DARPA PULSE program

By Jeff Hecht
Ultrafast laser research has produced some elegant science, from slicing time into incredibly thin slivers to generating combs of frequencies uniformly spaced across a wide band of the spectrum. These capabilities, in turn, have led to a similarly wide range of applications, including transferring time and frequency standards, measuring short intervals of time, and producing pulses so short that they generate extremely high peak powers with only modest amounts of energy.

However, ultrafast lasers traditionally have been bulky and complex things, custom-assembled on optical tables and delicately aligned in a laboratory. That complexity makes it hard to realize many potential practical applications such as putting frequency combs in space to boost the precision of GPS systems or to measure stellar spectra with extreme precision. Now the Defense  Advanced Research Projects Agency (Arlington, VA) is trying to do something about the problem by creating the Program in Ultrafast Laser Science and Engineering .

DARPA is not the first to think of making smaller and more durable ultrafast lasers. I mentioned the need for "robust frequency combs" for telecommunications systems or space-based instruments in the January Photonic Frontiers . A web search four pages which include the phrase "rugged femtosecond laser," but all of them cite an Army contract awarded last year to Arbor Photonics . However, such references are few and far between, and Google could not find a single page using the phrase "rugged frequency comb" (or combs) when I was writing this blog.








Shrinking the size and improving the robustness of ultrafast lasers is a big challenge, but success could pay off in important ways. DARPA cites some potential military applications that require rugged sources. One is using the time stability of the microwave-band repetition rate of a femtosecond laser to greatly reduce the close-to-carrier phase noise in a microwave oscillator. Others include transferring time or frequency measurements across the spectrum, and generating high-flux isolated attosecond pulses. Civilian science and technology also would benefit from compact  sources of ultrashort pulses.

As is normal with DARPA, success is not guaranteed, but the payoff could be high. In fact, somebody at DARPA surely should have already earned credit in the Pentagon bureaucracy for exceptional skill in acronym creation. Program in Ultrafast Laser Science and Engineering neatly translates into an entirely appropriate acronym -- PULSE.
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