Light amplification and lasing in a (meta-phenylene vinylene) copolymer

Abstract

We report on single pass optical gain and lasing measurements on a blue-emitting copolymer, poly ~ m -phenylene vinylene-co-2,5-dioctyloxy- p -phenylene vinylene ! under 0.5 ns pulsed photoexcitation. This soluble copolymer is designed and synthesized for light amplification and lasing applications. Blue photoluminescence is achieved by introduction of the meta linkage of the phenylene rings in the polymer backbone, which reduces the extent of delocalization of p electrons. The large Stokes shift of about 70 nm implies a low reabsorption rate, and leads to easier creation of population inversion and hence to efficient light amplification. A solution of the polymer exhibits amplified spontaneous emission evidenced by spectral narrowing and a superlinear increase of output intensity when it is photoexcited at 337 nm. By means of the variable excitation stripe length method, net gains of 18 and 24 cm 2 1 are deduced for different pump energies of 71 and 113 m J, respectively. Moreover, laser emission from the polymer solution is obtained in a simple cavity formed by Fresnel reflections at the cuvette?solution interfaces. A conversion efficiency as high as 27% and a wide tuning range between 470 and 492 nm in solutions are demonstrated.