films. As this flow-coating approach is a scalable technique, large area films such as the ones described here have a variety of crucial emerging applications in areas such as energy, catalysis, and chemical sensing.
Collapse
Affiliation(s)
- Qian Huang
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, Richland, Washington 99354, USA
| | - Brent M Devetter
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, Richland, Washington 99354, USA
| | - Timothy Roosendaal
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, Richland, Washington 99354, USA
| | - Max LaBerge
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, Richland, Washington 99354, USA
| | - Bruce E Bernacki
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, Richland, Washington 99354, USA
| | - Kyle J Alvine
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, Richland, Washington 99354, USA
| |
Collapse
|
10
|
Myers TL, Tonkyn RG, Danby TO, Taubman MS, Bernacki BE, Birnbaum JC, Sharpe SW, Johnson T. EXPRESS: Accurate Measurement of the Optical Constants n and k for a Series of 57 Inorganic and Organic Liquids for Optical Modeling and Detection. Appl Spectrosc 2017:3702817735817. [PMID: 28933194 DOI: 10.1177/0003702817735817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
|
11
|
Bernacki BE, Douglas M, Erchinger JL, Fuller ES, Keillor ME, Morley SM, Mullen CA, Orrell JL, Panisko ME, Warren GA, Wright ME. Optical design considerations for efficient light collection from liquid scintillation counters. Appl Opt 2015; 54:2413-2423. [PMID: 25968530 DOI: 10.1364/ao.54.002413] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 02/10/2015] [Indexed: 06/04/2023]
Abstract
Liquid scintillation counters measure charged particle-emitting radioactive isotopes and are used for environmental studies, nuclear chemistry, and life science. Alpha and beta emissions arising from the material under study interact with the scintillation cocktail to produce light. The prototypical liquid scintillation counter employs low-level photon-counting detectors to measure the arrival of the scintillation. For reliable operation, the counting instrument must convey the scintillation light to the detectors efficiently and predictably. Current best practices employ the use of two or more detectors for coincidence processing to discriminate true scintillation events from background events due to instrumental effects such as photomultiplier tube dark rates, tube flashing, or other light emission not generated in the scintillation cocktail vial. In low-background liquid scintillation counters, additional attention is paid to shielding the scintillation cocktail from naturally occurring radioactive material present in the laboratory and within the instrument's construction materials. Low-background design is generally at odds with optimal light collection. This study presents the evolution of a light collection design for liquid scintillation counting (LSC) in a low-background shield. The basic approach to achieve both good light collection and a low-background measurement is described. The baseline signals arising from the scintillation vial are modeled and methods to efficiently collect scintillation light are presented as part of the development of a customized low-background, high-sensitivity LSC system.
Collapse
|
12
|
Phillips MC, Taubman MS, Bernacki BE, Cannon BD, Stahl RD, Schiffern JT, Myers TL. Real-time trace gas sensing of fluorocarbons using a swept-wavelength external cavity quantum cascade laser. Analyst 2014; 139:2047-56. [DOI: 10.1039/c3an01642k] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
13
|
Johnson TJ, Bernacki BE, Redding RL, Su YF, Brauer CS, Myers TL, Stephan EG. Intensity-value corrections for integrating sphere measurements of solid samples measured behind glass. Appl Spectrosc 2014; 68:1224-1234. [PMID: 25280186 DOI: 10.1366/13-07322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Accurate and calibrated directional-hemispherical reflectance spectra of solids are important for both in situ and remote sensing. Many solids are in the form of powders or granules and to measure their diffuse reflectance spectra in the laboratory, it is often necessary to place the samples behind a transparent medium such as glass for the ultraviolet (UV), visible, or near-infrared spectral regions. Using both experimental methods and a simple optical model, we demonstrate that glass (fused quartz in our case) leads to artifacts in the reflectance values. We report our observations that the measured reflectance values, for both hemispherical and diffuse reflectance, are distorted by the additional reflections arising at the air-quartz and sample-quartz interfaces. The values are dependent on the sample reflectance and are offset in intensity in the hemispherical case, leading to measured values up to ~6% too high for a 2% reflectance surface, ~3.8% too high for 10% reflecting surfaces, approximately correct for 40-60% diffuse-reflecting surfaces, and ~1.5% too low for 99% reflecting Spectralon® surfaces. For the case of diffuse-only reflectance, the measured values are uniformly too low due to the polished glass, with differences of nearly 6% for a 99% reflecting matte surface. The deviations arise from the added reflections from the quartz surfaces, as verified by both theory and experiment, and depend on sphere design. Empirical correction factors were implemented into post-processing software to redress the artifact for hemispherical and diffuse reflectance data across the 300-2300 nm range.
Collapse
|
14
|
Spagnolo V, Patimisco P, Borri S, Scamarcio G, Bernacki BE, Kriesel J. Part-per-trillion level SF6 detection using a quartz enhanced photoacoustic spectroscopy-based sensor with single-mode fiber-coupled quantum cascade laser excitation. Opt Lett 2012; 37:4461-3. [PMID: 23114329 DOI: 10.1364/ol.37.004461] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
A sensitive spectroscopic sensor based on a hollow-core fiber-coupled quantum cascade laser (QCL) emitting at 10.54 μm and quartz enhanced photoacoustic spectroscopy (QEPAS) technique is reported. The design and realization of mid-IR fiber and coupler optics has ensured single-mode QCL beam delivery to the QEPAS sensor. The collimation optics was designed to produce a laser beam of significantly reduced beam size and waist so as to prevent illumination of the quartz tuning fork and microresonator tubes. SF(6) was selected as the target gas. A minimum detection sensitivity of 50 parts per trillion in 1 s was achieved with a QCL power of 18 mW, corresponding to a normalized noise-equivalent absorption of 2.7×10(-10) W·cm(-1)/Hz(1/2).
