How Did a Laser Cool This Semiconductor to Almost Absolute Zero?

By Andrew Liszewski on at

It's completely counterintuitive, but scientists at the Niels Bohr Institute have succeeded in cooling a semiconductor membrane to −269°C, almost four degrees above absolute zero, using a powerful laser we usually think of as only being able to burn.

With a thickness of just 160 nanometres and a surface area of 1 millimetre square, the semiconductor membrane is incredibly small by most standards. But compared to previous laser cooling experiments which have been conducted on clouds of particles, it's downright gigantic. And it's composed of a material called gallium arsenide, which has a unique crystal structure giving it special electronic and optical properties.

