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

拟议的项目旨在将太赫兹频段的高频天线技术从100 GHz提高到4000 GHz。这项拟议的研究将使用新材料、设计和制造工具来制造先进和更高效的太赫兹天线。预期中的新天线将能够提供更大的辐射功率，这将促进几个对社会具有重要意义的应用，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，乳腺癌的边缘在临床上仍然有限。新的天线将为探测爆炸物、非金属武器和可能隐藏在衣服中的毒品提供强大的天线，从而潜在地影响国土安全。拟议中的太赫兹天线还可能影响未来的5G无线通信系统，在未来的5G无线通信系统中，天线的工作频率超过100 GHz，以支持大量应用的更高数据需求。在教育方面，拟议中的研究将提供独特的培训机会，培养下一代领先的科学家和工程师，包括少数族裔和第一代大学生。将根据拟议研究中涉及的几项科学努力，开发互动式实验室演示。此外，天线教育的外联活动将参与该项目，目标是针对学区和其他教育项目，服务于阿肯色州代表不足的学生和少数族裔学生。太赫兹(THz)光导天线(PCA)是一种能够发射频率高达6 THz的宽带脉冲的器件，但从泵浦激光到太赫兹发射的低功率转换效率是主要挑战。拟议的研究旨在通过用覆盖着无损耗纳米球的薄层黑磷(BP)作为捕光层来取代低温砷化镓(GaAs)半导体来促进这一技术的发展。其目标是将辐射太赫兹的平均功率提高到传统主成分分析技术的10倍，将带宽提高2倍。第一个任务是利用具有强光吸收和高饱和速度的薄多层半导体BP来制作和建模PCA。这种新材料具有增加器件中载流子产生的潜力，目前还没有在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，以提供比损耗等离子体元件所达到的性能更高的性能。这个想法是为了避免金属层中的寄生吸收或反射，方法是使用透明的介电结构，通过消失波或其他光子波导将光传输到薄层中。第三项任务是测量所制造器件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比较。测量将在太赫兹时域光谱学系统上进行，其中发射器是建议的设备，而探测器和系统的其余部分将从商业系统获得。这项任务还将测试开发的BP-PCA设备在未来转化为商业系统的情况。研究成果将在存档论文和会议报告中传播。这一奖项反映了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。

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.