Acquisition of a Magneto-Optical Cryostat for Terahertz Studies of Semiconductor Heterostructures

这项主要研究仪器RUI拨款支持超快光学和半导体物理研究仪器以及马卡莱斯特学院的本科生研究培训。该仪器是一个具有光学接入的7 Tessa超导磁体低温恒温器。最初的研究将使用该仪器来支持一个由nsf资助的项目，研究半导体中的自旋和电荷动力学。项目包括半导体自旋动力学的超快太赫兹光谱；半导体中磁等离子体振荡的时间分辨测量强驱动半导体量子阱和异质结构中的量子跃迁。PI正在Macalester学院建造一个光谱带宽为0-30太赫兹的超快太赫兹系统。此次收购将大大加强该系统的能力，允许自旋现象和其他磁现象的研究。这些研究项目的共同目标是为高年级本科生提供教育和研究培训机会，并将允许在光子学和实验材料物理学方面进行实践培训。通过在高级课程、独立项目和高级荣誉项目中使用该仪器，学生的研究训练也将得到加强。随着电子器件的开关速率被推向越来越高的频率，在皮秒和飞秒时间尺度上理解半导体中的载流子输运现象变得越来越重要。利用超快太赫兹光谱学，可以用飞秒光脉冲或单周期电磁脉冲脉冲激发半导体，并及时记录由此产生的电荷运动。这允许在时间尺度上研究半导体和半导体异质结构中的载流子散射和电荷振荡等半经典现象，这将对未来的器件至关重要。此外，该技术非常适合研究半导体量子阱和异质结构中的电子跃迁（子带间跃迁）和自旋跃迁等量子现象。子带间跃迁对量子相干电子学和中、远红外半导体激光器的发展具有重要意义。在自旋输运装置中，电子的自旋而不是电荷被用来控制输运，这是电流研究的热点。其中最有前途的系统是窄间隙半导体中的量子阱。

This Major Research Instrumentation RUI grant supports instrumentation for research in ultrafast optics and semiconductor physics as well as undergraduate research training at Macalester College. The instrumentation is a 7 Tessa superconducting magnet cryostat with optical access. Initial research will use the instrument to support a NSF-funded program to study spin and charge dynamics in semiconductors. The Projects include ultrafast THz spectroscopy of spin-dynamics in semiconductors; time-resolved measurements of magneto-plasma oscillations in semiconductors; and quantum transitions in strongly driven semiconductor quantum wells and heterostructures. The PI is building an ultrafast THz system with spectral bandwidth of 0-30 THz at Macalester College. This acquisition will significantly strengthen the capabilities of the system, permitting investigation of spin phenomena and other magnetic phenomena. The research projects have a common objective of providing education and research training opportunities for advanced undergraduate students and will permit hands-on training in photonics and experimental materials physics. Student research training will also be enhanced through use of the instrument in advanced courses, independent projects and senior honors projects. As the switching rates in electronic devices are pushed to ever-higher frequencies, it becomes increasingly important to understand carrier transport phenomena in semiconductors on picosecond and femtosecond time-scales. Using ultrafast terahertz spectroscopy it is possible to impulsively excite a semiconductor with a femtosecond optical pulse or single-cycle electromagnetic pulse and record the resulting motion of charge in time. This allows the study of semiclassical phenomena such as carrier scattering and charge oscillations in semiconductors and semiconductor heterostructures on time-scales, which will be crucial to future devices. In addition, this technique is well suited to the study of quantum phenomena such as electronic transitions in semiconductor quantum wells and heterostructures (intersubband transitions) and spin transitions. Intersubband transitions are of interest for quantum coherent electronics and for the development of mid- and far-infrared semiconductor lasers. Spin-transport devices in which an electron's spin, rather than its charge, is used to control transport are of intense current interest. Among the most promising systems are quantum wells in narrow-gap semiconductors.