Three-dimensional mode multiplexer based on adiabatic-tapered waveguides forming vertical directional couplers over C + L band and beyond
Quandong Huang, Jiali Zhang, Lixi Zhong, Zhaoqiang Zheng, Jianping Li, Ou Xu
Abstract
We present a mode multiplexer based on vertical directional couplers that are formed by adiabatic-tapered waveguides. We design and fabricate the device via the micro-fabrication processing to (de)multiplex the E 11 , E 21 , and E 12 modes from the few-mode bus waveguide. Our experimental device shows a coupling ratio higher than 98.6% and 97.0% for the E 21 and E 12 modes, respectively, over the C + L band and beyond. The modal cross talk of this device can be lower than –17.1 dB, –18.4 dB, and –15.1 dB caused by the unintended E 11 , E 21 , and E 12 modes, respectively. This mode multiplexer can work over a broader wavelength range with weak polarization sensitivity, which could be used in the mode-division-multiplexing systems where mode (de)multiplexing is required in the expanded communication wavelength window other than the C-band.