Room temperature high-power terahertz semiconductor laser with high-quality beam shape and stable spectral emission

该项目寻求开发紧凑型和高功率太赫兹光源，以缩小微波和光学设备之间的重要技术差距。这是电子学和光学之间的过渡领域，也是经典力学和量子物理之间的过渡领域。太赫兹波在电磁频谱中的特定位置也赋予了它们过多的独特性质。例如，太赫兹波可以穿透各种物质，包括合成材料、纺织品、纸张和纸板。此外，许多生物分子、蛋白质、炸药或毒品在1至5太赫兹的频率上具有特征吸收特征。因此，太赫兹辐射的两个主要应用是成像、传感和光谱。此外，与X射线不同，太赫兹波没有任何电离效应，通常被认为在生物上是无害的。这使得太赫兹波在用于安全检查和医疗诊断时比X射线更安全、更健康。此外，由于太赫兹频率比用于传统无线互联网的频率高出几个数量级，因此有可能将太赫兹技术应用于下一代高速无线通信。不幸的是，目前商用的太赫兹辐射源要么非常大，要么需要低温冷却，这两种特性都不是广泛使用的理想特征。通过集成量子器件工程、非线性光学、光学相控阵和光子集成电路技术，现在有可能实现紧凑、大规模生产、室温下连续工作的高输出功率太赫兹光源。该光源将为上述所有应用提供一种使能技术。建议的太赫兹频率源基于双波长量子级联激光器(QCL)中的差频产生(DFG)，该激光器已配置为光学相控阵(OPA)，用于相干、高功率运行。OPA的用途是既管理废热，又为太赫兹发射提供接近衍射限制的光束质量。在适当的热管理和封装下，这将是第一个室温下输出功率为1 mW连续太赫兹的基于芯片的半导体激光器。这种类型的太赫兹光源继承了中红外QCL的所有优点，如室温工作、电抽运、体积紧凑、发射稳定，并具有大规模生产的潜力。这个多学科的项目是理论和实验的结合，涵盖了不同的领域，包括半导体物理、材料科学、量子力学、光电子学、非线性光学、热管理和微/纳米技术。除了将开发的技术的实际应用外，项目细节也是集成设备开发的优秀案例研究，将作为西北大学固态工程课程的一部分进行探索。该奖项反映了NSF的法定使命，并已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。

This project seeks to develop compact and high power THz sources in order to close an important gap in technology between microwave and optical devices. This is a transition area between electronics and optics as well as a transition area between classical mechanics and quantum physics. The specific location of THz waves in the electromagnetic spectrum also gives them a plethora of unique properties. For an example, THz waves can pass through a variety of substances, including synthetics, textiles, paper, and cardboard. Also, many biomolecules, proteins, explosives or narcotics feature characteristic absorption signatures at the frequencies between 1 and 5 THz. Therefore, two major applications of THz radiation are imaging, sensing and spectroscopy. Besides, unlike X-rays, THz waves do not have any ionizing effects and are generally considered biologically innocuous. This makes THz waves much safer and healthier than X-rays when used for security checks and medical diagnosis. In addition, as the THz frequency is orders of magnitude higher than tht used for traditional wireless internet, there is the potential to apply THz technology for the next-generation of high-speed wireless communications. Unfortunately, current commercial sources of THz radiation are either extremely large or require cryogenic cooling, neither of which are desirable traits for widespread use. By integrating quantum device engineering, nonlinear optics, optical phased arrays, and photonic integrated circuit technology, it may now be possible to realize a compact, mass-producible, and room temperature THz source with high output power in continuous operation. This source will represent an enabling technology for all of the applications mentioned above.The proposed THz frequency source is based on difference frequency generation (DFG) in a dual-wavelength quantum cascade laser (QCL) that has been configured as an optical phased array (OPA) for coherent, high power operation. The utility of the OPA is to both manage waste heat and provide near diffraction limited beam quality for THz emission. With proper heat management and packaging, this will be the first room chip-based semiconductor laser with 1 mW CW THz output power at room temperature. This type of THz source inherits all of the advantages of the mid-infrared QCLs, such as room temperature operation, electrical pumping, compact size, stable emission, and the potential for mass production. This multidisciplinary project is a combination of both theory and experiment covering diverse fields, including semiconductor physics, material science, quantum mechanics, optoelectronics, nonlinear optics, thermal management, and micro/nanotechnology. In additional to the practical use of the technology that will be developed, project details also make an excellent case study for integrated device development, which will be explored as part of the Solid State Engineering curriculum at Northwestern University.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.