title: Focusing subwavelength grating coupler for mid-infrared suspended membrane waveguide.
abstract: A mid-infrared (mid-IR)-focusing subwavelength grating (SWG) coupler and suspended membrane waveguide (SMW) on a silicon-on-insulator wafer are studied. For a transverse-electric mode uniform SWG, finite-difference time-domain simulation predicts 44.2% coupling efficiency with 1 dB bandwidth of about 220 nm and backreflection of 0.78% at 2.75 μm. Then the uniform SWG is curved to a focusing SWG using a phase-matching formula. The SMWs are analyzed by the finite element method and fabricated. An Er3+-Pr3+ co-doped mid-IR fiber laser is used for device characterization. The fabricated mid-IR SWG coupler has 24.7% coupling efficiency.
authors.affiliation: Department of Electronic Engineering, Chinese University of Hong Kong, Hong Kong, China. zzcheng@ee.cuhk.edu.hk
authors.forename: Zhenzhou
authors.initials: Z
authors.lastname: Cheng
authors.forename: Xia
authors.initials: X
authors.lastname: Chen
authors.forename: C Y
authors.initials: CY
authors.lastname: Wong
authors.forename: Ke
authors.initials: K
authors.lastname: Xu
authors.forename: Christy K Y
authors.initials: CK
authors.lastname: Fung
authors.forename: Y M
authors.initials: YM
authors.lastname: Chen
authors.forename: Hon Ki
authors.initials: HK
authors.lastname: Tsang