Study of the Fabrication of BCB Waveguide Devices by Ultraviolet Pulsed-Laser Illumination

Benzocyclobutene directional couplers and 1times2 multimode interference (MMI) power splitters fabricated by ultraviolet (UV) pulsed-laser illumination are presented. With an accurate control of the fabrication process, the measured coupling lengths of the directional couplers are in good agreement with those simulated by the beam propagation method. In particular, accurate power splitting ratios of the directional couplers can be achieved by controlling the number of laser shots to obtain the required index changes. Moreover, MMI power splitters with accurate interference lengths and low imbalances can be successfully fabricated. All those reveal that UV pulsed-laser illumination is an accurate and controllable technique for the device fabrication.