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. Low-threshold lasing has been demonstrated in two-dimensional photonic-bandgap materials, both with distributed feedback and defect modes. 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 structures. Although mirrorless lasing was predicted and observed in one-dimensional helical cholesteric materials and chiral ferroelectric smectic materials, 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.

Lasing Thresholds of Cholesteric Liquid Crystals Lasers

“…As a consequence, the fluorescent emission in these materials is suppressed in the reflection band and is enhanced at the band edges. This gain enhancement and distributed feedback effect can give rise to low threshold mirrorless lasing at the band edge in a variety of liquid crystal materials [2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

Topological zoo of free-standing knots in confined chiral nematic fluids

“…Ensuing conformations not only depend on the anchoring, but vary continuously with the cholesteric pitch. The structures with concentric layers found in cholesteric droplets with degenerate planar anchoring have lately attracted much attention with their use in advanced soft matter photonic elements such as Bragg resonators for micro lasers [28][29][30][31][32] . The recent detailed numerical and topological study of these systems shows 27 that the degenerate boundary conditions still allow enough degrees of freedom to at least partially accommodate the requirements of the intrinsic twisting and form rather simple defect structures.…”

Nematic colloids, topology and photonics

“…Once the optical gain and the production of photons inside the cavity are exceeding the losses, the laser emission takes place. In soft matter, lasers were realized a long time ago in cholesteric LCs [43], ferroelectric smectic phases [44] and in blue phases [45]. In cholesteric lasers, thin layers of a cholesteric LC with large lateral dimensions are used and the lasing is stimulated by an external pumping pulsed laser of shorter wavelength.…”