Photophysical and lasing properties of pyrromethene 567 dye in solid poly(trifluoromethyl methacrylate) matrices with different degrees of crosslinking

The effect of increasing the rigidity of the host matrix by controlled crosslinking of the polymeric chains on the lasing and photophysical properties of pyrromethene 567 (PM567) was evaluated. To this end, the dye was dissolved in 2,2,2-trifluoromethyl methacrylate (TFMA) together with different amounts of the crosslinking monomer ethylene glycol dimethacrylate (EGDMA). Increasing the concentration of this crosslinker monomer resulted in significant increases in both lasing efficiency and photostability. Good correlation between fluorescence and lasing properties has been observed, indicating the existence of an optimum degree of crosslinking for which lasing efficiency and photostabilty reach their highest values. These new solid materials show lasing efficiencies up to 18% when transversely pumped at 534 nm and good photostabilities, with a decrease in the initial laser output of 45% after 10000 pump pulses. Received: 16 February 2001 / Revised version: 9 April 2001 / Published online: 8 June 2001     

Efficient and highly photostable solid-state dye lasers based on modified dipyrromethene.BF2 complexes incorporated into solid matrices of poly(methyl methacrylate)

We report on the laser action of modified dipyrromethene.BF₂ complexes both dissolved in poly(methyl methacrylate) and copolymerized with methyl methacrylate. All recently synthesized dyes have the chromophore core of laser dye pyrromethene 567, differing in the substituent in position 8. The new dyes showed important and most significant increases in both lasing efficiency and photostability. When the laser samples were pumped transversely at 534 nm, laser emission was obtained with efficiencies of over 30% in most cases, to be compared with a lasing efficiency of 12% exhibited by reference dye pyrromethene 567 under the same experimental conditions. Some of the materials exhibited highly photostable laser action, with no sign of degradation in the laser output after 60000 pump pulses at the same position of the sample at a repetition rate of 10 Hz, whereas the laser emission of reference dye pyrromethene 567 dropped to zero after less than 40000 pump pulses. Received: 19 November 2002 / Revised version: 20 February 2003 / Published online: 9 April 2003 RID="*" ID="*"Corresponding author. Fax: +34-91/564-2431, E-mail: acostela@iqfr.csic.es     

Linear and cross-linked polymeric solid-state dye lasers based on 8-substituted alkyl analogues of pyrromethene 567

The lasing properties of analogues of the commercial laser dye pyrromethene 567 (PM567) incorporated (dissolved or copolymerized) into polymeric matrices have been studied using both linear and cross-linked methyl methacrylate-based copolymers with different degrees of functionalization. All synthesized dyes have the chromophore core of PM567 but with an ω-acyloxypolymethylene chain at position 8. In general, the new materials exhibited laser emission with higher efficiencies and much higher photostabilities than those containing the commercial dye PM567 under the same experimental conditions. Lasing efficiencies of up to 40% were obtained under transversal pumping at 534 nm. The highest photostabilities, with the laser output remaining stable or dropping by less than 15% after 100 000 pump pulses at the same position of the sample, were reached in cross-linked materials with dyes covalently linked to the polymeric chains. When the polymeric samples were incorporated into a grazing-incidence grating oscillator, narrow-line-width operation with tuning ranges of up to 40 nm was obtained. These results show that efficient and photostable solid-state dye lasers competitive with their liquid counterparts can be developed by adequate chemical modifications in the dye molecules, as well as by the selection of appropriate polymeric formulations.     

