Lasing in a three-dimensional photonic crystal of the liquid crystal blue phase II

Abstract

Photonic-bandgap materials, with periodicity in one, two or three dimensions, offer control of spontaneous emission and photon localization^1,2,3. Low-threshold lasing has been demonstrated in two-dimensional photonic-bandgap materials, both with distributed feedback and defect modes^4,5,6,7,8,9. Liquid crystals with chiral constituents exhibit mesophases with modulated ground states. Helical cholesterics are one-dimensional, whereas blue phases are three-dimensional self-assembled photonic-bandgap structures¹⁰. Although mirrorless lasing was predicted^11,12 and observed in one-dimensional helical cholesteric materials^13,14 and chiral ferroelectric smectic materials¹⁵, it is of great interest to probe light confinement in three dimensions. Here, we report the first observations of lasing in three-dimensional photonic crystals, in the cholesteric blue phase II. Our results show that distributed feedback is realized in three dimensions, resulting in almost diffraction-limited lasing with significantly lower thresholds than in one dimension. In addition to mirrorless lasing, these self-assembled soft photonic-bandgap materials may also be useful for waveguiding, switching and sensing applications.