Solid-state dye lasers based on polymethyl methacrylate doped with pyrromethene 650

Solid-state dye samples based on polymethyl methacrylate (PMMA) doped with different concentrations of the dye PM650 were prepared. With SHG of Q-switched Nd:YAG laser (532 nm, ∼15 ns) pumping the samples longitudinally, the fluorescence, lasing spectra and slope efficiencies of the samples were obtained. The highest slope efficiency 27.49% and laser output energy 22.0 mJ was achieved in the sample with a dye concentration of 2.0 × 10⁻⁴ mol/L. To our knowledge, the results are the best under the same condition so far. The maxima of output lasing spectrum is about 653.5 nm. Our results have shown that using solid-state samples doped with PM650 can extend the dye laser wavelength to the red.     

宽带输出PM580掺杂聚甲基丙烯酸甲酯固体染料激光器研究

采用高效激光染料PM580作为掺杂物质,聚甲基丙烯酸甲酯(PMMA)作为基质,在对固体染料光谱特性研究的基础上,重点研究了调Q倍频Nd:YAG抽运下不同染料掺杂浓度的固体染料激光输出特性.研究结果表明掺杂浓度对输出激光波长影响明显,随着掺杂浓度的增加,激光输出波长红移,从激光增益出发,对该现象给出了理论解释.掺杂浓度对激光转化效率也有影响,当掺杂浓度为2×10^－4mol/L时,获得染料激光输出斜率效率最高达53.8%,抽运能量410mJ时,获得染料激光输出220mJ,激光带宽～8nm 关键词： 固体染料 宽带染料激光 PM580 聚甲基丙烯酸甲酯     

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.     

Thermally induced nonlinear optical response and optical power limiting of acid blue 40 dye

We report the investigations of thermally induced third-order nonlinear optical and optical limiting characterizations for various concentrations of acid blue 40 dye in N,N-Dimethyl Formamide, studied by employing z-scan technique under cw He–Ne laser irradiation at 633 nm wavelength. The samples exhibited nonlinear absorption and nonlinear refraction under the experimental conditions. For lower concentration, the samples display both saturable absorption (SA) and reverse saturable absorption (RSA); whereas with increase in concentration, RSA behaviour prevails. The estimated values of the effective coefficients of nonlinear absorption β_eff, nonlinear refraction n₂ and third-order nonlinear susceptibility χ⁽³⁾ were found to be of the order of 10^?2 cm/W, 10^?4 esu and 10^?6 esu respectively. Multiple diffraction rings were observed when the samples were exposed to laser beam due to refractive index change and thermal lensing. The effect of concentration and the laser intensity on the self-diffraction ring patterns was studied experimentally. The acid blue 40 dye also exhibited strong optical limiting properties under cw excitation and reverse saturable absorption is found to be the dominant nonlinear optical process leading to the observed nonlinear behaviour.     

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.     

Photo-physical properties and amplified spontaneous emission of a new derivative of fluorescein

The synthesis of new high-performance dyes and the implementation of new ways of incorporating the organic molecules into the solid host matrices have produced a great deal of activity in the field of solid-state dye lasers. In this article, the new laser dye, 2-(6-allyl-3-oxo-3H-xanthen-9-yl)-benzoic acid ethyl ester [AXBE] has been synthesized, and its chemical structure was confirmed by ¹H NMR, ¹³C NMR, IR and elemental analysis. This new dye was covalently bonded with methyl methacrylate (MMA) and 2-hydroxy ethyl methacrylate (HEMA) copolymer backbone and evaluated as the active medium of the solid-state laser dye. Its optical properties were experimentally investigated. Amplified spontaneous emission (ASE) and photostability were studied by pumping the dye sample with 355 nm (8 ns) pulsed Nd-YAG laser.     

Investigation of inverse Raman scattering using the method of intra-cavity spectroscopy

The detectability of Raman absorption lines is enhanced by inserting the Raman sample into the cavity of a broad-band dye laser where the sample is simultaneously pumped by monochromatic radiation. With this technique we were able to detect Raman samples with good scattering efficiencies in a concention of 10^?3 mole/? or to obtain nearly complete Raman spectra within a time interval of 30 nsec.Exposures in which the dye laser radiation and the strong monochromatic radiation are polarized parallel or perpendicularly to each other are compared with spontaneous Raman spectra which are polarized parallel or perpendicularly.     

