Low Loss Tunable Optical Filter using Silicon Photonic Band Gap Mirrors

A fiber-pigtailed tunable optical filter is described, based on silicon-air photonic bandgap mirrors. The high reflectance achievable in these mirrors allows a short Fabry-Perot cavity to be employed, such that lensed fibers provide sufficient collimation without additional focusing elements. Mirror surface orientation and quality are shown to be crucial to performance, and a two-stage etch process is used to satisfy this requirement. MEMS elecrostatic actuation of one mirror is used for tuning, and the final device achieves fiber-to-fiber insertion loss of 11 dB, passband width 3 nm, and tuning range ≈ 10 nm.