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     

Solid Dye Lasers Based on 2-Hydroxypropyl Methacrylate and Methyl Methacrylate Copolymers

Polymers are a kind of attractive hosts for laser dyes because of their superior optical homogeneity, and high transparency in pumping and lasing range. Copolymers usually have higher damage threshold and better photostability than mono-polymers. Solid dye samples based on copolymer of methyl methacrylate （MMA） with 2-hydroxypropyl methacrylate （HPMA） doped with 1-, 3-, 5-, 7-, 8-pentamethyl-2, 6-diethylpyrromethene-BF2 （PM567） are prepared. Spectra and lasing properties of the samples are studied. Compared to the samples based on monopolymer polymethyl methacrylate （PMMA）, enhanced slope efficiency and photostability are obtained in the copolymers. The highest slope efficiency is 45.1%, and nearly one-fold increase of photostability is obtained. The longest useful lifetime of 4390 pumping pulses is presented with the pump energy as high as 183 mJ per pulse at repetition rate of 10 Hz. The results indicate that the laser performances of solid dye mediums can be greatly increased using copolymer of MMA with HPMA as host.     

Laser emission from mixtures of dipyrromethene dyes in liquid solution and in solid polymeric matrices

Laser emission from binary mixtures of different dyes both in liquid solution and incorporated into solid polymeric matrices, covering the spectral region from green to red, is investigated. Mixtures of two synthesized dyes, analogs of the commercial dye Pyrromethene 567 (PM567), allowed covering the spectral range from green to orange. Tuning ranges in solid state of up to 42 nm with good photostabilities were demonstrated. To extend the tuning range to the red, binary mixtures of the dyes Pyrromethene 597 (PM597)/Pyrromethene 650 (PM650), PM567/DCM, and PM597/DCM were also studied. In liquid solution, a mixture of dyes PM567 and DCM allowed for narrow-linewidth laser emission continuously tunable over a range of 85 nm. In solid-state, mixtures of dyes PM597 and PM650 allowed laser emission tunable over two separate spectral regions up to a wavelength of 619 nm.     

Solid-state lasers based on copolymers of methyl methacrylate and 2-hydroxyethyl acrylate doped with pyrromethene 567 dye

Solid-state dye laser samples based on copolymers of methyl methacrylate (MMA) and 2-hydroxyethyl acrylate (HEA) doped with pyrromethene 567(PM567) were prepared. The highest slope efficiency 46.4% was obtained. With pump repetition rate of 10 Hz and intensity of 0.1 J/cm², the output energy of the sample based on P (MMA: HEA 16:4) remained up to 82.10% of its initial value after approximate 100000 shots. To our knowledge, the achieved photostability is the best under the same condition so far. Compared with the sample based on the monopolymer, the slope efficiency and photostability of copolymer-based solid-state dye samples were both enhanced. The results indicate that the high laser performance using solid-state dye samples based on copolymers of MMA with HEA as solid hosts can be achieved.     

New organic–inorganic hybrid matrices doped with rhodamine 6G as solid-state dye lasers

We report on the laser action of rhodamine 6G (Rh6G) incorporated into new hybrid organic–inorganic monolithic materials. The synthesis of these materials proceeded via the simultaneous sol-gel process of the inorganic part (tetraethoxysilane or tetramethoxysilane) and the free-radical polymerization of an organic monomer part (2-hydroxypropyl methacrylate, 2-hydroxyethyl methacrylate and a 1:1 v/v copolymer of this monomer with methyl methacrylate). The wt. % proportion of the alkoxide was systematically varied in each organic formulation, and the effect of each organic–inorganic composition on the lasing properties of Rh6G was evaluated. The laser samples were transversely pumped and the influence on the laser action of dye concentration, pump wavelength and pump repetition rate was analyzed. Lasing efficiencies of up 26% and good stabilities, with a 90% drop in the initial laser output of up to 12000 pump pulses at 2.5 Hz, were obtained when the samples were pumped at 355 nm with 5.5 mJ/pulse from the third harmonic of a Q-switched Nd:YAG laser. Received: 31 July 2002 / Revised version: 14 October 2002 / Published online: 20 December 2002 RID="*" ID="*"Corresponding author. Fax: +34-91/564-4853, E-mail: ogarcia@ctp.csic.es     

