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This flat metalens is the first singlelens that can focus the entire visible spectrum of light -- including whitelight -- in the same spot and in high resolution. It uses arrays of titaniumdioxide nanofins to equally focus wavelengths of light and eliminate chromaticaberration.

这个扁平的超透镜（metalens）是第一个可以将包括白光在内的整个可见光谱，聚焦在同一点且具有高分辨率的单镜头。它用二氧化钛纳米薄膜阵列均匀的聚焦光的波长并消除色差。

Metalenses—flat surfaces that usenanostructures to focus light—promise to revolutionize optics by replacing thebulky, curved lenses currently used in optical devices with a simple, flatsurface. But, these metalenses have remained limited in the spectrum of lightthey can focus well. Now a team of researchers at the Harvard John A. PaulsonSchool of Engineering and Applied Sciences (SEAS) has developed the firstsingle lens that can focus the entire visible spectrum of light—including whitelight—in the same spot and in high resolution. This has only ever been achievedin conventional lenses by stacking multiple lenses.

超透镜（Metalenses）具有平坦表面，能利用纳米结构聚焦光线，通过用简单平坦的表面代替目前在光学器件中使用的庞大的弯曲透镜来保证光学革命。但是，超透镜（Metalenses）聚焦在特定光谱范围内保证精准聚焦。目前，哈佛大学John A. Paulson工程与应用科学学院（SEAS）的一个研究小组开发出了第一个单焦点镜头，它可以将同一光斑和高分辨率下的整个可见光谱（包括白光）聚焦。此前这只能通过堆叠多个透镜才能在传统的透镜中实现。

The research is published in NatureNanotechnology.

这项研究发表在Nature Nanotechnology上。

Focusing the entire visible spectrum andwhite light - combination of all the colors ofthe spectrum—is so challenging because each wavelength moves through materials at differentspeeds. Red wavelengths, for example, will move through glass faster than theblue, so the two colors will reach the same location at different timesresulting in different foci. This creates image distortions known as chromaticaberrations.

聚焦整个可见光谱和白光，也就是所有光谱颜色的组合，很具有挑战性，因为每个波长都以不同的速度穿过材料。例如，红色波长会比蓝色更快地通过玻璃，所以两种颜色将在不同的时间到达相同的位置，产生不同的焦点，而产生称为色差的图像失真。

Cameras and optical instruments usemultiple curved lenses of different thicknesses and materials to correct theseaberrations, which, of course, adds to the bulk of the device.

相机和光学仪器使用不同厚度和材料的多个曲面透镜来校正这些像差，这当然会增加装置的体积。

"Metalenses have advantages overtraditional lenses," says Federico Capasso, the Robert L. WallaceProfessor of Applied Physics and Vinton Hayes Senior Research Fellow inElectrical Engineering at SEAS and senior author of the research. "Metalensesare thin, easy to fabricate and cost effective. This breakthrough extends thoseadvantages across the whole visible range of light. This is the next bigstep."

应用物理学Robert L. Wallace教授、也是SEAS电机工程Vinton Hayes高级研究员，同时也是该研究的高级作者Federico Capasso说：“超透镜（Metalenses）比传统镜头具有优势。 “超透镜（Metalenses）较薄，易于制造，成本效益高，这一突破可以将这些优势延伸到整个可见光范围，是下一个重大步骤。

The Harvard Office of TechnologyDevelopment (OTD) has protected the intellectual property relating to thisproject and is exploring commercialization opportunities.

哈佛大学技术开发办公室（OTD）已经保护了与这个项目有关的知识产权，并且正在探索商业化的机会。

The metalenses developed by Capasso andhis team use arrays of titanium dioxide nanofins to equally focus wavelengthsof light and eliminate chromatic aberration. Previous research demonstratedthat different wavelengths of light could be focused but at different distancesby optimizing the shape, width, distance, and height of the nanofins. In thislatest design, the researchers created units of paired nanofins that controlthe speed of different wavelengths of light simultaneously. The paired nanofinscontrol the refractive index on the metasurface and are tuned to result indifferent time delays for the light passing through different fins, ensuringthat all wavelengths reach the focal spot at the same time.

Capasso和他的团队开发的超透镜（Metalenses）使用二氧化钛纳米薄膜阵列均匀聚焦光的波长并消除色差。先前的研究表明，通过优化纳米薄膜的形状，宽度，距离和高度，不同波长的光能被聚焦，但距离不同。在这个最新的设计中，研究人员创造了成对纳米薄膜的单位，同时控制不同波长的光的速度。成对的纳米薄膜扼制器控制着变换面上的折射率，并且为光线穿过不同膜片产生不同时间延迟，从而确保所有波长同时到达焦点。

"One of the biggest challenges indesigning an achromatic broadband lens is making sure that the outgoingwavelengths from all the different points of the metalens arrive at the focalpoint at the same time," said Wei Ting Chen, a postdoctoral fellow at SEASand first author of the paper. "By combining two nanofins into oneelement, we can tune the speed of light in the nanostructured material, toensure that all wavelengths in the visible are focused in the same spot, usinga single metalens. This dramatically reduces thickness and design complexitycompared to composite standard achromatic lenses."

“在设计消色差宽带透镜方面面临的最大的挑战之一就是要确保超透镜（Metalenses）所有不同点的输出波长同时到达焦点，”SEAS的博士后研究员也是论文的第一作者Wei Ting Chen说， “通过将两个纳米薄膜结合到一个元件中，我们可以调整纳米结构材料中的光速，以确保可见光中的所有波长都聚焦在同一个点上，和合成的标准消色差镜片相比，使用一个超透镜（Metalenses）大大减少了厚度和设计复杂度。”

"Using our achromatic lens, we areable to perform high quality, white light imaging. This brings us one stepcloser to the goal of incorporating them into common opticaldevices such as cameras," said Alexander Zhu, co-author of the study.

这项研究的作者之一亚历山大·朱（Alexander Zhu）说：“使用我们的消色差透镜，我们可以生成高质量的白光成像，这使我们更加接近将它们整合到相机等常见光学设备中的目标。”

Next, the researchers aim to scale up thelens, to about 1 cm in diameter. This would open a whole host of newpossibilities, such as applications in virtual and augmented reality.

下一步，研究人员的目标是放大镜头到直径约1厘米。这将打开一系列新的可能性，例如在虚拟和增强现实中的应用。

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