Design of a novel hybrid multimode interferometer operating with both TE and TM polarizations for sensing applications

A novel hybrid multimode interferometer for sensing applications operating with both TE and TM polarizations simultaneously is proposed and numerically demonstrated. The simulations were performed assuming an operating wavelength of 633 nm with the goal of future use as a biosensor, but its applications extend beyond that area and could be adapted for any wavelength or application of interest. By designing the mutimode waveguide core with a low aspect ratio, the confinement characteristics of TE modes and TM modes become very distinct and their interaction with the sample in the sensing area becomes very different as well, resulting in high device sensitivity. In addition, an excitation structure is presented, that allows good control over power distribution between the desired modes while also restricting the power coupled to other undesired modes. This new hybrid TE/TM approach produced a bulk sensitivity per sensor length of 1.798 rad center dot RIU-1 center dot mu m-1 and a bulk sensitivity per sensor area of 2.140 rad center dot RIU-1 center dot mu m-2, which represents a much smaller footprint when compared to other MMI sensors, contributing to a higher level of integration, while also opening possibilities for a new range of MMI devices.

Automated summary

A novel hybrid multimode interferometer is proposed and demonstrated for sensing applications operating with both TE and TM polarizations simultaneously. It can be used as a biosensor at a wavelength of 633 nm, but its applications are not limited to that area. The design of the multimode waveguide core and the excitation structure result in distinct confinement characteristics and high device sensitivity. The hybrid TE/TM approach achieves smaller footprint and opens possibilities for a new range of MMI devices.