二元振幅型面板用于光束空间整形

为了提高高功率激光系统的整体效率和充分利用光能,需要对前端注入的高斯光束进行空间整形,实现驱动器终端激光的均匀化输出。采用振幅型二元面板对激光光束进行空间强度整形,利用误差扩散法进行了理论设计,数值摸拟了整形效果,同时讨论了面板加工误差以及空间滤波器的小孔大小等因素带来的影响。根据理论设计,分别加工了反高斯透射率分布和抛物线透射率分布的二元面板,并进行了整形实验,实现了各自的整形功能,并做了误差分析。实验证明二元面板能对激光光束的空间强度分布实现了精确的整形。

改善高功率激光二极管阵列光束质量的一种新方法

根据波导模理论,推导了高功率激光二极管阵列的远场分布,根据其分布特点,设计了一种离轴外腔.运用这种外腔,在工作电流为17A时,光束的束宽积从自由运转时的1100mm.mrad减小到128mm.mrad,二极管阵列的光束质量提高了8.5倍左右,输出功率约为自由运转时的75%.

板条激光放大器中寄生振荡的研究

寄生振荡的存在使得放大器在信号光到达之前消耗了大量的反转粒子数,降低了放大器的激光增益和储能效率,严重地影响了激光放大器的性能,尤其对高功率激光放大器。在理论分析和实验研究的基础上,以Nd∶YAG晶体板条为例,用8条半导体激光阵列对晶体进行双侧抽运,研究了高功率激光放大器的寄生振荡现象,分析了板条晶体寄生振荡产生的原因,并详细比较了晶体在不同的抽运功率和表面处理下的放大效果,得到了2倍的单程放大,当输入能量为140 mJ时,获得了278 mJ的激光输出。

边缘泵浦被动调Q的Nd：YAG薄片激光器

文中报道了一台采用激光二极管部分边缘泵浦方式的高功率薄片激光器，晶体尺寸是1 mm×10 mm×60 mm。Cr4+：YAG被用来作为被动调Q晶体，在重复频率高于10kHz时，获得了脉宽10ns，平均功率70W，斜线效率为36\%的激光输出。通过控制泵浦光束直径的大小，我们在厚度方向得到了近似衍射极限的光束输出。整个激光器结构紧凑，大小为60 mm×174 mm×150 mm。

The analysis of the transient temperature distribution of double-slab Nd:YAG laser medium

A novel double-slab Nd:YAG laser, which uses face-pumped slab medium cooled by liquid with different temperatures on both sides, is proposed. The thermal distortion of wavefront caused by the non-uniform temperature distribution in the laser gain media can be self-compensated. According to the method of operation, the models of the temperature distribution and stress are presented, and the analytic solutions for the model are derived. Furthermore, the numerical simulations with pulse pumping energy of 10 J and repetition frequencies of 500 and 1000 Hz are calculated respectively for Nd:YAG laser medium. The simulation results show that the temperature gradient remains the approximative linearity, and the heat stress is within the extreme range. Then the absorption coefficient is also discussed. The result indicates that the doping concentration cannot be too large for the high repetition frequency laser. It has been proved that the high repetition frequency, high laser beam quality, and high average output power of the order of kilowatt of Nd: YAG slab laser can be achieved in this structure.

110-W fiber laser with homemade double-clad fiber

A high-power ytterbium-doped fiber laser (YDFL) with homemade double-clad fiber (DCF) is introduced in this letter. The geometric parameter and laser characteristics of the fiber have been studied. With one-end-pumping scheme, pumped by a high-power laser diode with launching power of 280 W, a maximum continuous wave (CW) output of 110 W is obtained with an optical-to-optical efficiency of 40%.

Experimental demonstration of phase locking of a two-dimensional fiber laser array using a self-imaging resonator

Phase locking of a two-dimensional fiber laser array is experimentally demonstrated by using a self-imaging resonator and a spatial filter. The stable beam profiles of in-phase mode and out-of-phase mode are observed by controlling the position of spatial filter. The phase locking fiber array with in-phase mode has produced 26 W coherent output. An antisymmetric eigenmode is also observed in our experiments. The phase locking is not sensitive to power variations among the pump beams and the configuration has the ability to repair a missing element. (C) 2008 American Institute of Physics.

Preparation and spectroscopic properties of Yb-doped and Yb-Al-codoped high silica glasses

Yb-doped and Yb-Al-codoped high silica glasses have been prepared by sintering nanoporous glasses. The absorption, fluorescent spectra and fluorescent lifetimes have been measured and the emission cross-section and minimum pump intensities were calculated. Codoping aluminum ions enhanced the fluorescence intensity of Yb-doped high silica glass obviously. The emission cross-sections of Yb-doped and Yb-Al-codoped high silica glasses were 0.65 and 0.82 pm(2), respectively. The results show that Yb-Al-codoped high silica glass has better spectroscopic properties for a laser material. The study of high silica glass doped with ytterbium is helpful for its application in Yb laser systems, especially for high-power and high-repetition lasers. (C) 2007 Elsevier B.V. All rights reserved.

