Adjustable slow light via the electro-optic effect in periodically poled thin-film lithium niobate

This study introduces and comprehensively investigates a novel tunable slow-light (SL) photonic crystal, the modulated lithium niobate photonic crystal waveguide (MLNPCW), which utilizes voltage-induced periodic refractive index modulation in periodically poled thin-film LN via the linear electro-optic effect. To optimize performance, we establish a theoretical model and utilize numerical simulations to analyze the device, focusing on its bandgap wavelength λ BG and maximum group index n g max . Based on these findings, we propose two design options, demonstrating the following advantages: at 200 V, we achieve a n g max of approximately 4.7 along with a low propagation loss α of 0.29 dB/cm, significantly surpassing conventional SL devices, and a group velocity dispersion GVD of 0.0073ns 2 /m. By increasing the voltage to 300 V, we attain a n g max of approximately 7.4, enabling tunable SL without affecting λ BG —a feat difficult to accomplish with the devices—while maintaining similar α but significantly affecting GVD (0.022ns 2 /m).