Room-Temperature Terahertz Lasers Are Possible

Investigators in the United States just published a paper that puts a serious dent in a theory holding that laser operating in the terahertz portion of the electromagnetic spectrum cannot be generated from laser devices functioning at room temperatures.

Lasers producing light in these wavelengths have a variety of practical, daily applications, but the issue is that conventional devices, such as the ones found in CD/DVD players, cannot produce this type of light under normal conditions.

They need to be supercooled, which makes them impractical for use in the field, on airport scanners or bomb squad tool kits. Scientific labs do operate terahertz lasers, but only for research.

So the problem with this range of wavelengths is that it cannot be produce by cheap, miniature-type lasers at room temperatures. This led some physicists to propose that solid state lasers generating such light cannot physically operate at room temperature, experts at the Massachusetts Institute of Technology say.

The idea was that a strict, unbreakable proportionality existed between laser frequency and operating temperature, and that this law of physics prevented the mass-production of terahertz lasers.

In the new research, the MIT team proved that this may not in fact be the case. Experts at the Institute developed a laser of this type that functions at twice the maximum temperature predicted by the proposed proportionality law.

Granted, the new device still requires low functioning temperatures, and is still unfit for practical applications at a wide scale, but it represents a proof-of-concept that will undoubtedly make many physicists doubt the proposed theory.

MIT experts conducted the investigation with colleagues from the Sandia National Laboratories, and the group published the results in the latest issue of the esteemed scientific journal Nature Physics.

“There are many naysayers saying that they can never be made operational at room temperature. We break this psychological, empirical barrier by a factor of two. No one will say that it’s a barrier anymore,” says MIT expert Qing Hu.

“In physics, there’s a standard way of thinking, that temperature equals energy, and if you want to go to smaller energies, and see quantum effects, you better go to smaller temperatures,” adds Benjamin Williams.

“And that’s the type of thinking that informs this idea about this limit,” says the expert, who is the director of the Terahertz Devices and Intersubband Nanostructures Laboratory.

The facility is located at the University of California in Los Angeles (UCLA). Williams was not a part of the research team that created the new terahertz laser.