Supramolecular interaction-induced self-assembly of organic molecules into ultra-long tubular crystals with wave guiding and amplified spontaneous emission

Ultra-long tubular crystals (length up to 10 mm and diameter of 70 mu m) of a small organic functional molecule, 1,4-bis(2-cyano-2-phenylethenyl)benzene (BCPEB), are successfully prepared through a physical vapor transport (PVT) method. On the basis of crystal structural analysis and density functional theory calculations, we show that the formation of such tubular crystals is drawn by the branched hydrogen bonds between the BCPEB molecules. High crystalline quality, highly ordered molecular orientation, and hollow-like topological structure enable the crystal to exhibit optical wave guided emission behaviors with low optical loss (3 dB mm(-1)) and highly polarized emission (the polarized ratio is about 20). Amplified spontaneous emission (ASE) characteristics of the tubular crystals were also studied; the net gain coefficients at the peak wavelength and the threshold are 91.7 cm(-1) and 36 kW cm(-2), respectively.