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.     

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     

超短脉冲染料放大器中的参数研究

对超短脉冲染料放大器(DLA)中放大的自发辐射(ASE)随泵浦强度变化的关系进行了实验研究,为了求得具有高储能、低自发辐射背景噪声的染料激光放大器的泵浦强度,我们用速率方程对实验结果进行了解析分析,获得了染料激光放大器的泵浦强度与染料参数(浓度、增益长度等)的近似关系式,以及相应条件下染料激光放大器储能和小信号增益的表达式,并与实验进行了比较.二者符合较好,从而为染料激光放大器的设计提供了参考.     

Generation and amplification of sub-picosecond pulses using a frequency-doubled neodymium YAG pumping source

Stable, tunable, sub-picosecond pulses have been obtained by synchronously pumping a Rhodamine 6G dye laser with a frequency-doubled CW modelocked neodymium YAG laser. Careful attention has been paid to minimize amplitude and timing instabilities, resulting in dye laser pulses shorter than 500 fs. The main advantage of this new pumping source over current synchronously pumped dye lasers is that it is particularly well suited to short pulse amplification. Using this technique amplification of 2 × 10⁶ has been achieved.     

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.     

Generation of nearly transform-limited pulses in subnanosecond region with TEA nitrogen-laser-pumped dye laser

A dye laser is transversely pumped by a TEA nitrogen laser with 700 ps duration. The dye laser pulse has a spectral linewidth of 0.007 nm and a pulse width of ≈ 140 ps, giving a time-bandwidth product of 1.5. It is pointed out that the fluorescence lifetime of the laser dye plays an important role in generation of laser emission using a long laser cavity under subnanosecond pulse pumping.     

光源稳定性对简并四波混频信噪比影响的实验研究

在碘蒸气中研究了染料激光稳定性对简并四波混频(DFWM)信噪比的影响。实验中采用多模Nd∶YAG激光器倍频的输出泵浦染料激光器(染料PM580溶于酒精)。在具有前向补偿分光系统和图像探测系统的帮助下,在常温常压条件下测得泵浦光在波长为554.013 nm时达到饱和光强为290 μJ。同时发现染料激光器的光稳定性(输出波长范围,光束质量和能量转换效率等)随使用时间,泵浦激光脉冲次数和能量的增加而逐渐减弱。另外通过对比发现在染料激光器输出不稳定时,光源单色性和指向性等指标的变化导致在同一泵浦强度不同时刻获得的DFWM信号强度相差很大,且DFWM信号信噪比低。染料激光器光源稳定性对DFWM信号影响的研究结果对物质的痕迹量探测以及无荧光物质光谱定标等方面的应用具有重要意义。     

Spectrally Adjustable Picosecond Dye Laser Pulses Generated with Nanosecond Nitrogen Lasers

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Gain studies of Coumarin 503 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 503 (C503) doped polymethyl methacrylate (PMMA) rods modified with ethyl alcohol (EtOH) 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 gain of Coumarin 503 in solid medium is compared with the gain of Coumarin 503 in liquid medium and it is found that the gain of the dyes in the solid environment is less than that in the liquid environment. The photobleaching of dye in polymer medium under nitrogen laser excitation is also studied by keeping the rod in a fixed position and by rotating the rod about its cylindrical axis. It is found that the photobleaching rate is faster when the rod is in a fixed position.     

Coherence and beam geometry of a superradiant dye laser

This paper reports the observation of a well defined radiation mode emitted from a superradiant dye laser pumped by a pulsed nitrogen laser. Beam geometry and spatial coherence of the dye laser are studied in connection with the pumping geometry. It is shown that under favorable pumping conditions most of the excited molecules radiate into the same spatial mode by stimulated emission. The associated mode structure is also calculated based on a model of a properly phased dipole distribution. The calculated emission pattern reproduces the observed far field pattern closely. Work supported in part by CNPq and FINEP.     

A mode-locked dye laser pumped by a xenon ion laser

Passive mode-locking of a rhodamine 6G dye laser has been achieved, using a pulsed xenon ion laser as a pumping source. A pulse width of 5 ps and a peak power of 4 kW have been obtained. Thermal problems were encountered, which adversely affected the operation of the dye laser. Work is in progress to improve these results.     

Dye laser spectrum narrowing by “double pulse” flashlamp pumping

A novel simple “two-step lasing” technique for flashlamp dye laser spectrum narrowing is proposed. The laser spectrum is locked by double pulse pumping at the preliminary narrowed prepulse emission. Experimental check on the example of waveguide flashlamp pumped dye laser is reported.     

Polarization and power characteristics of pulsed dye lasers with transverse pumping

Starting from the classical theory on molecular luminescence in liquids, rate equation for two-polarization-mode laser oscillation under transverse pumping with intense excitation have been set forth neglecting the influence of orientational relaxation of the dye molecules. Hence, the laser output power and polarization under different configurations have been obtained. The results show that the dye laser is partially polarized even when the pump beam is unpolarized and no polarizing elements exist in the cavity. If we define a reference plane consisting of the axes of the pump beam and the dye laser, the laser system has to adopt the plane perpendicular to the reference plane as the polarization direction in order to yield a highly efficient, linearly polarized laser output. Experiments on a copper-vapor laser pumped dye laser verified these analytical results.     

Astigmatically compensated cw dye laser resonators using lenses

The compensation of the astigmatism of Brewster-angled dye cells can be performed with lenses as well as with spherical mirrors. The advantages of cw dye laser resonators using lenses lie in the linear configuration of the optics and the convenient adjustability of astigmatism compensation. An output efficiency of 30% already at 1.6W pumping power has been observed. In addition, ring laser resonators with lenses have been investigated and they delivered up to 400 mW single mode power in travelling wave operation at less than 2 W pumping power.     

双泵染料激光器

本文讨论了双泵染料激光器的可能性和途径。讨论表明,引进辅助的T₁→S₁抽运,对于降低激光器的阈值,提高增益和荧光量子效率,扩大激光染料的种类和调频波段,将是有益的。 关键词：     

Tertiary amines as possible tunable laser materials in the ultraviolet

Two photon excitation by a tunable dye laser is used to determine the decay kinetics of some aliphatic tertiary amines. The feasibility of obtaining laser action from trimethylamine and triethylamine by KrF laser pumping is quantitatively discussed.     

Stilbene 420激光染料的光谱特性分析

配制了Stilbene 420染料溶液。测量了其吸收光谱。以调Q倍频Nd∶YAG激光为抽运源,实现了对Stilbene 420染料的激光光谱和荧光光谱的分析。激光光谱在425 nm处获得最强峰值,半峰高宽(FWHM)为1 nm,光谱范围为420～440 nm。荧光光谱峰值在428.5 nm,与激光最强峰值相差3.5 nm。最高染料转换效率为9.26%。     

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.     

A 110 J Highly Energetic Flashlamp-Pumped Dye Laser

A highly energetic flashlamp-pumped dye laser of 110 J output energy and overall efficiency of 1.1% is developed. For such a powerful laser particular considerations must be taken in order to reduce thermal distortion in the dye solution caused by high-energy pumping. The laser system is therefore composed of a laser head with a four-fold elliptical cylindrical reflector, extended Marx-bank driver circuit, a large aperture dye cell of 44 mm inner diameter and an unstable resonator.This paper is based on a presentation given at the 17th International Laser Radar Conference held in Sendai International Center, Japan, from 25–29 July 1994.     

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.