Electro optic tuning optimization of segmented periodically poled LiNbO₃ optical parametric oscillators via segment length ratio variation

We present a theoretical study of segment length-ratios dependent wavelength tuning in optical parametric oscillators (OPOs) employing a three-segment quasi-phase-matched (QPM) device configuration based on the electro-optic effect. The device structure consists of two periodically poled lithium niobate (PPLN) section with a 50% duty cycle, separated by a central uniform (single-domain) region. In this work, the relative length ratios of the central segment are systematically varied while maintaining fixed outer segment ratios and a constant total crystal length to analyze its influence on the achievable tuning bandwidth. The analysis shows that the equal segment-length configuration (1: 1: 1) provides the maximum tuning bandwidth of approximately 102 nm. The numerical simulation results obtained using MATLAB demonstrate the significant role of segment-length engineering in enhancing the tunability characteristics of segmented QPM-based OPO devices.