title: Widely tunable long-period waveguide grating couplers.
abstract: We demonstrate experimentally two widely tunable optical couplers formed with parallel long-period polymer waveguide gratings. One of the couplers consists of two parallel gratings and shows a peak coupling efficiency of ~34%. The resonance wavelength of the coupler can be tuned thermally with a sensitivity of 4.7 nm/ degrees C. The experimental results agree well with the coupled-mode analysis. The other coupler consists of an array of ten widely separated gratings. A peak coupling efficiency of ~11% is obtained between the two best matched gratings in the array and the resonance wavelength can be tuned thermally with a sensitivity of -3.8 nm/ degrees C. These couplers have the potential to be further developed into practical broadband add/drop multiplexers and signal dividers.
authors.forename: Y
authors.initials: Y
authors.lastname: Bai
authors.forename: Q
authors.initials: Q
authors.lastname: Liu
authors.forename: K P
authors.initials: KP
authors.lastname: Lor
authors.forename: K S
authors.initials: KS
authors.lastname: Chiang