Photonic Band Gap Materials: Light Control at Will




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Decay properties a laser-driven four-level atom in photonic crystals



Xiangqian Jiang and Xiudong Sun

Department of Physics, Harbin Institute of Technology, Harbin 150001, China


Abstract


We study the spontaneous emission steady state behavior of a laser-driven four-level atom embedded in photonic crystals considering the both transitions coupled to the same modified reservoir. The influence of photonic band gap and detuning of external driving field on the atomic spontaneous emission spectra was discussed. The photonic band gap and external driving field will impact strongly the atomic spontaneous emission properties. Some interesting phenomena were found such as laser-induced dark line, laser-induced spectral-line narrowing, and laser-induced pushing of a dressed state out of the band gap. For resonant case, when both transition frequencies are outside the band-gap, the individual spectrum lines show a superposition of two Lorentzian peaks with the same width. If one transition frequency is inside the band-gap and the other is outside, the individual spectrum lines show a superposition of non-Lorentzian and an approximate Lorentzian. For the larger detuning, the one of two dressed states is pushed out of the band-gap, which leads to the change of the width or peak value of the two peaks in individual spectrum lines. When both transition frequencies are inside deeply the bang-gap, the individual spectrum lines show a strong non-Lorentzian whether the driving detuning is large or small.


The Research of Direct Fabrication Process of 3D Photonic Crystal by Stereolithography﹡



Liang qingxuan, Li dichen, Sun kun, Hu yawen, Wang minjie,

Chen shibin, Zhang wei

(State key laboratory of Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049 China)


Abstract


The fabrication process has always been the key to the development of 3D photonic crystals with complex structures. In this paper, a new process for direct fabrication of 3D photonic crystal by Stereolithography has been introduced based on aqueous ceramic suspensions. The research showed that the cure depth which depends on the dispersant concentration, the scanning speed and mean diameter of powders is the key factor of direct fabrication by Stereolithography; In addition, the higher the volume loading of ceramic powder, the smaller the shrinkage of photonic crystals. In experiment the optimum process parameters were determined. The process which is simple, low costing and of high manufacture precision, can be used for the fabrication with any complex structure.

Keywords: stereolithography; photonic crystals; fabrication; cured depth; solid volume loading.


﹡Supported by Program for Changjiang Scholars and Innovative Research Team in University(IRT0646)and by Key Program of National Natural Science Fundation of China(50835007)


Comparison of exciting of SPPs by metallic and dielectric gratings



Yongqi Luo,Limin Liu

( Science College, Beijing University of Chemical Technology, Beijing 100029 )

Yi Liu

(Beijing Technology and Business University, Beijing 100048 )


Abstract


The surface plasmon polaritons(SPPs) excited at a metal nanostructure surface is an interesting subject. In this work we simulate the stimulation of surface plasmon polaritons by metallic grating and dielectric grating, respectively. Base on results of simulation, the function of material and geometry of grating has been discussed.

First, the fundamental properties of SPPs are reviewed and thus give the background of the numerical simulation. Actually, SPPs are electromagnetic surface waves that propagate along the interface between metallic and dielectric surfaces. Therefore, most of its properties can be derived from Maxwell's theory, such as the dispersion relation and propagation length, etc. Because SPPs can not be excited directly, ATR coupler and grating coupler are two of the most popular structures for raising the wave vector of photons.

The second object of this paper consists in the conception and techniques of finite-difference time-domain (FDTD) method. It is shown that a flexible and robust FDTD algorithm is capable for simulating the interaction between electromagnetic sources and metallic structures. The analysis of numerical simulation illustrates that dielectric grating can as well excite SPPs. In comparison with metallic structures, it can hardly be affected by geometry of grating, and offer advantages for industrial application.


Key words: surface plasmon polaritons, finite-difference time-domain method, numerical simulation, grating coupling

responsible author


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