Efficient laser oscillation of Yb : Y3Al5O12 single crystal grown by temperature gradient technique

Low-threshold and highly efficient continuous-wave laser performance of Yb:Y3Al5O12 (Yb:YAG) single crystal grown by a temperature gradient technique (TGT) was achieved at room temperature. The laser can be operated at 1030 and 1049 nm by varying the transmission of the output coupler. Slope efficiencies of 57% and 68% at 1049 and 1030 nm, respectively, were achieved for 10 at. % Yb:YAG sample in continuous-wave laser-diode pumping. The effect of pump power on the laser emission spectrum of both wavelengths is addressed. The near-diffraction-limited beam quality for different laser cavities was achieved. The excellent laser performance indicates that TGT-grown Yb:YAG crystals have very good optical quality and can be potentially used in high-power solid-state lasers.

Efficient tunable diode-pumped Yb : LYSO laser

We demonstrated efficient laser action of a new ytterbium-doped oxyorthosilicate crystal Yb:LuYSiO5 ( Yb: LYSO) under high-power diode-pumping. The spectroscopic features and laser performance of the alloyed oxyorthosilicate crystal are compared with those of ytterbium-doped lutetium and yttrium oxyorthosilicates. In the continuous-wave laser operation of Yb: LYSO, a maximal slope efficiency of 96% and output power of 7.8 W were respectively achieved with different pump sources. The Yb: LYSO laser exhibits not only little sensitivity to the pump wavelength drift but also a broad tunability. By using a dispersive prism as the intracavity tuning element, we demonstrated that the continuous-wave Yb: LYSO laser exhibit a continuous tunability in the spectral range of 1014-1091 nm. (c) 2006 Optical Society of America.

Rare-earth-doped silica microchip laser fabricated by sintering nanoporous glass

We report a new method for fabricating rare-earth-doped silica glasses for laser materials obtained by sintering nanoporous silica glasses impregnated with rare-earth-doped ions. The fabricated materials have no residual pores and show good optical and mechanical properties. Good performance from a Nd3+-doped silica microchip laser operating at 1.064 mum is successfully demonstrated, suggesting that the fabricated silica glasses have potential for use as active materials for high-power solid-state lasers. (C) 2005 Optical Society of America.

Continuous-wave and passively mode-locked Yb : GYSO lasers pumped by diode lasers

We report both continuous-wave and passively mode-locked laser actions in a Yb3+-doped gadolinium yttrium oxyorthosilicate Yb:GdySiO(5) (Yb:GYSO) crystal. Continuous-wave (CW) laser operations were compared under different pump conditions with high-power diodes of different wavelengths and fiber cores. CW mode-locking was obtained with a semiconductor saturable absorber mirror.

Laser-induced damage morphology of high-reflective optical coatings

Two different kinds of 1064 nm high-reflective (HR) coatings, with and without SiO2 protective layer, were prepared by electron beam evaporation. Three-dimensional damage morphology, caused by a Nd:YAG pulsed laser, was investigated for these HR coatings. Development of laser-induced damage on HR coatings was revealed by both temperature field calculation and discrete meso-element simulation. Theoretical results met experimental very well. (C) 2004 Elsevier B.V. All rights reserved.

Effects of annealing on laser-induced damage threshold of TiO2/SiO2 high reflectors

The mechanism of improving 1064 nm, 12 ns laser-induced damage threshold (LIDT) of TiO2/SiO2 high reflectors (HR) prepared by electronic beam evaporation from 5.1 to 13.1 J/cm(2) by thermal annealing is discussed. Through optical properties, structure and chemical composition analysis, it is found that the reduced atomic non-stoichiometric defects are the main reason of absorption decrease and LIDT rise after annealing. A remarkable increase of LIDT is found at 300 degrees C annealing. The refractive index and film inhomogeneity rise, physical thickness decrease, and film stress changes from compress stress to tensile stress due to the structure change during annealing. (c) 2007 Elsevier B.V. All rights reserved.

Influence of substoichiometer on the laser-induced damage characters of HfO2 thin films

HfO2 is one of the most important high refractive index materials for depositing high power optical mirrors. In this research, HfO2 thin films were prepared by dual-ion beam reactive sputtering method, and the laser-induced damage thresholds (LIDT) of the sample were measured in 1-on-1 mode for laser with 1064 nm wavelength. The results indicate that the LIDT of the as-grown sample is only 3.96 J/cm(2), but it is increased to 8.98 J/cm(2) after annealing under temperature of 200 degrees C in atmosphere. By measuring the laser weak absorption and SIMS of the samples, we deduced that substoichiometer is the main reason for the low LIDT of the as-grown sample, and the experiment results were well explained with the theory of electronic-avalanche ionization. (C) 2008 Elsevier B.V. All rights reserved.