Electrically switchable bistable dual frequency liquid crystal light shutter with hyper-reflection in near infrared

Bistable light shutter based on dual frequency cholesteric liquid crystals (LCs) have attracted intensive interests due to low energy consumption. Herein, we demonstrated an electrically switchable bistable dual frequency LC light shutter with a hybrid structure of cholesteric LC and chiral polymer film. The fabricated device can be switched between planar state which is transparent and focal conic state which is opaque in visible light through voltage pulse while keeping hyper-reflection in near infrared light in both states. The increase of reflection in near infrared light dramatically reduces the interior heat from solar energy, thus making it quite useful in temperature control. In addition, the reflection of near infrared light can be further improved by using cholesteric LC with larger birefringence. The proposed device is useful in smart windows of automobiles, energy-saving buildings and other photonic applications.