title: 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 SiNx/SiON/SiO2system is explored using inductively coupled plasma chemical vapor deposition, and a SiNxcladded Si waveguide is demonstrated.
authors.forename: Kim Peng
authors.initials: KP
authors.lastname: Lim
authors.forename: Doris Keh Ting
authors.initials: DK
authors.lastname: Ng
authors.forename: Jing
authors.initials: J
authors.lastname: Pu
authors.forename: Yeow Teck
authors.initials: YT
authors.lastname: Toh
authors.forename: Tjiptoharsono
authors.initials: T
authors.lastname: Febiana
authors.forename: Krishnamurthy
authors.initials: K
authors.lastname: Vivek
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang