Plasmonics refers to the manipulation of signals at optical frequencies along metal-dielectric interfaces on the nanometer scale. Key to our technology is the coupling between light and electrons at a metal surface (Surface Plasmon Polariton, or SPP). In our electro-optic modulators, these SPPs are strongly confined in a metal-insulator-metal (MIM) waveguide. In this MIM waveguide, SPPs interact with an electro-optic material, see Figure. When a voltage is applied, the optical properties of the electro-optic material change, so that we can manipulate the phase of the SPPs. In a Mach-Zehnder configuration, these phase modulators are used as amplitude or intensity modulator.

The tight confinement enables our modulators to efficiently modulate light on an ultra-compact footprint. The short interaction length, typically in the range of 10 µm, limits the influence of relatively high propagation losses of MIM waveguiding.

Plasmonic devices use metal for guiding SPPs, which has the advantage that they serve as their own electrical contacts.  As devices are small, capacitances are small too, thus boosting the switching speed, due to small RC time constants. Further, in contrast to traditional electro-optic modulators, they are not hindered by the walk-off between electrical and optical waves. 

Photonics and plasmonics complement each other: Given the right conditions, optical signals can be converted to plasmonic ones and vice versa. Polariton’s modulators are seamlessly integrated into the existing silicon photonics platform, enabling a broad range of applications.