Brown University, School of Engineering, Providence, RI, 02912, USA.
Osaka University, Graduate School of Engineering Science, Toyonaka Osaka, 560-8531, Japan.
Sci Rep. 2017 Jul 19;7(1):5909. doi: 10.1038/s41598-017-06297-7.
We demonstrate a simple and effective strategy for implementing a polarizing beamsplitter for the terahertz spectral region, based on an artificial dielectric medium that is scalable to a range of desired frequencies. The artificial dielectric medium consists of a uniformly spaced stack of metal plates, which is electromagnetically equivalent to a stacked array of parallel-plate waveguides. The operation of the device relies on both the lowest-order, transverse-electric and transverse-magnetic modes of the parallel-plate waveguide. This is in contrast to previous work that relied solely on the transverse-electric mode. The fabricated polarizing beamsplitter exhibits extinction ratios as high as 42 dB along with insertion losses as low as 0.18 dB. Building on the same idea, we also demonstrate an isolator with non-reciprocal transmission, providing high isolation and low insertion loss at a select design frequency. The performance of our isolator far exceeds that of other experimentally demonstrated terahertz isolators, and indeed, even rivals that of commercially available isolators for optical wavelengths. Because these waveguide-based artificial dielectrics are low loss, inexpensive, and easy to fabricate, this approach offers a promising new route for polarization control of free-space terahertz beams.
我们展示了一种简单而有效的策略，用于在太赫兹光谱区域实现偏振分束器，该策略基于可扩展到一系列所需频率的人工介电介质。人工介电介质由金属板的均匀间隔堆叠组成，其在电磁上等效于平行板波导的堆叠阵列。该器件的工作依赖于平行板波导的最低阶横电和横磁模式。这与以前仅依赖横电模式的工作形成对比。所制造的偏振分束器具有高达 42 dB 的消光比和低至 0.18 dB 的插入损耗。基于相同的理念，我们还展示了一种具有非互易传输的隔离器，在选择的设计频率下提供高隔离度和低插入损耗。我们的隔离器的性能远远超过其他实验演示的太赫兹隔离器，实际上甚至可以与用于光学波长的商业可用隔离器相媲美。由于这些基于波导的人工介电材料具有低损耗、低成本和易于制造的特点，因此这种方法为自由空间太赫兹光束的偏振控制提供了一条有前途的新途径。
