Highly confining planar proton exchanged waveguides on z-cut LiNbO 3 without degrading its nonlinear coefficients: the HISoPE process

—We propose a new proton exchange process to repro-ducibly realize on lithium niobate highly confining (δne = 0.1) planar waveguides without degrading the nonlinear coefficient of the crystal. Waveguides were fabricated with different acidic baths and the crystallographic changes, the index profiles and the local SHG response were measured. We show that for certain fabrications conditions, characteristic of the so-called High Index Soft Proton Exchange process (HISoPE), the high index modification can be obtained without degrading the crystal nonlinear coefficient. This result should open the way to the fabrication of very efficient nonlinear devices.