Proton exchanged imbalanced Ti:LiNbO3 Mach-Zehnder modulator

We describe the fabrication process of a LiNbO3 integrated Mach-Zehnder interferometer featuring a large path-imbalance between the arms. This path-imbalance is created by the proton exchange located on one arm. The proton exchange increases the extraordinary refractive index ne of lithium niobate and modifies the effective index of the guided mode. Path-differences of 80 μm per mm of proton exchange length are obtained with the fabrication process reported here.