Compact optical 90° hybrid based on hybrid plasmonic multimode interferometer

This paper presents an optical 90° hybrid based on a general 4×4 multimode interferometer (MMI), which is realized on hybrid plasmonic waveguides (HPW). First, we analyze the propagation characteristics of multi-order hybrid plasmonic modes in the HPW-MMI, and reveal that the optimal positions of self-images would shift from the theoretical ones. By optimizing the thickness of the dielectric interlayer of the HPW structure, the width and length of the multimode section, and especially by adjusting the position of the input and output waveguides, this HPW hybrid shows a maximum phase error of 0.7°, a transmission imbalance of 0.6 dB, and CMRRs of below −20 dB at the wavelength of 1550 nm.