Highly photostable solid-state dye lasers based on mixed pyrromethene 567 and coumarin 500

Solid-state dye samples based on polymethyl methacrylate (PMMA) co-doped with pyrromethene 567 (PM567) and coumarin 500 (C500) were prepared. The effects of C500 concentration on the performances of the solid state dye mediums, including spectra property, slope efficiency and photostability were studied. The highest slope efficiency 64.25% was obtained in the sample (PM567: C500 = 2: 8). Pumping the samples at a rate of 5Hz with a pulse energy as high as 100 mJ (the fluence was 0.26 J/cm²), the output energy dropped to half of its initial value after approximate 116130 pulses and the normalized photostability reached 75.48 GJ/mol in the sample (PM567: C500 = 2: 1). Our results have shown that it is possible to obtain a high-efficiency with a long-lifetime for a solid-state dye laser co-doped with PM567 and C500.     

Highly efficient and photostable solid-state dye lasers based on modified copolymers doped with PM567

Solid-state dye samples based on modified copolymers of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) with methanol doped with PM567 were first prepared. The volume proportions of methanol have great effects on the laser's characteristics including spectra, lasing output and thermal properties. The highest slope efficiency of 64.25% was achieved in the sample MP (MMA:HEMA = 85:15 + 10% methanol). Pumping the samples at a repetition rate of 5 Hz with a pulse energy as high as 100 mJ (the fluence was 0.26 J/cm²), the maximum lifetime of 278,000 shots was obtained in the sample MP (MMA:HEMA = 85:15 + 15% methanol), and the corresponding normalized photostability reached 180.7 GJ/mol. The obtained ten-shots damage thresholds were as high as 6.7 J/cm². The results indicate that the laser properties of solid-state dyes can be greatly enhanced by using modified copolymers of MMA and HEMA with methanol as solid hosts.     

PM567-Doped solid dye lasers based on PMMA

Polymers are a kind of attractive hosts for laser dyes due to their high transparency in both pumping and lasing ranges and superior optical homogeneity. In this paper solid dye samples based on polymethyl methacrylate (PMMA) doped with different concentrations of 1, 3, 5, 7, 8 -pentamethyl-2, 6-diethylpyrromethene-BF$_{2 }$ (PM567) are prepared. The absorption, fluorescence and lasing spectra of the samples are obtained. Wide absorption and fluorescence bands are obtained and a red shift of the maxima of the lasing emission spectra is observed. With the second-harmonic generation of Q-switched Nd:YAG laser (532\,nm, $\sim $20\,ns) pumping the samples longitudinally, the slope efficiencies of the samples are obtained. There is an optimal dye concentration for the highest slope efficiency when the pumping energy is lower than some typical value ($\sim $250\,mJ), and the highest slope efficiency 35.6{\%} is obtained in the sample with a dye concentration of $2\times10^{ - 4}$\,mol/L. Pumping the samples at a rate of 10Hz with a pulse energy as high as 200\,mJ (the fluence is 0.2\,J/cm$^{2})$, the output energy drops to one-half of its initial value after approximate 15500 pulses and the normalized photostability is 5.17\,GJ/mol. A kind of solid dye laser which could have some applications is built.     

Highly efficient and photostable solid-state dye lasers doped with PM567 with the addition of Tinuvin770

Solid-state dye samples based on polymethyl methacrylate (PMMA) doped with pyrromethene 567 (PM567) with the addition of Tinuvin770 were prepared. The effects of a light stabilizer and concentration on the laser performances of the solid state dye PM567, including spectra properties, slope efficiency and photostability were investigated. The highest slope efficiency 66.6% was obtained in the sample (PM567:Tinuvin770 = 2.0:0.5). The addition of Tinuvin770 resulted in a dramatic enhancement of photo-stability. Pumping the samples at a rate of 5 Hz with a pulse energy as high as 100 mJ (the pump energy density was 0.26 J/cm²), the output energy dropped to half of its initial value after approximate 149500 shots and the normalized photostability reached 97.2 GJ/mol in the sample (PM567:Tinuvin770 = 2:5). All results have shown that a high efficient and photostable solid-state dye laser with the addition of Tinuvin770 can be obtained.     

