Plasmonic Multi-Mode Interference Couplers

The MMI coupler is a key component in optical integrated circuits. Its main function is to combine or split optical signals, enabling the development of powerful multiplexing devices and integrated sensors. In a paper published in Optics Express (September 28, 2009 issue), Yu-Ju Tsai and co-workers investigate metallic MMI couplers that support long-range surface plasmons instead of conventional electromagnetic waves. Although the use of metals introduces material losses in the system, the authors show both numerically and experimentally that useful MMI devices can be implemented by careful design, opening up new possibilities to leverage and exploit the unique properties associated to surface plasmons.