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.     

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.     

Nonlinear responses and optical limiting behavior of Basic Violet 16 dye under CW laser illumination

Nonlinear optical properties of Basic Violet 16 dye solution in water are studied employing different optical techniques. Experiments are performed using the second harmonic of a continuous Nd-Yag laser beam at 532 nm wavelength and 100 mW power. The effect of nonlinearity of Basic Violet 16 dye in broadening the laser beam is observed. The optical limiting behavior is investigated by measuring the transmission of the samples. The third-order nonlinearity, χ³ of Basic Violet 16 dye, is measured using Z-scan data. The nonlinear absorption coefficient is calculated using the open aperture Z-scan data, while its nonlinear refractive index is measured using the closed aperture Z-scan data. All experiments are done for different concentrations and thicknesses of Basic Violet 16 dye solution. The effect of intensity of input laser beam on the nonlinear susceptibility is studied experimentally. Results indicate that Basic Violet 16 dye is a potential candidate for low-power optical limiting applications.     

Two-photon photoemission from Ni (1 1 0) and (1 1 1) surfaces

Photoemission was observed when the samples were irradiated with photons in the energy range from 2.5 to 3.3 eV from a tunable dye laser with an intensity of 10⁸Wcm^?2. The emission shows a quadratic intensity dependence. The variation with angle of incidence and polarization is different for the two surfaces. The result obtained from the (1 1 0) surface is discussed with help of the band structure as a two-photon surface photoelectric effect.     

A narrowband grazing incidence pulsed dye laser improved by using an active multiregion

A novel and simple laser cavity is proposed in which the active medium is separated spatially into three regions in a single dye cell. This configuration permits to improve laser performance in spectral linewidth, purity and energy conversion. Using only one 5 cm-grazing incidence grating as a selective element, a tunable narrow band dye laser has been constructed having a simple-mode spectrum of about 750 MHz depending on dye concentration (5 x 10^-4 M-10^-3 M). Continuous scanning of a 1.3 GHz (FWHM) line over the entire lasing region of the dye is obtained with an efficiency of 6%. The advantages of using an active multiregion are discussed in relevance to possible applications.     

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.     

Holographic recording on the basis of forbidden singlet-triplet electronic transitions

The possibility of recording holograms in thick layers of a photopolymeric material on the basis of a forbidden singlet-triplet transition of a sensitizing dye, erythrosine, is theoretically substantiated and experimentally confirmed. A single hologram and 16 superimposed holograms are recorded with a low-power He-Ne laser (632 nm) at high concentrations of the sensitizing dye and high optical densities in the range of its main absorption. The diffraction efficiency of the single hologram is ～50%. The dependence of the increase in the diffraction efficiency of a transmission grating in samples of photopolymeric material on the intensity of incident radiation of a Kr⁺ laser (647 nm) is studied. The observed linear dependence of the maximal rate of increase in the diffraction efficiency in the photopolymer on the incident light intensity is explained by the manifestation of a two-step excitation of the dye (T ₁←S ₀, T ₂←T ₁) in the samples studied.     

Detection of atomic oxygen in flames by absorption spectroscopy

The absolute concentration of atomic oxygen in an atmospheric pressure hydrogen/air flame has been measured using Intracavity Laser Spectroscopy (ICLS) based on a dye laser pumped by an argon-ion laser. Absorptions at the highly forbidden transitions at 630.030 nm and 636.380 nm were observed at an equivalent optical length of up to 10 km. The relatively low intensity of the dye laser avoids photochemical interferences that are inherent to some other methods for detecting atomic oxygen. The detection sensitivity is about 6 × 10¹⁴ atom/cm³ and can be improved with better flame and laser stabilization.     

