Experimental Studies on Sonic-Crystal Defect-Mode Waveguides Composed of a Periodic Chain of Single-Defects

根据申请文件中描述的研究目的和计划，我们取得了以下成果。在本文中，由单缺陷或点缺陷组成的周期链构成的波导称为缺陷模波导。(1)分析人工晶体中缺陷的时间和频率特性的两种方法，即通过缺陷中的激励脉冲或爆发声压来研究缺陷的内部激励方法和从晶体外部激励缺陷的外部方法。(2)用外部和内部两种方法研究了声晶体中单个缺陷或点缺陷的空间约束和频率特性。通过对t-…的fdtd模拟，研究了构成缺陷模光波导元的两个相邻单缺陷的时间响应和频率特性。用实验外激方法和耦合模理论，得到了更多的He波传播。通过FDTD模拟和实验外部激励，证明了这三种方法的有效性。(4)通过FDTD模拟和实验外部激励，证明了由单个缺陷链组成的有和没有尖锐弯曲的直波导在通带内具有良好的100%的透过率。(5)用频率为20~40 kHz的超声波在空气中测量了具有尖锐弯曲和分支或十字路口的长缺陷模波导的传输特性。证实了它们在通带内的每晶格常数具有较高的透过率，在通带外的禁带内有较高的抑制，并且具有良好的分叉特性。(6)在直缺陷模波导和相邻的具有尖锐弯曲的缺陷模波导之间获得了高达50%的模耦合。(7)我们建立了一个新的耦合模理论，它描述了一系列缺陷模链中任意多个耦合模的行为。FDTD仿真和实验结果验证了该理论推导结果的定量准确性。较少

We have obtained the following results according to the purpose and plan of the research described in the application documents. In this report, a waveguide composed of a periodic chain of single-defects, or point-defects, are called a defect-mode waveguide.(1) Two methods to analyze the temporal and frequency characteristics of defects in an artificial crystal, namely, an internal excitation method which investigates them by exciting impulse, or burst sound pressure in a defect, and an external method by an excitation of a defect from the outside of the crystal.(2) Spatial confinement and frequency characteristics of a single-defect, or point-defect, embedded in a sonic crystal are investigated by both the external and internal methods, and the theoretical and experimental results had a good coincidence.(3) Temporal responses and frequency characteristics of two adjacent single-defects, which compose elementary parts of defect-mode waveguides, are investigated by FDTD simulations of t … More he wave propagation, by experimental external excitation method and by a coupled-mode theory. Well quantitatively agreed results indicated validity of the three methods.(4) Straight waveguides with and without a sharp bend composed of a chain of single defects proved to have a good 100% transmission in the pass-band by means of a FDTD simulation and an experimental external excitation.(5) Transmission characteristics of long defect-mode waveguides, which have a sharp bend and a branch or a crossroads, were measured by the ultrasonic waves of a frequency of 20〜40 kHz in air. The following items were confirmed, namely their high transmission per lattice constant in the pass band, and a high suppression in the forbidden band outside the pass band, and a good branching characteristics.(6) A high 50% mode coupling was obtained between a straight defect-mode waveguide and a neighboring defect-mode waveguide which has a sharp bend to remove from the former waveguide.(7) We have established a new coupled-mode theory which describes the behaviors of an arbitrary number of coupled modes of a chain of defect-modes. Quantitative preciseness of the results deduced by this theory was confirmed by the FDTD simulation and the experimental results described above. Less