Mendis Rajind, Nagai Masaya, Wang Yiqiu, Karl Nicholas, Mittleman Daniel M
Brown University, School of Engineering, Providence, RI 02912, USA.
Osaka University, Graduate School of Engineering Science, Toyonaka Osaka 560-8531, Japan.
Sci Rep. 2016 Mar 14;6:23023. doi: 10.1038/srep23023.
We have designed, fabricated, and experimentally characterized a lens for the THz regime based on artificial dielectrics. These are man-made media that mimic properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. For our lens, the artificial-dielectric medium is made up of a parallel stack of 100 μm thick metal plates that form an array of parallel-plate waveguides. The convergent lens has a plano-concave geometry, in contrast to conventional dielectric lenses. Our results demonstrate that this lens is capable of focusing a 2 cm diameter beam to a spot size of 4 mm, at the design frequency of 0.17 THz. The results further demonstrate that the overall power transmission of the lens can be better than certain conventional dielectric lenses commonly used in the THz regime. Intriguingly, we also observe that under certain conditions, the lens boundary demarcated by the discontinuous plate edges actually resembles a smooth continuous surface. These results highlight the importance of this artificial-dielectric technology for the development of future THz-wave devices.
我们基于人工电介质设计、制造并通过实验表征了一种用于太赫兹波段的透镜。这些是人造介质，它们模仿天然电介质的特性，甚至展现出自然界中通常不会出现的特性。例如，众所周知的介电特性——折射率，通常大于1，但在人工电介质中可能小于1。对于我们的透镜，人工电介质由100μm厚的金属板平行堆叠组成，形成平行板波导阵列。与传统介电透镜不同，这种会聚透镜具有平凹几何形状。我们的结果表明，在0.17太赫兹的设计频率下，该透镜能够将直径2厘米的光束聚焦到4毫米的光斑尺寸。结果还进一步表明，该透镜的整体功率传输性能优于太赫兹波段常用的某些传统介电透镜。有趣的是，我们还观察到在某些条件下，由不连续板边缘划定的透镜边界实际上类似于光滑的连续表面。这些结果凸显了这种人工电介质技术对未来太赫兹波器件发展的重要性。
