Beaming light from a subwavelength aperture

Light usually diffracts in all directions when it emerges from a subwavelength aperture, which puts a lower limit on the size of features that can be used in photonics. This limitation can be overcome by creating a periodic texture on the exit side of a single aperture in a metal film. The transmitted light emerges from the aperture as a beam with a small angular divergence (approximately +/-3 degrees ) whose directionality can be controlled. This finding is especially surprising, considering that the radiating region is mainly confined to an area with lateral dimensions comparable to the wavelength of the light. The device occupies no more than one cubic micrometer and, when combined with enhanced transmission, suggests that a wide range of photonic applications is possible.     

Transformation optics using graphene

Metamaterials and transformation optics play substantial roles in various branches of optical science and engineering by providing schemes to tailor electromagnetic fields into desired spatial patterns. We report a theoretical study showing that by designing and manipulating spatially inhomogeneous, nonuniform conductivity patterns across a flake of graphene, one can have this material as a one-atom-thick platform for infrared metamaterials and transformation optical devices. Varying the graphene chemical potential by using static electric field yields a way to tune the graphene conductivity in the terahertz and infrared frequencies. Such degree of freedom provides the prospect of having different "patches" with different conductivities on a single flake of graphene. Numerous photonic functions and metamaterial concepts can be expected to follow from such a platform.     

Active optics, adaptive optics, and laser guide stars

Optical astronomy is crucial to our understanding of the universe, but the capabilities of ground-based telescopes are severely limited by the effects of telescope errors and of the atmosphere on the passage of light. Recently, it has become possible to construct inbuilt corrective devices that can compensate for both types of degradations as observations are conducted. For full use of the newly emerged class of 8-meter telescopes, such active corrective capabilities, known as active and adaptive optics, are essential. Some physical limitations in the adaptive optics field can be overcome by artificially created reference stars, called laser guide stars. These new technologies have lately been applied with success to some medium and very large telescopes.     

黄色灯对金纹细蛾的防治作用

通过田间调查,研究了黄色灯对苹果园金纹细蛾发生量的影响。结果表明,黄色灯对金纹细蛾的种群数量有一定的控制作用,其相对防效在50%以上。因此,该方法与其他害虫防治措施相结合,可以更好地减少虫害的发生。     

氯吡嘧磺隆对番茄田间杂草的控制效果

为明确75％氯吡嘧磺隆水分散粒剂对番茄田间杂草管理的重要性,采用田间试验和仪器测定分析的方法,观察了药剂对番茄田间主要杂草的控制效果、杂草防除后田间的透光率和施药后番茄产量的影响.结果表明:施用75％氯吡嘧磺隆水分散粒剂能有效控制番茄田间主要阔叶杂草和莎草科杂草的危害;药剂处理后对番茄田间香附子、野苋菜、马松子、铁苋菜...     

水稻轻型栽培地区三化螟发生特点及防治对策

1997年法国提出干浸膏指标是含24%的银杏黄酮糖甙和6%的银杏萜类物质,仅明示了萜类总量;1998年时提出含黄酮糖甙24%,萜类6%,其中银杏内酯3.1%,白果内酯2.9%,进一步突出了萜类主要成分银杏内酯与白果内酯间的比例与含量,使我国的干浸膏及其制剂难以达标.因此,必须依靠科技支撑,如突破现有"乙醇热提"大孔树脂吸附工艺、提取设备及关键技术,加大创新力度,尽快和国际动态质量标准及规范接轨,以增强产品竞争能力[6].     

Phonon optics and phonon propagation in semiconductors

Recent experiments involving the propagation of extremely high frequency, short-wavelength acoustic phonons in semiconductors are described. Such phonons, which play an important role in thermal energy transpor and nonradiative recombination processes, can be used as sensitive microscopic probes of electronic, defect, and interface states. Experiments on phonon transmission thrugh epitaxially grown bulk material as well as thin-film superlattice structures in the semiconductor gallium arsenide are described. Such thin-film periodic structures can be used to build frequency-selective phonon filters and reflectors, which can in turn be used to manipulate phonon diagnostic beams in technologically important materials.     

Scenes from a marriage--of optics and electronics

BALTIMORE-Exploring the common ground between optics and electronics, more than 6800 physicists, spectroscopists, and engineers gathered here from 21 to 26 May at the joint meetings of the Conference on Lasers and Electro-Optics and the Quantum Electronics and Laser Science conference. Participants unveiled new technologies that have sprung up on this common ground, such as an imaging technique that can gauge the chemical composition of materials. They also described ways to broaden that ground, such as a novel approach for integrating lasers and silicon chips-a challenge that has slowed progress toward a new generation of high-speed computers and communications.     

水稻轻型栽培田杂草发生规律及防除技术

在对肥床旱育秧田、抛秧田、水直播田、麦套稻田杂草发生的种类、数量发生特点进行了调查,掌握了轻型栽培制度下水稻田杂草的发生规律的基础上,进行了田间药剂对杂草的防除效果比较试验,选择出各类田块最佳防除药剂,制定了相应的防除措施。     

Direct interaction of Arabidopsis cryptochromes with COP1 in light control development

Arabidopsis seedling photomorphogenesis involves two antagonistically acting components, COP1 and HY5. COP1 specifically targets HY5 for degradation via the 26S proteasome in the dark through their direct physical interaction. Little is known regarding how light signals perceived by photoreceptors are transduced to regulate COP1. Arabidopsis has two related cryptochromes (cry1 and cry2) mediating various blue/ultraviolet-A light responses. Here we show that both photoactivated cryptochromes repress COP1 activity through a direct protein-protein contact and that this direct regulation is primarily responsible for the cryptochrome-mediated blue light regulation of seedling photomorphogenic development and genome expression profile.