Gain studies of coumarin 307 dye doped polymer laser

Solid state dye doped polymer is an attractive alternative to the conventional liquid dye solution. In this paper the laser characteristics of coumarin 307 (C307) doped polymethyl methacrylate rods modified with dioxane are studied under nitrogen laser excitation in a transverse pumping configuration and the variation of gain of the dye in solid medium for different pumping powers is studied. The photobleaching of dye doped polymer rod is also studied.     

Comparative photophysical and energy transfer studies of C480:C535 binary dye mixture in solid and liquid environments

The spectral behaviour of the individual dyes (C480 and C535) is discussed. The absorption and fluorescence spectral profiles of the dyes, in solid and liquid environments, are identical. Dye doped polymer rods of donor dye (C480) without the acceptor dye (C535), acceptor dye (C535) without the donor dye (C480) and donor dye with acceptor dye at different acceptor concentrations are synthesized. Energy transfer technique is studied, in detail, using these rods. The results obtained are compared with their respective liquid mixtures. Optical gain of the acceptor dye with and without the donor dye is determined experimentally, in both solid and liquid media. The gain of the acceptor with donor increases and then decreases with increase in acceptor concentration. Both solid and liquid media show similar trends. But, the gain coefficient in the solid matrix is less than that in the liquid medium. The photobleaching of the dye doped polymer rod under nitrogen laser excitation is studied.     

Effect of different donors and a polymer environment on photophysical and energy transfer studies using C540 as the acceptor

The dyes (C450, C480 and C540) and their dye mixtures (C450:C540 and C480:C540) were doped in polymer matrices (solid). Their photophysical studies were recorded. These results were analysed by comparing them with the data of the dyes and the dye mixtures in monomer compositions (liquid). The absorption and fluorescence spectral profiles of the dyes in the polymer matrix were found to be identical to those in the monomer compositions. The effect of different donors on the energy transfer technique using C540 as acceptor, in polymer matrix and monomer compositions, was studied in detail. The results obtained for the energy transfer technique in two binary dye mixtures containing different donors but same acceptor, in solid and liquid media, were intercompared. The gain of the acceptor without donor and with different donors was determined experimentally. The gain coefficient in the polymer matrix (solid) was less than that in the monomer medium (liquid). Also, the gain of the acceptor C540 was found to be more when C450 was used as the donor compared to that when C480 was used as the donor. Using nitrogen laser, the photobleaching effect in the two binary dye-doped polymer rods (with different donors but same acceptor) was studied. It was observed that photobleaching of the acceptor C540 in the presence of C450 as donor is slower than that in the presence of C480 as donor.     

Two-photon pumping of random lasers by picosecond and nanosecond lasers

We experimentally demonstrated two-photon pumping of random lasers using picosecond and nanosecond pump lasers. The picosecond laser pumping experiment was performed with 400 ps laser pulses at 770 nm, and the gain media was a Coumarin 480D dye solution doped with TiO₂ nanoparticles. Onset of laser action was observed at a pump laser pulse energy below 500 μJ. The nanosecond laser pumping experiment was performed with 7 ns laser pulses at 1064 nm, and the gain media was a Rhodamine 640 dye solution doped with TiO₂ nanoparticles. Onset of laser action was observed at a pump laser energy ∼18 mJ. Our results suggest that there exists an optimal pulse duration of the pumping laser in two-photon pumped random lasing that leads to minimum photodamage of the gain media and still keeps a high pumping efficiency. PACS 33.50.Dq; 42.55.Mv; 42.55.Zz     

蓝光波段染料Coumarin461掺杂的凝胶材料的光学性质

采用溶胶－凝胶技术合成了掺杂蓝光段激光染料Ｃｏｕｍａｒｉｎ４６１的ＳｉＯ２基固体材料，用波长为３０８ｎｍ的Ｘｅｃｌ激光器做泵浦源，横向泵浦，获得了峰值波长为４６５ｎｍ的蓝光波段激光输出，在泵浦光强度为１０ｍＪ时激光输出达到０．５３ｍＪ，转换效率为５．３％。     

Unprecedented solid-state laser action from BODIPY dyes under UV-pumping radiation

Highly efficient and stable laser emission is demonstrated under drastic UV pumping conditions from recently synthesized BODIPY dye incorporated into polymer host. Under transversal pumping at 355 nm, lasing efficiencies of up to 29%, similar to those obtained in liquid phase, were obtained, with useful lifetimes (drop of the emission by 50%) of 70,000 pulses at 5 Hz repetition rate. The obtained efficiency and photostability are much higher than those obtained with usual commercial dyes emitting in the same spectral region, such as Coumarin 540A, under the same experimental conditions.     

