Bruce Bernacki - Academia.edu (original) (raw)
Papers by Bruce Bernacki
IEEE Photonics Technology Letters, 2008
We report divergence, astigmatism, and beam propagation factor (M 2) measurements of quantum casc... more We report divergence, astigmatism, and beam propagation factor (M 2) measurements of quantum cascade lasers (QCLs) with emission wavelengths of 8.77 m. Emission profiles from the facet showed full-width at half-maximum divergence angles of 62 and 32 6 2 for the fast and slow axes, respectively. Diffraction-limited Ge aspheric microlenses were designed and fabricated to efficiently collect, collimate, and focus QCL emission. A confocal system comprised of these lenses was used to measure M 2 yielding 1.8 and 1.2 for the fast and slow axes, respectively. Astigmatism at the exit facet was calculated to be about 3.4 m, or less than half a wave. To the best of our knowledge, this is the first experimental measurement of astigmatism and M 2 reported for midinfrared QCLs.
Observations at mas-resolution scales and high dynamic range hold a central place in achieving, f... more Observations at mas-resolution scales and high dynamic range hold a central place in achieving, for instance, the spectroscopic characterization of exo-Earths or the detailed mapping of their protoplanetary disc birthplace. Ground or space-based multi-aperture infrared interferometry is a promising technique to tackle these goals. But significant efforts still need to be undertaken to achieve a simplification of these instruments if we want to combine the light from a large number of telescopes. Integrated-optics appears as an alternative to the current conventional designs, especially if its use can be extended to a higher number of astronomical bands. This article reports for the first time the experimental demonstration of the feasibility of an integrated-optics approach to mid-infrared beam combination for single-mode stellar interferometry. We have fabricated a 2-telescope beam combiner prototype integrated on a substrate of chalcogenide glasses, a material transparent from 1 t...
Optical Sensors and Sensing Congress
Optical Engineering
Since solids are only sometimes seen en masse in a pure bulk form, and for liquids other than wat... more Since solids are only sometimes seen en masse in a pure bulk form, and for liquids other than water almost never, a capability to model reflectance spectra from analytes deposited on various substrates would be highly advantageous. If available, the real, nðνÞ, and imaginary, kðνÞ, components of the complex refractive index, n ∼ ¼ n þ ik, can be used to simulate infrared spectra, accounting for reflection, refraction, and absorption phenomena as a function of wavelength. We focus on using the Pacific Northwest National Laboratory (PNNL) derived n∕k vectors for solid and liquid analytes deposited as thin layers on different types of substrates including conductors, such as aluminum, and inorganic dielectrics, such as glass. The model is an adaptation of the Monte Carlo ray trace modeling program, TracePro, extended through the use of its macrolanguage. The model is tested using thin films of organic liquids including silicone oil and no. 2 diesel fuel, as well as organic solids such as caffeine and acetaminophen on aluminum and glass. The predicted spectra for the solid films were compared to experimental hemispherical reflectance data measured using a Fourier transform spectrometer with an integrating sphere. The thickness of the calculated layer is a parameter for predicting the (transflectance) spectra and is obtained using the areal density measured from gravimetric methods to generate the thin-layer samples. Comparison of the calculated spectra with experimental hemispherical reflectance data shows excellent agreement, indicating promise for the use of measured n∕k data to synthesize reference spectral data. In particular, accounting for the inhomogeneity of the deposits greatly improved the match with experimental data. Finally, the theoretical modeling shows that for thicker layers (ca. 20 to 100 μm) of typical organics possessing moderately strong k values, the longwave infrared features are often saturated and better spectral contrast is obtained from the overtone/combination bands in the shortwave infrared. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
Journal of Analytical Atomic Spectrometry
Image of the filament ablation with femtosecond laser and filament ablation craters.
