Terahertz Electro-Optics in Semiconductor Nanostructures

该研究项目探索了半导体器件的基本物理，制造和材料科学，这些器件可以在太赫兹（10^12Hz）频率下调制光。 感兴趣的是这些设备的响应，同时照明与强电场在太赫兹频率加上弱近红外（NIR）辐射。 先前的工作已经表明，在NIR频率加上THz频率的倍数处存在NIR辐射的尖锐且窄的边带。 所提出的实验将确定边带生成过程的效率。 边带的产生将在包含嵌入电磁环境中的单半导体量子威尔斯的设备中进行研究，该电磁环境被设计为最大化它们与NIR辐射的耦合。 其他研究将试图制造半导体器件，调制近红外辐射在光纤通信波段近1.5微米波长，而不是在0.8微米波段，以前已经研究。 最后，研究了电子掺杂量子威尔斯阱的太赫兹电光特性。 以前的实验使用未掺杂的样品。 这项工作将测试由强THz辐射驱动的掺杂量子阱可以表现出分叉和混沌等非线性现象的预测。 首次研究了掺杂量子威尔斯阱中边带的产生，以寻找新的量子非线性现象。 参加该研究项目的学生将接受非常广泛的培训，其中包括半导体器件制造，近红外和太赫兹频率的光学，低温学和电子学。 这为学术界，政府或行业的职业生涯提供了强大的背景。太赫兹（10^12 Hz）正在成为信息技术的自然频率标度。 单根光纤每秒可以传输40太比特（Tbit）波长接近1.5微米的光。 光纤通信的40太赫兹（THz）带宽已经被分成大约5 THz宽的光放大器频带和目前间隔为0.1 THz的信道。 然而，对于电子产品，自然频率标度仍然是GHz（10^9 Hz），这是典型的现代个人计算机的时钟速度。 电子学和光子学速度之间的不匹配是信息技术的主要瓶颈。 技术的发展使电信公司能够经济地利用地下光纤的巨大带宽，这将使整个经济中的企业和个人受益。 根据这项资助进行的研究探索了能够在太赫兹频率下调制光的半导体器件的基础物理，制造和材料科学。 除了它们在光通信领域的可取性之外，半导体太赫兹电光器件在量子力学、强驱动、多体物理和耗散的影响都很重要的情况下工作。 这一机制是凝聚态物理学的前沿领域之一。 参加该研究项目的学生将接受非常广泛的培训，包括半导体器件制造，近红外和太赫兹频率的光学，低温学和电子学。 这为学术界，政府或行业的职业生涯提供了强大的背景。

The research project explores the basic physics, fabrication, and materials science of semiconductor devices that can modulate light at TeraHertz (10^12Hz) frequencies. Of interest is response of these devices to simultaneous illumination with intense electric fields at a THz frequency plus weak near-infrared (NIR) radiation. Previous work has shown the presence of sharp and narrow sidebands of the NIR radiation at the NIR frequency plus multiples of the THz frequency. The proposed experiments will determine the efficiency of the side-band generation process. Side-band generation will be studied in devices that contain single semiconductor quantum wells embedded in an electromagnetic environment engineered to maximize their coupling to NIR radiation. Other research will attempt to fabricate semiconductor devices that modulate NIR radiation in the fiber-optic communications band near 1.5 microns wavelength, rather than in the 0.8 micron band that has been previously studied. Finally, the THz electro-optic properties of quantum wells doped with electrons will be studied. Previous experiments have used undoped samples. The work will test predictions that a doped quantum well driven by strong THz radiation can exhibit nonlinear phenomena like bifurcations and chaos. Sideband generation in doped quantum wells will be studied for the first time, to search for new quantum nonlinear phenomena. Students participating in this research program emerge with a very broad training, which includes semiconductor device fabrication, optics at near infrared and THz frequencies, cryogenics and electronics. This provides a strong background for careers in academia, government or industry. The Terahertz (10^12 Hz) is emerging as a natural frequency scale for information technology. A single optical fiber has the capacity to carry 40 Terabits (TBit) per second on light with wavelengths near 1.5 microns. The 40 Terahertz (THz) bandwidth of fiber optic communications has been divided into optical amplifier bands roughly 5 THz wide, and into channels whose spacing is currently 0.1 THz. However, for electronics, the natural frequency scale is still the GHz (10^9 Hz), the clock speed of a typical modern personal computer. The mismatch between the speed of electronics and photonics is a major bottleneck in information technology. The development of technology to allow telecommunications companies to economically utilize the enormous bandwidth of optical fibers already in the ground would benefit businesses and individuals throughout the economy. The research conducted under this grant explores the basic physics, fabrication, and materials science of semiconductor devices that are able to modulate light at THz frequencies. In addition to their desirability in the field of optical communications, semiconducting THz electro-optic devices operate in a regime where the effects of quantum mechanics, strong driving, many-body physics, and dissipation are all important. This regime is one of the frontiers of condensed matter physics. Students participating in this research program emerge with a very broad training which includes semiconductor device fabrication, optics at near-infrared and THz frequencies, cryogenics and electronics. This provides a strong background for careers in academia, government or industry.