Photo-physical Characterisation of Novel Organic Dye-doped Solid-state Laser Materials

1 Results The development of tuneable solid-state organic dye lasers is a subject of considerable interest and research activity.Compared to conventional liquid dye lasers they have the advantage of being free of solvent handling,having small size,and being easy to operate.For high-performance solid-state dye lasers highly photo-stable dyes with low quantum yield of triplet formation and low triplet-triplet absorption cross-section in the lasing wavelength region are required.For solid state dye lasers organic molecules have been incorporated in inorganic glasses (mainly sol-gel glasses),in organic polymer matrices,and into hybrid compositions of inorganic-organic hosts.Here samples of the BODIPY dye (dipyrromethene-BF2 dye) PM597 incorporated in copolymers resembling inorganic-organic hybrid matrices are characterized by optical spectroscopic methods towards their application as solid-state laser rods.The inorganic function is entered by the constituent 3-(trimethoxysilyl)propyl methacrylate (TMSPMA).The organic constituents are monomers with one polymerizable group methyl methacrylate (MMA),or 2-hydroxyethyl methacrylate (HEMA)],two ethylene glycol dimethacrylate (EGDMA)],three pentaerythriol triacrylate (PETA)],and four pentaerythriol tetraacrylate (PETRA)] polymerizable groups.The copolymers were obtained by radical bulk polymerization with 2,2'-azobis(isobutyronitrile) (AIBN) as polymerization initiator.TMSPMA and MMA were also copolymerized by "in-situ" and simultaneous hydrolysis-condensation of the methoxy groups of TMSPMA during the free radical polymerization of MMA using AIBN in order to fully approach a sol-gel inorganic glass-organic polymer hybrid solid-state dye laser material.Structural and thermo-mechanical studies (thermogravimetry,differential scanning calorimetry,and infrared spectroscopy) revealed the highest thermo-mechanical stability for high-degree inter-crossing copolymerisation COP(TMSPMA-PETA),COP(TMSPMA-PETRA)] and hydrolysis-polymerization COPH(MMA-TMSPMA)].Concerning the optical spectroscopy characterisation,all studied PM597 doped copolymer samples exhibited high fluorescence quantum yields (60 % to 70 %),negligibly small excited-state absorption cross-sections (5% to 10 % of ground-state absorption at 527 nm),and high photo-stability (typically up to 3 million excitation cycles before degradation after some initial fading).The laser properties of the PM597 doped copolymers were evaluated by transversal pumping with 6 ns laser pulses of 5.5 mJ energy at 532 nm.Most of the studied samples surpassed 100 000 laser shots with no or only less than 50 % of laser output power reduction.