Optics Express
chemical plume detection in turbulent atmospheric conditions with a sweptwavelength external cavi... more chemical plume detection in turbulent atmospheric conditions with a sweptwavelength external cavity quantum cascade laser," Opt. Express 28, 7408-7424 (2020)
Physical Chemistry Chemical Physics
2D plume and spectral imaging illustrate expansion dynamics and corresponding chemical evolution ... more 2D plume and spectral imaging illustrate expansion dynamics and corresponding chemical evolution of atoms and molecules in filament produced plasmas.
Applied spectroscopy, 2017
For optical modeling and other purposes, we have created a library of 57 liquids for which we hav... more 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...
Review of Scientific Instruments
We describe the development of a custom-built two-axis flow coater for the deposition of polymeri... more 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.
Journal of Visualized Experiments
Applied Physics Letters, 2017
The spectral signature of nanoplasmonic films are both robust and tailorable with optical respons... more The spectral signature of nanoplasmonic films are both robust and tailorable with optical responses ranging from the visible to the near-infrared. We present the development of flexible, elastomeric nanoplasmonic films consisting of periodic arrays of gold nanocups as tamper indicating films. Gold nanocups have polarization-sensitive optical properties that may be manufactured into films that offer unique advantages for tamper indication. These flexible films can be made quickly and at low-cost using commercially available monodisperse polystyrene nanospheres through self-assembly followed by plasma etching, metal deposition, and lift-off from a sacrificial substrate. Polarization-and angle-dependent optical spectroscopic measurements were performed to characterize the fabricated films. Using polarization-sensitive hyperspectral imaging, we demonstrate how these films can be applied to tamper indication and counterfeit resistance applications. Plasmonic nanomaterials have shown a great deal of promise in applications ranging from robust color displays, 1 colorimetric sensors, 2 and highly sensitive chemical detection. 3 When illuminated with certain frequencies of light, the free electron gas in subdiffraction-limited metallic nanostructures coherently and collectively oscillates. 4 This effect, called the localized surface plasmon resonance (LSPR), grants ensembles of coinage metal nanostructures unique macroscopic optical properties that may be engineered for exciting photonics applications. In this letter, we focus on the design, fabrication, and characterization of anisotropic plasmonic nanostructures-gold nanocups-applied to tamper indication and counterfeit resistant proof-of-concept applications. Advances in tamper indication technologies are highly sought after in areas as varied as nuclear nonproliferation, 5 supply chain management and logistics, 6 food and pharmaceutical safety, 7 and consumer anti-identity theft protection. 8 To help combat illicit activities in these areas, plasmonic nanomaterials offer exciting possibilities. Nano-based tamper indicating films are particularly attractive because it is exceedingly difficult to counterfeit nanostructured films without advanced instrumentation and highly specialized knowledge. In the case of plasmonic nanofilms, the unique spectral response is dependent on factors such as sample orientation, the shape and size of the plasmonic metal, and the refractive index of the backing film material. To date, researchers have investigated tamper indicating substrates using precisely patterned plasmonic nanoparticles primarily based on the near-field coupling between structures. 9 This approach can provide anti-tampering _____________________________
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2015
Neutron multiplicity counters are used in safeguards to provide rapid assay of samples which cont... more Neutron multiplicity counters are used in safeguards to provide rapid assay of samples which contain an unknown amount of plutonium in a potentially unknown configuration. A project at PNNL is using regular and nickel-quenched 6LiF/ZnS neutron-scintillator sheets and wavelength shifting plastic for light pipes in place of 3He. A combination of laboratory and modeling work predicts a LiF/ZnS-based system to be able to match or exceed the performance of the best 3He-based systems available. Also, the Ni-quenched material is expected to allow for improved neutron/gamma-ray discrimination at twice the event rate relative to the non-Ni-quenched LiF/ZnS. A new system based on the LiF/ZnS material is under construction and components are being used to optimize the detection efficiency and neutron/gamma-ray discrimination properties. Components of the new system are partially constructed and undergoing performance testing utilizing high-speed digitizers with field programmable gate arrays to perform the neutron/gamma-ray discrimination. The expected performance of the full-scale system is expected to be nearly the same as for 3He-based systems and is due for completion in 2016.
