Refractive index modulating Raman spectroscopy based on perovskite PMN-PT ceramics

A three-layer planar waveguide structure comprising a perovskite (1-x)Pb(Mg_1/3Nb_2/3Nb_2/3)O_3-xPbTiO₃ (PMN-PT) ceramic sandwiched by two silver films is designed and called PMPW. Using the high sensitivity of ultrahigh-order modes, theoretical analysis is performed to calculate the effective refractive index (ERI) of the PMPW. A detailed analysis of the Raman spectrum of PMN-PT at 795  cm^-1 is performed. A comparison of the numerical analysis and experimental results reveals that the nonlinear change in ERI plays a primary role in the Raman signal variation. Analysis of the Raman spectrum of a sample deposited on PMPW confirms that it is effective for modulating Raman signals.