Enhanced holographic polymer-dispersed liquid crystal gratings through RAFT photopolymerization

Holographic polymer-dispersed liquid crystal (HPDLC) gratings have great potential for applications in displays and data storage due to their exceptional optical modulation capabilities. Since their optical performance strongly depends on the phase separation between the polymer and liquid crystal (LC) induced by the photopolymerization, it is essential for improving the performance of HPDLC through the photokinetic aspect. In this work, we report (for the first time, to our knowledge) an enhanced HPDLC grating by using the reversible addition-fracture chain transfer (RAFT) agent. Experimental results show that a p-polarization diffraction efficiency (η) of 84% and a refractive index modulation (Δn) as high as 0.07 with the addition of RAFT are achieved in a 3-μm HPDLC grating. Significantly, comparing with the undoped grating, this corresponds to a near two-fold enhancement on η and an improvement of 62% on Δn. Moreover, we confirm that an increase in the size of LC-rich phase leads to a decreasing in the threshold voltage. We believe that the enhancement of HPDLC performance by RAFT provides an effective path to optimize the holographic photopolymer materials for uses of AR display and holographic data storage.