Euler-modified pulley-type microring on lithium niobate platform

Microring resonators, as essential components of photonic integrated circuits, offer compact size, wavelength selectivity, and strong resonance effects, making them invaluable in optical computing, on-chip interconnects, and quantum photonics. The proposal of the pulley-type microring enhances the coupling strength, but also brings about issues such as mode mismatch and the excitation of higher-order modes. Here, a lithium niobate microring resonator coupled with a pulley bus waveguide based on modified Euler curves is proposed. This Euler-modified pulley bus minimizes mode mismatch at bending junctions, effectively suppressing higher-order mode excitation. The design achieves a high Q factor (exceeding 10⁵) and strong coupling efficiency (83%) within a compact structure of 70 μm radius. Due to its simple structure and ease of fabrication, the Euler-modified pulley-type microring holds practical value for applications requiring high-quality microring resonators.