Syneresis of vitreous by carbon dioxide laser radiation

In carbon dioxide laser surgery of the vitreous a process of vaporization has been advocated. In this report syneresis, a thermal liquefaction of gel, is shown to be over ten times more efficient on an energy basis than vaporization. Syneresis of vitreous is experimentally shown to be a first-order kinetic process with an activation energy of 41 +/- 0.5 kilocalories per mole. A theory of laser surgery in which this figure is used agrees closely with results from laser experiments on human eye-bank vitreous. The syneresis of vitreous by carbon dioxide laser radiation could lead to a more delicate form of ocular microsurgery, and application to other biological systems may be possible.     

激光技术在农作物检测中的应用进展

激光技术现已成功应用于农作物组分检测、长势监测、病虫害监测、农药残留检测、田间杂草识别及辅助精细农业操作等方面,并日益凸显出检测准确、快速、低成本等优势,在农作物检测中应用较多的激光技术主要包括激光漫反射技术、激光诱导荧光光谱技术和激光拉曼光谱技术。笔者重点介绍了这3种技术用于农作物检测的原理、系统构成、应用进展和发展趋势。     

大功率半导体激光阵列远场光强分布研究

针对Bar和Stack两种类型激光器,运用双峰模型,对各个发光单元的光强进行非相干叠加,得出Bar和Stack两种激光器的远场光强模型,并根据此模型模拟出Bar和Stack的远场光强分布。分别定量描述了Bar和Stack光强分布均匀的区域以及开始出现类似单发光单元的双峰分布的位置,并给出了相应的经验计算公式。利用这些公式以及器件数据手册给出的参数即可方便的计算出Bar和Stack的均匀区域以及出现类似单发光单元的双峰分布的位置。理论分析与实验结果基本吻合。可为Bar和Stack在实际应用中设计光学系统以及光束质量评价提供理论依据。     

激光共聚焦显微镜的样品前处理技术研究

激光共聚焦显微镜是近代生物医学图像应用中最重要的仪器之一,在定量共聚焦图像分析、定量荧光测量、三维重组分析生物结构等方面具有重要的作用.该研究主要介绍了实验室中最常用的激光共聚焦显微镜的几种样品前处理技术,即FM4-64染色法、BFA处理、双分子荧光互补技术（BiFC）等,同时介绍这些方法的原理、使用范围以及在相关领域中的应用情况等,以期更好地将激光共聚焦显微镜技术应用于科研实践中.     

激光散斑技术在农产品检测中的应用

[目的]研究激光散斑技术在农产品检测中的应用。[方法]介绍了激光散斑技术的基本原理,综述了激光散斑技术在农产品检测应用的发展概况,分析了激光散斑技术在农产品检测中需要解决的问题,同时叙述了激光散斑技术在农产品检测中的发展前景。[结果]激光散斑技术是可以用于农产品的品质检测的一种无损的检测技术,可以根据农产品的品质质量,对农产品进行合理分级。[结论]为激光散斑检测技术的研究提供借鉴和参考。     

Detection of trace molecular species using degenerate four-wave mixing

Spectroscopies that make use of laser light have provided an important tool to modern researchers for the nonintrusive analysis of chemical systems. The strengths and limitations of these spectroscopic techniques often determine the viability of scientific investigations. The unique properties of degenerate four-wave mixing, a nonlinear optical technique, have recently been found to provide powerful capabilities for a wide range of applications.     

泄漏监测系统应用中的认识误区

泄漏监测系统在长输管道上的应用日趋普遍,但是管道运营单位对泄漏监测系统性能在认识上存在误区。这些误区一方面妨碍了运行人员有效利用泄漏监测系统来辅助分析工况变化,另一方面也使运营单位无法合理地评价泄漏监测系统的性能,无法有效分辨不同泄漏监测系统之间的优劣,严重削弱了管道运营单位的实际泄漏监测能力。总结了输油管道泄漏监测系统应用过程中常见的认识误区,并逐一进行纠正;分析了错误认识产生的原因,从用户角度给出了提高泄漏监测系统性能的具体措施。结果表明:这些措施有助于管道运营单位纠正对于泄漏监测系统的错误认识,制订适合的检测、评价及管理办法,从而有效提升泄漏监测能力。     

激光扫描共聚焦显微镜在生物科学研究中的应用

介绍了激光扫描共聚焦显微镜的工作原理和特点,在此基础上,综述了激光扫描共聚焦显微镜在生物科学研究中的应用和应用技巧.     

微生物激光诱变育种应用研究进展

介绍了激光育种的知识背景和原理,综述了利用激光进行微生物育种的研究进展及相关产业化生产,探讨了微生物激光诱变育种的发展方向。     

Divalent carbon intermediates: laser photolysis and spectroscopy

A brief review is given of the structures of an important class of reactive intermediates, divalent carbon species (carbenes). The electronic properties of carbenes force an unusual electronic character upon these species that, in turn, leads to intriguing physical and chemical properties. Because of the fleeting nature of carbenes, which are extraordinarily reactive, direct investigation of their structural and chemical behavior has presented a challenge to the experimentalist. The application of spectroscopic and ultrafast laser techniques has met this challenge. With the use of laser methods, along with conventional techniques, quantitative evaluation of the energetics, dynamics, and reactivities of a variety of carbenes has been possible.     

Phase diagram of degenerate exciton systems

Degenerate exciton systems have been produced in quasi-two-dimensional confined areas in semiconductor coupled quantum well structures. We observed contractions of clouds containing tens of thousands of excitons within areas as small as (10 micron)2 near 10 kelvin. The spatial and energy distributions of optically active excitons were determined by measuring photoluminescence as a function of temperature and laser excitation and were used as thermodynamic quantities to construct the phase diagram of the exciton system, which demonstrates the existence of distinct phases. Understanding the formation mechanisms of these degenerate exciton systems can open new opportunities for the realization of Bose-Einstein condensation in the solid state.     