Distributed feedback dye laser holographically induced in improved organic–inorganic photocurable nanocomposites

Distributed feedback (DFB) lasing in permanent volume transmission gratings formed in a laser dye-doped organic–inorganic nanocomposite has been investigated. DFB laser cavities were fabricated using one-step two-beam holographic exposure of Pyrromethene 567 (PM567) doped photopolymerizable acrylate monomers containing inorganic (LaPO₄) nanoparticles. Compared to the formulation previously utilized, the material composition presented provides longer lifetime of the laser. Spectral and polarization properties, input–output and stability characteristics of the laser output have been investigated by varying the material composition and the patterning parameters. DFB lasing emission of the second and the third diffraction orders has been demonstrated. The spectral linewidth of ∼0.08 nm has been observed at a pump energy threshold of about 0.2 μJ/pulse for the second-order DFB lasing when pumped with 532 nm 500 ps laser pulses. Spectral tuning of the lasing output over ∼56 and ∼7 nm was obtained by varying the grating period and the content of inorganic nanoparticles in the polymer matrix, respectively.     

Lasing mechanism in two-dimensional photonic crystal lasers

We conduct a comprehensive investigation of the lasing mechanism in a photonic crystal slab laser with a refractive index that is periodic in two dimensions. Experimental spectra of laser structures fabricated with organic gain media are presented. It is found that lasing frequencies can be explained in terms of Van Hove singularities in the density of modes. We also observe lasing spectra that cannot be obtained from structures with one-dimensional periodicity, such as traditional distributed feedback lasers. Lasing frequencies are computed using numerical techniques. Received: 7 April 1999 / Accepted: 12 April 1999 / Published online: 19 May 1999     

Distributed-feedback laser actions in zirconia-ORMOSIL waveguides based on energy transfer between co-doped laser dyes

Laser dyes such as pyrromethene 567 (PM567), perylene red (P-red) and coumarin 540A (C540A) were doped into zirconia-organically modified silicate (ORMOSIL) materials prepared by low temperature sol-gel technique. Narrow line-width distributed feedback (DFB) laser actions were induced in the PM567 and/or P-red doped sol-gel planar waveguide. Tuning of the output wavelength was achieved by varying the period of the gain modulation generated by a nanosecond Nd:YAG laser at 532 nm. Compared with those of PM567 and P-red solely doped thin films, tuning range of C540A, PM567 and P-red co-doped sol-gel planar waveguide was greatly extended, from 564.5 nm to 635.1 nm.     

Enhanced laser performances based on energy transfer in multi-dyes co-doped solid media

Various coumarin dyes are co-doped with perylene red (P-red) and pyrromethene 567 (PM567) into vinyltriethoxysilane-derived solid media, respectively. Energy transfer among laser dyes has been observed, and the effect of coumarin dye concentration on the laser properties has been investigated. With the presence of coumarin dye and pyrromethene 567, enhanced laser performances based on energy transfer of perylene red have been exhibited. The laser efficiency can be improved by two-fold and broad tunable range as wide as 80 nm can be achieved. At the pump intensity of 1.0 J/cm², the laser output of co-doping perylene red decreases less than 30% after 30,000 pulses.     

