Determination of refractive index variation of a glass-integrated optical waveguide by the acousto-optic effect

Ion exchange on a glass substrate is now a well-known technology that enables the realization of optical waveguide devices. In recent years, the hybridization of ion-exchanged glass waveguides has become a promising method for functional integration. In this context, an integrated Mach–Zehnder interferometer (MZI), made by ion exchange on a glass substrate, was used to realize an acousto-optic modulator. Over one arm of the MZI a PZT ceramic driven by a high-voltage signal was glued. The acoustic waves cross the light waveguide and locally modify the refractive index of the glass. The optical intensity observed at the output of the interferometer varies according to the piezoelectric ceramic excitation. This component is used to find the relation between the refractive index change induced and the applied stress. Measurements were made for two linear polarizations: TE and TM. The proposed method was validated on a specific glass substrate and can be directly extended to any kind of glass