Dual amplified spontaneous emission and laser action from a model oligo(phenylene vinylene): comparison with the corresponding polymer M. Fakis a , I. Polyzos a , G. Tsigaridas a , V. Giannetas a , P. Persephonis a, * , I. Spiliopoulos b , J. Mikroyannidis b a Department of Physics, University of Patras, 26500 Patras, Greece b Department of Chemistry, University of Patras, 26500 Patras, Greece Received 1 October 2003; accepted 13 March 2004 Available online 16 September 2004 Abstract We report a comparative study of the spectroscopic and stimulated emission properties of a model oligo(phenylene vinylene) with those of the corresponding partially conjugated poly(phenylene vinylene). The model oligomer exhibits dual Amplified Spontaneous Emission (ASE) at 430 and 450 nm attributed to two independent vibrational modes in the excited state of the molecule. The cor- responding polymer exhibits single ASE at 453 nm implying that in the polymer chains the amplification originates from a single vibrational mode. The efficiency of ASE and laser action is lower in the polymer than in the oligomer because of defects in the pol- ymer chains. Ó 2004 Elsevier B.V. All rights reserved. PACS: 42.55.h; 42.70.a; 42.70.Hj; 42.70.Jk Keywords: Laser materials; Dual amplified spontaneous emission; Laser action; Conjugated oligomers; Conjugated polymers 1. Introduction Conjugated oligomers are important materials be- cause of their high efficiency as active media in lasers [1–3] and Organic Light Emitting Diodes [4,5]. They have a well-defined chemical structure with a specific conjugated segment and they are easily synthesized. However, the last years, much work is focused on the study of conjugated polymers which exhibit high photo- luminescence efficiency, similar to oligomers and addi- tionally enhanced mechanical and semiconducting properties [6,7]. In this study, many oligomers serve as low-molecular weight model compounds for certain conjugated polymers. Thus, an integrated photophysical study of model oligomers in comparison to the corre- sponding polymers contributes to the understanding of structure to property relationship of these polymers [8–12]. Such comparative studies concerning stimulated emission have not been reported to date. In this letter, we report the spectroscopic and stimu- lated emission properties of a model oligo(phenylene vin- ylene) in comparison to those of its corresponding partially conjugated poly(phenylene vinylene) (PPV) [13]. Dual Amplified Spontaneous Emission (ASE) is demonstrated for the oligomer and a reduction of the stimulated emission efficiency is observed in the polymer. 2. Experimental The structure of the oligo(phenylene vinylene) O1 and the synthesis of the corresponding polymer P1 are 0925-3467/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.optmat.2004.03.016 * Corresponding author. Tel./fax: +32 610997470. E-mail address: pet-per@physics.upatras.gr (P. Persephonis). www.elsevier.com/locate/optmat Optical Materials 27 (2004) 503–507