A Transparent, High Refractive Index and Abbe Number Polymer for Visible Metalens by High Fidelity Nanoimprinting

Simultaneously achieving high visible transparency, high refractive index (n), and a large Abbe number (υ_D) in organic polymers remains a fundamental challenge. Here, a facile and efficient dual sulfur-mediated Michael addition strategy is reported to synthesize transparent high refractive index polymers (HRIPs) with large υ_D. By combining main backbone de-conjugation to preserve visible transparency with rational side-chain engineering for n-tuning, the optimal polymer (H4) achieves an ultrahigh n of 1.86 at 589 nm alongside a large υ_D of 34.93 and robust stability. Moreover, polymer H4 exhibits remarkable performance in nanoimprint lithography, replicating features down to 75 nm with aspect ratios up to 8.5 and a low volumetric shrinkage of only 3.23%. Notably, a nanoimprinted metalens prototype fabricated from H4 delivers a relative focusing efficiency of 49.8% at 550 nm (NA = 0.5), approaching the theoretical design value (52.94%). Therefore, the high refractive index polymer H4 bridges molecular design and manufacturable meta-optics, showing tremendous potential in scalable, flexible, next-generation photonic platforms by translating side-chain polarizability engineering into practical wavefront control.