美研究人员实现纳米级硅波导开启硅光通讯时代

美国能源部旗下的劳伦斯伯克利国家实验室(Lawrence Berkeley National Laboratory)近日宣布研发出全球首创的，可实现芯片上光通讯的“真正纳米级”硅波导(silicon waveguide)。

劳伦斯伯克利实验室藉由新研发的一种称为“混合等离极化激元(hybrid plasmon polariton，HPP)”的准粒子(quasi-particle)，解除了前人尝试开发硅光子元件的新运作模式、以最佳化光子与等离子系统之路途上所遭遇的光学损失(optical losses)障碍。

该实验室采用的方法，结合了高量子局限(quantum confinement)与低讯耗损失，也为实现纳米等级的芯片上激光(on-chip lasers)、量子运算以及单光子全光学开关(single -photon all-optical switches)等技术开启一扇门。

创造以上研究成果的，是劳伦斯伯克利实验室材料科学部门研究员暨美国加州大学伯克利分校的纳米科学与工程中心总监Xiang Zhang；共同参与的还包括博士研究生Volker Sorger与Ziliang Ye。他们表示，HPP将为支持芯片内光通讯、信号调制，以及芯片上激光、生物医疗传感等应用的纳米级波导，开启一个新时代。

被称为表面等离极化激元(surface plasmon polaritons，SPPs)的准粒子，是已知可用在将光波导向横跨金属表面，以产生表面电子波──也就是等离子(plasmons)──然后能与光子产生交互作用。但遗憾的是，SPP在传导通过金属时，会遭遇严重的信号损失。

伯克利实验室的研究人员解决以上问题的方法，是在金属与光波导半导体元件之间，添加了一层低K电介质(low-k dielectric)层，形成一种金属氧化物半导体架构，能将导入的光波重分配(redistributes)到光学损失较少的低K电介质间隙中。

劳伦斯伯克利实验室研究团队成员

采用上述方法所产出的HPP，能以更自由的方式进行传导，让工程师能以标准CMOS芯片打造出光学特性媲美罕见三五族半导体化合物的纳米级波导。研究人员估计，这种新技术在2~5年内就可推向商业市场。

点击参考原文：Nanoscale waveguide lifts silicon photonics

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Nanoscale waveguide lifts silicon photonics

R. Colin Johnson

The world's first "truly nanoscale" silicon waveguide for integrated on-chip optical communications was recently claimed by the U.S. Department of Energy's Lawrence Berkeley National Laboratory. Based on its invention of a new type of quasi-particle called a hybrid plasmon polariton, Berkeley Lab's HPP sidesteps optical losses plaguing earlier attempts at silicon photonics with a new operating mode that makes the best of photonic and plasmonic systems—combining high quantum confinement with low signal loss, thus opening the door to the nanoscale on-chip lasers, quantum computing, and single-photon all-optical switches.

Created in the lab of Xiang Zhang, principal investigator with Berkeley Lab’s Materials Sciences Division and director of the University of California at Berkeley’s Nano-scale Science and Engineering Center, the breakthrough was also facilitated by doctoral candidates Volker Sorger and Ziliang Ye, who claim that HPPs will enable a new era of nanoscale waveguides for intra-chip optical communication, signal modulation, on-chip lasers and bio-medical sensing.

Quasi-particles called surface plasmon polaritons (SPPs) were already known to be created by directing waves of light across a metal surface to generate electronic surface waves—called plasmons—that then interact with photons. Unfortunately, SPPs suffer significant signal losses when propagating through metal. The Berkeley Lab researchers solved this problem by adding a low-k dielectric layer between the metal and the semiconductor to form a metal-oxide-semiconductor architecture that redistributes incoming light waves into the low dielectric gap where optical losses are less.

3-D image overlap of the deep sub-wavelength HPP mode signal (red spot) that indicates the waveguide's potential to create strong light-matter-interaction for compact and highly functional photonic components. (Photo courtesy of Zhang group).

The resulting HPPs propagate more freely, providing designers with a best-of-both-world's scenario where nanoscale waveguides can be cast on standard CMOS chips with optical properties rivaling exotic III-V compounds. The researchers estimate that it will take two to five years to commercialize the technique.

Funding for the project was provided by the National Science Foundation’s Nano-Scale Science and Engineering Center.