Achievement of 0.005 % combined transfer uncertainties in the NIST detector calibration facility

Improvements in a lamp-monochromator-based facility at the National Institute of Standards and Technology (NIST), the Visible near-infrared Spectral Comparator Facility (VisSCF) which is used to calibrate optical detectors for spectral radiant power responsivity from 300 nm to 1100 nm, are described. These changes include extending the VisSCF operational range down to 300 nm from 350 nm, thereby fully covering the ultraviolet-A (UVA) spectral region and partially covering the UVB range. These improvements have lowered the magnitudes of most of the components in the uncertainty budget and have led to combined 0.005 % transfer (k=1) uncertainties in the spectral power responsivity calibrations over most of the spectral range. Redevelopment of the uncertainty budget results in total expanded uncertainties of spectral responsivities of less than 0.1 % (k=2) over the spectral range from 380 nm to 980 nm, with the greatest uncertainty term coming from the calibrations of the transfer standards.

Синхронное управление прошедшим и отраженными светом в полупроводниковых хромхалькогенидных шпинелях

A way for synchronous control of the intensity of transmitted and reflected light in magnetic semiconductors by an external magnetic field is proposed in the infrared spectral region. For illustration, we obtained the magnetoreflection and magnetotransmission spectra of unpolarized light in single crystals of Hg(Cd)Cr2Se4 spinel.

DEVELOPMENT OF A BROADBAND ELECTROMAGNETIC RADIATION ABSORBER BASED ON MULTIWALL CARBON NANOTUBES AND ITS APPLICATION IN BOLOMETRIC RECEIVERS

This work is devoted to the development of a technique for obtaining an array of multi-walled vertically aligned carbon nanotubes (VACNT) with a thickness of up to 120 μm on Si/Al2O3/Fe substrates and to the study of their absorbing properties in the THz spectral region, as well as to the assessment of their prospects as a broadband THz radiation absorber based on calculations of the spectral dependence of absorption coefficient for traditional and inverted-type bolometric devices. It is shown that the absorption of the VACNT array transferred onto the Revalpha polymer substrate reaches 70–80% in the wavelength range of 40–200 µm. Calculations show that traditional bolometers with an absorber based on VACNT have the best sensitivity at wavelengths less than 100 μm, and inverted bolometers also having a VACNT layer have the best sensitivity at wavelengths exceeding 50 μm, which makes them complementary to each other.

Dependence of the Xe flash lamps’ UV radiation efficiency on the volumetric power density of the discharge

The study results of the peak and average electrical volumetric power density influence on the radiation efficiency and brightness temperature in the 200–300 nm bactericidal spectrum range are presented. A linear dependence of the radiation efficiency change in the 5.1–8.4 % range was obtained with the average volumetric power density increase from 177 to 390 kW/cm3. The brightness temperature dependence in the specified spectral region on the peak volumetric power density is a logarithmic character with decreasing growth rate when approaching 9 kK. This effect can be associated with both radiation blocking by vaporized quartz fumes and with UV light shielding by outer plasma layers

Impact of Structural, Photochemical and Instrumental Effects on Leaf and Canopy Reflectance Variability in the 500–600 nm Range

Current rapid technological improvement in optical radiometric instrumentation provides an opportunity to develop innovative measurements protocols where the remote quantification of the plant physiological status can be determined with higher accuracy. In this study, the leaf and canopy reflectance variability in the PRI spectral region (i.e., 500–600 nm) is quantified using different laboratory protocols that consider both instrumental and experimental set-up aspects, as well as canopy structural effects and vegetation photoprotection dynamics. First, we studied how an incorrect characterization of the at-target incoming radiance translated into an erroneous vegetation reflectance spectrum and consequently in an incorrect quantification of reflectance indices such as PRI. The erroneous characterization of the at-target incoming radiance translated into a 2% overestimation and a 31% underestimation of estimated chlorophyll content and PRI-related vegetation indexes, respectively. Second, we investigated the dynamic xanthophyll pool and intrinsic Chl vs. Car long-term pool changes affecting the entire 500–600 nm spectral region. Consistent spectral behaviors were observed for leaf and canopy experiments. Sun-adapted plants showed a larger optical change in the PRI range and a higher capacity for photoprotection during the light transient time when compared to shade-adapted plants. Outcomes of this work highlight the importance of well-established spectroscopy sampling protocols to detect the subtle photochemical features which need to be disentangled from the structural and biological effects.

Evolution of Ocean Color Atmospheric Correction: 1970–2005

Retrieval of water properties from satellite-borne imagers viewing oceans and coastal areas in the visible region of the spectrum requires removing the effect of the atmosphere, which contributes approximately 80–90% of the measured radiance over the open ocean in the blue spectral region. The Gordon and Wang algorithm originally developed for SeaWiFS (and used with other NASA sensors, e.g., MODIS) forms the basis for many atmospheric removal (correction) procedures. It was developed for application to imagery obtained over the open ocean (Case 1 waters), where the aerosol is usually non-absorbing, and is used operationally to process global data from SeaWiFS, MODIS and VIIRS. Here, I trace the evolution of this algorithm from early NASA aircraft experiments through the CZCS, OCTS, SeaWiFs, MERIS, and finally the MODIS sensors. Strategies to extend the algorithm to situations where the aerosol is strongly absorbing are examined. Its application to sensors with additional and unique capabilities is sketched. Problems associated with atmospheric correction in coastal waters are described.

Changes in Spectral Fluorescence Properties of a Near-Infrared Photosensitizer in a Nanoform as a Coating of an Optical Fiber Neuroport

In this work, we tested a new approach to assess the presence of inflammatory process in the implant area using spectral methods and the technique of fiber fluorescence analysis of photosensitizers in nanoform. First of all, the spectral characteristics of the photosensitizer when interacting with the porous surface of the implant, based on hydroxyapatite under in vitro and in vivo conditions, were determined. Thus, it was shown that spectral characteristics of photosensitizers can be used for judgement on the process of inflammation in the implant area and thus on the local presence of the immunocompetent cells. The analysis was performed at a sufficient depth in the biotissue by using the near-infrared spectral region, as well as two different methods: fiber-based laser spectroscopy and fiber-optic neuroscopy, which served to monitor the process and regular fluorescence diagnosis of the studied area. Fluorescence spectroscopic analysis was performed on experimental animals in vivo, i.e., under conditions of active immune system intervention, as well as on cell cultures in vitro in order to judge the role of the immune system in the interaction with the implant in comparison. Thus, the aim of the study was to determine the relationship between the fluorescence signal of nanophotosensitizers in the near infrared spectral region and its parameters with the level of inflammation and the type of surface with which the photosensitizer interacts in the implant area. Thus, fiber-optic control opens up new approaches for further diagnosis and therapy in the implant area, making immune cells a prime target for advanced therapies.