Ultra-Low-Power Tunable Topological Photonic Filter on Hybrid Integrated Lithium Tantalite and Silicon Platform

Integrated tunable optical filters are essential components in photonic signal processors, telecom systems, sensors, and quantum optical devices. Two of the most important features of a tunable filter are its dimensions and power consumption. Herein, the design and experimental validation of an on-chip optical filter composed of a 1D topological photonic crystal cavity based on a hybrid integrated lithium tantalite-silicon platform is presented. The strong optical confinement of the boundary state allows the fabrication of a tunable filter with an ultra-compact size of 1.14 × 75 µm² is demonstrated. Moreover, lithium tantalite has excellent electro-optic properties and enables ultra-low-power wavelength tuning of the topological boundary state. The measured power consumption and tuning efficiency of the device are 0.0218 nW pm⁻¹ and 6.64 pm V⁻¹, respectively. The anisotropy of thin-film lithium tantalite is verified by evaluating its tuning efficiency at different optical angles. The device can compensate for thermally induced refractive index changes ≈20 °C, exhibiting operational robustness. High-speed transmission experiments confirm the stability of the developed tunable filter. This optical filter implements a topological structure with a compact size and can potentially be applied in on-chip quantum optics, nonlinear optics, and optical sensing.