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Xiaodong Zhang, Shuangyan He, Afshin Shabani, Peng-Wang Zhai, Keping Du
In examining the dependence of the sea surface reflectance of skylight ρs on sky conditions, wind speed, solar zenith angle, and viewing geometry, Mobley [Appl. Opt.38, 7442 (1999).10.1364/AO.38.007442] assumed ρs is independent of wavelength. Lee et al. [Opt. Express18, 26313 (2010).10.1364/OE.18.026313] showed experimentally that ρs does vary spectrally due to the spectral difference of sky radiance coming from different directions, which was ignored in Mobley's study. We simulated ρs from 350 nm to 1000 nm by explicitly accounting for spectral variations of skylight distribution and Fresnel reflectance...
February 20, 2017: Optics Express
Ke Xu, Qiong Wu, Yongqiang Xie, Ming Tang, Songnian Fu, Deming Liu
The 2-μm optical band has gained much attention recently due to its potential applications in optical fiber communication systems. One constraint in this wavelength region is that the electrical bandwidth of components like modulators and photodetectors is limited by the immature manufacturing technologies. Here we experimentally demonstrated the high-speed signal generation and transmission under bandwidth-constrained scenario at 2-μm. It is enabled by the direct-detection optical filter bank multicarrier (FBMC) modulation technique with constant amplitude zero autocorrelation (CAZAC) equalization...
February 20, 2017: Optics Express
Guofei An, You Wang, Juhong Han, He Cai, Shunyan Wang, Hang Yu, Kepeng Rong, Wei Zhang, Liangping Xue, Hongyuan Wang, Jie Zhou
A diode-pumped alkali laser (DPAL) is thought to provide the significant promise for construction of high-powered lasers in the future. To examine the kinetic processes of the gas-state media (cesium vapor in this study), a mathematical model is developed while the processes including normal 3-enegry-level transition, energy pooling, and ionization are taken into account in this report. The procedures of heat transfer and laser kinetics are combined together in creating the model. We systemically investigate the influences of the temperature, cell length, and cell radius on the output features of a diode-pumped cesium vapor laser...
February 20, 2017: Optics Express
Pablo Benitez, Milena Nikolic, Juan C Miñano
We investigate a new afocal two freeform mirror design problem in first order optics. The resulting first-order partial differential equations for the freeform two mirror system have an analytic solution with the sole condition that the x-y and x'-y' axes are parallel. Two selected solutions are presented. One of them is semiaplanatic (fulfilling the aplanatic condition only for the x-coordinates), while the other is, to our knowledge, the first example of an aplanatic two-mirror system without rotational symmetry...
February 20, 2017: Optics Express
Hyosun Kim, Young-Jun Seo, Byungchoon Yang, Hye Yong Chu
Black perception (perceived blackness of gray 0) of transparent OLED displays was studied in this paper. In pre-test, maximum luminances of acceptable black level under various surround conditions were found in a non-transparent display. In the first experiment, the luminance of a transparent patch was compared with that of an opaque one in order to find the effect of transparency on black perception. As a result, participants perceived the transparent patch darker than the opaque one even when the two were in similar luminance levels, which we termed as the "Transparency Effect...
February 20, 2017: Optics Express
E Al-Rawachy, R P Giddings, J M Tang
A DSP-based cross-channel interference cancellation (CCIC) technique with initial condition-free, fast convergence and signal modulation format independence, is experimentally demonstrated in a two-channel point-to-point digital filter multiple access (DFMA) PON system based on intensity-modulation and direct-detection (IMDD). The CCIC-induced transmission performance improvements under various system conditions are fully investigated for the first time. It is shown that with one iteration only the CCIC technique can achieve a reduction in individual OFDM subcarrier BERs of more than 1000 times, an increase in transmission capacity by as much as 19 times and an increase in optical power budget by as much as 3...
February 20, 2017: Optics Express
Huu-Dat Nguyen, Airán Ródenas, Javier R Vázquez de Aldana, Guillermo Martín, Javier Martínez, Magdalena Aguiló, Maria Cinta Pujol, Francesc Díaz
We report mid-infrared LiNbO<sub>3</sub> depressed-index microstructured cladding waveguides fabricated by three-dimensional laser writing showing low propagation losses (~1.5 dB/cm) at 3.68 µm wavelength for both the transverse electric and magnetic polarized modes, a feature previously unachieved due to the strong anisotropic properties of this type of laser microstructured waveguides and which is of fundamental importance for many photonic applications. Using a heuristic modeling-testing iteration design approach which takes into account cladding induced stress-optic index changes, the fabricated cladding microstructure provides low-loss single mode operation for the mid-IR for both orthogonal polarizations...
