The most common are in the micromachining of materials and in Lasik eye surgery - which was enabled by the development of robust femtosecond pulsed lasers.
“It’s a hot field at the moment,” he adds.īeyond basic research, femtosecond lasers have many practical applications as well. This is called diffraction before destruction. “If the pulse is short enough, all the X-rays diffract from the protein before it is destroyed,” Kaertner says. But high-energy X-ray pulses that can probe these complex structures also destroy them in the process, so the pulse has to be so quick that the image can be obtained before the pieces fly apart. High-energy X-ray pulses with femtosecond duration could make it possible to obtain detailed images, and ultimately movies, of the dynamics of complex protein molecules, Kaertner says - something that can’t be done with existing techniques, and could be of great interest for biomedical research. So far, Kaertner says, “the shortest pulse people have measured is 80 attoseconds.” But various groups are working to push the limits even further, he says, using several different methods, including large-scale electron accelerators such as the Stanford Linear Accelerator. Achieving that requires pushing technology to produce pulses using higher-wavelength sources, and also producing pulses that encompass a wider range of frequencies - a more broadband source.
To understand the movements of electrons, and eventually those of subatomic particles, requires attaining the attosecond and ultimately zeptosecond (sextillionths of a second) range, Kaertner says. The ability to observe events on such timescales is important for basic physics - to understand how atoms move within molecules - as well as for engineering semiconductor devices, and for understanding basic biological processes at the molecular level.īut physicists and engineers are interested in pushing these limits ever further. Haus developed the underlying theory of how those systems actually worked. “Erich and Chuck Shank, at that time working at Bell Laboratories, were the first to make femtosecond pulses, which were very difficult to create back then and are routine today,” Kaertner says. The technology was pioneered by Erich Ippen and Herman Haus in MIT’s Research Laboratory of Electronics. The basic technological innovation that made it possible to observe changes at such tiny timescales was something called a pulsed laser, explains MIT adjunct professor of electrical engineering Franz Kaertner, who specializes in such devices. It encompasses a total of 20 prefixes, 10 of them for decimal amounts, and 10 more for large multiples of the basic units (mega, giga, tera and so on). The system was officially adopted in 1960, and has been updated periodically, most recently in 1991. Those prefixes - micro, nano, pico, femto and atto - are part of an internationally agreed-upon system called SI units (from the French Système International d’Unités, or International System of Units). Continuing the progress, today’s top-shelf technologies are beginning to make it possible to observe events that last less than 100 attoseconds, or quintillionths of a second. Today, researchers can easily reach into the realm of femtoseconds - quadrillionths (or millionths of a billionth) of a second, the timescale of motions within molecules.įemtosecond laser research led to the development, in 2000, of a system that revolutionized the measurement of optical frequencies and enabled optical clocks. The cutting edge of research passed through nanoseconds (billionths of a second) and picoseconds (trillionths) in the 1970s and 1980s. Nowadays, microsecond-resolution imagery is almost ho-hum. This led to now-famous images such as one of a bullet piercing an apple, captured in midflight. Back in the first half of the 20th century, when MIT’s famed Harold “Doc” Edgerton was perfecting his system for capturing fast-moving events on film, the ability to observe changes unfolding at a scale of microseconds - millionths of a second - was considered a remarkable achievement.
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