采用微模法制备了三维光子能降(PBG,photonic band gap)材料,得到了TiO_2为骨架的条状光子能隙材料样品。其微观结构为fcc密堆积的直径200nm左右的空气球,宏观结构为彼此相距10μm的横截面为矩形的长条,矩形宽度为10μm,高度600nm。用...采用微模法制备了三维光子能降(PBG,photonic band gap)材料,得到了TiO_2为骨架的条状光子能隙材料样品。其微观结构为fcc密堆积的直径200nm左右的空气球,宏观结构为彼此相距10μm的横截面为矩形的长条,矩形宽度为10μm,高度600nm。用光纤导入激光的方法对条状结构光子能隙材料的光学性质进行了测量,结合SEM的测量结果并与通常的静置重力堆积制备的光子能隙材料样品进行了比较,证实了这是一种方便、有效的制备具有图形的光子能隙材料的方法。展开更多
We introduce a new model of one-dimensional （1D） photonic crystal composed of alternately arranged RHM and LHM layers with positive and negative refractive indices respectively, for which the transmission spectra of...We introduce a new model of one-dimensional （1D） photonic crystal composed of alternately arranged RHM and LHM layers with positive and negative refractive indices respectively, for which the transmission spectra of the model are calculated numerically with the transfer matrix method, and the bandgap structure and the polarization properties are analyzed. We found that the introduction of negative refractive index layers （i.e. LHM medium layers） gives rise to some peculiar band-gap structure and polarization properties as follows. Firstly, the forbidden bands are extremely wide and the transmission bands are very sharp without oscillation;and secondly, the change of incident angle has different influences on the forbidden bands of TE and TM modes. For the TM mode, the forbidden band width decreases substantially and finally vanishes, and for the TE mode with central wavelength, the total reflection happens at anv incident anale.展开更多
Monodispersed silica microspheres with diameter of 353nm were assembled into photonic crystal in ethanol colloidal suspensions of varied silica volume fraction at different temperature and humidity by means of control...Monodispersed silica microspheres with diameter of 353nm were assembled into photonic crystal in ethanol colloidal suspensions of varied silica volume fraction at different temperature and humidity by means of controllable vertical deposition method. The surface morphology and optical properties were studied by SEM and UV-Vis-NIR. It was found that the high-quality silica colloidal photonic crystals were obtained from ethanol solutions with environment temperature between 45℃ and 55℃, humidity between 66% and 76%, the volume fraction of microspheres is between 0.8% and 1.5%. The ordered close-packed photonic crystal fabricated by controllable vertical deposition method had the two photonic bandgaps in the visible light band and near infrared band.展开更多
In this paper, collective excitations in the boson-fermion model are investigated by means of functional integration method. The equations of energy gap and excitation spectrum are derived. Moreover, the Bose energy s...In this paper, collective excitations in the boson-fermion model are investigated by means of functional integration method. The equations of energy gap and excitation spectrum are derived. Moreover, the Bose energy spectrum of zero wave vector Fermi fields is also calculated.展开更多
We investigate the position dependent spontaneous emission spectra of a A-type three-level atom with one transition coupled to the free vacuum reservoir and the other one coupled to a double-band photonic band gap res...We investigate the position dependent spontaneous emission spectra of a A-type three-level atom with one transition coupled to the free vacuum reservoir and the other one coupled to a double-band photonic band gap reservoir with a defect mode in the band gap. It is shown that, for the atom at the defect location, we have a two-peak spectrum with a wide dark line due to the strong coupling between the atom and the defect mode. While, when the atom is far from the defect location （or in the absence of the defect mode）, the spectrum has three peaks with two dark lines due to the coupling between the atom and the photonic band gap reservoir with the largest density of states near the band edges. On the other hand, we have a four-peak spectrum for the atom at the space in between. Moreover, the average spontaneous emission spectra of the atoms uniformly embedded in high dielectric or low dielectric regions are described. It is shown that the atoms embedded in high （low） dielectric regions far from the defect location, effectively couple to the modes of the lower （upper） photonic band. However, the atoms embedded in high dielectric or low dielectric regions at the defect location, are coupled mainly to the defect modes. While, the atoms uniformly embedded in high （low） dielectric regions with a normal distance from the defect location, are coupled to both of defect and lower （upper） photonic band modes.展开更多
The results of an experiment on discharges in long atmospheric pressure air gaps at a pulsed voltage of amplitude up to 800 kV and risetime 150-200 ns are analyzed. In the experiment, a radiation pulse of photon ener...The results of an experiment on discharges in long atmospheric pressure air gaps at a pulsed voltage of amplitude up to 800 kV and risetime 150-200 ns are analyzed. In the experiment, a radiation pulse of photon energy 〉 5 keV and duration 10-20 ns has been detected. It has been shown that the x-ray pulse is due to the ＂runaway＂ of electrons from the head of an anode-directed streamer. The estimated maximum bremsstrahlung energy is about 5-10 keV. The presence of a maximum in the bremsstrahlung spectrum is due to that the photons emitted by electrons are absorbed by atoms of the gas in which the discharge operates.展开更多
Based on the density functional theory （DFT）, the electronic structures and optical properties of Mg2Pb are calculated by using the local density approximation （LDA） and plane wave pseudo-potential method. The cal...Based on the density functional theory （DFT）, the electronic structures and optical properties of Mg2Pb are calculated by using the local density approximation （LDA） and plane wave pseudo-potential method. The calculation results show that the indirect band gap width of Mg2Pb is 0.02796 eV. The optical properties of MgzPb have isotropic characteristics, the static dielectric function of Mg2Pb is ε1（0） = 10.33 and the refractive index is n0 = 3.5075. The maximum absorption coefficient is 4.8060×10^5 cm-1. The absorption in the photon energy range of 25-40 eV approaches to zero, shows the optical colorless and transparent behaviors.展开更多
