ENGINEERING

ANN ARBOR, MI -- Nanotechnology is in the news. Forecasters paint a vision of microscopic machines that can fight viruses or alter the functioning of bodily systems, of power generators smaller than a penny, of entire medical laboratories in an area smaller than a credit card. The problem is, there is a huge gap between the devices we can design and those we can implement, given current technology. A technique that will greatly improve the study of nanostructures and help shorten the development time for quantum computers and similar devices has been demonstrated by a team of University of Michigan researchers. The methodology, which combines coherent nonlinear optical spectroscopy with low-temperature near-field microscopy, is featured in the Sept. 21 issue of Science. Authors of the paper are Profs. Bradford Orr and Duncan Steel, research fellow Jeffrey Guest, and graduate students Todd Stievater, Gang Chen, and Elizabeth Tabak, all of the Department of Physics. Dan Gammon and Scott Katzer of the Naval Research Laboratory also are co-authors. As the study of fundamental physics and the development of nanotechnologies produces smaller and smaller nanostructures, there have been significant advances in material preparation techniques and in the growth of novel diagnostic and control capabilities. Coherent optical control and optical manipulation play a fundamental role in the functioning of many of these proposed devices. Unfortunately, the resolution available with traditional far-field optical techniques is not adequate to access the new devices. Near-field scanning optical microscopy expands the standard resolution limit, but often produces ambiguous results. Using a technique which combines the direct optical probe and spectral selectivity of coherent nonlinear optical spectroscopy with the spatial selectivity of near-field microscopy, the U-M team was able to both optically induce and detect quantum coherence in an extended structure, with sub-wavelength resolution. "This just puts us another step closer to closing the gap between our present-day capabilities and the sophisticated nanodevices and quantum computers of the future," Steel said. "The beauty of this technique is that it is applicable to any optically active system, which means it can easily be adapted in the ever-changing world of nano-optics and quantum-information technology."