Slow light enabled high-modulation-depth graphene modulator with plasmonic metasurfaces

Graphene has attracted the interest of researchers seeking to develop compact optical modulators with the flexible tunability of graphene conductivity by tuning the Fermi level. Plasmonic structures have provided a robust way to enhance the modulation depth (MD) of graphene optical modulators, but the available schemes suffer from low MD, fabrication complexities, or both. Here, an ultra-thin plasmonic metasurface structure capable of guiding slow surface plasmons (SPs) is proposed to construct graphene-based optical modulators. The designs take advantage of the strong field enhancement of slow SP modes as well as the orientation match between the electric field and the graphene plane. A typical 0.96-mu m-long metasurface-based graphene modulator presents a significantly improved MD of 4.66 dB/mu m and an acceptable insertion loss of 1.4 dB/mu m, while still having ease of fabrication. (C) 2019 Optical Society of America