Electro-optic modulator and methods of forming the same

An electro-optic modulator comprising:

• a substrate having a first channel of waveguide material embedded therein, the substrate and the waveguide material together providing a substantially flat upper surface,
• a first insulative layer on and across the upper surface, wherein the first insulative layer comprises a silicon nitride layer directly on the upper surface, and further comprises a metal oxide layer on the silicon nitride layer;
• a graphene layer arranged on the first insulative layer and over at least a first portion of the first channel of waveguide material;
• and
• a second insulative layer provided on and across the graphene layer;
• wherein the graphene layer provides a first electrode, and wherein a second electrode is either:
• (i) provided on the second insulative layer at least overlapping the first portion of the first channel of waveguide material, or
• (ii) provided within the substrate at least underlapping the first portion of the first channel of waveguide material.