Enhanced photostability of photoluminescent dye-doped solutions and polymers with the addition of dielectric-oxide micro-particles

Organic dye molecules in both solid polymethyl methacrylate and in solution have been found to display greatly enhanced photostability with the addition of micro-particles. Micro-particle doped poly(methyl methacrylate) samples and solutions were prepared doped with the laser dye pyrromethene 567 and rhodamine 6G. Study of the composite dye material as a gain medium in a laser provided a controlled and sensitive test of the photostability. The micro-particle doped samples used as the active laser medium demonstrated a doubling in service life to 0.4 million pulses compared with undoped samples before the output intensity was reduced to one-half. Further addition of a singlet oxygen quencher (DABCO) enhanced the photostability to 0.6 million pulses. Possible explanations discussed include cavity QED effects, surface photophysical and photochemical interactions and thermo-mechanical effects. These observations are relevant to photoluminescent devices and in general to the photostability of organic molecules.     

High pulse energy output from tunable solid-state dye laser based on MPMMA doped with PM567

Tunable solid-state dye laser sample based on modified polymethyl methacrylate (MPMMA) with methanol co-doped with pyrromethene 567 (PM567) and Coumarin 440 (C440) was prepared. Tunable dye laser output wavelength from 546 to 594 nm was obtained in an oscillator-amplifier configuration. With the input seed laser energy being about 1.5 mJ, the highest dye laser output energy reached 113.9 mJ, and the corresponding conversion slope efficiency was 51.39%. To the best of our knowledge, the tuning range and narrow linewidth dye output energy is the best under the same condition so far. The linewidth for the seed laser and amplified laser were measured with the result of less than 0.2 nm. With the amplified medium being pumped at a repetition rate of 10 Hz with a pulse energy as high as 120 mJ (the fluence was 0.42 J/cm²), the laser output energy dropped to half of its initial value after approximate 43000 pulses.     

不同谐振腔分步合成法制备的固态染料P567可调谐激光器

利用新型分步合成法制备的激光染料P567掺杂有机改性凝胶玻璃,建立了基于全息光栅的两种不同腔型可调谐激光器.采用光栅零级作为输出的激光器,调谐范围近70nm (543～610nm), 获得的最高斜效率为17%;采用腔镜耦合输出方式,调谐范围超过30 nm (553～585 nm),获得的最高斜效率为9.7%.并对激光器的可调谐范围、阈值、斜效率及线宽等参数进行了深入的分析比较.     

Medium performance effect on the high output energy from a xenon lamp-pumped pyrromethene-567 solid-state dye laser

In order to obtain a high output energy from a xenon lamp-pumped solid-state dye laser, homogeneities of laser mediums and flatnesses of medium faces with different processing treatments are discussed in the paper. The medi- ums without aging treatment, which are prepared by using a prepolymer process and have diamond-machined end faces to produce the required optical finish, give a highest laser output of 281.9 mJ with 0.215% slope efficiency at 2.0×10 4 mol/L. The best medium lifetime is 21 shots to 50% of original output equating 74.6 kJ/liter.     

Solid State Dye Lasers Based on Coumarin 440 and Pyrromethene 567 Codoped Polymethyl Methacrylate

Laser dye coumarin 440（C440） is codoped with pyrromethene 567 （PM567） into polymethyl methacrylate （PMMA） The effects of C440 concentration on the performance of the solid state dye medium, including spectra property, slope efficiency and photostability, are studied. When C440 is codoped with PM567 at the same concentration 1 × 10^-4 mol/L, the highest efficiency and photostability can be obtained. Compared with the medium based on pure PM567 doped PMMA, about 50% increase in slope efficiency and at least five-fold enhancement in the photostability are observed.     

新型全固态激光器作用过程中的激光参数分析

对影响LD泵浦的Nd∶GdVO4,Nd∶YVO4和Nd∶YAG激光器输出特性的增益介质长度、腔内损耗、输出镜透过率、泵浦光和振荡光的光斑大小进行了分析和数值模拟。当腔内固有损耗为2%,输出镜透过率为10%时,Nd∶Gd-VO4,Nd∶YVO4和Nd∶YAG晶体的振荡阈值分别为1.77W、0.55W和3.34W。在25W泵浦功率下,利用1mm长的Nd∶GdVO4,Nd∶YVO4和Nd∶YAG晶体可分别得到13.17W,13.26W和8.43W的输出功率,相应的输出镜最佳透过率分别为24%,44%和16%。     

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.     

