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We present a closure experiment between new inherent optical properties (IOPs: absorption a, scattering b, back-scattering b(b)) and apparent optical properties (AOPs: remote-sensing reflectance R-rs, irradiance reflectance R, and anisotropic factor at nadir Q(n)) data of Ionian and Adriatic seawaters, from very clear to turbid waters, ranging across one order of magnitude in R-rs. The internal consistency of the IOP-AOP matchups was investigated though radiative transfer closure. Using the in situ IOPs, we predicted the AOPs with the commercial radiative transfer solver Hydrolight. Closure was limited by two unresolved issues, one regarding processing of in situ data and the other related to radiative transfer modeling. First, different correction methods of the absorption data measured by the Wetlabs ac-s produced high variations in simulated reflectances, reaching 40% for the highest reflectances in our dataset. Second, the lack of detailed volume scattering function measurements forces us to adopt analytical functions that are consistent with a given particle backscattering ratio. The analytical phase functions named Fournier-Forand and two-term Kopelevich presented reasonable angular shapes with respect to measurements at a few backward angles. Between these phase functions, induced changes were within 4% for R-rs, within 11% for R, and within 10% for Q(n). Additionally, closure of Q(n) was generally not successful considering radiometric uncertainties. Simulated Q(n) overestimated low values and underestimated high values, especially at 665 nm, where Hydrolight was unable to predict measured Q(n) values greater than 6 sr. The physical nature of Q(n) makes this mismatch almost independent of the measured IOPs, thus precluding Q(n) tuning by varying the former. The non-closure of Q(n) might be caused by an inaccurate phase function and, to a lesser extent, by the modeling of the incoming radiance. For the future, this remains the task of accurate absorption and phase function measurements, especially at red wavelengths. (C) 2016 Optical Society of America

The Monte Carlo model was developed to simulate the collimated solar irradiation transfer and energy harvest in a hollow louver made of silica glass and filled with water. The full solar spectrum from the air mass 1.5 database was adopted and divided into various discrete bands for spectral calculations. The band-averaged spectral properties for the silica glass and water were obtained. Ray tracing was employed to find the solar energy harvested by the louver. Computational efficiency and accuracy were examined through intensive comparisons of different band partition approaches, various photon numbers, and element divisions. The influence of irradiation direction on the solar energy harvest efficiency was scrutinized. It was found that within a 15° polar angle of incidence, the harvested solar energy in the louver was high, and the total absorption efficiency reached 61.2% under normal incidence for the current louver geometry.

A new procedure is presented for-determining in situ the solar calibration constant, i.e., the Sun-sky radiometer counts for a direct normal solar flux extrapolated to the top of the atmosphere. The method makes use of a modified version of the Langley plot based on the use of an inversion code of column-integrated aerosol size distribution, and it is ordinarily applied to calibrate Prede Sun-sky radiometers. To analyze how such an in situ method can work accurately, the technique has been applied to a five-month dataset obtained from measurements taken in Rome, Italy, by a Prede Sun-sky radiometer from 22 April to 5 November 2001. The precision of the in situ method has been estimated to within 1-2.5%, depending on the wavelength. © 2004 Optical Society of America.

In this study, a novel gonio-hyperspectral imaging system based on light-emitting diodes for the analysis of automotive coatings was validated colorimetrically and spectrally from 368 to 1309 nm. A total of 30 pearlescent, 30 metallic, and 30 solid real automotive coatings were evaluated with this system, the BYK-mac and X-Rite MA98 gonio-spectrophotometers, and also with the SPECTRO 320 spectrometer for further comparison. The results showed very precise correlations, especially in the visible range. In conclusion, this new system provides a deeper assessment of goniochromatic pigments than current approaches due to the expansion of the spectral range to the infrared. Ministerio de Ciencia e Innovación (MICINN) (DPI2011-30090-C02-01); European Union. Francisco J. Burgos-Fernández thanks the Government of Catalonia for his Ph.D. grant.

A processing technique for the determination of the average refractive index and thickness of a two-layer system is presented. It is based on a single measurement with a standard terahertz time-domain spectrometer and the multilayer system thickness. The technique relies on the interference caused by the main pulse with the echoes produced in each material. This approach allows noninvasive inspection of double-layer compound products. (C) 2014 Optical Society of America, The authors thank the Spanish Ministerio de Economia y Competitividad for partially supporting this work through project TEC2012-35797. Federico Sanjuan also thanks Dr. Jorge Tocho and Dr. Alberto Lencina for their encouragement and support.

