title: Broadband polarization independent nanophotonic coupler for silicon waveguides with ultra-high efficiency.
abstract: Coupling of light to and from integrated optical circuits has been recognized as a major practical challenge since the early years of photonics. The coupling is particularly difficult for high index contrast waveguides such as silicon-on-insulator, since the cross-sectional area of silicon wire waveguides is more than two orders of magnitude smaller than that of a standard single-mode fiber. Here, we experimentally demonstrate unprecedented control over the light coupling between the optical fiber and silicon chip by constructing the nanophotonic coupler with ultra-high coupling efficiency simultaneously for both transverse electric and transverse magnetic polarizations. We specifically demonstrate a subwavelength refractive index engineered nanostructure to mitigate loss and wavelength resonances by suppressing diffraction effects, enabling a coupling efficiency over 92% (0.32 dB) and polarization independent operation for a broad spectral range exceeding 100 nm.
authors.forename: Pavel
authors.initials: P
authors.lastname: Cheben
authors.forename: Jens H
authors.initials: JH
authors.lastname: Schmid
authors.forename: Shurui
authors.initials: S
authors.lastname: Wang
authors.forename: Dan-Xia
authors.initials: DX
authors.lastname: Xu
authors.forename: Martin
authors.initials: M
authors.lastname: Vachon
authors.forename: Siegfried
authors.initials: S
authors.lastname: Janz
authors.forename: Jean
authors.initials: J
authors.lastname: Lapointe
authors.forename: Yves
authors.initials: Y
authors.lastname: Painchaud
authors.forename: Marie-Josée
authors.initials: MJ
authors.lastname: Picard