A. Costela

Correlations between photophysics and lasing properties of dipyrromethene–BF2 dyes in solution

Abstract UV–Vis absorption, fluorescence (steady-state and time-correlated) and lasing properties of three pyrromethene–BF 2 dyes (PM546, PM556 and PM567) have been determined in several solvents. Good correlations between photophysical properties and lasing characteristics of these dyes have been obtained not only for a given dye in several solvents but also for the three dyes in a common solvent. Both the observed spectral changes and the deactivation mechanism affecting the lasing gain are explained on the basis of the possible resonance structures of the chromophore.

Polymeric solid-state dye lasers: Recent developments

An up-to-date overview of the results obtained by our group on the development of polymeric solid-state dye lasers based on dipyrromethene·BF2 complexes is presented. It is shown that appropriate chemical modifications in the dye molecules can yield dyes that lase efficiently and with remarkable photostability when properly incorporated into adequate polymeric matrices. Our results compare favourably with those reported by other authors with the dyes incorporated into organic materials and open the way to the development of solid-state dye lasers competitive with their liquid counterparts.

Pulsed liquid lasers from proton transfer in the excited state

Abstract The application of photoinduced intramolecular proton transfer to generate stimulated radiation is reported. Tunable laser pulses are produced with a 10% efficiency using sodium salicylate or 2-( o -hydroxyphenyl)benzimidazole as the active medium. In both compounds a large population inversion results from the proton transfer taking place in the electronically excited state.

New 8‐Amino‐BODIPY Derivatives: Surpassing Laser Dyes at Blue‐Edge Wavelengths

The development of highly efficient and stable blue-emitting dyes to overcome some of the most important shortcomings of available chromophores is of great technological importance for modern optical, analytical, electronic, and biological applications. Here, we report the design, synthesis and characterization of new tailor-made BODIPY dyes with efficient absorption and emission in the blue spectral region. The major challenge is the effective management of the electron-donor strength of the substitution pattern, in order to modulate the emission of these novel dyes over a wide spectral range (430-500 nm). A direct relationship between the electron-donor character of the substituent and the extension of the spectral hypsochromic shift is seen through the energy increase of the LUMO state. However, when the electron-donor character of the substituent is high enough, an intramolecular charge-transfer process appears to decrease the fluorescence ability of these dyes, especially in polar media. Some of the reported novel BODIPY dyes provide very high fluorescence quantum yields, close to unity, and large Stokes shifts, leading to highly efficient tunable dye lasers in the blue part of the spectrum; this so far remains an unexploited region with BODIPYs. In fact, under demanding transversal pumping conditions, the new dyes lase with unexpectedly high lasing efficiencies of up to 63 %, and also show high photostabilities, outperforming the laser action of other dyes considered as benchmarks in the same spectral region. Considering the easy synthetic protocol and the wide variety of possible substituents, we are confident that this strategy could be successfully extended for the development of efficient blue-edge emitting materials and devices, impelling biophotonic and optoelectronic applications.

8-PropargylaminoBODIPY: unprecedented blue-emitting pyrromethene dye. Synthesis, photophysics and laser properties

Highly emitting 8-propargylaminoBODIPY (8-PAB) 2 was prepared in 94% yield. Unlike any other BODIPY structure hitherto described in the literature, 2 displays efficient emission in the blue region of the visible spectrum with a fluorescence quantum yield up to 0.94 and high laser efficiency (35%) at 483 nm.

Solid-state dye lasers based on copolymers of 2-hydroxyethyl methacrylate and methyl methacrylate doped with rhodamine 6G

Rhodamine 6G has been dissolved in copolymers of 2-HydroxyEthyl MethAcrylate (HEMA) and Methyl MethAcrylate (MMA) and the resulting solid-state solutions have been pumped at 337 nm and 532 nm. Lasing efficiencies similar to those found in ethanol solution have been obtained with a 1:1 vol/vol HEMA: MMA copolymer matrix, and lifetimes of ca. 10 000 (337 nm pumping) and ca. 75 000 (532 nm pumping) pulses at repetition rates up to 15 Hz and 10 Hz, respectively, have been demonstrated.

Solid-state dye laser based on Coumarin 540A-doped polymeric matrices

Abstract Coumarin 540-A has been dissolved in a copolymer of 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) 1:1 v/v and in a pure poly(methyl methacrylate) homopolymer (PMMA). Laser action has been induced in the resulting solid-state solutions pumped with 1.2 mJ pulses at 337 nm from a nitrogen laser. The effects on the laser performance of different polymerization methods, dye concentration and polymeric matrix composition have been evaluated. Energy conversion efficiencies of 11% and lifetimes of about 2000 pulses at 2 Hz repetition rate have been demonstrated.

Proton-transfer lasing from solid organic matrices

Abstract Solid-state laser oscillation has been induced in 2-(2′-hydroxy-5′-fluorophenyl)benzimidazole dissolved in poly(methyl methacrylate), based on a four-level excited-state proton-transfer mechanism. The energy conversion efficiency at 493 nm was ≈ 1% for N2 laser pumping with pulses of 2 mJ at 337 nm.

Laser action from rhodamine 6G-doped poly (2-hydroxyethyl methacrylate) matrices with different crosslinking degrees

Abstract The lasing properties of rhodamine 6G dissolved in poly (2-hydroxyethyl methacrylate) matrices with different amounts of ethylene glycol dimethacrylate as crosslinking monomer are investigated. Increasing the rigidity of the matrix by decreasing the polymer free volume results in significant increases of both lasing efficiency and photostability. There exists an optimum degree of crosslinking for which efficiency and photostability reach the highest values.

Solid‐state dye lasers based on modified rhodamine 6G dyes copolymerized with methacrylic monomers

Modified rhodamine 6G molecules with polymerizable double bonds have been copolymerized with methacrylic monomers and the resulting polymers have been pumped at 337 nm with a N2 laser in a transversal configuration. The preparation of these new materials is described in detail and their lasing properties are evaluated. Important increases in photostability, with lasing efficiencies similar to those found for the parent dye rhodamine 6G in ethanol solution, have been obtained for some of these materials. Lifetimes (measured as an 80% efficiency drop) in excess of 20 000 shots at repetition rates of 2 Hz have been demonstrated. Strong dependence on pump repetition rate was observed. Possible mechanisms and processes responsible for the behavior of these materials are discussed. By using a rotating system where the sample is scanned in a continuous way, the laser output remained stable, with no sign of degradation, after 500 000 shots.