Two-dimensional thin film lithium niobate photonic crystal waveguide for integrated photonic chips

The photonic crystal waveguide (PCW) possesses remarkable capabilities in manipulating light beams and light–matter interactions within the subwavelength range. This property renders it a highly promising structure for the miniaturization of optical devices. We delve into the mode characteristics in two-dimensional PCWs on thin film lithium niobate, establish the correlation between the single-mode region in the PCW and its photonic crystal duty cycle, and observe mode hybridization in the waveguide. A lithium niobate PCW with sidewall angles can realize single-mode transmission or mode conversion by adjusting the width of its defective waveguides, and it is theoretically and experimentally verified that a change in the width of the waveguide shifts the operating wavelength. The results of the mode analysis are useful in the design of waveguide structures for photonic crystal-based electro-optical modulators and optical sensors.