Plasmon-assisted optical vias for photonic ASICS
The present invention relates to optical vias to optically connect multilevel optical circuits. In one example, the optical via includes a surface plasmon polariton waveguide, and a first optical waveguide formed on a first substrate is coupled to a second optical waveguide formed on a second substrate by the surface plasmon polariton waveguide. In some embodiments, the first optical waveguide includes a transition region configured to convert light from an optical mode to a surface plasmon polariton mode or from a surface plasmon polariton mode to an optical mode.
1. A multilevel optical circuit, comprising:
a first layer that contains one or more first optical waveguides;
a second layer that contains one or more second optical waveguides; and
one or more optical vias, each of the optical vias being configured to optically connect a first optical waveguide to a second optical waveguide, wherein:
each of the optical vias comprises a surface plasmon polariton (SPP) waveguide; the circuit further comprises a respective photon-to-plasmon transition region that couples each of the optical vias to a first optical waveguide; and
the circuit further comprises a respective plasmon-to-photon transition region that couples each of the optical vias to a second optical waveguide.
2. The multilevel optical circuit of claim 1 , wherein the first and second layers extend laterally in two horizontal dimensions and have respective thicknesses in a vertical dimension, and wherein the one or more optical vias are substantially perpendicular to the first and second layers so that said vias extend substantially in the vertical dimension.
3. The multilevel optical circuit of claim 1 , wherein at least part of each photon-to-plasmon transition region is coplanar with its connected first optical waveguide or at least part of each plasmon-to-photon transition region is coplanar with its connected second optical waveguide.
4. The multilevel optical circuit of claim 1 , wherein at least part of each photon-to-plasmon transition region is collinear with its connected SPP waveguide.
5. The multilevel optical circuit of claim 1 , wherein at least part of each plasmon-to-photon transition region is collinear with its connected SPP waveguide.
6. The multilevel optical circuit of claim 1 , wherein each optical via extends through a dielectric layer that separates the first layer from the second layer.
7. The multilevel optical circuit of claim 1 , wherein:
one of the first and second waveguides is a semiconductor waveguide, and
the other of the first and second waveguides is a polymer waveguide.
8. The multilevel optical circuit of claim 1 , wherein each SPP waveguide comprises a metal film on a dielectric layer.
9. The multilevel optical circuit of claim 1 , wherein each of the optical vias connects a first optical waveguide to a second optical waveguide with an optical coupling loss less than about 10 percent and an optical propagation loss less than about 1 dB in polarization contrast.
10. The multilevel optical circuit of claim 1 , wherein the optical coupling effectuated by each of the optical vias and its respective photon-to-plasmon and plasmon-to-photon transition regions occupies a footprint that is no larger than 10 μm×10 μm.
11. The multilevel optical circuit of claim 1 , wherein each of the SPP waveguides is less than 100 μm long.
12. The multilevel optical circuit of claim 1 , wherein each of the photon-to-plasmon transition regions has a tapered shape.
13. The multilevel optical circuit of claim 12 , wherein the tapered shape is triangular.
14. The multilevel optical circuit of claim 1 , wherein each of the plasmon-to-photon transition regions has an expanded shape.
15. The multilevel optical circuit of claim 14 , wherein the expanded shape is trapezoidal.