Collapse
Affiliation(s)
- Vincenzo Spagnolo
- Dipartimento Interateneo di Fisica, University and Politecnico of Bari, CNR-IFN UOS BARI, Bari, Italy.
| | | | | | | | | | | |
Collapse
|
15
|
Krishnaswami K, Bernacki BE, Hô N, Allen PJ, Anheier NC. Lateral shearing interferometer for measuring photoinduced refractive index change in As(2)S(3). Rev Sci Instrum 2008; 79:095101. [PMID: 19044448 DOI: 10.1063/1.2973640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We have built and demonstrated a lateral shearing interferometer as a process engineering and control tool for the fabrication and characterization of direct-laser-written waveguide structures in chalcogenide glasses. Photoinduced change in refractive index of 0.154+/-0.002 was measured for as-deposited amorphous As(2)S(3) thin films at 633 nm with an estimated measurement uncertainty of 1.3% for this air-gap interferometer configuration. The simple design of this interferometer can easily be adapted to other wavelengths including mid- and long-wave infrared regions to measure changes in refractive index or material inhomogeneities in transmissive materials.
Collapse
Affiliation(s)
- Kannan Krishnaswami
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, USA
| | | | | | | | | |
Collapse
|
16
|
Bernacki BE, Mansuripur M. Causes of focus-error feedthrough in optical-disk systems: astigmatic and obscuration methods. Appl Opt 1994; 33:735-743. [PMID: 20862069 DOI: 10.1364/ao.33.000735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
High-density magneto-optical recording systems require sensitive and robust focus position sensors that are immune to transient changes in the amplitude and the phase of the light diffracted from pregrooved media during the seek operation. The false focus-error signal produced by track crossing during seeking is termed feedthrough. Total immunity to feedthrough is never achieved, although some focus-error detection methods, notably the obscuration method, perform better in this regard. The astigmatic focus-error detection method is usually operated with a large astigmatic foci separation distance to facilitate detector alignment and to permit push-pull tracking, which increases pattern noise and contributes to its poor resistance to feedthrough. Pattern noise is caused by the projection of the intensity pattern at the exit pupil of the objective lens onto the detector plane, at which it produces false focus-error signals. The obscuration method, a diffraction-limited method of focus-error sensing, evens out his pattern noise and is therefore more resistant to feedthrough. We present numerical modeling results that compare the feedthrough performance of the astigmatic and the obscuration methods of focus-error detection.
Collapse
|
17
|
Abstract
Substrates for magneto-optical disks are produced economically and efficiently by injection molding of polycarbonate plastics. Unfortunately, most plastics are birefringent, with different refractive indices in the plane of the disk (lateral birefringence) and perpendicular to the plane of the disk (vertical birefringence). One manifestation of media birefringence is the existence of a focus offset between the two distinct best-focus positions for data detection and tracking. This focus offset degrades overall system performance as the compromise focus position between the two best-focus points reduces the operating margin of the individual data and tracking channels. We present detailed numerical modeling results on the role of substrate birefringence in causing this focus offset.
Collapse
|
18
|
Bernacki BE, Bates K, Mansuripur M, Hansen D, Cisneros D. Characterization of a novel focusing/tracking technique with increased feedthrough immunity for optical-disk applications: the double-astigmatic method. Appl Opt 1993; 32:5789-5796. [PMID: 20856401 DOI: 10.1364/ao.32.005789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The astigmatic-focusing/push-pull tracking-error detection method is an elegant and sensitive optical servo technique. Unfortunately the formation of error signals far from either line focus of the astigmat (for relaxing alignment tolerances and broadening the servo's acquisition range) gives rise to undesired diffraction effects in the focus servo channel owing to track crossings of the pregrooved disk by the optical stylus, especially if certain aberrations are present. These undesired effects are given several names: pattern noise, optical servo cross talk, and feedthrough. By combining two astigmatic lenses and their associated detectors, one can configure a differential variant of the astigmatic technique. This double-astigmatic method greatly reduces pattern noise caused by the presence of spurious astigmatism oriented with its line foci at ±45° to the disk tracks. In this paper we present numerical modeling and experimental data that demonstrate the effectiveness of this focusing/tracking technique in feedthrough suppression.
Collapse
|
19
|
Bernacki BE, Hemmer PR, Smith SP, Ezekiel S. Alignment-insensitive technique for wideband tuning of an unmodified semiconductor laser. Opt Lett 1988; 13:725-727. [PMID: 19746016 DOI: 10.1364/ol.13.000725] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Using simple optical components and an unmodified commercial semiconductor laser, a frequency-selective self-aligning optical-feedback technique has been devised that allows a semiconductor laser to be tuned to and scanned about any optical frequency within the laser gain curve. This technique employs a graded-index rod lens cat's eye and an intracavity étalon.
Collapse
|