Photophysical and laser characteristics of pyrromethene 567 dye: Experimental and theoretical studies

Narrow-band laser performance of alcohol solutions of pyrromethene 567 (PM567) and rhodamine 6G (RH6G) dye was investigated using a home-made GIG-configured dye laser, excited by the second-harmonic radiation (at 532 nm) of a pulsed Nd:YAG laser. Higher laser efficiency was observed with PM567 dye (∼23% peak) in comparison to the commonly used RH6G dye (16.5%), in spite of much lower fluorescence quantum efficiency of the PM567 (0.83) vis-à-vis RH6G (0.98) dye solutions in ethanol. First principle-based electronic structure calculations were performed on PM567 dye in the ground (S ₀) and excited states (S ₁) using density functional theory to elucidate the structure and photophysical properties of the dye.     

Influence of various coumarin dyes on the laser performance of laser dyes co-doped into ORMOSILs

Several kinds of coumarin dyes (C440, C460, C500, C503 and C540A) were co-doped with perylene red (p-red) or pyrromethene 567 (p567) into VTES- and MTES-derived organically modified silicates (ORMOSILs) respectively, by the sol-gel process. The effects of coumarin dyes and their concentration on the laser properties and photostabilities of p-redand p567 were studied and the mechanisms involved were discussed. At optimized coumarin dye concentration, the slope efficiency of co-doped p-redincreased by a factor of 2 while only minor increases in the laser efficiency of p567 were observed. A broader tunable range with increased conversion efficiency and at least a 3-fold improvement in the photostabilities of p-redand p567 in the presence of coumarin family dyes have also been achieved. The mechanism responsible for the improvement in the laser performances and photostabilities of p-redand p567 resulted from the energy transfer between p-red/567 and coumarin dyes. PACS PACS 42.55.Mv; 42.55.Rz; 42.70.Hj     

Characterisation of solid-state dyes and their use as tunable laser amplifiers

This paper reports on the spectroscopic and photo physical characteristics of solid-state dyes and their use as tunable high-gain laser amplifiers. A comparison of the absorption and fluorescence spectra is made for the dyes pyrromethene 567, pyrromethene 597, pyrromethene 650, rhodamine 6G in the solid hosts, polymethyl methacrylate, polycom and ormosil, and compared to the case of the dyes in the solvent methanol. Results show a reduced Stokes shift and an increased fluorescence lifetime for dyes in the solid hosts compared to the solvent. The use of pyrromethene 650 in polymethyl methacrylate as a tunable laser amplifier was investigated. The dye amplifier was shown to exhibit photo-induced birefringence, and the fluorescence polarisation and intensity dependent anisotropy effects of gain and refractive index was characterised. The molecular reorientation time for pyrromethene 650 in the solid host was calculated to be 6.8 ns. The solid-state dye exhibited a single pass gain of 500at 616 nm. The saturation behaviour was investigated and values of emission cross-section determined. Operation of the solid-state dye in a laser oscillator showed effects of strong shift in the lasing wavelength as a function of the cavity Q due to the small Stokes shift of the dye in the solid host. PACS 42.55.Mv; 42.50.Lh; 42.70.Jk     

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.     

A binary solvent of water and propanol for use in high-average power dye lasers

Water is an inherently safe solvent for laser dyes and posses far better photo thermal characteristics in comparison to the commonly used organic solvents in dye lasers. However, water solution of dye needs a suitable deaggregating additive to suppress non-radiative dimers and to achieve similar laser efficiency. We have carried out systematic studies on comparative performances of dye lasers, pumped by low-repetition-rate Nd-YAG, as well as high-repetition-rate copper vapour lasers using Rhodamine 6G dye solutions in ethanol and various binary solvents of water. Among different additives in water, for the first time, the results of our studies on the application of water solvent in dye lasers could clearly establish that binary solvent comprising of normal or heavy water and about 18% to 25% n-propanol has produced similar efficiency, better photochemical stability and superior thermo-optic properties than ethanol solvent in high-repetition rate oscillator-amplifier operation. PACS 42.55.Mv; 32.50.+d; 42.70.jk     

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.     

New efficient laser dye for pulsed and CW operation in the UV

A new laser dye for pulsed and cw operation has been synthesized which can be tuned from 362 nm up to 412 nm. For pulsed excitation with a XeCl excimer laser an energy conversion of 18.5% has been measured at the tuning maximum of the dye; this is the highest efficiency for any known dye in the UV. For cw operation a low laser threshold and a goof efficiency have been observed. The range of tuned cw dye lasers is extended by 30 nm to shorter wavelengths. The dye shows high photochemical stability even at high pump laser power.     

