Planar LiNbO3 waveguides with a 5-mm tapered region and a 10-mm homogeneous slab waveguide region were fabricated by a double proton-exchange process. The 4-µm waveguide entrance gives rise to a coupling efficiency as high as 93%; the precise control of the depth profile of the tapered region results in a low 1-dB power transfer loss from the tapered region to the 0.4-µm-depth working region. The techniques developed provide an alternative to prism coupling into planar waveguides in Čerenkov second-harmonic generation applications.
© 1996 Optical Society of America
Gary Y. Wang and Elsa Garmire, "Efficient coupling into tapered proton-exchanged LiNbO3 waveguides fabricated by vertically controlled immersion," Opt. Lett. 21, 42-44 (1996)