Tunable waveguide transmission gratings based on active gain control

Mode loss or gain can have a significant effect on the operation of waveguide transmission gratings as optical filters. Taking for example a long-period grating (LPG), we present a computer simulation that accounts for these effects. We show that cladding loss or gain result in qualitatively different LPG spectral behavior that can be used as a tuning mechanism in guiding structures where cladding mode properties can be controlled. One possible control mechanism is to have pump-driven gain in a doped cladding, which can perform gradual loss compensation and eventually gain excitement. Based on simulation results, we propose new approaches to tuneable amplifying filter designs in special fibers, as well as grating assisted co-directional couplers for integrated optics platforms.