Integrated planar composite coupling structures transform between a small mode size and a large mode size waveguide

摘要

Composite optical waveguide structures or mode transformers(1300) and their methods of fabrication and integration are disclosed, wherein the structures or mode transformers are capable of bi-directional light beam transformation between a small mode size waveguide and a large mode size waveguide. One aspect of the present invention is directed to an optical mode transformer (1300) comprising a waveguide core (1345) having a high refractive index contrast between the waveguide core (1345) and the cladding (1350 or 1310), the optical mode transformer (1300) being configured such that the waveguide core (1345) has a taper wherein a thickness of the waveguide core tapers down (1348) to a critical thickness value, the critical thickness value being defined as a thickness value below which a significant portion of the energy of a light beam (1341) penetrates into the cladding layers (1350 or 1310) surrounding the taper structure thereby enlar in the small mode size.