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     

Polarization and threshold energy variation of distributed feedback lasing of oxazine dye in zirconia waveguides and in solutions

Distributed feedback lasing characteristics of oxazine dye in zirconia waveguides and in solutions were investigated. Oxazine-dye-doped waveguides were characterized by ellipsometry. Intensity modulation and polarization modulation were used to generate laser action. Tunable narrow line width laser action was achieved for the first, second, third and fourth Bragg orders. It was observed that the threshold pump energy decreased with the decrease of the Bragg order. The degree of polarization of the laser output also changed from 0.8 at the third Bragg order to 0.1 at the first Bragg order. Wide-band tuning of the distributed feedback laser output from 700 nm to 870 nm was achieved for the first-order action during intensity modulation. PACS 42.55.Mv; 42.70.Jr; 42.79.Gn     

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     

A linearly polarized continuous-wave 1357-nm Nd:YAG laser

We demonstrated a linearly polarized continuous-wave Nd:YAG laser operating at a 1357-nm single-wavelength, by a 808-nm diode as an end-pump source. We chose a Brewster-angle-cut Nd:YAG laser host crystal, due to its two salient features as follow: linearly polarized laser output and single-wavelength oscillation can be easily obtained. In this paper, a continuous-wave all-solid-state single-wavelength laser operating at 1357 nm is demonstrated with a diode-end-pumped Brewster-cut Nd:YAG laser. The laser had a 1.03-W maximum output power under an incident pump power of 15.0 W, a 12.7% slope efficiency, a 6.9% optical-to-optical conversion efficiency, a 0.14-nm spectral linewidth and a 3% power-output stability within 30 min. PACS 42.55.Rz; 42.55.Xi; 42.70.Hj     

Highly photostable laser solution and solid-state media based on mixed pyrromethene and coumarin

A substantial increase in the photostability of pyrromethene 567 laser dye solutions and in solid polymer media has been achieved by the addition of coumarin C540 laser dye. Up to five times increase in photostability of pyrromethene 567 in solid and two times in solution has been observed. The enhanced photostability is attributed to reduction in the effectiveness of in situ oxygen degradation of pyrromethene by the addition of the coumarin.     

Tunable narrow linewidth laser output from PM567 doped nematic liquid crystal under holographic pumping

LC cell injected the mixture of dye pyrromethene 567 (PM567) and nematic liquid crystal (NLC) by capillary action was prepared. Holographic pumping with a Nd:YAG laser (532 nm, 1 Hz, 10 ns) to form gain distributed feedback in the cell, tunable laser output from the cell was investigated. Through changing the intersection angles of the two coherent light beams from 46° to 50°, the tuning range we obtained is about 37 nm (550–587 nm). Additionally, the FWHM of the laser under such experimental setup was less than 0.1 nm even without the resonant cavity, and the threshold of the laser was about 26 μJ, which was very low as we known.     

New efficient and stable laser dyes for cw operation in the blue and violet spectral region

Sulphonated bis-styryles and triazinyl-stilbenes have been investigated for cw dye laser operation. These promising new classes of laser dyes have proven to be superior to the known coumarins with respect to threshold, slope efficiency and photochemical stability. They shift the short wavelength tuning limit of the cw dye laser down to 403 nm. Broad tuning ranges of more than 4500 cm^-1 and efficiencies up to 20% were found. In contrast to the coumarins these new dyes showed no photochemical degradation even at high pump power levels.     

Collective spontaneous emission of dye molecules and lasing

The threshold pump power density for lasing in dye solutions is found to depend on the photon energy of pumping radiation. An increase in the pumping photon energy can significantly lower the threshold pump power of dye lasers. For an ethanol solution of rhodamine 6G with a concentration of 4×10¹⁸ cm^?3, the threshold power density for pumping radiation with a wavelength of 532 nm is 20-fold higher than for pumping radiation with a wavelength of 347 nm. This phenomenon is associated with the competition of collective spontaneous emission, which can lead to the efficient deactivation of excited molecules in femtosecond times, and the dephasing of excited molecules due to the intramolecular nonradiative processes of absorbed-energy conversion. An increase in the dephasing rate with the increasing energy of exciting photons lowers the efficiency of collective spontaneous emission and increases the concentration of dephased excited molecules responsible for lasing.     

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.     

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.     

A polarization-stabilized microchip laser using a resonant grating mirror

A resonant grating mirror was monolithically integrated to an ytterbium-doped ceramic Y₃Al₅O₁₂ microchip laser to produce a linearly polarized laser beam emitting at 1030 nm with a polarization contrast ratio up to 1000. The device was pumped with a fiber-coupled laser diode bar emitting 2-ms pulses at 50 Hz at 940 nm. Up to 13-W peak output power was obtained from 20-W absorbed pump power at room temperature. The obtained slope efficiency with respect to the absorbed pump power was about 80%. PACS 42.40.Lx; 42.55.-f; 42.60.Jf; 42.60.Lh; 42.55.Xi; 42.70.Hj     

Tunable ultraviolet laser source based on solid-state dye laser technology and CsLiB(6)O(10) harmonic generation

Tunable UV radiation centered at 289nm was obtained from a 532-nm Nd:YAG pumped high-brightness solid-state dye laser, frequency doubled in CsLiB(6)O(10). Frequency doubling to 284-294 nm was demonstrated from a singly doped, rotating pyrromethene dye plastic disk with damage threshold >3 J/cm(2) . UV energies up to 44 mJ at 10 Hz were obtained with a 15% absolute conversion efficiency from 532 nm.