Overcoming plasmonic loss to realize high performance telecommunication devices

非技术摘要：今天，光技术是我们信息社会的支柱，支持虚拟医疗咨询、访问存储在云中的数据以及大型数据中心的高能效高性能计算等有影响力的服务。由于光的优势，如多太比特带宽、千米低损耗传播和低串扰，光子解决方案特别适合实现这些服务。事实上，一些互联网提供商已经开始完全通过光(光纤)提供服务。因此，光子电信技术的进步将通过提高基于互联网的服务的性能、降低能源消耗以及降低网络建设/运营成本，对我国产生深远的影响。目前的光子调制器是将电信号转换为光脉冲的小开关，由于光和物质的弱相互作用，它们的速度受到限制。最近，金属被用来增强这种相互作用，促进了器件尺寸的减小和速度的提高。然而，这些设备很难实现10%的有效传输，这对于许多应用来说是远远不够的。在这里，我们希望利用这两种方法的优点，允许有损金属性质在需要时接合和脱开。这种方法限制了结构的损失，同时仍然保持了金属等离子体结构的好处。通过与国内大学现有的项目合作，这项研究将为当地高中生、教师和本科生提供途径，了解光技术对我们社会的影响，同时提供一个培训高技能劳动力的平台。技术摘要：尽管在基于光子和等离子体的方法领域进行了大量的研究，但还没有一种器件能够实现有效的综合性能(调制强度、插入损耗、能量消耗、尺寸和速度)。光子方法存在光-物质相互作用差的问题，需要限速谐振器和较长的相互作用长度，而等离子体方法还需要克服与其金属组件相关的巨大插入损失。该方案试图通过一种新的设计方法来解决这一难题，其中等离子体元件在断开(传输)状态下脱离以最小化插入损耗，而在接通状态下则在短距离内实现大调制。这是通过一组特别选择的氧化层实现的，这些氧化层在没有电偏置的情况下对光学模式表现为介电，但可以被调制到epsilon-近零状态(有效地利用等离子体性质)，以通过自由载流子积累和耗尽来实现有效的调制。结果表明，该方法能够设计出第一个综合性能良好的调制器：面积为3平方微米，消光比为1.5分贝，消光比为9分贝，功耗为12 fJ/bit，带宽为112 GHz。尽管它对集成系统有影响，但这种方法是通用的，也可能在相关领域找到应用，如超材料和传感器。此外，该装置的实现将表明等离子体系统不是损失的同义词，这种系统的好处(限制、增强的光-物质相互作用)可以在不造成有害损失的情况下使用。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non Technical Abstract:Today, optical technologies are the backbone of our information society, empowering impactful services such as virtual medical consultations, access to data stored in the cloud, and energy-efficient high-performance computing in largescale datacenters. Photonic solutions are particularly suited to enable these services due to the advantages of light such as multi-terabit bandwidths, low-loss propagation over kilometers, and low cross-talk. In fact, some internet provides have begun providing service entirely through light (fiber optics). As a result, the advancement of photonic telecommunications technologies will have a profound impact upon our nation by providing improved performance of internet-based services, reduced energy consumption, and a lower cost of construction/operation for networks. Current photonic modulators, small switches which convert electrical signals into optical pulses, are limited in their speed due to the weak interaction of light and matter. More recently, metals have been utilized to enhance this interaction, facilitating a reduction of device size and increase of speed. Yet, these devices struggle to achieve efficient transmission ~10%, which is simply insufficient for many applications. Here, we look utilize the benefits of both approaches by allowing the lossy metallic nature to be engaged and disengaged when desired. This approach limits the loss of the structure while still maintaining the benefits of metal plasmonic structures. By partnering with existing programs at the home university, the research will provide avenues for local high school students, teachers, and undergraduates to learn about impact of light-based technologies on our society while providing a platform to train a highly skilled workforce. Technical Abstract:Despite significant research in the areas of photonic and plasmonic-based approaches, there is yet to be a device which achieves efficient all-around performance (modulation strength, insertion loss, energy consumption, size, and speed). Photonic approaches suffer from poor light-matter interactions, requiring speed restricting resonators and long interaction lengths, while plasmonic approaches have yet to overcome the large insertion loss associated with their metallic components. This proposal seeks to solve this dilemma through a new design approach in which plasmonic elements are disengaged in the off- (transmissive) state to minimize insertion loss, yet are engaged in the on-state to achieve large modulation in a short distance. This is achieved through a specifically chosen set of oxide layers which appear dielectric to the optical mode under no electrical bias, yet can be modulated into an epsilon-near-zero condition (effectively engaging the plasmonic nature) to achieve efficient modulation through free-carrier accumulation and depletion. It is shown that this approach is able to produce the first modulator design capable of efficient all-around performance: area of 3 square microns, 1.5 dB, 9dB extinction ratio, 12 fJ/bit energy consumption, and 112 GHz bandwidth. Although it is impactful for integrated systems, the approach is general and may also find applications in related areas such as metamaterials and sensors. Additionally, the realization of the device will demonstrate that plasmonic systems are not synonymous with loss and the benefits of such systems (confinement, enhanced light-matter-interaction) can be employed without detrimental loss.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.