We show that the interface between gold and thermally formed cuprous oxide, which emits terahertz radiation when illuminated with ultrafast femtosecond lasers, is in fact an AuCu/Cu2O interface due to the formation of the thermal diffusion alloy AuCu. The alloy enables the formation of a Schottky-barrier-like electric field near the interface which is essential to explain the THz emission from these samples. We confirm the formation of this AuCu layer by x-ray diffraction measurements, ellipsometry, and visual inspection. We determined the frequency-dependent complex refractive indices of the Cu2O and AuCu layer and verified them using reflection spectroscopy measurements. These refractive indices can be used for optimizing the thickness of Cu2O for maximum THz emission from these interfaces.

Scattering characteristics of multilayer fluoride coatings for 193 nm deposited by ion beam sputtering and the related interfacial roughnesses are investigated. Quarter- and half-wave stacks of MgF(2) and LaF(3) with increasing thickness are deposited onto CaF(2) and fused silica and are systematically characterized. Roughness measurements carried out by atomic force microscopy reveal the evolution of the power spectral densities of the interfaces with coating thickness. Backward-scattering measurements are presented, and the results are compared with theoretical predictions that use different models for the statistical correlation of interfacial roughnesses.

8 págs.; 8 figs.; OCIS codes: (260.7200) Ultraviolet, extreme; (120.4530) Optical constants; (350.2450) Filters, absorption; (230.4170) Multilayers; (310.6860) Thin films, optical properties., © 2015 Optical Society of America. The low expected absorption of Ca in the extreme ultraviolet (EUV) makes it an attractive material for multilayers and filters because most materials in nature strongly absorb the EUV. Few optical constant data had been reported for Ca. In this research, Ca films of various thicknesses were deposited on gridsupported C films and their transmittance measured in situ from the visible to the soft x-rays. The measurement range contains M2,3 and L2,3 absorption edges. Transmittance measurements were used to obtain the Ca extinction coefficient k. A minimum k of 0.017 was obtained at ∼23 eV, which makes Ca a promising low-absorption material for EUV coatings. A second spectral range of interest for its low absorption is below the Ca L3 edge at ∼343 eV. Measured k data and extrapolations were used to calculate the refractive index n using Kramers.Kronig relations. This is the first self-consistent data set on Ca covering a wide spectral range including the EUV., We acknowledge support by the European Community—Research Infrastructure Action under the FP6 “Structuring the European Research Area” Programme (through the Integrated Infrastructure Initiative “Integrating Activity on Synchrotron and Free Electron Laser Science”) through proposal number Ref. 2007655. This work was also supported by the National Programme for Space Research, Subdirección General de Proyectos de Investigación, Ministerio de Ciencia y Tecnología, project numbers AYA2010-22032 and AYA2013-42590-P. L. Rodrí- guez-de Marcos and S. García-Cortés are thankful to Consejo Superior de Investigaciones Científicas (CSIC) for funding under the Programa JAE, partially supported by the European Social Fund. M. Vidal-Dasilva acknowledges financial support from an FPI fellowship number BES-2006-14047

Photographs of a 120 degrees parhelion and a 22 degrees parhelion within persistent contrails are presented. These phenomena result from hexagonal plate-shaped ice crystals oriented horizontally with diameters between 300 mum and 2 mm. From our observations and reinvestigation of previous reports, we conclude that a subset of the population in persistent contrails can consist of highly regular, oriented, hexagonal plates or columns comparable to the most regular crystals in natural cirrus clouds. This is explained by measured ambient humidities below the formation conditions of natural cirrus. The resulting strong azimuthal variability of the scattering phase function impacts the radiative transfer through persistent contrails.

In the present study we determine the optical parameters of thin metal–dielectric films using two different characterization techniques based on nonparametric and multiple oscillator models. We consider four series of thin metal–dielectric films produced under various deposition conditions with different optical properties. We compare characterization results obtained by nonparametric and multiple oscillator techniques and demonstrate that the results are consistent. The consistency of the results proves their reliability.

A standard quarter wave (λ/4) Fresnel rhomb laterally displaces the output beam with respect to the input beam. This lateral displacement can cause problems when inserting the rhomb in an already aligned optical setup. This note describes the use of two λ/8 rhombs to construct a λ/4 rhomb. The output of the proposed rhomb is colinear with the input beam, and allows a much more flexible optical alignment.

We studied the spherical aberration of an intraocular lens, using third-order theory, ray tracing, and bench measurements by the Ronchi test. Good agreement was obtained for these three methods of investigation. In particular we found that the Ronchi test is an accurate method for quantifying this aberration.

The index of refraction of a-Si(1-x)C(x):H thin films obtained by dc magnetron sputtering was determined by means of IR absorption measurements. Structural and compositional changes that take place by increasing x make the film a mixture of different species, giving an effective value of the refractive index.