Electrically tunable polarisation-independent blue-phase liquid crystal binary phase grating via phase-separated composite films

A simple method for fabricating polarisation-independent blue-phase liquid crystal phase grating is demonstrated by implementing photopolymerisation-induced phase separation through a binary photomask. The dynamic focusing property of the proposed liquid crystal grating is independent of the polarisation state of incident light. The efficiency of various diffraction orders for the phase grating was measured as a function of the applied voltage. Experimental results show that the maximum diffraction efficiency reaches 36% for the ±1 order, which approaches the theoretical limit ~41%. The measured rise time is 1.4 ms and fall time is 2.2 ms. Such a tunable grating has great potential for photonic applications.