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991.
992.
V.A. Kheraj C.J. Panchal P.K. Patel B.M. Arora T.K. Sharma 《Optics & Laser Technology》2007,39(7):1395-1399
The optical output power of a laser diode can be enhanced by anti-reflection (AR) and high-reflection (HR) facet coatings, respectively, at the front and back facet. AR and HR coatings also serve the purpose of protection and passivation of laser diode facets. In this work, we have designed and optimized a single layer λ/4 thick Al2O3 film for the AR coating and a stack of λ/4 thick Al2O3/λ/4 thick Si bi-layers for the HR coating for highly strained InGaAs quantum-well edge emitting broad area (BA) laser diodes. Effect of the front and back facet reflectivities on output power of the laser diodes has been studied. The light output versus injected current (L–I characteristics) measurements were carried out on selected devices before and after the facet coatings. We have also carried out the numerical simulation and analysis of L–I characteristics for this particular diode structure. The experimental results have been compared and verified with the numerical simulation. 相似文献
993.
S. Surendra Babu C.K. Jayasankar W. Sievers G. Wortmann 《Journal of luminescence》2007,126(1):109-120
Phosphate (P2O5+K2O+BaO+Al2O3+Eu2O3) and fluorophosphate (P2O5+K2O+BaO+BaF2+Al2O3+Eu2O3) glasses with different Eu3+ ion concentrations have been prepared and characterized through optical absorption, photoluminescence and decay times. An intense red luminescence is observed from the 5D0 emitting level of Eu3+ ions in these glasses. The relative luminescence intensity ratio of 5D0→7F2→5D0→7F1 transitions has been evaluated to estimate the local site symmetry around the Eu3+ ions. The emission spectra of these glasses show a complete removal of degeneracy for the 5D0→7F1 and 5D0→7F2 transitions. Second and fourth rank crystal-field (CF) parameters have been calculated together with the CF strength parameter by assuming the C2v symmetry for the Eu3+ ions in both the phosphate and fluorophosphate glasses. Judd-Ofelt parameters have been evaluated from the luminescence intensity ratios of 5D0→7FJ (J=2, 4 and 6) to 5D0→7F1 transitions. These parameters have been used to derive radiative properties such as transition probabilities, branching ratios, radiative lifetimes and peak stimulated emission cross-sections for the 5D0→7FJ transitions. Decay curves of the 5D0 level of Eu3+ ions in these two Eu3+:glass systems have been measured by monitoring the 5D0→7F2 transition (611 nm) at room temperature. The experimental lifetime of the 5D0 level in the title glasses is found to be higher than Eu3+-doped niobium phosphate glasses. The analysis indicates that the lifetime of the 5D0 level is found to be less sensitive to the Eu3+ ion concentration and addition of BaF2 has no significant effect on the optical properties of Eu3+-doped phosphate glasses. 相似文献
994.
《Quaestiones Mathematicae》2013,36(6):759-769
AbstractSibling curves were demonstrated in papers [2, 3] as a novel way to visualize the zeros of complex valued functions. In this paper, we continue the work done in those papers by focusing solely on polynomials. We proceed to prove that the number of sibling curves of a polynomial is the degree of the polynomial. 相似文献
995.
996.
Sangtae Jeong 《Journal of Number Theory》2011,131(6):1089-1104
We revisit hyperderivatives to build on the integral theory of calculus in positive characteristic p. In particular, we give necessary and sufficient conditions for the exactness of a hyperdifferential form associated with hyperderivatives and then propose a closed formula for finding the hyperantiderivative of an exact form. 相似文献
997.
Nelly Durand Bruno Ameduri Bernard Boutevin 《Journal of polymer science. Part A, Polymer chemistry》2011,49(1):82-92
The synthesis and characterizations of fluorinated telomers based on vinylidene fluoride (VDF) by iodine transfer polymerization (ITP) are presented. These telomers were prepared in the presence of ω‐iodoperfluorinated functional chain transfer agents, C6F13I or C4F9I. ITPs were initiated by thermal decomposition of bis(4‐tert‐butylcyclohexyl) peroxydicarbonate (BBCHPDC), in solution (in the presence of acetonitrile). The obtained telomers were characterized by different analyses such as elemental analyses, nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy, size exclusion chromatography, X‐ray diffraction (XRD), and finally by thermal analyses such as differential scanning calorimetry (DSC) and thermogravimetric analyses. These technical analyses enabled one to assess their chemical structures, various thermal properties, and their crystalline forms. The assignments of the characteristic signals obtained by 19F NMR spectroscopy enabled one to calculate the average degrees of polymerization (DPn) and percentages of ? CH2CF2I end group functionalities that depend on the initiator and the fractionation process after reaction. A good control of polymerization was shown by the absence of reversed ? CH2CF2? CF2CH2? (VDF–VDF dyads) and narrow polydispersity indices (<1.2). The XRD and DSC evidenced the influence of the chain length of the telomers on the crystallinity rate (>70%) and indicated two crystalline forms, α and β, that depended on DPn values. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
998.
This paper studies particle propagation in a one-dimensional inhomogeneous medium where the laws of motion are generated by chaotic and deterministic local maps. Assuming that the particle’s initial location is random and uniformly distributed, this dynamical system can be reduced to a random walk in a one-dimensional inhomogeneous environment with a forbidden direction. Our main result is a local limit theorem which explains in detail why, in the long run, the random walk’s probability mass function does not converge to a Gaussian density, although the corresponding limiting distribution over a coarser diffusive space scale is Gaussian. 相似文献
999.
We study Brauer–Manin obstructions to the Hasse principle and to weak approximation on algebraic surfaces over number fields. A technique for constructing Azumaya algebra representatives of Brauer group elements is given, and this is applied to the computation of obstructions. 相似文献
1000.
We investigate orthogonal and symplectic bundles with parabolic structure, over a curve. 相似文献