Analysis of Lithium Niobate Electrooptic Long-Period Waveguide Gratings

We present an approximate step-index waveguide model for the study of lithium-niobate (LiNbO
₃
) electrooptic (EO) long-period waveguide grating filters. The model takes into account the non-uniform spatial distributions of the EO coefficient and the applied electric field. Using this model, we analyze in detail the effects of the grating and waveguide parameters on the performance of the filter with the objective of identifying a set of optimal design parameters for the realization of an efficient filter. Guided by the results from the analysis, we fabricated a 12-mm-long EO grating, which produced a 24-dB rejection band at a driving voltage of 49 V.