394 nm ultraviolet amplified spontaneous emission (ASE) with a low pumping power threshold, from a thin film of an organic semiconductor 4,4′-bis(9-carbazolyl)-2,2′-biphenyl (CBP) is demonstrated. It is done under the pulse excitation of a N2 gas laser (337 nm). It is found that 3,6-dimethyl and 3-methyl substituted CBP derivatives also exhibited ASE in the deep-blue region of 406 and 401 nm. The results show that the ASE gain is correlated with the radiative decay rate (kf) i.e. larger kf resulted in a larger ASE gain.
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