Electric Field-Driven Shifting and Expansion of Photonic Band Gaps in 3D Liquid Photonic Crystals

Highly tunable 3D liquid photonic crystals are demonstrated using low-dc-field-driven polymer-stabilized blue-phase liquid crystals. The central wavelength of the photonic band gap can be reversibly shifted to more than 200 nm away from the original position. Besides, by controlling the polymerization-induced morphology variations, the band gap can also be expanded from a bandwidth of around 30 nm to at least 310 nm, the first time a white blue phase is observed. Both types of band-gap modulation, namely, shifting and expansion, can be independently manipulated in any crystal axis without affecting the lattice spacings in the other dimensions. We envision polymer-stabilized blue-phase liquid crystals as a fascinating platform for photonic applications, such as 3D lasers, nonlinear optics, and photonic integrated circuits.