Standoff Detection of Oil and Powder Mixtures at 12 Meters Using a Tunable Quantum Cascade Laser-Based System with a Close Focus Telescope and Uncooled Infrared Detector

We have designed and demonstrated a quantum cascade laser (QCL) based standoff system that utilizes an uncooled mercury cadmium telluride (MCT) detector with lock-in signal processing for chemical identification at a distance of 12.5 meters in indoor ambient light conditions. In the system, a tunable quad-QCL operating (1 MHz) in quasi-continuous wave mode between 8.45 and 10.03 μm (∼1182 to 1000 cm−1) serves as the active mid-infrared source for remotely interrogating mineral, powder, and thin film oil samples including powder mixtures (6, 12.5, 25, and 50%) of crystalline quartz (SiO2) in KBr. Light as reflected from a given sample is collected using a 10-inch (25.4 cm) Dall Kirkham telescope and coupled with ZnSe optics to an uncooled MCT detector. The mixture dependence of the highly transparent KBr and strongly absorbing quartz was found to fit a modified version of the Schatz reflectance model for compacted powder mixtures. All reflectance spectra reported are relative to an Au-coated diffuse reflector. A NIST traceable polystyrene standard reflector was also used to determine the QCL wavelength tuning range and calibration.

Mapping the Morphology and Kinematics of a Lyα-selected Nebula at z = 3.15 with MUSE

Recent wide-field integral-field spectroscopy has revealed the detailed properties of high-redshift Lyα nebulae, most often targeted due to the presence of an active galactic nucleus (AGN). Here, we use VLT/MUSE to resolve the morphology and kinematics of a nebula initially identified due to strong Lyα emission at z ∼ 3.2 (LABn06). Our observations reveal a two-lobed Lyα nebula, at least ∼173 pkpc in diameter, with a light-weighted centroid near a mid-infrared source (within ≈17.2 pkpc) that appears to host an obscured AGN. The Lyα emission near the AGN is also coincident in velocity with the kinematic center of the nebula, suggesting that the nebula is both morphologically and kinematically centered on the AGN. Compared to AGN-selected Lyα nebulae, the surface-brightness profile of this nebula follows a typical exponential profile at large radii (>25 pkpc), although at small radii, the profile shows an unusual dip at the location of the AGN. The kinematics and asymmetry are similar to, and the C iv and He ii upper limits are consistent with, other AGN-powered Lyα nebulae. Double-peaked and asymmetric line profiles suggest that Lyα resonant scattering may be important in this nebula. These results support the picture of the AGN being responsible for powering a Lyα nebula that is oriented roughly in the plane of the sky. Further observations will explore whether the central surface-brightness depression is indicative of either an unusual gas or dust distribution or variation in the ionizing output of the AGN over time.

Near Centimeter-scale FT-MIR Spectrometer based on NZIM Perfect Absorption using Inverted TanCirc Conformal Mapping Geometry

A long sought objective of MEMS research within the oil & gas industry has been the realization of “FT-IR on a chip,” which could hold the potential to migrate laboratory grade chemical spectroscopy into downhole sensor suites. A fundamental obstacle to this research has been the cooling demands of conventional technologies which conflict with the miniaturized sensor volumes required in downhole logging systems and environmental conditions that routinely exceed 125 • C. Near centimeter scale spectroscopic devices are required by a majority of downhole sensor suites, which stands in stark contrast to multiple-decimeter size conventional devices. Here we report a near-centimeter scale FT-MIR ATR spectrometer compatible with downhole volumetric and temperature constraints. The spectrometer is based upon a high-temperature broadband mid-infrared metasurface detector/source combination derived from a geometric inversion of a set of conformal mapping contours. The metasurface elemental structure is derived from a geometric inversion of the canonical TanCirc conformal mapping contours and was found to exhibit a near zero index metamaterial (NZIM) behavior over a spectral range of interest for downhole chemical spectroscopy. The NZIM properties of the metasurface lead to an absorption phenomenon characterized by surface plasmon resonances which confine the absorption mechanism within the ultrathin (λ /300) metasurface plane and make the absorption properties of the microbolometer design relatively insensitive to the material properties of the remaining laminae. This unusual feature allows the metasurface to be integrated on a single VO 2 material thermometric layer and operated at elevated downhole temperatures despite corresponding to the VO2 metal-insulator-transition (MIT) region. Within this transition region however the VO2 layer exhibits a substantially beneficial property in that the VO 2 layer exhibits more than an order of magnitude enhancement in its ambient thermometric properties, leading to an uncooled microbolometer design with predicted maximum detectivity D * = 1.5 × 10 10 cm √ Hz/W and noise equivalent difference temperature NEDT of 1 mK at a modulation frequency of 500 Hz. A sub-millimeter scale thermal infrared source with intrinsic mid-infrared band-limited emission is formed from the same cellular geometric building block, enabling the spectrometer miniaturization. These performance parameters compare well with lower tier laboratory grade FT-MIR spectroscopic instruments and could represent a significant step in the effort towards deploying miniaturized high-temperature mid-infrared spectroscopy into oilfield downhole logging applications.