Opto-acoustic study of tinuvin-P and rhodamine 6G in solid polymeric matrices

Laser-induced opto-acoustic calorimetry has been used to examine the thermo-elastic properties of two polymer matrices doped with tinuvin-P and the radiation-less decay processes of rhodamine 6G (Rh6G) in them. The matrices assayed were methyl methacrylate (MMA) homopolymers P(MMA), and methyl methacrylate and 2-hydroxyethyl methacrylate (HEMA) copolymers P(MMA:HEMA). A slight difference in the thermo-elastic properties of the polymers, namely their adiabatic expansion coefficients, has been detected and found to correlate with the long-term stability of the laser material. This suggests a key role of the heat-dissipation processes in the photostability of these polymeric materials. On the other hand, the fluorescence quantum yield of Rh6G is shown to vary with the polymer-matrix composition in a way consistent with its lasing efficiency. The Rh6G absorption and fluorescence quantum yield also change dramatically upon increasing its concentration, which suggests the co-existence of different Rh6G forms with different photophysical properties. Received: 10 February 2000 / Revised version: 12 June 2000 / Published online: 10 January 2001     

Environment effects on the lasing photostability of Rhodamine 6G incorporated into organic-inorganic hybrid materials

The effect on the lasing photostability of Rhodamine 6G (Rh6G), and the rigidity of a hybrid inorganic-organic matrix by controlled addition of di-, tri- and tetrafunctionalized alkoxides has been evaluated. The dye was incorporated into hybrid matrices of (2-hydroxyethyl methacrylate) (HEMA) or vol/vol copolymers of methyl methacrylate (MMA) and HEMA with different weight proportions of polycondensated dimethyldiethoxysilane (DEOS), methyltriethoxysilane (TRIEOS), and tetraethoxysilane (TEOS). The laser samples were transversaly pumped at 534 nm at 5.5 mJ/pulse and up to a 10 Hz repetition rate. The dependence of the laser photostability on organic-inorganic composition, pH of the medium, and thermal treatment of the samples was studied. Good stability, with a drop of the initial laser output of only 13% after 10000 pump pulses at 10 Hz in a thermally postcured (HEMA-15 wt%TRIEOS) matrix was obtained. Careful control of the synthesis process is required to reach the necessary photostability for a solid-state dye laser based on hybrid matrices to become competitive with liquid dye lasers. PACS 81.05.Lg; 81.05.Zx; 81.20.Fw; 42.55.Mv; 42.55.Rz; 42.60.Lh; 42.62.b; 42.70a; 42.70-Hj; 42.70.Jk     

Solid-state dye lasers based on polymethyl methacrylate modified with methanol

Solid-state dye samples based on modified polymethyl methacrylate with methanol (MPMMA) doped with pyrromethene 567 (PM567) were first prepared. The effects of volume percentage of methanol on the laser performances of the samples, including spectra properties, slope efficiency and photostability were studied. The highest slope efficiency 66.39% was obtained in the sample (MMA:methanol = 16:4). Pumping the samples at a repetition rate of 5 Hz with a pulse energy as high as 100 mJ (the fluence was 0.26 J/cm²), the output energy dropped to half of its initial value after approximate 156720 shots and the corresponding normalized photostability reached 101.86 GJ/mol in the sample (MMA:methanol = 17:3). Our results indicate that it can obtain a high slope efficiency and good photostability for a solid-state dye laser using MPMMA as solid hosts.     

Spectroscopic and lasing properties of Er3+:Yb3+-doped fluoride phosphate glasses

Er³⁺ emission and lasing properties at 1.5 μm were studied in fluoride phosphate glasses (FP20) with different doping concentrations as well as in a commercial phosphate glass (Kigre QX). Emission decay behaviour at 1 μm and 1.5 μm was examined with respect to energy transfer between ytterbium and erbium. Emission cross-sections were determined using the reciprocity and Füchtbauer–Ladenburg methods. Gain spectra were calculated for the glasses and related to differences in the tuning curves and lasing properties. The temperature rise due to the quantum defect was determined via the ratios of green upconversion luminescence for different pump powers. The results from the laser and tuning experiments indicate that the FP20 glass offers good possibilities in broadband amplification and the generation of ultrashort pulses. Received: 24 August 2000 / Revised version: 27 October 2000 / Published online: 7 February 2001