title: Effect of metal coating in all-fiber acousto-optic tunable filter using torsional wave.
abstract: Torsional mode acousto-optic tunable filter (AOTF) is demonstrated using a metal-coated birefringent optical fiber for an improved robustness. The changes in acoustic and optical properties of a metal-coated birefringent optical fiber induced by the thin metal coating were analyzed experimentally and theoretically. The filter wavelength shift is successfully explained as a result of combined effect of acoustic wavelength change and optical birefringence change. We also demonstrated a small form-factor configuration by coiling the fiber with 6 cm diameter without performance degradation. The center wavelength of the filter can be tuned >35 nm by changing the applied frequency, and the coupling efficiency is higher than 92% with <5 nm 3-dB bandwidth.
authors.forename: Du-Ri
authors.initials: DR
authors.lastname: Song
authors.forename: Chang Su
authors.initials: CS
authors.lastname: Jun
authors.forename: Sun
authors.initials: S
authors.lastname: Do Lim
authors.forename: Byoung Yoon
authors.initials: BY
authors.lastname: Kim