IEEE Photonics Technology Letters, 2008
We report divergence, astigmatism, and beam propagation factor (M 2) measurements of quantum casc... more We report divergence, astigmatism, and beam propagation factor (M 2) measurements of quantum cascade lasers (QCLs) with emission wavelengths of 8.77 m. Emission profiles from the facet showed full-width at half-maximum divergence angles of 62 and 32 6 2 for the fast and slow axes, respectively. Diffraction-limited Ge aspheric microlenses were designed and fabricated to efficiently collect, collimate, and focus QCL emission. A confocal system comprised of these lenses was used to measure M 2 yielding 1.8 and 1.2 for the fast and slow axes, respectively. Astigmatism at the exit facet was calculated to be about 3.4 m, or less than half a wave. To the best of our knowledge, this is the first experimental measurement of astigmatism and M 2 reported for midinfrared QCLs.
Observations at mas-resolution scales and high dynamic range hold a central place in achieving, f... more Observations at mas-resolution scales and high dynamic range hold a central place in achieving, for instance, the spectroscopic characterization of exo-Earths or the detailed mapping of their protoplanetary disc birthplace. Ground or space-based multi-aperture infrared interferometry is a promising technique to tackle these goals. But significant efforts still need to be undertaken to achieve a simplification of these instruments if we want to combine the light from a large number of telescopes. Integrated-optics appears as an alternative to the current conventional designs, especially if its use can be extended to a higher number of astronomical bands. This article reports for the first time the experimental demonstration of the feasibility of an integrated-optics approach to mid-infrared beam combination for single-mode stellar interferometry. We have fabricated a 2-telescope beam combiner prototype integrated on a substrate of chalcogenide glasses, a material transparent from 1 t...
Optical Sensors and Sensing Congress
Optical Engineering
Since solids are only sometimes seen en masse in a pure bulk form, and for liquids other than wat... more Since solids are only sometimes seen en masse in a pure bulk form, and for liquids other than water almost never, a capability to model reflectance spectra from analytes deposited on various substrates would be highly advantageous. If available, the real, nðνÞ, and imaginary, kðνÞ, components of the complex refractive index, n ∼ ¼ n þ ik, can be used to simulate infrared spectra, accounting for reflection, refraction, and absorption phenomena as a function of wavelength. We focus on using the Pacific Northwest National Laboratory (PNNL) derived n∕k vectors for solid and liquid analytes deposited as thin layers on different types of substrates including conductors, such as aluminum, and inorganic dielectrics, such as glass. The model is an adaptation of the Monte Carlo ray trace modeling program, TracePro, extended through the use of its macrolanguage. The model is tested using thin films of organic liquids including silicone oil and no. 2 diesel fuel, as well as organic solids such as caffeine and acetaminophen on aluminum and glass. The predicted spectra for the solid films were compared to experimental hemispherical reflectance data measured using a Fourier transform spectrometer with an integrating sphere. The thickness of the calculated layer is a parameter for predicting the (transflectance) spectra and is obtained using the areal density measured from gravimetric methods to generate the thin-layer samples. Comparison of the calculated spectra with experimental hemispherical reflectance data shows excellent agreement, indicating promise for the use of measured n∕k data to synthesize reference spectral data. In particular, accounting for the inhomogeneity of the deposits greatly improved the match with experimental data. Finally, the theoretical modeling shows that for thicker layers (ca. 20 to 100 μm) of typical organics possessing moderately strong k values, the longwave infrared features are often saturated and better spectral contrast is obtained from the overtone/combination bands in the shortwave infrared. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
Journal of Analytical Atomic Spectrometry
Image of the filament ablation with femtosecond laser and filament ablation craters.
