New hope for terahertz
Terahertz rays — radiation between microwaves and infrared rays on the electromagnetic spectrum — are a promising means of detecting explosives, but they’ve proven hard to generate cost effectively. So far, solid-state lasers — the cheap, miniature type of laser found in CD players — have been unable to produce terahertz rays unless they’re supercooled, which makes them impractical for mass deployment. Some researchers had even begun to suspect that a room-temperature, solid-state terahertz laser was physically impossible. The performance of experimental terahertz lasers built in the lab has suggested a linear correlation between operating temperature and frequency, in which halving the frequency requires roughly halving the temperature. This led some scientists to speculate that frequency and temperature are linked by some fundamental physical law, a strict proportionality that couldn’t be violated.That hypothesis, however, turns out to be wrong. In the latest issue of the journal Nature Physics, a group...