Adjustment of the coupling ratio by laser ablation of Ti:LiNbO3 directional couplers

Abstract The coupling ratio of directional couplers in Z-cut Y-propagation and X-cut Z-propagation LiNbO 3 crystals was adjusted by laser ablation. The coupling ratio change is more efficient for the TM-mode of Z-cut couplers. The method can be used to correct the uncertainty of the coupling ratio for directional couplers that occurs during fabrication process.