title: Large one-time photo-induced tuning of directional couplers in chalcogenide-on-silicon platform.
abstract: The stable one-time tuning of silicon-photonic directional couplers, over a broad range of coupling ratios, is achieved through the selective photo-removal of an upper cladding layer of chalcogenide glass. Analysis shows that the coupling coefficient per unit length between two parallel fully-etched silicon waveguides may be changed by 45%. The power coupling ratio of a 50 µm-long directional coupler between two such waveguides may be tuned arbitrarily between 0 and 1, with weak residual wavelength dependence. Smaller modifications in the coupling coefficient per unit length are obtained between two partially-etched ridge waveguides, on the order of 10%. The proposed procedure is demonstrated in the post-fabrication tuning of transmission notches of a race-track resonator, from over-coupling through critical coupling to weak coupling. The extinction ratio of specific resonances is varied between 4 and 40 dB. The coupling ratio of a tuned device remains stable following three months of storage.
authors.forename: R
authors.initials: R
authors.lastname: Califa
authors.forename: D
authors.initials: D
authors.lastname: Munk
authors.forename: H
authors.initials: H
authors.lastname: Genish
authors.forename: Yu
authors.initials: Y
authors.lastname: Kaganovskii
authors.forename: I
authors.initials: I
authors.lastname: Bakish
authors.forename: M
authors.initials: M
authors.lastname: Rosenbluh
authors.forename: A
authors.initials: A
authors.lastname: Zadok