文摘采用微模法制备了三维光子能降(PBG,photonic band gap)材料,得到了TiO_2为骨架的条状光子能隙材料样品。其微观结构为fcc密堆积的直径200nm左右的空气球,宏观结构为彼此相距10μm的横截面为矩形的长条,矩形宽度为10μm,高度600nm。用光纤导入激光的方法对条状结构光子能隙材料的光学性质进行了测量,结合SEM的测量结果并与通常的静置重力堆积制备的光子能隙材料样品进行了比较,证实了这是一种方便、有效的制备具有图形的光子能隙材料的方法。
文摘We introduce a new model of one-dimensional （1D） photonic crystal composed of alternately arranged RHM and LHM layers with positive and negative refractive indices respectively, for which the transmission spectra of the model are calculated numerically with the transfer matrix method, and the bandgap structure and the polarization properties are analyzed. We found that the introduction of negative refractive index layers （i.e. LHM medium layers） gives rise to some peculiar band-gap structure and polarization properties as follows. Firstly, the forbidden bands are extremely wide and the transmission bands are very sharp without oscillation;and secondly, the change of incident angle has different influences on the forbidden bands of TE and TM modes. For the TM mode, the forbidden band width decreases substantially and finally vanishes, and for the TE mode with central wavelength, the total reflection happens at anv incident anale.
基金Aeronautic Science Foundation Programof China( 05G53038)
文摘Monodispersed silica microspheres with diameter of 353nm were assembled into photonic crystal in ethanol colloidal suspensions of varied silica volume fraction at different temperature and humidity by means of controllable vertical deposition method. The surface morphology and optical properties were studied by SEM and UV-Vis-NIR. It was found that the high-quality silica colloidal photonic crystals were obtained from ethanol solutions with environment temperature between 45℃ and 55℃, humidity between 66% and 76%, the volume fraction of microspheres is between 0.8% and 1.5%. The ordered close-packed photonic crystal fabricated by controllable vertical deposition method had the two photonic bandgaps in the visible light band and near infrared band.
基金The project supported by the Science Foundation of Sichuan Normal University
文摘In this paper, collective excitations in the boson-fermion model are investigated by means of functional integration method. The equations of energy gap and excitation spectrum are derived. Moreover, the Bose energy spectrum of zero wave vector Fermi fields is also calculated.
文摘We investigate the position dependent spontaneous emission spectra of a A-type three-level atom with one transition coupled to the free vacuum reservoir and the other one coupled to a double-band photonic band gap reservoir with a defect mode in the band gap. It is shown that, for the atom at the defect location, we have a two-peak spectrum with a wide dark line due to the strong coupling between the atom and the defect mode. While, when the atom is far from the defect location （or in the absence of the defect mode）, the spectrum has three peaks with two dark lines due to the coupling between the atom and the photonic band gap reservoir with the largest density of states near the band edges. On the other hand, we have a four-peak spectrum for the atom at the space in between. Moreover, the average spontaneous emission spectra of the atoms uniformly embedded in high dielectric or low dielectric regions are described. It is shown that the atoms embedded in high （low） dielectric regions far from the defect location, effectively couple to the modes of the lower （upper） photonic band. However, the atoms embedded in high dielectric or low dielectric regions at the defect location, are coupled mainly to the defect modes. While, the atoms uniformly embedded in high （low） dielectric regions with a normal distance from the defect location, are coupled to both of defect and lower （upper） photonic band modes.
文摘The results of an experiment on discharges in long atmospheric pressure air gaps at a pulsed voltage of amplitude up to 800 kV and risetime 150-200 ns are analyzed. In the experiment, a radiation pulse of photon energy 〉 5 keV and duration 10-20 ns has been detected. It has been shown that the x-ray pulse is due to the ＂runaway＂ of electrons from the head of an anode-directed streamer. The estimated maximum bremsstrahlung energy is about 5-10 keV. The presence of a maximum in the bremsstrahlung spectrum is due to that the photons emitted by electrons are absorbed by atoms of the gas in which the discharge operates.
基金supported by the National Natural Science Foundation of China(Grant Nos.50425204,50272032&90401012)the Ministry of Sciences and Technology of China through 973-Project(Grants 2002CB61306&2001CB6104).
基金supported by the National Natural Science Foundation of China(Grant No.51201079)the Scientific Research Foundation for Introduced Talents of KMUST(Grant No.KKSY201251033)the Scientific Research Fund of Department of Education of Yunnan Province(Grant No.2012Z099)
文摘Based on the density functional theory （DFT）, the electronic structures and optical properties of Mg2Pb are calculated by using the local density approximation （LDA） and plane wave pseudo-potential method. The calculation results show that the indirect band gap width of Mg2Pb is 0.02796 eV. The optical properties of MgzPb have isotropic characteristics, the static dielectric function of Mg2Pb is ε1（0） = 10.33 and the refractive index is n0 = 3.5075. The maximum absorption coefficient is 4.8060×10^5 cm-1. The absorption in the photon energy range of 25-40 eV approaches to zero, shows the optical colorless and transparent behaviors.