激光技术在作物诱变育种上的应用与展望

简述了激光诱变发生的机理,以及激光在作物育种中的应用,以期为今后的激光育种工作提供参考。     

Cavity cooling below the recoil limit

Conventional laser cooling relies on repeated electronic excitations by near-resonant light, which constrains its area of application to a selected number of atomic species prepared at moderate particle densities. Optical cavities with sufficiently large Purcell factors allow for laser cooling schemes, avoiding these limitations. Here, we report on an atom-cavity system, combining a Purcell factor above 40 with a cavity bandwidth below the recoil frequency associated with the kinetic energy transfer in a single photon scattering event. This lets us access a yet-unexplored regime of atom-cavity interactions, in which the atomic motion can be manipulated by targeted dissipation with sub-recoil resolution. We demonstrate cavity-induced heating of a Bose-Einstein condensate and subsequent cooling at particle densities and temperatures incompatible with conventional laser cooling.     

Diode laser--pumped solid-state lasers

Diode laser-pumped solid-state lasers are efficient, compact, all solid-state sources of coherent optical radiation. Major advances in solid-state laser technology have historically been preceded by advances in pumping technology. The helical flash lamps used to pump early ruby lasers were superseded by the linear flash lamp and arc lamp now used to pump neodymium-doped yttrium-aluminum-garnet lasers. The latest advance in pumping technology is the diode laser. Diode laser-pumped neodymium lasers have operated at greater than 10 percent electrical to optical efficiency in a single spatial mode and with linewidths of less than 10 kilohertz. The high spectral power brightness of these lasers has allowed frequency extension by harmonic generation in nonlinear crystals, which has led to green and blue sources of coherent radiation. Diode laser pumping has also been used with ions other than neodymium to produce wavelengths from 946 to 2010 nanometers. In addition, Q-switched operation with kilowatt peak powers and mode-locked operation with 10-picosecond pulse widths have been demonstrated. Progress in diode lasers and diode laser arrays promises all solid-state lasers in which the flash lamp is replaced by diode lasers for average power levels in excess of tens of watts and at a price that is competitive with flash lamp-pumped laser systems. Power levels exceeding 1 kilowatt appear possible within the next 5 years. Potential applications of diode laser-pumped solid-state lasers include coherent radar, global sensing from satellites, medical uses, micromachining, and miniature visible sources for digital optical storage.     

Earth Strain Measurements with a Laser Interferometer: An 800-meter Michelson interferometer monitors the earth's strain field on the surface of the ground

The development of the laser as a source of coherent optical radiation has permitted the application of interferometric techniques to the problem of earth strain measurement. By use of this technology, an 800-meter laser strain meter has been developed which operates above the surface of the ground. The instrument has a strain least count of 10(-10), requires no calibration, and has a flat and linear response from zero frequency to 1 megahertz. The linearity and large dynamic range of the laser strain meter offer unprecedented versatility in the recording of seismic strains associated with earthquakes and nuclear blasts. The extremely wide bandwidth opens new areas of the strain spectrum to investigation. A key to the understanding of the state of stress of the earth and the association phenomona of tectonic activity and earthquakes is a knowledge of the spatial distribution of the earth strain. Measurements of secular strain and earth tides indicate that, even at these long periods, surface strain measurements are valid representations of earth strain at depth. The LSM thus provides a means of making crustal strain measurements at points selected for maximum geophysical interest and ultimately allow the mapping of strain field distributions.     

抗菌肽基因异源表达系统研究进展

抗菌肽是机体天然免疫系统的重要组成部分,因具有抗菌谱广、活性稳定、不易产生耐药性等优点而在食品、饲料、农业、医药领域具有重要的应用价值.由于化学合成的成本较高,利用基因工程技术构建高效的生物表达系统成为一个新的途径.综述了抗菌肽在细菌、酵母、植物、动物等表达系统中异源表达的研究进展,为抗菌肽的研究应用提供理论依据.     

不同腔长下调Q激光器输出脉冲特性研究

从Nd3+:YAG脉冲激光器调Q技术出发,研究了不同腔长条件下电光调Q激光器输出脉冲的宽度、能量和峰值功率特征,得到了不同腔长的调Q激光器输出脉冲特性曲线。研究结果表明,激光器腔长的改变能较好地调节脉冲的输出特性,对脉冲激光器的灵活应用具有一定的指导意义。     

抗菌肽基因异源表达系统研究进展

抗菌肽是机体天然免疫系统的重要组成部分,因具有抗菌谱广、活性稳定、不易产生耐药性等优点而在食品、饲料、农业、医药领域具有重要的应用价值。由于化学合成的成本较高,利用基因工程技术构建高效的生物表达系统成为一个新的途径。综述了抗菌肽在细菌、酵母、植物、动物等表达系统中异源表达的研究进展,为抗菌肽的研究应用提供理论依据。     

A quantum laser pointer

The measurement sensitivity of the pointing direction of a laser beam is ultimately limited by the quantum nature of light. To reduce this limit, we have experimentally produced a quantum laser pointer, a beam of light whose direction is measured with a precision greater than that possible for a usual laser beam. The laser pointer is generated by combining three different beams in three orthogonal transverse modes, two of them in a squeezed-vacuum state and one in an intense coherent field. The result provides a demonstration of multichannel spatial squeezing, along with its application to the improvement of beam positioning sensitivity and, more generally, to imaging.