Hyun Jaeyub, Choi Wonjae, Wang Semyung, Park Choon-Su, Kim Miso
School of Mechatronics, Gwangju Institute of Science and Technology (GIST), 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea.
Center for Medical Metrology, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon, 34113, Republic of Korea.
Sci Rep. 2018 May 8;8(1):7288. doi: 10.1038/s41598-018-25696-y.
A systematic process is described to realize double-zero-index phononic crystals with Dirac-like points experimentally. This type of crystal normally has softer inclusion material than its surroundings medium, allowing mapping into a zero-index medium under certain conditions but also making experimental implementation difficult. On the other hand, realizing phononic crystals with hard inclusions can be experimentally more feasible, but the mapping conditions cannot be directly applied to hard-inclusion crystals such that mapping is not systematically guaranteed in these cases. Moreover, even if such crystals become realizable, there is a lack of a systematic design process which can be used to optimize or to redesign the crystals, which largely limits their potential applications. In this paper, we discover the essential conditions for realizing phononic crystals with hard inclusions and propose a methodology for the systematic design of these crystals using homogenization based on the effective medium theory. Using the proposed method, a double-zero-index phononic crystal with hard inclusions is optimized and experimentally realized for an underwater ultrasonic wave collimator.
本文描述了一种通过实验实现具有类狄拉克点的双零折射率声子晶体的系统方法。这类晶体通常具有比周围介质更软的夹杂材料，这使得在特定条件下可将其映射为零折射率介质，但也给实验实现带来了困难。另一方面，实现具有硬夹杂的声子晶体在实验上可能更可行，但映射条件不能直接应用于硬夹杂晶体，因此在这些情况下不能系统地保证映射。此外，即使这类晶体变得可实现，也缺乏一种可用于优化或重新设计晶体的系统设计方法，这在很大程度上限制了它们的潜在应用。在本文中，我们发现了实现具有硬夹杂的声子晶体的基本条件，并基于有效介质理论提出了一种使用均匀化方法对这些晶体进行系统设计的方法。使用所提出的方法，对一种用于水下超声波准直器的具有硬夹杂的双零折射率声子晶体进行了优化并通过实验实现。
