Reconfigurable and Transferable Liquid Crystal Claddings Enabled by Polymer Network Templates for Tunable Silicon Nitride Microring Resonators

Reconfigurable and low-power tuning of integrated photonic devices is essential to mitigate fabrication-induced variability. However, conventional liquid crystal (LC) integration often requires complex cell-like encapsulation and surface alignment layers. In this work, we demonstrate an alignment-free and transferable LC cladding platform for silicon nitride (Si3N4) microring resonators (MRRs) utilizing a free-standing polymer network template (PNT). The PNT film, fabricated via asymmetric photopolymerization, is directly laminated onto the MRR, providing robust molecular alignment and strong evanescent-field interaction without top-glass substrates. Experimental results reveal a large resonance blueshift of −0.332 nm/°C using a 5CB-based PNT, representing an approximately 25-fold sensitivity enhancement compared to air-cladded devices. Furthermore, the platform’s reconfigurability is validated through a “wash-out-and-refill” process, enabling the modular exchange of the LC host (e.g., to E7) while preserving alignment quality. By incorporating azo-doped LC, we also achieve reversible all-optical resonance switching via photoisomerization. This PNT-based strategy decouples material functionality from device fabrication, offering a versatile route for adaptive photonic systems.