Broadband Mode Multiplexer Formed With Non-Planar Tapered Directional Couplers

Abstract

We propose a broadband mode multiplexer based on the structure of cascaded planar and non-planar tapered directional couplers (DCs), which are designed for processing vertically symmetric and anti-symmetric modes. The DCs are tapered to widen the operating bandwidth, reduce the polarization dependence, and improve the fabrication tolerance. As an example, we design and fabricate a five-mode (de)multiplexer with polymer material to combine or separate the E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> , E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> , E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> , E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> , and E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sub> modes. Our typical fabricated device has a length of 2.1 cm and shows the mode coupling efficiency of almost larger than 94.5% for each DC over the C t L band with weak polarization dependence. The proposed structure is scalable and can be implemented with different material platforms.