High-performance unidirectional electrooptic modulator based on polymeric highly multi-mode waveguides

A unidirectional electrooptic modulator based on an asymmetrical highly multi-mode waveguide coupler is proposed. Firstly, the energy distributions of all the modes within two highly multi-mode waveguides are analyzed with eigenstate theory. Then, to achieve high switching performance in a guided-wave coupler, a dumping wall is placed on the larger waveguide of an asymmetric pair of waveguides, so that the larger waveguide has a dumping effect. This dumping effect makes the asymmetric highly multi-mode waveguide coupler possess a highly efficient unidirectional coupling process. Due to the large cross-section of the waveguide, a new modulation electrode structure is built. Based on this dumping effect, the unidirectional coupling process is theoretically modeled. Furthermore, in both scenarios, i.e., the unmodulated state and the electrooptically modulated state, the unidirectional coupling efficiencies are studied. As a result, not only can a high unidirectional coupling efficiency of 100% be achieved, but a high electrooptic modulation depth more than 90% can also be implemented in theory, and a high thermooptic modulation depth more than 90% under a low modulation voltage of 30 volts is also experimentally achieved. This device can be used for multi-mode optical interconnection systems such as data communication and fiber sensor networks.