Photonic crystal fibers (PCFs) with anomalous dispersion in short wavelength region are significant for some applications, such as short wavelength soliton propagation, super continuum generation and short pulse fiber...Photonic crystal fibers (PCFs) with anomalous dispersion in short wavelength region are significant for some applications, such as short wavelength soliton propagation, super continuum generation and short pulse fiber lasing.In this paper,a systematic method for designing PCFs with required anomalous dispersion region is proposed by using a finite difference solver and the scaling transformation of the waveguide dispersion of PCFs.Designed PCF can be anomalously dispersive in the region less than 1.3 μm,which is very difficult to realize in the traditional standard single-mode fibers.The effectiveness of the proposed method is approved by numerical results.展开更多
In this paper, a boundary element formulation in the wave-number space domain for solving the wave equation for a borehole with arbitrary shape in acoustic logging problems is presented. The problem is treated as a tw...In this paper, a boundary element formulation in the wave-number space domain for solving the wave equation for a borehole with arbitrary shape in acoustic logging problems is presented. The problem is treated as a two-dimensional medium with the discrete wave- number method in the vertical direction. The method is validated by comparing the results obtained by this method with those obtained by the finite-difference method. The method is used to study the effect on wave propagation in a vertical borehole of a vertical fracture. For a monopole source, the dispersion curves for Stoneley waves yield three branches. For dipole and quadrupole sources, different orientations of the source yield different results. When the dipole source is orthogonal to the fracture, the dispersion curve is similar to that of the open hole, while the curves are quite different when the source is parallel to the fracture. These characteristics enable us to determine the orientation of the vertical fracture.展开更多
We utilize the anomalous dispersion of planar photonic crystals near the dielectric band edge to control the wavelength-dependent propagation of light. We typically observe an angular swing of up to 10°as the inp...We utilize the anomalous dispersion of planar photonic crystals near the dielectric band edge to control the wavelength-dependent propagation of light. We typically observe an angular swing of up to 10°as the input wavelength is changed from 1290 nm to 1310 rim, which signifies an angular dispersion of 0.5°/am （＂Superprism＂ phenomenon）. Such a strong angular dispersion is of the order required for WDM systems. By tuning the incident angle, light beams with up to 20° divergence were collimated over a 25 nm （1285 nm to 1310 nm） bandwidth using a triangular lattice （＂Supercollimator＂ phenomenon）. The wavelength collimating range can be extended from 25 nm to 40 nm by changing the lattice from triangular to square. These two devices can be realized in the same configuration, simply by tuning the wavelength. Sources of loss are discussed.展开更多
基金This work was supported by National Natural Science Foundationof China(No.60407011 and No.60277018)Zhejiang Provin-cial Natural Science Foundation of China (No.Y104073)
文摘Photonic crystal fibers (PCFs) with anomalous dispersion in short wavelength region are significant for some applications, such as short wavelength soliton propagation, super continuum generation and short pulse fiber lasing.In this paper,a systematic method for designing PCFs with required anomalous dispersion region is proposed by using a finite difference solver and the scaling transformation of the waveguide dispersion of PCFs.Designed PCF can be anomalously dispersive in the region less than 1.3 μm,which is very difficult to realize in the traditional standard single-mode fibers.The effectiveness of the proposed method is approved by numerical results.
基金Acknowledgements We thank the thoughtful comments from two anonymous reviewers. This work is partly supported by a contract with Schlumberger-Doll Research, Schlumberger and partly by the National Science Foundation of China under D40521002.
文摘In this paper, a boundary element formulation in the wave-number space domain for solving the wave equation for a borehole with arbitrary shape in acoustic logging problems is presented. The problem is treated as a two-dimensional medium with the discrete wave- number method in the vertical direction. The method is validated by comparing the results obtained by this method with those obtained by the finite-difference method. The method is used to study the effect on wave propagation in a vertical borehole of a vertical fracture. For a monopole source, the dispersion curves for Stoneley waves yield three branches. For dipole and quadrupole sources, different orientations of the source yield different results. When the dipole source is orthogonal to the fracture, the dispersion curve is similar to that of the open hole, while the curves are quite different when the source is parallel to the fracture. These characteristics enable us to determine the orientation of the vertical fracture.
文摘We utilize the anomalous dispersion of planar photonic crystals near the dielectric band edge to control the wavelength-dependent propagation of light. We typically observe an angular swing of up to 10°as the input wavelength is changed from 1290 nm to 1310 rim, which signifies an angular dispersion of 0.5°/am （＂Superprism＂ phenomenon）. Such a strong angular dispersion is of the order required for WDM systems. By tuning the incident angle, light beams with up to 20° divergence were collimated over a 25 nm （1285 nm to 1310 nm） bandwidth using a triangular lattice （＂Supercollimator＂ phenomenon）. The wavelength collimating range can be extended from 25 nm to 40 nm by changing the lattice from triangular to square. These two devices can be realized in the same configuration, simply by tuning the wavelength. Sources of loss are discussed.
