The band structure of 2D photonic crystals (PCs) and localized states resulting from defects are analyzed by finite-difference time-domain (FDTD) technique and Padé approximation.The effect of dielectric constant...The band structure of 2D photonic crystals (PCs) and localized states resulting from defects are analyzed by finite-difference time-domain (FDTD) technique and Padé approximation.The effect of dielectric constant contrast and filling factor on photonic bandgap (PBG) for perfect PCs and localized states in PCs with point defects are investigated.The resonant frequencies and quality factors are calculated for PCs with different defects.The numerical results show that it is possible to modulate the location,width and number of PBGs and frequencies of the localized states only by changing the dielectric constant contrast and filling factor.展开更多
Radio detection of pulsars in the Galactic disk is strongly affected by the dispersion and scattering effect of the interstellar medium and the Galactic background radio emission. In order to know the best conditions ...Radio detection of pulsars in the Galactic disk is strongly affected by the dispersion and scattering effect of the interstellar medium and the Galactic background radio emission. In order to know the best conditions for discovery of pulsars, we select and simulate pulsar samples in the Galactic disk, and calculate the detection probability with various observation conditions (such as observational frequency, telescope aperture, receiver bandwidth and integration time). We have found that the detection fraction increases with the telescope aperture, receiver bandwidth and integration time. To detect pulsars in the nearer half of the Galactic disk, the observation frequency should be in the range of 1-2 GHz, while for pulsars in the farther half of the disk, the frequency should be in the range of 3.5-4.5 GHz. Due to the strong influence of scattering, the short period pulsars are hard to be detected, especially for pulsars in the farther half of the Galactic disk.展开更多
文摘The band structure of 2D photonic crystals (PCs) and localized states resulting from defects are analyzed by finite-difference time-domain (FDTD) technique and Padé approximation.The effect of dielectric constant contrast and filling factor on photonic bandgap (PBG) for perfect PCs and localized states in PCs with point defects are investigated.The resonant frequencies and quality factors are calculated for PCs with different defects.The numerical results show that it is possible to modulate the location,width and number of PBGs and frequencies of the localized states only by changing the dielectric constant contrast and filling factor.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10773016, 10821001 and 10833003)the Initialization Fund for President Award Winner of Chinese Academy of Sciences
文摘Radio detection of pulsars in the Galactic disk is strongly affected by the dispersion and scattering effect of the interstellar medium and the Galactic background radio emission. In order to know the best conditions for discovery of pulsars, we select and simulate pulsar samples in the Galactic disk, and calculate the detection probability with various observation conditions (such as observational frequency, telescope aperture, receiver bandwidth and integration time). We have found that the detection fraction increases with the telescope aperture, receiver bandwidth and integration time. To detect pulsars in the nearer half of the Galactic disk, the observation frequency should be in the range of 1-2 GHz, while for pulsars in the farther half of the disk, the frequency should be in the range of 3.5-4.5 GHz. Due to the strong influence of scattering, the short period pulsars are hard to be detected, especially for pulsars in the farther half of the Galactic disk.