February 20, 2017: Optics Express
Carlos Mateo, Pedro L Carro, Paloma García-Dúcar, Jesús De Mingo, Íñigo Salinas
This article proposes an optimized version of a canonical piece-wise-linear (CPWL) digital predistorter in order to enhance the linearity of a radio-over-fiber (RoF) LTE mobile fronthaul. In this work, we propose a threshold allocation optimization process carried out by a genetic algorithm (GA) in order to optimize the CPWL model (GA-CPWL). Firstly, experiments show how the CPWL model outperforms the classical memory polynomial DPD in an intensity modulation/direct detection (IM/DD) RoF link. Then, the GA-CPWL predistorter is compared with the CPWL model in several scenarios, in order to verify that the proposed DPD offers better performance in different optical transmission conditions...
February 20, 2017: Optics Express
Xifeng Xiao, David G Voelz, Santasri R Bose-Pillai, Milo W Hyde
In a previous paper [Opt. Express22, 31691 (2014)] two different wave optics methodologies (phase screen and complex screen) were introduced to generate electromagnetic Gaussian Schell-model sources. A numerical optimization approach based on theoretical realizability conditions was used to determine the screen parameters. In this work we describe a practical modeling approach for the two methodologies that employs a common numerical recipe for generating correlated Gaussian random sequences and establish exact relationships between the screen simulation parameters and the source parameters...
February 20, 2017: Optics Express
Kazuki Nakamura, Hin Channa, Masaki Asobe, Takeshi Umeki, Hirokazu Takenouchi
We devised a method for the measurement of the phase-matching curve of multiple quasi-phase-matched (QPM) LiNbO<sub>3</sub> waveguide under conditions of high-power second-harmonic generation. The data obtained revealed that the phase-matching condition can be preserved due to the high damage resistance of the directly bonded LiNbO<sub>3</sub> waveguide. Based on this evaluation, we tried to generate multiple optical carriers using multi-stage frequency mixing in the multiple QPM device...
February 20, 2017: Optics Express
Sungjae Park, Jinyoung Roh, Soobin Kim, Juseong Park, Hoon Kang, Joonku Hahn, Youngjin Jeon, Shinwoong Park, Hwi Kim
The complex modulation characteristics of a light field through an amplitude-phase double-layer spatial light modulator are analyzed based on the wave-optic numerical model, and the structural conditions for the optimal double-layer complex modulation structure are investigated. The relationships of interlayer distance, pixel size, and complex light modulation performance are analyzed. The main finding of this study is that the optimal interlayer distance for the double-layer structure can be found at the Talbot effect condition...
February 20, 2017: Optics Express
Lisl Robertson Lain, Stewart Bernard, Mark W Matthews
The accurate description of a water body's volume scattering function (VSF), and hence its phase functions, is critical to the determination of the constituent inherent optical properties (IOPs), the associated spectral water-leaving reflectance, and consequently the retrieval of phytoplankton functional type (PFT) information. The equivalent algal populations (EAP) model has previously been evaluated for phytoplankton-dominated waters, and offers the ability to provide phytoplankton population-specific phase functions, unveiling a new opportunity to further understanding of the causality of the PFT signal...
February 20, 2017: Optics Express
Seoung-Hwan Park, Doyeol Ahn, Chan-Yong Park
Intersubband absorption properties of lattice-matched BGaN/AlN quantum well (QW) structures grown on AlN substrate are theoretically investigated using an effective mass theory considering the nonparabolicity of the conduction band. These results are compared with those of GaN/AlN QW structures. The intersubband absorption coefficient of the BGaN/AlN QW structure is shown to be enhanced significantly, compared to that of the conventional GaN/AlN QW structure. This can be explained by the fact that the BGaN/AlN QW structure exhibits larger intersuband dipole moment and quasi-Fermi-level separation than the GaN/AlN QW structure, due to the increase in the carrier confinement by a larger internal field...
February 20, 2017: Optics Express
Achut Giree, Mark Mero, Gunnar Arisholm, Marc J J Vrakking, Federico J Furch
During amplification in a noncollinear optical parametric amplifier the spatial and temporal coordinates of the amplified field are inherently coupled. These couplings or distortions can limit the peak intensity, among other things. In this work, a numerical study of the spatiotemporal distortions in BBO-based noncollinear optical parametric chirped-pulse amplifiers (NOPCPAs) is presented for a wide range of parameters and for different amplification conditions. It is shown that for Gaussian pump beams, gain saturation introduces strong distortions and high conversion efficiency always comes at the price of strong spatiotemporal couplings which drastically reduce the peak intensity even when pulse fronts of the pump and the signal are matched...
