Graded-index thin-film stack for cladding and coupling

Abstract

A graded-index multilayer thin-film stack is optimized to act as a cladding layer on top of a silicon (Si) nanowaveguide and also a collimator for chip coupling where the waveguide ends. The numerical example shows an optimized graded-index profile from 2.35 to 1.45 provides an optical coupling to the standard single-mode fiber with efficiency close to 90% while retaining tight light confinement for the Si nanowaveguide. The corresponding material realization of a graded-index profile with a Si-rich nitride SiN_x/SiON/SiO₂ system is explored using inductively coupled plasma chemical vapor deposition, and a SiN_x cladded Si waveguide is demonstrated.

Processing method, properties and application of functionally graded polymer materials based on the mixtures of poorly compatible epoxy resins

“…19 In comparison with materials fabricated by layer-by-layer deposition, graded materials have no sharp interfaces, consequently, it allows to avoid stresses arising in contact layers. Such graded materials are successfully used as optical films and fibers, 20,21 materials for electrical industry and mechanical engineering, 22 implants in orthopedic applications. 23 Distribution of filler concentration in one, two or three dimensions 24 is the next step in development of graded materials which can be classified as Functionally Graded Materials (FGMs).…”

“…19 In comparison with materials fabricated by layer-by-layer deposition, graded materials have no sharp interfaces, consequently, it allows to avoid stresses arising in contact layers. Such graded materials are successfully used as optical films and fibers, 20,21 materials for electrical industry and mechanical engineering, 22 implants in orthopedic applications. 23…”