Topological Photodetectors

光电探测器是探测光的存在的设备，是光谱学、成像、诊断和驱动我们的信息技术基础设施的非常重要的组件。传统的光电探测器检测光功率，即将照射在有源区上的光子总数转换为相应的电流。因此，大多数涉及光的应用利用强度来加密或解密信息，即通过调制不同波长的光的强度来编码信息并对探测器端的光子总数进行计数。然而，光也可以被改造成携带更多的信息，编码在它的相位和电场振荡的方向上。涡旋光是一种复杂类型的光，它可以用来携带比传统光束更多的信息。然而，对于片上应用来说，检测和区分不同类型的涡旋光束并不容易。在这个项目中，将探索新型量子材料以及专门设计的装置，以组装芯片上的光电探测器，该探测器将根据光涡的性质和类型产生不同的电流。与传统系统相比，这些新型光电探测器可以利用更多的光自由度来增加光学系统的信息承载能力，从而使我们能够继续满足对设备处理更多信息的日益增长的需求。研究和教育活动将通过本科生参与研究计划，将最新研究成果纳入教学模块，并培训来自费城地区的高中和大学教师，学生人口来自少数族裔和代表性较低的地区。将开发出在室温下工作的对拓扑(涡旋)光的不同自旋(SAM)和轨道角动量(OAM)状态敏感的片内拓扑光电探测器。这些拓扑型光电探测器可以实现仍然主要依赖光学功率的光学系统的信息承载能力的非线性缩放。从根本上讲，这些研究将为通过对称性和几何概念理解和设计量子拓扑材料中新颖的光电响应铺平道路。该项目将扩展这些想法，以设计具有增强功能的下一代光电探测器，以取代目前用于传感OAM光模式的笨重的桌面光学装置。为了开发片上拓扑光电探测器，将探索对复杂相位和OAM模的强度分布以及对光子自旋(偏振)敏感的光响应材料。大多数材料既不对光偏振敏感，也不对光束的空间或相位梯度敏感，这使得这项任务具有挑战性。为此，拓扑Weyl半金属由于其独特的对称性可以支持OAM-SAM敏感和室温下强烈的非局域光响应而被研究。通过使用人工神经网络算法，这些设备将被训练为读取高保真的OAM-SAM模式，用于成像、光谱和集成系统中的应用，以处理更大的带宽信息。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。

Photodetectors are devices which detect the presence of light and are very important components for applications in spectroscopy, imaging, diagnostics and for driving our information technology infrastructure. Conventional photodetectors detect optical power, i.e., convert the total number of photons impinging on the active area into a corresponding current. Therefore, most applications involving light utilize intensity to encrypt or decrypt information, i.e., by modulating the intensity of light at different wavelengths to encode information and counting the total number of photons at the detector end. However, light can also be engineered to carry much more information encoded in its phase and the direction of the oscillation of electric field. Vortex light is an example of a complex type of light which can be used to carry much more information that conventional light beams. However, it is not easy to detect and distinguish different types of vortex beams for on-chip applications. In this project, new types of quantum materials will be explored along with specially designed devices to assemble on-chip photodetectors that will produce different currents depending on the nature and type of light vortices. These new types of photodetectors can increase the information carrying capacity of our optical systems by utilizing more degrees of freedom of light than conventional systems that can enable us to continue to meet the ever-increasing demands on our devices to process more information. Research and educational activities will be integrated by the involvement of undergraduates in the research program, incorporating latest research results in the teaching modules, and training high school and college teachers from the Philadelphia district with student population from minority and underrepresented sections.On-chip topological photodetectors working at room temperature that are sensitive to different spin (SAM) and orbital angular momentum (OAM) states of topological (vortex) light will be developed. These topological photodetectors can enable a nonlinear scaling of information carrying capacity of optical systems that still mostly rely on optical power. At a fundamental level, the proposed studies will pave the way to understanding and engineering novel optoelectronic response in quantum topological materials via symmetry and geometry concepts. The project will extend these ideas to design the next generation of photodetectors with enhanced functionalities to replace bulky table-top optics currently used for sensing OAM modes of light. To develop on-chip topological photodetectors, materials that have a photoresponse sensitive to complex phase and intensity distribution of the OAM modes along with sensitivity to photon spin (polarization) will be explored. Most materials are neither sensitive to optical polarization nor the spatial or phase gradients of the optical beam, which makes this task challenging. For this purpose, topological Weyl semimetals will be studied due to their unique symmetry that can support OAM-SAM sensitive and strong nonlocal photoresponse at room temperature. By utilizing artificial neural network algorithms, these devices will then be trained to read out the OAM-SAM modes with high fidelity for applications in imaging, spectroscopy, and integrated systems for processing much larger bandwidth information.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.