Segmented optical waveguides in KTiOPO4are fabricated by ion exchange of Rb/Ba for K using molten nitrate salts. The waveguides have been utilized to generate efficient second‐harmonic generation (SHG) of blue light. Four techniques are described which demonstrate that the ion exchange can produce domain reversal in these waveguides, and quasi‐phase matching is utilized to obtain blue light. The experiments involve surface SHG, electrostatic toning, selective etching, and piezoelectric measurements.