Optics Express
chemical plume detection in turbulent atmospheric conditions with a sweptwavelength external cavi... more chemical plume detection in turbulent atmospheric conditions with a sweptwavelength external cavity quantum cascade laser," Opt. Express 28, 7408-7424 (2020)
Physical Chemistry Chemical Physics
2D plume and spectral imaging illustrate expansion dynamics and corresponding chemical evolution ... more 2D plume and spectral imaging illustrate expansion dynamics and corresponding chemical evolution of atoms and molecules in filament produced plasmas.
Applied spectroscopy, 2017
For optical modeling and other purposes, we have created a library of 57 liquids for which we hav... more 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...
Review of Scientific Instruments
We describe the development of a custom-built two-axis flow coater for the deposition of polymeri... more 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.
Journal of Visualized Experiments
Applied Physics Letters, 2017
The spectral signature of nanoplasmonic films are both robust and tailorable with optical respons... more The spectral signature of nanoplasmonic films are both robust and tailorable with optical responses ranging from the visible to the near-infrared. We present the development of flexible, elastomeric nanoplasmonic films consisting of periodic arrays of gold nanocups as tamper indicating films. Gold nanocups have polarization-sensitive optical properties that may be manufactured into films that offer unique advantages for tamper indication. These flexible films can be made quickly and at low-cost using commercially available monodisperse polystyrene nanospheres through self-assembly followed by plasma etching, metal deposition, and lift-off from a sacrificial substrate. Polarization-and angle-dependent optical spectroscopic measurements were performed to characterize the fabricated films. Using polarization-sensitive hyperspectral imaging, we demonstrate how these films can be applied to tamper indication and counterfeit resistance applications. Plasmonic nanomaterials have shown a great deal of promise in applications ranging from robust color displays, 1 colorimetric sensors, 2 and highly sensitive chemical detection. 3 When illuminated with certain frequencies of light, the free electron gas in subdiffraction-limited metallic nanostructures coherently and collectively oscillates. 4 This effect, called the localized surface plasmon resonance (LSPR), grants ensembles of coinage metal nanostructures unique macroscopic optical properties that may be engineered for exciting photonics applications. In this letter, we focus on the design, fabrication, and characterization of anisotropic plasmonic nanostructures-gold nanocups-applied to tamper indication and counterfeit resistant proof-of-concept applications. Advances in tamper indication technologies are highly sought after in areas as varied as nuclear nonproliferation, 5 supply chain management and logistics, 6 food and pharmaceutical safety, 7 and consumer anti-identity theft protection. 8 To help combat illicit activities in these areas, plasmonic nanomaterials offer exciting possibilities. Nano-based tamper indicating films are particularly attractive because it is exceedingly difficult to counterfeit nanostructured films without advanced instrumentation and highly specialized knowledge. In the case of plasmonic nanofilms, the unique spectral response is dependent on factors such as sample orientation, the shape and size of the plasmonic metal, and the refractive index of the backing film material. To date, researchers have investigated tamper indicating substrates using precisely patterned plasmonic nanoparticles primarily based on the near-field coupling between structures. 9 This approach can provide anti-tampering _____________________________
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2015
Neutron multiplicity counters are used in safeguards to provide rapid assay of samples which cont... more Neutron multiplicity counters are used in safeguards to provide rapid assay of samples which contain an unknown amount of plutonium in a potentially unknown configuration. A project at PNNL is using regular and nickel-quenched 6LiF/ZnS neutron-scintillator sheets and wavelength shifting plastic for light pipes in place of 3He. A combination of laboratory and modeling work predicts a LiF/ZnS-based system to be able to match or exceed the performance of the best 3He-based systems available. Also, the Ni-quenched material is expected to allow for improved neutron/gamma-ray discrimination at twice the event rate relative to the non-Ni-quenched LiF/ZnS. A new system based on the LiF/ZnS material is under construction and components are being used to optimize the detection efficiency and neutron/gamma-ray discrimination properties. Components of the new system are partially constructed and undergoing performance testing utilizing high-speed digitizers with field programmable gate arrays to perform the neutron/gamma-ray discrimination. The expected performance of the full-scale system is expected to be nearly the same as for 3He-based systems and is due for completion in 2016.