Chip-to-chip optical interconnection using high refractive index couplers

A method for establishing optical coupling between a first planar waveguide and a second waveguide that are spatially separated from one another, comprising:

• arranging an optical interconnect on the first planar waveguide, the optical interconnect being defined by a single waveguide having first and second end portions and an intermediate portion, each of the end portions having an inverse taper;
• and
• arranging the second waveguide on the optical interconnect so that the second waveguide overlaps with the first end portion of the optical interconnect but not the second end portion of the optical interconnect such that the first end portion of the optical interconnect is located between the first planar waveguide and the second waveguide to thereby enable an adiabatic transition of an optical signal from the first planar waveguide to the second waveguide
• via the optical interconnect, the first planar waveguide and the second waveguide having different refractive indices from one another at an operating wavelength and the optical interconnect having a higher refractive index at the operating wavelength than the refractive indices of a core of the first planar waveguide and a core of the second waveguide, wherein at least a portion of the second waveguide is located on a different substrate than the first planar waveguide and the optical interconnect is entirely located on a substrate on which the first planar waveguide is located.