Characteristics of proton-exchanged wet etching on z-cut nickel-indiffused lithium niobate

In this letter, the wet etching technique is utilized to determine the proton exchange (PE) depth of z-cut nickel-indiffused lithium niobate under different nickel indiffusion parameters. It is demonstrated that the existence of nickel atoms reduces the PE depth. While this result was applied to the fabrication of a ridge-type waveguide, the tilt angle of the sidewall on the ridge waveguide was about 70°, which has been successfully increased.