Fabrication of Flip-Chip Optical Couplers Between Single-Mode Fibers and LiNbO3Channel Waveguides

Highly efficient end-fire optical coupling is described between single-mode fibers and Ti-diffused LiNbO3 channel waveguides using a Si V-groove/flip-chip Configuration. The preparation and alignment of the LiNbO3 and the Si wafer are discussed. The LiNbO3 substrate is arranged face down on the Si wafer. The fibers are placed in the Si V-grooves which provide lateral and angular alignment, and approximate vertical alignment, with respect to the channel waveguide. Deep transverse grooves, with tapered fibers lying under the Coupling fibers, allow submicron vertical positioning. The fiber ends are prepared by cleaving; the LiNbO3channel ends are optically polished.