Large-Area Microtransfer-Printed Thin-Film Lithium Niobate-Silicon Nitride Microring Optical Filter with Nanosecond Tuning Speed

The silicon nitride (Si₃N₄) platform has garnered significant attention as a promising integrated photonics platform. However, it encounters substantial challenges in achieving power-efficient and high-speed phase shifting. The heterogeneous integration of thin-film lithium niobate (TFLN) onto commercially available ultralow-loss Si₃N₄ platforms combines the strengths of both materials, enabling the development of advanced integrated photonic devices. Recently, micro-transfer printing (MTP) has emerged as a versatile heterogeneous integration technique. However, the limited size of transferable coupon restricts the integration of large devices. In this letter, we propose a novel MTP method to transfer a TFLN coupon over 250 × 750 μm² onto a Si₃N₄ chip. This approach facilitates the first demonstration of an MTP-based TFLN-Si₃N₄ heterogeneously integrated tunable microring resonator, featuring a 3 dB optical bandwidth of 1.2 GHz, a tuning efficiency of 2 pm/V, and a response time of less than 3 ns. To further reduce insertion loss, we design an efficient coupler (∼0.5 dB/facet) with a large misalignment tolerance (more than ±1.75 μm) for MTP, capable of operating within the misalignment errors of our MTP process. The measured loss is approximately 0.5 dB/facet at the C-band. Moreover, using this MTP method, we demonstrate MTP-available coupons with sizes exceeding 230 × 2000 μm². This research enhances the versatility of MTP and broadens its potential applications.