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Stephen Rand
photo of Stephen  Rand

Professor, Electrical Engineering & Computer Science
Professor, Physics and Applied Physics

office : 1112 EECS Building
address : 1301 Beal Avenue - Ann Arbor, MI 48109-2122
email : scr@eecs.umich.edu
phone : (734)763-6810
fax : (734)647-2718

Research Group : Nonlinear & Ultrafast Laser Spectroscopy Laboratory

Publications : Reference List (6 listed)

Current research comprises two quite different areas: cooperative nonlinear optics and ultrahigh-resolution laser spectroscopy of point defects in wide-bandgap semiconductors. Cooperative nonlinear optics focuses on the interaction of light with clusters of neighboring impurities in solids (or colliding atoms in gases).

Near-neighbor atoms are coupled with clusters of neighboring impurities in solids (or colliding atoms in gases). Near-neighbor atoms are coupled oscillators which exhibit nonlinear emission or absorption at unexpected frequencies in a manner quite different from conventional nonlinear optics. We study coupled pairs and trios of atoms in rare-earth-doped solids, and have demonstrated several upconversion lasers and novel nonlinear devices based on them.

Upconversion lasers are distinctive in providing output frequencies higher than their excitation or pump frequency. Bistable devices based on cooperative interactions should also exhibit unusually low power requirements; however, fundamental aspects of pair interactions with light are of principal concern. Hence we are also currently developing a rigorous quantum theory for avalanche upconversion, and exploring the implications of spatial coherence in such processes for population pulsations and possibly chaotic behavior.

Nonlinear spectroscopy emphasizing hole-burning, four-wave mixing and coherent transient techniques are used to study the physical and electronic structure of point defects and dopants in solids. Centers of interest in diamond and ALxGA1-xN influence semiconducting properties in important ways. Alternatively, they may be candidate centers for short-wavelength tunable injection lasers and detectors.

However, very little detailed knowledge is available for many of the centers in these novel electronic materials and the materials themselves are rare. Although our primary interest is in precision spectroscopy, we have therefore found it necessary, for example, to grow our own CVD diamond films in order to prepare spectroscopic samples with desired concentrations of impurities or color centers, using particle beams and annealing procedures.

Coherent optical spectroscopy with both femtosecond pulses (giving rise to photon echoes) and continuous-wave lasers (cw four-wave mixing and phase conjugation) is then used to determine energy levels, decay times, and symmetry information about simple point defects. The objective is to furnish the necessary knowledge base for applications of the type mentioned above.

Stephen Rand received his Bachelor's Degree in Science (Physics) from McMaster University in Hamilton, Ontario, and his M.Sc. and Ph.D. (Physics) at the University of Toronto. In 1989 he was a CNRS invited professor at the University of Grenoble. In 1994 he was a Fulbright scholar and a College de France visiting professor. He is Topical Editor for the Journal of the Optical Society of America B.

Recent Theses :

David Redman
"Electronic Structure of the Nitrogen-Vacancy Center in Diamond"
Ping Xie
"Cooperative Upconversion Lasers"
H. Ni
"Avalanche Upconversion"
Q. Shu
"Cooperative Optical Nonlinearities"
S. Brown
"Electronic Excitations of Widegap Semiconductors: Diamond and AlxGa1-xN"
Alan Lenef
"Dephasing of Cooperative Optical Transitions"


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