Variable optical attenuator for large-scale integration

A polymer thermooptic variable optical attenuator (VOA) was designed and demonstrated for dense waveguide device integration. The waveguide bend design is compatible with photolithography fabrication techniques and operates by controlling waveguide bend radiation loss. The design optimizes the compromise between integration capability, integration cost, and attenuation efficiency. For a 5 mm bend length, optical attenuation of >40 dB has been achieved with an applied electrical power of 250 mW. The fiber-to-fiber insertion loss was 1.5 dB for a 20-mm total waveguide length. The design's compact size makes it practical for both VOA arrays and dense integrated optical circuits.