Single‐Crystal Organic Heterostructure for Single‐Mode Unidirectional Whispering‐Gallery‐Mode Laser

Abstract Organic single crystals have attracted great attention for solid‐state lasers owing to their smooth morphologies with inherent optical microcavity, ordered molecular packing mode with minimized defects density, and high photoluminescence quantum efficiency. However, the organic single‐crystal lasers, including whispering‐gallery‐mode (WGM) lasers with nondirectional emission and Fabry–Perot (F–P) lasers with inherent high‐lasing threshold, cannot achieve state‐of‐the‐art performance. Herein, the hierarchical self‐assembly of organic single‐crystal heterostructures made from cube‐shaped microdisks with optical gain and microwires with optical waveguide characteristics is demonstrated, which realize the unidirectional WGM laser action with a low‐lasing threshold of ≈600 nJ cm⁻². The lattice mismatch rate principle contributes to the growth of these single‐crystal organic heterostructures. More significantly, the waveguide‐coupled WGM microcavity with a coupling coefficient of 28.8% proves that the unidirectional outcoupling of the single‐crystal WGM lasers from the single‐crystal wire waveguides is achieved. The results will pave an alternative avenue for high‐performance organic single‐crystal lasers.