A tunable dual-narrowband band-pass filter using plasma quantum well structure

A tunable dual-narrowband pass-band filter is designed. A one-dimensional photonic crystal(1D PC) is comprised of alternate dielectric layer and vacuum layer. Two quantum wells(QWs) as defects can be constructed by sandwiching two plasma slabs symmetrically in the 1D PC, and a dual-narrowband pass-band filter is formed. The conventional finitedifference time-domain(FDTD) method and piecewise linear current density recursive convolution(PLCDRC)–FDTD method are applied to the dielectric and plasma, respectively. The simulation results illustrate that the dual-narrowband frequencies can be tuned by changing the plasma frequency. The pass band interval and the half-power bandwidths(-3-dB band widths) are related to the space interval between two QWs.     

刍议大学物理的几个教学问题

现行大学物理教材存在一些不足,主要有：1）没有“矢量的虚拟方向和虚拟大小”的相关知识;2）安培环路定理等知识点的讲解方法;3）单缝衍射部分有错误;4）光栅衍射部分“可观察到的最大条纹数”问题实际意义不大,且解法也有问题。逐一分析这些不足,提出改进的建议。