Enhancing Diffraction Efficiency in Polarization Volume Gratings via Polymer-Stabilized Cholesteric Liquid Crystal Bilayers

Polarization volume gratings (PVGs), formed using patterned cholesteric liquid crystals (CLCs), offer high diffraction efficiency, polarization selectivity, and broad angular bandwidth—making them ideal for advanced photonic applications. However, traditional CLC-based PVGs are intrinsically limited to a maximum reflectivity of 50% for unpolarized light, capping their diffraction efficiency. To overcome this limitation, a recently proposed approach is presented that achieves hyper-reflectivity in a single polymer-stabilized cholesteric liquid crystals CLC (PSCLC) cell using a bilayer helical structure fabricated via photo-polymerization-enforced stratification (PES). This method enables the coexistence of two CLC layers with orthogonal helical handedness, facilitating reflection of both left- and right-handed circularly polarized light. Experimental results confirm that through precise material composition and photo-polymerization processing, PVGs with either multi-band reflection or high diffraction efficiency can be realized. Moreover, the bilayer architecture exhibits tunable optical behavior under electric fields and temperature variation, underscoring its potential in adaptive and reconfigurable optical systems.