Post-fabrication tuning of a polymeric grating-assisted codirectional coupler filter by photobleaching

Abstract

We present a convenient post-fabrication tuning method that uses photobleaching to adjust the center wavelength of the polymeric grating-assisted codirectional coupler filter. The passive polymer waveguide is used as a low-loss optical path and the electro-optic (EO) polymer waveguide is used for dropping the optical signal at a given wavelength. Photobleaching reduces the effective index of the EO polymer waveguide, which makes it possible to adjust the center wavelength. We can easily realize the filters with a desired center wavelength by exposing ultraviolet light on them with a proper energy even after finishing the device fabrication. The center wavelength is decreased by 25 nm with a photobleaching energy of 180 J/cm 2 without extra loss.