Fiber-to-waveguide coupling using ion-milled grooves in lithium niobate at 13-μm wavelength

A new method for fiber-Ti:LiNbO(3) waveguide coupling is described. Ion-milled grooves in LiNbO(3) permit repeatable, rigid location of fibers that have been chemically etched and then polished. The constituent loss mechanisms are analyzed and waveguide parameters optimized to minimize insertion loss resulting from modal mismatch by using experimental data on the optical fields. A total insertion loss of -3.1 dB has been measured for the coupler.