122-W high-power single-frequency MOPA fiber laser in all-fiber format

We demonstrate a high-power single-frequency master oscillator power amplifier (MOPA) fiber laser.The central wavelength of the single-frequency fiber laser seed is 1 063.8 nm,with a linewidth narrower than 20 kHz and output power of 120 mW.By using two-stage amplification,a single-frequency fiber laser with an output power of 122 W is obtained,and the optical-optical conversion efficiency is 72%.No significant amplified spontaneous emission (ASE) or stimulated Brillouin scattering (SBS) is observed.The output power can be further increased by launching more pump power.     

脉冲激光辐照硅材料引起表面波纹的特性研究

叙述了激光与材料相互作用过程中引起相干受激光散射的机制,以及形成材料表面波纹的特性。在激光波长1．06μm、能量15mJ、光斑直径2mm、脉冲半峰全宽约10ns和入射方向为布儒斯特角的条件下,进行了脉冲激光辐照硅材料形成表面波纹的实验研究。在脉冲激光辐照硅材料表面功率密度略大于材料损伤阈值的条件下,发现了硅材料表面形成的平行等间距直线条纹结构。用光学显微镜和原子力显微镜分别测量了被辐照硅材料表面的波纹形貌特征。在假设硅材料表面波纹的产生与声波在材料中的传播速度有关的条件下,由声波传播速度和激光辐照硅材料的脉冲宽度较好地解释了材料表面形成条纹的宽度．并认为在形成表面波纹的过程中,热应力起主要作用。     

掺铒光纤环镜中超短光孤子的放大与压缩Ⅰ.基本原理

用常规掺铒光纤放大器放大超短光孤子存在一个重大困难 ,就是在放大过程中光纤非线性效应会引起孤子波形及频谱畸变 ,使得输出脉冲不再具有孤子特性 ,从而影响系统性能。提出一种利用掺铒光纤环镜放大超短光孤子的新方法 ,数值计算表明 ,该方法不仅可实现无畸变的光孤子放大 ,而且能同时实现孤子宽度的有效压缩。当宽度为 2 ps的基阶孤子经过长度为 92 .6m、增益为 14 .4dB的环镜后 ,其峰值功率被放大 16 5倍 ,脉冲宽度被压缩到 0 .19ps ,时间带宽积为 0 .30 3,脉座能量仅占整个脉冲能量的 3.8% ,表明由环镜输出的放大脉冲很大程度上具有基阶孤子特性。     

OLED/LCD器件中的γ校正

阐述了OLED／LCD器件中γ校正的基本原理,通过考虑人眼视觉非线性和液晶电光非线性,得到了CRT相对于OLED／LCD的灰度级亮度特性曲线。以所设计的26．4cn VGA(行反转)的TFT—LCD为例,采用源驱动器μPD16641芯片,通过γ校正电路和输入数据、灰度级和基准电压的关系,进行了实际的γ校正。得到了驱动电路中的γ校正的外部电压设定值,将设定目标值与实际驱动测定值进行了比较,从比较的结果可以看到,两者十分接近的,解决了实际的TFT液晶驱动电路中Gamma(γ)校正问题,达到了预期的设计目的,使图像的质量满足了用户的要求。     

近红外光谱检测技术在农业和食品分析上的应用

近红外光谱是 2 0世纪 90年代以来发展最快、最引人注目的光谱分析技术。阐述了近红外光谱的原理、技术特点 ,介绍了近红外光谱仪、光谱预处理方法以及化学计量学研究的发展过程 ,重点列举了近红外光谱在农业和食品分析中的成功应用实例。资料表明 ,近红外光谱以其速度快、不破坏样品、操作简单、稳定性好、效率高等特点 ,已广泛应用于各个领域。特别是在欧美及日本等发达国家 ,很多近红外光谱分析法被列为标准方法。而我国近红外光谱的应用研究起步较晚 ,虽然某些方面已具国际领先水平 ,但就总体来看与国际水平还有大的差距。文章首次提出了集中优势资源 ,包括人力资源和设备资源 ,利用现代网络技术 ,建立终端用户和中心数据库资源共享的模式 ,以推动近红外光谱技术在我国农业科技和生产中的应用。     

Novel cyclization reactions of mono- and dichloroazodienes. A new synthesis of substituted pyridazines

Cyclization of the in—situ generated chloroazodienes with a variety of enamines was found to give chloro-substituted tetrahydropyridazines which could be aromatized to pyridazines by base treatment. This sequence appears to be a formal 4 + 2 hetero Diels-Alder reaction with a high degree of regio and stereo control and constitutes a new synthesis of substituted pyridazines. However, cyclization of the corresponding dichloroazodienes with acyclic enamines gave not only the expected pyridazine product, but also gave an N-aminopyrrole product. Combination of the dichloroazodiene with cyclic enamines gave bicyclic dihy-dropyridazines, bicyclic pyridazines, and acyclic enamines which could be forced to close to the bicyclic dihydropyridazines upon further heating. These results would indicate a stepwise mechanism. The scope and mechanistic speculations on these reactions will be presented. While exploring the novel cyclization reactions of 4-chloroazodienes with electron rich olefins we developed a new and general synthesis of substituted 3-phenypyridazines. A number of these analogs were found to exhibit bleaching herbicidal activity (phytoene desaturase inhibition). Further methodology development coupled with analog synthesis led to the preparation of 3-heteroaryloxy and 3-aryloxypyridazines with increased unit activity and selectivity as well as good environmental properties. These compounds were found to be more active than current commercial standards on a number of important weed species with selectivity in corn in the US and small grains in Europe. Greenhouse activity of the most active analogs ranged from 17–140 g/hectare on important narrow-leaf species.