Hybrid plasmonic waveguide crossing based on the multimode interference effect

The waveguide crossings based on the hybrid plasmonic waveguides (HPW) are demonstrated by using the self-imaging effect of the multimode interferometer. The single self-imaging formed at the crossing center mitigates the wavefront expansion due to the light diffraction at the crossing area. The plasmonic waveguide comprises a 30 nm hydrogen silesquixsane layer sandwiched between a 220 nm silicon layer and a 100 nm silver layer. The total length of the crossing is 4870 nm. Its insertion loss and crosstalk at 1550 nm are 4.9±0.3 dB and −22 dB. The optical bandwidth is more than 40 nm. This device could be a fundamental building block in future HPW based optical circuits.