基于正方和六角排列结构光子晶体对发光二极管出光效率的研究

采用时域有限差分（finite-difference time-domain, FDTD）方法计算正方和六角排列圆形光子晶体的能带结构,研究了光子晶体占空比对能带的影响,找到一组获得带隙个数最多的二维光子晶体的几何结构参数;采用FDTD方法计算具有该参数的光子晶体的发光二极管（LED）出光效率,模拟表明该结构参数的正方和六角排列圆形光子晶体提高了GaN基蓝光LED出光效率5—6倍,六角排列优于正方排列;利用禁带理论、等效介质理论分析了增透机理. 关键词： 光子晶体 能带 出光效率 发光二极管     

Particle swarm optimization and its application to the design of a compact tunable guided-mode resonant filter

A compact tunable guided-mode resonant filter(GMRF) in the telecommunication region near the 1550 nm wavelength is proposed in this paper. Particle swarm optimization(PSO) is used to design the GMRF. The tunability of the GMRF is achieved by an MEMS-based physical movement(in the horizontal or vertical direction) combined with an incident angle in a certain range. The results show that the resonant wavelength tuning of 110 nm(140 nm) is obtained by horizontal movement of 168 nm(vertical movement of 435 nm) combined with an about 11~° variation of incident angle.     

超陷光黑硅结构研究

研究了超陷光黑硅表面圆锥阵列结构的设计.将圆锥结构分为五层,利用等效媒质理论进行了参数设计.考虑了硅材料折射率随波长的变化,用严格耦合波理论对不同入射角,圆锥阵列结构高度以及占空比时的反射率进行了计算分析.发现,圆锥阵列超陷光结构的周期为135 nm,高度为480 nm时,在0°～60°入射角范围内,对波长为300～1...     

Light trapping characteristics of glass substrate with hemisphere pit arrays in thin film Si solar cells

In this paper, the light trapping characteristics of glass substrate with hemisphere pit(HP) arrays in thin film Si solar cells are theoretically studied via a numerical approach. It is found that the HP glass substrate has good antireflection properties. Its surface reflectance can be reduced by ～ 50% compared with planar glass. The HP arrays can make the unabsorbed light return to the absorbing layer of solar cells, and the ratio of second absorption approximately equals 30%.Thus, the glass substrate with the hemisphere pit arrays(HP glass) can effectively reduce the total reflectivity of a solar cell from 20% to 13%. The HP glass can also prolong the optical path length. The numerical results show that the total optical path length of the thin film Si solar cell covered with the HP glass increases from 2ω to 4ω. These results are basically consistent with the experimental results.