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

根据申请文件中所描述的研究目的和计划，我们得到了以下结果：在本报告中，由单缺陷或点缺陷的周期链组成的波导称为缺陷模式波导。(1)分析人造晶体中缺陷的时间和频率特性的两种方法，即内部激励法和外部激励法。内部激励法是通过在缺陷中激发脉冲或爆裂声压来研究缺陷的时间和频率特性。(2)采用外部和内部方法研究了声晶体中单缺陷或点缺陷的空间约束和频率特性，理论和实验结果吻合较好。(3)采用实验外激励法和耦合模理论对缺陷模波导中相邻的两个单缺陷进行时域有限差分模拟，研究了缺陷模波导的时域响应和频率特性。定量一致的结果表明了三种方法的有效性。(4)通过时域有限差分仿真和实验外激励，证明了由单缺陷链组成的具有和不具有尖角弯曲的直波导在通带内具有良好的100%透射率。(5)利用空气中频率为20 ~ 40 kHz的超声波测量了具有急弯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具有较高的每晶格常数透射率，在通带外具有较高的禁带抑制率，具有良好的分支特性。(6)在直线型缺陷模波导和相邻的缺陷模波导之间获得了50%的高模耦合，相邻的缺陷模波导有一个尖锐的弯曲，可以从原波导中移除。(7)建立了一种新的耦合模理论，该理论描述了缺陷模链中任意数目的耦合模的行为。时域有限差分仿真和上述实验结果证实了该理论推导结果的定量准确性。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