Abstract Photonic crystals manipulate light propagation via periodic structures, enabling control over optical phenomena across specific frequency ranges. Among these, liquid crystals (LC) with chiral molecules produce twisted, periodic structures that exhibit photonic bandgaps. Blue Phases (BPs), in particular, are 3D cubic LC phases with sub‐micron lattice constants, behaving as 3D soft photonic crystals with distinct Bragg reflections. However, their application is limited by spontaneous polycrystalline growth, which introduces optical scattering and degrades performance. In this work, the first demonstration of directional lasing from millimeter‐scale stabilized monocrystalline BP photonic crystals is shown—a significant advance, as only random lasing from polycrystalline samples has been previously observed. These structures exhibit directional distributed lasing, with emission guided through the crystalline lattice, producing highly directional and circularly polarized laser output. The laser action is attributed to resonant polarization modes of the BP lattice, characterized by angular dispersion and strong chiral selectivity. These findings establish BP monocrystals as viable platforms for integrated photonic systems and mirrorless lasing.
Otón et al. (Thu,) studied this question.