Picosecond fluorescence studies by intracavity gain spectroscopy in a modelocked dye laser

This article presents measurements which combine modelocking technique with intracavity spectroscopy. To test this approach, a sample (10^–5 m ethanolic solution of 1,4-dihydroxyanthranquinone) was inserted in a modelocked Ar⁺ ion laser and probed by intracavity pulses of a synchronously pumped dye laser. The probing of the sample results in an amplification of the dye laser output. Maximum output was measured if the pulses of the dye laser temporally overlapped with those of the Ar⁺ ion laser inside the sample. Under this condition, the spectral laser intensity was shaped by the spectrum of stimulated fluorescence which originated from a molecular vibronic state populated by pump laser excitation.Presented at LASERION '91, June 12–14, 1991, München (Germany)     

Enhanced laser characteristics of pyrromethene 650 using modified PMMA as solid hosts

Solid-state samples based on modified polymethyl methacrylate (MPMMA) with methanol doped with the dye pyrromethene 650 (PM650) are prepared.The effects of a volume percentage of methanol on the laser characteristics of the sample,including spectra properties,slope efficiency,photostability and tunable properties,are investigated.The broadband dye laser output wavelength is around 655 nm and a highest slope efficiency of 32.23% is achieved.Pumping the samples at a repetition rate of 5 Hz with a pulse energy of as high as 100 mJ (the fluence is 0.26 J/cm 2),the longest lifetime (168000 shots) is obtained in the sample (MMA:methanol=18:2),and the corresponding normalized photostability reaches 109.19 GJ/mol.When the sample (MMA:methanol=18:2) is placed in a Shoshan-type oscilla-tor,the narrow-linewidth operation is a continuous tuning range (up to 64 nm).The results indicate that the laser characteristics of solid-state dyes can be greatly enhanced by using modified PMMA with methanol serving as the solid host.     

Pulse properties of a synchronously mode-locked,cavity dumped,picosecond dye laser system

A synchronously mode-locked, cavity-dumped picosecond dye laser is described. The structure and intensity of the picosecond pulses measured under different conditions are reported. It was found that the structure of the pulses from the synchronously pumped dye laser depends critically on the length of the Ar⁺ laser pulses. At the shortest Ar⁺ laser pulses of about 70 ps the dye pulses are as short as 1.1 ps. With Ar⁺ laser pulses of 200 ps the dye laser pulses contains a broad satellite pulse which contains a large fraction of the total intensity. When a cavity dumper is added to the system one gets dye laser pulses 15–20 ps long with a substructure, which indicates incomplete mode-locking. Well mode-locked 1.5–2.0 ps pulses were obtained in the red part of the dye laser action spectrum, i.e. 620–650 nm for R6G, 595–608 nm for R 110 and 657–662 nm for RB, respectively. Addition of mode-locking dyes also improved the pulse quality at some wavelengths.     

Polychromatic N2 Laser-Pumped Dye Lasers

Recently, Nakashima and Sousa have reported² a scheme for the generation of laser³ pulses consisting of several wavelengths in the visible, which are rather widely separated spectrally, but ovelap spatially and temporally⁴. In their scheme (ref. 2), several cells-each containing a distinct dye solution - were placed in tandem and were pumped from one side with a focussed N₂ laser (337.1 nm) beam. Under these conditions each dye solution lased in its distinct wavelength and, by careful alighment of the dye cells, the emissions could be spatially superimosed to produce a single multi-wavelength laser pulse.     

Solid-state dye lasers based on PMMA co-doped with PM597 and PM650

In order to enhance the laser performances, solid-state samples based on polymethyl methacrylate (PMMA) co-doped with pyrromethene 597 (PM597) and pyrromethene 650 (PM650) were prepared. With SHG of Q-switched Nd:YAG laser (532 nm, ∼15 ns) pumping the samples, laser emission from the mixtures of PM597 and PM650 both in liquid solution and incorporated into solid polymeric matrices were investigated. The highest slope efficiency of co-doped solid-state dye samples 30.8% was achieved. Through the dye PM650 being co-doped into the dye PM597, the dye laser output wavelength was extended for the existence of energy transfer from the dye PM597 to the dye PM650.