February 20, 2017: Optics Express
V Bock, M Plötner, O De Vries, J Nold, N Haarlammert, T Schreiber, R Eberhardt, A Tünnermann
We present modal content measurements (S<sup>2</sup>) of two different negative curvature hollow-core photonic crystal fibers: a kagome fiber and an ice cream cone fiber. Their sensitivity towards mode matching, bending and polarization is analyzed. For the kagome fiber, a higher order mode suppression of 17dB under optimal conditions was achieved, and for the ice cream cone fiber there was a suppression of up to 42dB. Polarization turned out to be a critical parameter for good higher order mode suppression in both fibers...
February 20, 2017: Optics Express
Weidong Huang, Hongjuan Yu, Chaojie Liu, Guoxiang Liu, Qunhong Wu, Jin Zhou, Xin Zhang, Xiaowen Zhao, Linmei Shi, Xiaoxue Xu
This study aimed to assess health-related quality of life (HRQOL) of Heilongjiang adult populations by using the EuroQol five-dimension three-level (EQ-5D-3L) questionnaire and to identify factors associated with HRQOL. Data from the National Health Services Survey (NHSS) 2008 in Heilongjiang province were obtained. Results of EQ-5D-3L questionnaires completed by 11,523 adult respondents (18 years or older) were converted to health index scores using a recently developed Chinese value set. Multivariate linear regression and logistic regression models were established to determine demographic, socioeconomic, health, and lifestyle factors that were associated with HRQOL and reported problems in the five dimensions of EQ-5D-3L...
February 23, 2017: International Journal of Environmental Research and Public Health
Mingzhang Luo, Weijie Li, Bo Wang, Qingqing Fu, Gangbing Song
Rock bolts, as a type of reinforcing element, are widely adopted in underground excavations and civil engineering structures. Given the importance of rock bolts, the research outlined in this paper attempts to develop a portable non-destructive evaluation method for assessing the length of installed rock bolts for inspection purposes. Traditionally, piezoelectric elements or hammer impacts were used to perform non-destructive evaluation of rock bolts. However, such methods suffered from many major issues, such as the weak energy generated and the requirement for permanent installation for piezoelectric elements, and the inconsistency of wave generation for hammer impact...
February 23, 2017: Sensors
Bernd Stratmann, Bernhard Goldstein, Paul J Thornalley, Naila Rabbani, Diethelm Tschoepe
Hyperglycemia results in accumulation of the reactive dicarbonyl methylglyoxal (MG). Methylglyoxal is detoxified by the glyoxalase system (glyoxalase 1 and 2). The influence of glyoxalase 1 knockdown on expression of collagens 1, 3, 4, and 5 in L6 myoblasts under hyperglycemic conditions was investigated. Increased biosynthesis of collagens 1, 3, 4, and 5 was detected at mRNA-level following knockdown of glyoxalase 1 (GLO1). At the protein level a significant elevation of the concentration of collagen 1 and 4 was shown, whereas no increase of collagen 5 and a non-significant increase in collagen 3 were detectable...
February 23, 2017: International Journal of Molecular Sciences
Izabela Michalak, Agnieszka Dmytryk, Agnieszka Śmieszek, Krzysztof Marycz
The green seaweed Enteromorpha prolifera was used as a feedstock for the production of enzymatic hydrolysate using cellulase. The selection of the conditions for enzymatic hydrolysis of the biomass was carried out for different enzyme doses and incubation periods. The obtained extract was examined in terms of its multielemental composition, content of polyphenols and antibacterial properties (tested against Escherichia coli and Staphylococcus aureus). Additionally, its influence on the metabolic activity of human colon epithelial cells (Caco-2) was analyzed...
February 23, 2017: International Journal of Molecular Sciences
Olga Deda, Helen G Gika, Ioannis Taitzoglou, Νikolaos Raikos, Georgios Theodoridis
Aging is an inevitable condition leading to health deterioration and death. Regular physical exercise can moderate the metabolic phenotype changes of aging. However, only a small number of metabolomics-based studies provide data on the effect of exercise along with aging. Here, urine and whole blood samples from Wistar rats were analyzed in a longitudinal study to explore metabolic alterations due to exercise and aging. The study comprised three different programs of exercises, including a life-long protocol which started at the age of 5 months and ended at the age of 21 months...
February 23, 2017: Metabolites
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