Fluoroindate Glass Co-Doped with Yb3+/Ho3+ as a 2.85 μm Luminescent Source for MID-IR Sensing

This work reports on the fabrication and analysis of near-infrared and mid-infrared luminescence spectra and their decays in fluoroindate glasses co-doped with Yb3+/Ho3+. The attention has been paid to the analysis of the Yb3+→ Ho3+ energy transfer processed ions in fluoroindate glasses pumped by 976 nm laser diode. The most effective sensitization for 2 μm luminescence has been obtained in glass co-doped with 0.8YbF3/1.6HoF3. Further study in the mid-infrared spectral range (2.85 μm) showed that the maximum emission intensity has been obtained in fluoroindate glass co-doped with 0.1YbF3/1.4HoF3. The obtained efficiency of Yb3+→ Ho3+ energy transfer was calculated to be up to 61% (0.8YbF3/1.6HoF3), which confirms the possibility of obtaining an efficient glass or glass fiber infrared source for a MID-infrared (MID-IR) sensing application.

Observing the influence of the youngest super star clusters in NGC 1569: Keck Brackett α spectroscopy

ABSTRACT We report Keck–NIRSPEC observations of the Brackett α 4.05 μm recombination line across the two candidate embedded super star clusters (SSCs) in NGC 1569. These SSCs power a bright H ii region and have been previously detected as radio and mid-infrared sources. Supplemented with high-resolution VLA mapping of the radio continuum along with IRTF–TEXES spectroscopy of the [S iv] 10.5 μm line, the Brackett α data provide new insight into the dynamical state of gas ionized by these forming massive clusters. Near-infrared sources detected in 2 μm images from the slit-viewing Camera are matched with Gaia sources to obtain accurate celestial coordinates and slit positions to within ∼0${_{.}^{\prime\prime}}$1. Br α is detected as a strong emission peak powered by the less luminous infrared source, MIR1 (LIR ∼ 2 × 107 $\rm L_\odot$). The second candidate SSC MIR2 is more luminous (LIR ≳ 4 × 108 $\rm L_\odot$) but exhibits weak radio continuum and Br α emission, suggesting the ionized gas is extremely dense (ne ≳ 105 cm−3), corresponding to hypercompact H ii regions around newborn massive stars. The Br α and [S iv] lines across the region are both remarkably symmetric and extremely narrow, with observed line widths Δv ≃ 40 $\rm km\, s^{-1}$, full width at half-maximum. This result is the first clear evidence that feedback from NGC 1569’s youngest giant clusters is currently incapable of rapid gas dispersal, consistent with the emerging theoretical paradigm in the formation of giant star clusters.

Characterization and potential for reducing optical resonances in Fourier transform infrared spectrometers of the Network for the Detection of Atmospheric Composition Change (NDACC)

Although optical components in Fourier transform infrared (FTIR) spectrometers are preferably wedged, in practice, infrared spectra typically suffer from the effects of optical resonances (“channeling”) affecting the retrieval of weakly absorbing gases. This study investigates the level of channeling of each FTIR spectrometer within the Network for the Detection of Atmospheric Composition Change (NDACC). Dedicated spectra were recorded by more than 20 NDACC FTIR spectrometers using a laboratory mid-infrared source and two detectors. In the indium antimonide (InSb) detector domain (1900–5000 cm−1), we found that the amplitude of the most pronounced channeling frequency amounts to 0.1 ‰ to 2.0 ‰ of the spectral background level, with a mean of (0.68±0.48) ‰ and a median of 0.60 ‰. In the mercury cadmium telluride (HgCdTe) detector domain (700–1300 cm−1), we find even stronger effects, with the largest amplitude ranging from 0.3 ‰ to 21 ‰ with a mean of (2.45±4.50) ‰ and a median of 1.2 ‰. For both detectors, the leading channeling frequencies are 0.9 and 0.11 or 0.23 cm−1 in most spectrometers. The observed spectral frequencies of 0.11 and 0.23 cm−1 correspond to the optical thickness of the beam splitter substrate. The 0.9 cm−1 channeling is caused by the air gap in between the beam splitter and compensator plate. Since the air gap is a significant source of channeling and the corresponding amplitude differs strongly between spectrometers, we propose new beam splitters with the wedge of the air gap increased to at least 0.8∘. We tested the insertion of spacers in a beam splitter's air gap to demonstrate that increasing the wedge of the air gap decreases the 0.9 cm−1 channeling amplitude significantly. A wedge of the air gap of 0.8∘ reduces the channeling amplitude by about 50 %, while a wedge of about 2∘ removes the 0.9 cm−1 channeling completely. This study shows the potential for reducing channeling in the FTIR spectrometers operated by the NDACC, thereby increasing the quality of recorded spectra across the network.

Mergers of Binary Neutron Star Systems: A Multimessenger Revolution

On August 17, 2017, less than two years after the direct detection of gravitational radiation from the merger of two∼30 M⊙ black holes, a binary neutron star merger was identified as the source of a gravitational wave signal of ∼100 s duration that occurred at less than 50 Mpc from Earth. A short gamma-ray burst was independently identified in the same sky area by the Fermi and INTEGRAL satellites for high energy astrophysics, which turned out to be associated with the gravitational event. Prompt follow-up observations at all wavelengths led first to the detection of an optical and infrared source located in the spheroidal Galaxy NGC4993 and, with a delay of ∼10 days, to the detection of radio and X-ray signals. This article revisits these observations and focusses on the early optical/infrared source, which was thermal in nature and powered by the radioactive decay of the unstable isotopes of elements synthesized via rapid neutron capture during the merger and in the phases immediately following it. The far-reaching consequences of this event for cosmic nucleosynthesis and for the history of heavy elements formation in the Universe are also illustrated.

Mid-infrared parametric wavelength conversion seeded with fiber optical parametric sources

A new method of seeding X2 optical parametric converters with X3 fiber optical parametric sources is introduced. We demonstrate a tunable mid-infrared source operating at around 3 µm with the technique and discuss the potential of this architecture.