Award Abstract #0215717
Acquisition of a Magneto-Optical Cryostat for Terahertz Studies of Semiconductor Heterostructures

NSF Org:	DMR Division of Materials Research
Initial Amendment Date:	August 5, 2002
Latest Amendment Date:	August 5, 2002
Award Number:	0215717
Award Instrument:	Standard Grant
Program Manager:	Charles E. Bouldin DMR Division of Materials Research MPS Directorate for Mathematical & Physical Sciences
Start Date:	September 1, 2002
Expires:	August 31, 2004 (Estimated)
Awarded Amount to Date:	$104800
Investigator(s):	James Heyman heyman@macalester.edu (Principal Investigator)
Sponsor:	Macalester College 1600 Grand Avenue Saint Paul, MN 55105 612/696-6000
NSF Program(s):	MAJOR RESEARCH INSTRUMENTATION
Field Application(s):	0106000 Materials Research
Program Reference Code(s):	AMPP, 9161, 9141, 1682
Program Element Code(s):	1189

ABSTRACT

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.

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