Topological Interface-state Lasing in a Polymer-Cholesteric Liquid Crystal Superlattice

Abstract

The advance of topological photonics has heralded a revolution for manipulating light as well as for the development of novel photonic devices such as topological insulator lasers. Here, we demonstrate topological lasing of circular polarization in a polymer-cholesteric liquid crystal (P-CLC) superlattice, tunable in the visible wavelength regime. By use of the femtosecond-laser direct-writing and self-assembling techniques, we establish the P-CLC superlattice with a controlled mini-band structure and a topological interface defect, thereby achieving a low threshold for robust topological lasing at about 0.4 mJ. Thanks to the chiral liquid crystal, not only the emission wavelength is thermally tuned, but the circularly polarized lasing is readily achieved. Our results bring about the possibility to realize compact and integrated topological photonic devices at low cost, as well as to engineer an ideal platform for exploring topological physics that involves light-matter interaction in soft-matter environments.

Tunable Topological Lasing of Circularly Polarized Light in a Soft‐Matter‐Based Superlattice

“…Surface relief gratings present on the sidewalls of the ribbons ensure that the CLC is well aligned (out‐of‐plane orientation technology). [ 61 ] Its helical axis is perpendicular to the ribbons, i.e., along the y direction. The helical periodicity p (pitch) of the CLC, which is determined by the concentration of the doped chiral agent and the temperature, is assumed to be p = 348 nm here.…”

“…The CLC regions between the ribbons also look dark when the crossed polarizers are oriented parallel/perpendicular to the direction of the polymer ribbons, but they become bright when the two crossed polarizers are rotated by 45°. This indicates that the surface relief structures on the sidewalls of the ribbons enable good alignment of the CLC, [ 61 ] and that the helical axis of the CLC is perpendicular to the direction of the ribbons. Our experimental setup for excitation and characterization of the topological lasing can be found in the Supporting Information.…”