Whispering Gallery Mode Laser Based on a Self‐Assembled Organic Octahedron Microcrystal Microresonator

powerful tool for bottom-up fabrication. Recently, single-crystalline organic nanowires self-assembled from π-conjugated semiconductors had shown strong optical confi nement effect as optical waveguides [ 16 ] and optically pumped lasers. [ 17 ] For example, Chandrasekar et al. have reported the self-assembly of the nano-tubular structure, which can effectively guide laser light from one end to another exit end, exhibiting good passive optical waveguides property. [ 16a-c ] Takazawa et al. fabricated the wires structure by self-assembly of 3-ethyl-2-[(3-ethyl-2(3H)-benzothiazolylidene) methyl]benzothiazolium iodide to form wire structures through cooling the hot solutions, and then studied the active optical waveguiding behavior of the wires. [ 16d-g ] In 2007, Redmond et al. reported microcavity effects and optically pumped lasing in single conjugated polymer (poly(9,9dioctylfl uorene)) based nanowires, which was commented on as ‘nanowire lasers go organic’. [ 17a ] Subsequently, the single wire active optical waveguides and ultraviolet lasers were realized in as-prepared TPI nanowires by Yao.et.al, demonstrating that nanowire waveguides and lasers can also be extended to small organic molecules. [ 17b ] However the axial FP cavity defi ned between the two wire-end-faces has to be larger than 10 μm to build up enough gain for lasing. Recently, we have demonstrated that highly emissive H-aggregated thiomethyl-terminated oligo(phenylene vinylene)s (OPV) can be superior gain materials for laser applications and a low threshold lasing are realized in the high-quality, ultra-small radial FP cavity along the two lateral-faces of single nanowires self-assembled. [ 18 ]