Light plays a central role in modern technology, powering everything from televisions and satellites to the fiber optic cables that carry internet data across the globe. Now, physicists at Stanford have developed a way to push light even further. They created a compact optical amplifier, about the size of a fingertip, that can strengthen light signals while using very little energy and maintaining full bandwidth.

Optical amplifiers work much like audio amplifiers, except they boost light instead of sound. Traditional compact versions require significant power to operate, which limits their efficiency.…