经济学人下载:光的种子(1)

"Lens" is the Latin word for lentil. And it is indeed true that the shape of biconvex lenses—
“Lens”是拉丁词小扁豆的意思。双凸透镜的形状确实如此—

the familiar sort used as magnifying glasses—resembles those leguminous seeds.
放大镜常用的一种镜片—它们和那些豆科种子很相似。

But that resemblance may soon be a thing of the past.
但这种相似性可能很快就会成为过去。

For a group of engineers at Columbia University, in New York, led by Nanfang Yu,
因为纽约哥伦比亚大学一支由虞南方带领的团队

has worked out how to make magnifying lenses that are flat, and thinner than a hair.
发明了一种平的、比头发还细的放大透镜。

A lens works by slowing down a light wave as it traverses one of the lens's faces
这种透镜的工作原理是当光波穿过透镜的一面时，使其速度慢下来

(the speed of light in glass is about two-thirds of that in air).
（玻璃中的光速大约是空气中的三分之二）。

Slowing a wave changes its direction, a process called refraction.
放慢光波改变了其方向，这个过程被称为折射。

The angle through which it is refracted depends on its angle of incidence to the refracting surface—
它被折射的角度取决于它与折射表面的入射角—

an angle that, on a curved surface, varies continuously. When the light leaves the lens it picks up speed again,
这是一种在曲面上连续变化的角。当光离开透镜时，它又加快速度，

and thus goes through a second refraction. The trick of the lensmaker's art is to grind the two surfaces into such shapes
然后经过第二次折射。制镜师的技巧是把两个表面磨成这样的形状，

that the sum of all this refraction brings the light passing through the lens to a focus.
让所有这些折射的总和带着穿过透镜的光线聚焦在一起。

Dr Yu's flat lens achieves a similar result in a different way.
虞博士的平面透镜以一种不同的方式获得了类似的结果。

Instead of holding the change of speed constant while varying the angle of incidence,
新透镜没有在改变入射角的同时保持速率常数不变

the new lens holds the angle of incidence constant while varying the amount that the speed changes on different parts of the lens.
而是在改变透镜不同部位的速度变化量的同时，保持入射角常数。

It can do this because its surface is covered with millions of tiny antennae.
透镜能做到这一点是因为它的表面覆盖着数百万个微小的天线。

These antennae are of different designs, each with a cross section smaller than the average wavelength of the light it is interacting with,
这些天线的设计各不相同，每一个的横截面都一个小于与之相互作用的光的平均波长，

and are arranged in concentric circles. The antennae scatter the light falling on them in such a way that,
并且呈同心圆排列。天线将落在自己身上的光散开，

when the individual changes are added up,
当个体变化叠加时，

the combined effect is the same as if different parts of the beam had passed through the lens at different speeds.
这种组合效果就像光线的不同部分以不同的速度穿过透镜一样。

Dr Yu is not the first person to make a lens in this way, but previous efforts worked only with single colours,
虞博士不是用这种方式制作透镜的第一人，但之前的努力只适用于单一颜色，

and also required the light to be polarised. Dr Yu's lens works with all colours and in natural light, which is unpolarised.
并且还需要对光线进行极化。虞博士的透镜适用于所有颜色并在在没有极化的自然光线也能工作。