Spectroscopic and lasing properties of Xanthene dyes encapsulated in silica and polymeric matrices

The photo-physical properties of Xanthene dyes: Basic Rhodamine Yellow (BRY), Rhodamine590perchlorate (R590p), SulforhodamineB (SRB) doped in tetramethylorthosilicate (TMOS) and poly-methylmethacrylate (PMMA) are observed. The various parameters viz. full-width at half-maxima (FWHM), peak emission wavelength, quantum yield and excited state lifetime at different concentrations ranging from ∼0.05 to ∼1 mM of the dye under excitation by Copper Vapor Laser (CVL) of high repetition rate (∼5.6 kHz) of are investigated. In order to identify photostability in dyes, normalized photostability has been studied and found that silica gel samples containing dye are more stable than that of polymeric samples. This has been further understood in terms of number density of unbleached dye molecules that infers that photobleaching of dye molecules is not prominent at higher concentrations in glassy solid matrices. Pump intensity dependent optical gain of the samples has also been reported and efforts have been made to study the efficiency of solid-state laser samples in a cavity for the performance of the dye laser.     

共振线俘获对碰撞激发X光激光增益特性的影响

 以类氖-锗离子为例,用逃逸概率方法研究了共振线俘获效应对电子碰撞激发X光激光增益特性的影响。对波长为19.6nm,23.2nm和23.6nm等三条激光线,讨论了增益特性对增益区宽度ΔR和介质速度梯度dV/dZ的依赖关系.     

Solid-state laser based on PMMA doped with Coumarin 540A

Solid-state dye laser materials based on polymethyl methacrylate (PMMA) doped with different concentrations of Coumarin 540A were prepared. The absorption, fluorescence and blue-green lasing spectra of the samples were obtained and studied in this latter. With the third harmonic generation (THG) of Q-switched Nd:YAG laser pumping the samples longitudinally, the highest slope efficiency is 12.8%, which is achieved in the sample with a dye concentration of 1.0×10^?3 mol/L.     

太阳光抽运激光器抽运系统优化

太阳光抽运激光器中,抽运系统提供的太阳抽运光与激活晶体之间的耦合决定了激光输出的总体效率。使用Tracepro软件,建立了菲涅耳透镜、锥形抽运腔二级抽运系统模型,并对该系统进行优化。通过分析菲涅耳透镜焦斑能量沿轴线的分布,得到了锥形腔入射窗口的口径和窗口距菲涅耳透镜的距离。通过改变锥形抽运腔的腔长和锥度,分析晶体棒轴向抽运功率密度分布,得到了锥形腔的最佳结构,并对镜面反射腔和陶瓷腔进行了详细的介绍。     

用蒙特卡罗方法计算棒状放大器内的泵浦能量分布

建立了用蒙特卡罗和光线跟踪法计算高功率固体激光系统棒状放大器能量沉积分布的模拟程序。在本文的模型中正确考虑了光线在反射器激光棒上的多次反射，氙灯的辐射光谱以及钕玻璃的吸收光谱。计算结果与作者用阈值法测量的增益均匀性以及用哈特曼网格法测量的氙灯泵浦对激光波面畸变的影响是一致的。     

Experimental investigations on energy-transfer characteristics and performance of some laser dye mixtures

Energy transfer from both Coumarin 120 (C120) and p-Bis(o-methylstyryl)-benzene (Bis-MSB), energy donors, to coumarin 7(C7) (acceptor) individually has been studied by steady-state emission measurements in methanol. The dye laser characteristics of the above-mentioned dyes have also been studied with respect to the energy transfer mechanism in the same solvent using a pulsed nitrogen laser as a pumping source. The large values of the critical transfer distances, R₀, indicate that the dominant mechanism responsible for energy transfer is due to long-range dipole–dipole interaction between the excited donor and ground state acceptor molecule. Both photophysical and photochemical stability of the donors has been examined under the effect of N₂ laser pumping.     

Spectral behavior and laser activity of 3-(4′-dimethylaminophenyl)-1-(1H-pyrrol-2-yl) prop-2-en-1-one (DMAPrP). A new laser dye

The photophysical properties of DMAPrP have been investigated in different solvents. DMAPrP dye exhibits a large change in dipole-moment upon excitation due to an intramolecular charge transfer interaction. A crystalline solid of DMAPrP give an excimer like emission at 546 nm. The ground and excited state protonation constants of DMAPrP are calculated. DMAPrP acts as good laser dye upon pumping with nitrogen laser in some organic solvents. The laser parameters such as the tuning range, gain coefficient (α), emission cross section (σ_e) and half-life energy (E_1/2) are also calculated. The photoreactivity and net photochemical quantum yield of DMAPrP in chloromethane solvents are also studied.     