Laser performance of pyrromethene 567 dye in solid matrices of methyl methacrylate with different comonomers

Laser performance of pyrromethene 567 (PM567) dye dissolved in pure poly(methyl methacrylate) homopolymer and its copolymers with 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 1-vinyl-2-pyrrolidone, 2-phenoxyethyl acrylate, and 2,2,2-trifluoromethyl methacrylate has been investigated. The chosen monomers were selected to mimic solvents used in a previous study on the photophysical and lasing properties of PM567 in liquid solution in order to establish correlations between the lasing properties of PM567 in liquid and solid solutions. The vol/vol proportion of the different comonomers in each copolymer formulation was systematically varied, and the effect of each composition on the lasing properties of PM567 was evaluated. The laser samples were transversely pumped at 534 nm with 5.5-mJ pulses from a frequency-doubled Q-switched Nd:KGW laser. Lasing efficiencies of up to 30% and good photostabilities, with a drop of the initial laser output of 20% after 10000 pump pulses in some of the solid samples, were demonstrated. Received: 2 June 1999 / Revised version: 18 July 1999 / Published online: 3 November 1999     

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 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.     

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.     

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.     

Reconstruction evaluation of intensity ratio distribution for extraction of absorber information in homogeneous scattering medium

To extract effectively the absorber information embedded in a homogeneous scattering medium in the transmission geometry, a method of taking the ratio of the output intensity in a measured medium to that in a reference medium is evaluated. The reference medium is a virtual one with the same scattering coefficient distribution as that of the measured medium, but with a uniform absorption coefficient distribution. Numerical results show that the proposed method can enhance the output signal by extracting the ballistic-like component. We also apply a backprojection method to reconstruct the single absorber using many pairs of input and output intensity ratio distributions. The reconstruction position error and the quantitative measurement of absorption coefficient are discussed.     

强散射过程中基于奇异值分解的光学传输矩阵优化方法

通过测量散射介质的传输矩阵能够控制光在此介质中的传输,但目前没有通过优化传输矩阵(即搜索介质本征传输矩阵)来提高光传输效率的研究.通过测量介质的传输矩阵进行奇异值分解与背景滤波,初步优化了传输矩阵后,提出通过遗传算法再次优化传输矩阵,实现了进一步优化传输矩阵,提高了聚焦效率和信噪比.所提方法为可见光在生物组织中的成像提供了一种新的思路和方法.     

激光二极管泵浦Nd：FAP激光器

报道激光二极管泵浦的掺钕氟磷酸钙固体激光器，该器件在重复频率为１００Ｈｚ的准连续状态下运行，当耦合输出透过率为８％时，得到３１％的斜效率，比较了ＦＡＰ和ＹＡＧ这两种介质的激光器的性能，理论分析得出的两者的阈值泵浦功率的相对值与实验结果相一致，并证实ＦＡＰ是一种有前途的适合激光二极管泵浦的激光介质。     

Energy transfer in solid-state dye lasers based on methyl methacrylate co-doped with sulforhodamine B and crystal violet

Laser action in methyl methacrylate(MMA)co-doped with sulforhodamine B and crystal violet dyes was investigated.The dye mixture was incorporated into a solid polymeric matrix and was pumped by a 532-nm Nd:YAG laser.Distributed feedback dye laser(DFDL)action was induced in the dye mixture using a prism arrangement both in the donor and acceptor regions by an energy transfer mechanism.Theoretically,the characteristics of acceptor and donor DFDLs,and the dependence of their pulse widths and output powers on acceptor–donor concentrations and pump power,were studied.Experimentally,the output energy of DFDL was measured at the emission peaks of donor and acceptor dyes for different pump powers and different acceptor–donor concentrations.Tuning of the output wavelength was achieved by varying the period of the gain modulation of the laser medium.The laser wavelength showed continuous tunability from 563 nm to648 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.     

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.     

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.