Efficient THz Emission Using Thin Black Phosphorus Photoconductive Absorber and Loss-free Dielectric Light Trapping

拟议项目旨在推进100 GHz至4000 GHz太赫兹波段高频天线技术。拟议的研究将使用新材料、设计和制造工具来提供先进和更高效的太赫兹天线。预期的新天线将能够提供更高的辐射功率，这将推动对社会具有重要意义的几个应用，如癌症检测，国土安全，通信和教育。新的太赫兹天线可能会推进乳腺癌肿瘤边缘的成像，由于太赫兹天线缺乏足够的辐射功率，乳腺癌肿瘤边缘的成像在临床上仍然有限。新天线将通过提供强大的天线来检测可能隐藏在衣服中的爆炸物，非金属武器和毒品，从而可能影响国土安全。拟议中的太赫兹天线也可能影响未来的5G无线通信系统，其中天线预计将在高于100 GHz的频率下工作，以支持大量应用的更高数据需求。在教育方面，拟议的研究将提供独特的培训机会，为下一代领先的科学家和工程师做好准备，包括少数民族和第一代大学生。将根据拟议研究中涉及的多项科学工作开发交互式实验室演示。此外，天线教育的推广活动将参与该项目的目标学区和其他教育方案，为代表性不足和少数民族学生在阿肯色州。 太赫兹（THz）光电导天线（PCA）是具有发射宽带脉冲的吸引人的能力的设备，该宽带脉冲提供高达6 THz的频率，但是遭受从泵浦激光到太赫兹发射的低功率转换效率的主要挑战。拟议的研究旨在通过将低温砷化镓（GaAs）半导体替换为覆盖有无损耗纳米球的黑磷（BP）薄层来推进这项技术。我们的目标是增加辐射的太赫兹平均功率的一个因素的十倍和带宽的一个因素的两个传统的PCA技术。第一个任务是利用薄的多层半导体BP来制造和建模PCA，该半导体BP具有强的光吸收性并且具有高的饱和速度。这种新材料具有增加器件中载流子产生的潜力，并且尚未在THz薄膜发射器中进行研究。第二个任务是结合低损耗介电纳米光子结构，以提供超出有损等离子体元件所实现的性能提升。该想法是通过使用透明电介质结构来设计经由倏逝波或其他光子波导将光传输到薄层中来避免金属层中的寄生吸收或反射。第三个任务是测量制造设备的宽带太赫兹发射光谱，通过建模迭代优化其性能，并将新平台与传统技术进行基准测试。测量将在THz时域光谱系统上进行，其中发射器是拟议的设备，而检测器和系统的其余部分将从商业系统中获得。这项任务还将测试开发的BP-PCA设备在未来进入商业系统的转移。该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

The proposed project aims at advancing the technology of antennas at high frequencies in the terahertz band from 100 GHz to 4000 GHz. The proposed research will use new materials, design and fabrication tools to deliver advanced and more efficient terahertz antennas. The anticipated new antennas will be capable of providing increased radiated power that will advance several applications of significant importance to society, such as cancer detection, homeland security, communications, and education. The new terahertz antennas will likely advance the imaging of breast cancer tumor margins that remains clinically limited due to the lack of adequate radiated power from terahertz antennas. The new antennas will potentially impact homeland security by providing powerful antennas for the detection of explosives, non-metallic weapons, and drugs that could be hidden in clothing. The proposed terahertz antennas will also likely impact future 5G wireless communications systems where antennas are envisioned to operate at frequencies greater than 100 GHz to support higher data demands from a vast number of applications. For education, the proposed research will offer unique training opportunities to prepare the next generation of leading scientists and engineers, including minority and first-generation college students. Interactive laboratory demonstrations will be developed based on several scientific efforts involved in the proposed research. Furthermore, outreach activities on antenna education will be engaged in the project to target school districts and other educational programs serving underrepresented and minority students in Arkansas. Terahertz (THz) photoconductive antennas (PCAs) are devices with the attractive capability to emit broadband pulses that provide frequencies up to 6 THz but suffer a primary challenge of low power conversion efficiency of 10-5 from pump laser to terahertz emission. The proposed research aims at advancing this technology by replacing the low temperature gallium arsenide (GaAs) semiconductor with thin layer of black phosphorus (BP) covered with loss-free nanospheres acting as a light trapping layer. The goal is to increase the radiated terahertz average power by a factor of ten and bandwidth by a factor of two over the conventional PCA technology. The first task is to fabricate and model PCAs utilizing the thin multi-layered semiconductor BP, which is strongly light absorbing and has a high saturation velocity. This new material has a potential to increase the carrier generation in the device and has not been investigated in THz thin film emitters yet. The second task is to incorporate low-loss dielectric nanophotonic structures to provide a performance boost beyond what has been achieved with lossy plasmonic elements. The idea is to avoid parasitic absorption or reflection in metallic layers by using transparent dielectric structures to engineer light transport into thin layers via evanescent waves or other photonic waveguiding. The third task is to measure the broadband terahertz emission spectrum of the fabricated devices, iteratively optimize their performance through modeling, and benchmark the new platform against conventional technologies. The measurements will be conducted on a THz time-domain spectroscopy system in which the emitter is the proposed device while the detector and the rest of the system will be obtained from a commercial system. This task will also test the transfer of the developed BP-PCA device into commercial systems in the future. The research results will be disseminated in archived papers and conference presentations.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.