Abstract In this work, a terahertz (THz) fiber directional coupler with a symmetric dual-suspended core structure has been proposed for realizing low loss and polarization-insensitive coupling length in the THz frequency region. The fiber core of the directional coupler consists of two round solid dielectric rods supported by two intersecting thin dielectric layers. Numerical simulations performed using the full-vector finite element method show that a short polarization-independent coupling length can be obtained by adjusting the geometric parameters of the fiber. Moreover, a low-loss THz fiber directional coupling performance can also be achieved at a central frequency of 1.00-THz and approximately 0.16THz of bandwidth. For example, a coupler with a length of 0.421 cm has a transmission loss of 0.30 dB and 0.26 dB for the x- and y-polarization modes, respectively.

中文翻译：

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对称双悬芯结构太赫兹光纤定向耦合器的低损耗偏振不敏感耦合长度

摘要 在这项工作中，提出了一种具有对称双悬空芯结构的太赫兹 (THz) 光纤定向耦合器，用于在太赫兹频率范围内实现低损耗和偏振不敏感耦合长度。定向耦合器的纤芯由两个圆形固体介质棒组成，由两个相交的薄介质层支撑。使用全矢量有限元方法进行的数值模拟表明，通过调整光纤的几何参数可以获得较短的偏振无关耦合长度。此外，在1.00-THz的中心频率和大约0.16THz的带宽下也可以实现低损耗的太赫兹光纤定向耦合性能。例如，长度为 0.421 cm 的耦合器的传输损耗为 0.30 dB 和 0。