Ultrafast optical shutter is switched entirely by l...( Its a rare case of all light and no ...)

Its a rare case of all light and no heat: A new study reports that a laser can be used to switch a film of vanadium dioxide back and forth between reflective and transparent states without heating or cooling it.

It is one of the first cases that scientists have found where light can directly produce such a physical transition without changing the materials temperature.

It is also among the most recent examples of coherent control, the use of coherent radiation like laser light to affect the behavior of atomic, molecular or electronic systems. The technique has been used to control photosynthesis and is being used in efforts to create quantum computers and other novel electronic and optical devices. The new discovery opens the possibility of a new generation of ultra-fast optical switches for communications.

The study, which was published in the Sept. 18 issue of Physical Review Letters, was conducted by a team of physicists from Vanderbilt University and the University of Konstanz in Germany headed by Richard Haglund of Vanderbilt and Alfred Leitenstorfer from Konstanz.

Vanadium dioxides uncanny ability to switch back and forth between transparent and reflective states is well known. At temperatures below 154 degrees Fahrenheit, vanadium dioxide film is a transparent semiconductor. Heat it to just a few degrees higher, however, and it becomes a reflective metal. The semiconducting and metallic states actually have different crystalline structures. Among a number of possible applications, people have experimented with using vanadium dioxide film as the active ingredient in thermochromic windows that can block sunlight when the temperature soars and as microscopic thermometers that could be injected into the body.

In 2005, a research collaboration teaming Haglund and Ren Lopez (now at the University of North Carolina, Chapel Hill) with Andrea Cavalleri and Matteo Rini from the Lawrence Berkeley National Laboratory tested the vanadium dioxide t
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