title: Monolithically integrated asymmetric graded and step-index couplers for microphotonic waveguides.
abstract: A monolithically integrated asymmetric graded index (GRIN) or step-index (GRIN) mode converters for microphotonic waveguides are proposed and described. The design parameters and tolerances are calculated for amorphous silicon (a-Si) couplers integrated with silicon-on-insulator waveguides. The GRIN and step-index couplers operate over a wide wavelength range with low polarization dependence, and the lithographic resolution needed is only +/-1 microm. Finally, experimental results are presented for a single layer 3 microm thick step-index a-Si coupler integrated on a 0.8 microm thick SOI waveguide. The measured variation of coupling efficiency with coupler length is in agreement with theory, with an optimal coupling length of 15 microm for this device.
authors.forename: A
authors.initials: A
authors.lastname: Delâge
authors.forename: S
authors.initials: S
authors.lastname: Janz
authors.forename: B
authors.initials: B
authors.lastname: Lamontagne
authors.forename: A
authors.initials: A
authors.lastname: Bogdanov
authors.forename: D
authors.initials: D
authors.lastname: Dalacu
authors.forename: D-X
authors.initials: DX
authors.lastname: Xu
authors.forename: K P
authors.initials: KP
authors.lastname: Yap