The size of a conventional laser is dictated by the wavelength of the light it uses, and the distance between the reflective surfaces can’t be smaller than half the wavelength of the light–in the case of visible light, about 200 nanometers. The “beauty” of the spaser is that it gets around this limitation by using plasmons, says Noginov. Spasers could probably be made as small as one nanometer. Any smaller than that, Noginov explains, and the nanoparticles’ functionality breaks down.
Noginov and his collaborators are not the first to make a nanolaser. This July, researchers led by Cun-Zheng Ning, professor of electrical engineering at Arizona State University, and Martin Hill of Eindhoven University in the Netherlands created a nanolaser about 100 nanometers wide, using different materials. Ning and Hill’s nanolaser was the first to overcome the wavelength constraints on the size of lasers. The work published today, however, is the first example of a spaser.
“The spaser works about a thousand times faster than the fastest transistor, while having the same nanoscale size,” says Mark Stockman, professor of physics at Georgia State University. “This opens up the possibility to build ultrafast amplifiers, logic elements, and microprocessors working about a thousand times faster than conventional silicon-based microprocessors.”
Stockman predicted the phaser in 2003 with David Bergman, professor of physics at Tel Aviv University in Israel. The creation of the spaser, says Bergman, “is a beautiful piece of work.”
Spasers are likely to find their first application not in optical computing but in places where conventional lasers are used today, says Noginov. Indeed, “a more near-term application is in the magnetic data-storage industry,” says Sakhrat Khizroev, professor of electrical engineering at the University of California, Riverside, who is also developing nanolasers. The magnetic data-storage media used for today’s hard disks are reaching their physical limits; one way of extending its capabilities is to heat the media with very small spots of light during recording, which could be done with nanolasers, says Khizroev. However, the researchers caution, any applications are probably years away.