Science fiction usually deploys lasers to annihilate objects (and aliens) in pyrotechnic displays of heat and light. Today’s scientists are doing the opposite. By tuning lasers to just the right frequency, they are cooling matter down to temperatures that could one day approach "absolute zero," the -459.67 Fahrenheit point when atomic motion (and heat) falls to virtually nothing.
Laser cooling works because photons emitted at just the right frequency are absorbed by individual atoms heading in the opposite direction of the laser, slowing down their motion. Since atoms are very picky about which wavelengths of light they will absorb, scientists can selectively choose the type of atoms they target (and the direction in which they are moving). By reducing their motion, they lower the heat in the system, since temperature is determined by the speed of atoms in a substance (also expressed as its kinetic energy).
While this isn’t the stuff of great space operas, it does offer a potentially transformative way to cool down objects from microchips to refrigerators. If successful outside the lab, refrigerators could one day ditch the bulky machinery and damaging chemicals for beams of light.
Researchers at Nanyang Technological University, publishing in the journal Nature this January, have already claimed a victory earlier this year by using lasers to drop the temperature of a superconductor from 62 degrees to well below zero. That’s nowhere near the temperatures that they would like to achieve (-452.2 degrees Fahrenheit is the goal), but real-world applications for optical refrigeration now appear to be within reach. Laser cooling would allow engineers to shrink today’s refrigeration units into far smaller, cost-effective packages, and to build fan-less computers, long-lived batteries, and machines free of toxic chemicals and inefficient compressors.
Researchers still have a long way to go: Laser cooling was first proposed in 1929, and it took more than half a century for the first examples to start operating in labs. Practical advances in laser cooling didn’t win the Nobel Prize until 1997. Today, labs can manipulate matter using lasers, but getting these experiments ready for your next tablet or vehicle will take another technological leap forward. Given the accelerating pace of discoveries in the field, it’s possible you may not need to cool your heels for that long.