Laser performance and photostability of Rhodamin B in solid host matrices

Laser dye Rhodamine B was incorporated at different concentrations in GMA polymer, sol–gel glass and organic–inorganic hybrid material synthesized using the sol–gel process. The amplified spontaneous emission (ASE) was studied using Nd-YAG laser of 532 nm. The effect of laser excitation in transfer pumping configuration and the influence of dye concentration on the ASE were studied. Also, the gain and the energy conversion efficiencies were investigated. Relatively high efficiencies (to ～48%) were obtained with good photostabilities where a decrease to ～30% of the initial amplified spontaneous emission output energy were observed after pumping by 35000 shots at relatively high repetition rate (10 Hz) and energy (15 mJ). The composition and the properties of the matrix were found that optimize the laser performance and photostability of an investigated dye.     

Modeling laser generation in cholesteric liquid crystals using kinetic equations

The paper presents the results of calculating the threshold pumping power necessary for laser generation in cholesteric liquid crystals doped with fluorescent dyes. Calculations have been performed with allowance for (i) specific spectral properties of the chiral cholesteric medium as a photonic structure and (ii) the spatially distributed character of feedback in the active medium. The dependences of the threshold pumping power on the sample thickness, dye concentration, and leading front widths of long pumping pulses have been studied.     

Stimulated emission processes in highly excited CdS at 80 K

The stimulated emission from CdS at 80 K under high excitation density is studied by means of quasi-resonant dye laser pumping. The evidence of exciton-exciton (P line) and exciton-electron (E line) scattering and, at the highest excitation level, of electron-hole plasma (EHP) recombination are reported and discussed also by means of optical gain measurements.     

Nonlinear optical absorption and NIR to blue conversion in highly stable polymeric dye rod

A simple method for preparing transparent crack-free solid polymeric matrices is presented. Different dopants may be hosted in the polymeric matrix. The method is applied to prepare Glycidyl-methacrylate polymeric rods doped with solutions of coumarin 500 laser dye (ethanol and chloroform). The solvent??s effect has appeared as a shift in the absorption and photoluminous spectral bands of the laser dye in the solid polymeric host. The prepared solid samples showed nonlinear optical response on excitation with 532?nm of nanosecond laser pulses using the open aperture z-scan technique. Each sample shows different nonlinear behavior in response to the irradiating laser beam. The theoretical fitting of the experimental data indicates that the dominant mechanism of nonlinear absorption is the two-photon absorption process. Visible amplified spontaneous emission is reported in both polymeric dye rods by NIR pumping. High photostability is reported for the samples.     

香豆素440/荧光素钠/藏红混合染料体系的光谱研究

通过对C440/Fl.Na/Saf.-T三元混合染料体系的荧光光谱研究,了解到这三种染料之间有较充分的能量转移。又通过对C440/Fl.Na和Fl.Na/Saf.-T两个混合染料体系的荧光寿命测量,讨论了分子间能量转移过程和机理,并做了一些定量的分析。     

轴向隐失波激励的回音壁模式光纤激光器

采用轴向隐失波激励增益的方式,使激光增益区域局限在光纤回音壁模式的模场区域内,显著地降低了回音壁模式光纤激光辐射的抽运阈值,由此形成一种低阈值的回音壁模式光纤激光器.在微焦耳量级的低抽运能量条件下,用回音壁模式光纤激光器研究了激光染料的浓度效应.实验结果表明,随着激光染料浓度的增加,回音壁模式激光辐射的波长向长波方向移动,激光波长范围变宽.用回音壁模式染料激光的四能级模型得到激光上能级和所有能级上的分子数比值γ(λ)曲线后,很好地解释了实验结果.低抽运阈值的回音壁模式光纤激光器,为研究液体激光现象提供了极为便利的手段.     

新型电光陶瓷调Q光纤激光器

报道了基于OptoCeramic(R)电光陶瓷材料的新型调Q光纤激光器.采用976 nm半导体激光器作为抽运源,电光陶瓷调制器作为Q开关,峰值吸收系数1200 Db/m的高掺杂镱纤作为增益介质构成环形腔激光器.增益光纤的高掺杂浓度使得激光器的腔长得到缩短,输出光脉冲的宽度得到压缩.通过调节电光元件的电压,控制材料的折射率,调节谐振腔的损耗,实现Q开关作用.实验中通过改变腔长、抽运功率和重复频率,研究了脉冲的输出特性.获得最窄脉宽104 ns,重复频率3～40 kHz连续可调的调Q脉冲输出.