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  Ask Professor of Physics Elizabeth McCormack  
Elizabeth McCormack in the lab

Professor of Physics Elizabeth McCormack is the project director for a feasibility study of laser-trapped mirrors in space that is funded by the NASA Institute for Advanced Concepts.

What is laser trapping and how might it help in the search for extraterrestrial life?

Lasers whose beams are aimed in opposite directions and overlap create interference fringes, or patterns of high- and low-intensity light. Certain kinds of particles, like ordinary glass or silica particles, are attracted to the areas of increasing light intensity and thus can be localized in the interference fringes. Controlling minute particles this way is what's known as laser trapping.

Our collaboration of astronomers, physicists and engineers has proposed laser trapping as a promising technology for creating an entirely new type of reflective surface, the Laser Trapped Mirror (LTM), which is how it might aid in astronomical research. Telescopes need mirrors. Basically, the size of the mirror surface determines how powerful the telescope is, and the current technology has more or less hit its limit at a mirror size of about 10 meters across. A mirror this wide, even one that's "ultralightweight" by contemporary standards, weighs approximately 16 tons. And what do you get? A telescope that is very difficult and expensive to transport beyond earth's atmosphere, where optical distortions limit the kinds of observations that can be made. The LTM could provide a means to make very large and extremely lightweight mirrors for operation in space. A space telescope made with such a mirror could directly contribute to several planned NASA missions including those to search for distant earth-like planets that might support life in other star systems.

In an LTM, counter-propagating lasers whose beams strike deflectors would be made to produce fringe surfaces in the shape of a parabola. Reflective particles could be held in place by the fringes and manipulated in to a single fringe by tuning the lasers, creating a mirror-shaped surface without material support. Theoretically, there is no limit to the size of such a surface, and the absence of a support structure would make it extremely light: a surface as large as 35 meters across could have a mass of just 100 grams and be only a few microns thick. A lot of practical problems have to be solved before a laser-trapped mirror can be created in outer space, but LTMs have the potential to revolutionize astronomical research. 

More about laser-trapped mirrors in space
(A PowerPoint presentaion by Elizabeth McCormack)

Elizabeth McCormack's homepage




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