Time-resolved thermal lens study on the heat dissipation effects in solid polymeric matrices used as laser dyes

A dual-beam pulsed-laser time-resolved thermal lens (TRTL) has been used to study the heat dissipation effects in solid polymers employed as laser dyes. The laser-dye samples studied are polymer solutions of rhodamine 6G (Rh6G), namely homopolymers of methyl methacrylate (MMA) and copolymers of methyl methacrylate and 2-hydroxyethyl methacrylate (HEMA) with MMA:HEMA compositions 1:1 and 7:3 vol./vol., where the dye is either dissolved or modified and copolymerized with methacrylate monomers. The long-term stability of the laser material is independent of the thermal diffusivity of the samples, as determined by the TRTL technique. This suggests that the rate of heat dissipation does not play a major role in the photostability of the samples. In contrast, the TRTL experiments have revealed permanent changes in the optical properties of the polymers when subjected to a large number of laser pulses. This is explained in terms of permanent plastic deformation of the matrices. Received: 19 June 2002 / Revised version: 1 August 2002 / Published online: 15 November 2002 RID="*" ID="*"Dedicated to Prof. S.E. Braslavsky on the occasion of her 60th birthday. This work was presented at the V Congreso de Fotoquímica, Torremolinos, Spain, 2001 RID="**" ID="**"Corresponding author. Fax: +34-93/205-6266, E-mail: s.nonell@iqs.es