Cited research: Opt. Exp. 18, 13385–13395 (2010)

Laser beams are usually hard to miss, but a new laser is notable for its lack of light.

Steven Cundiff at the University of Colorado in Boulder and his colleagues built the device by modifying a standard quantum-dot diode laser. Normally, lasers are amplified using two mirrors that reflect light between them, but Cundiff's group deposited light-absorbing material onto one of the mirrors. The laser still emitted light, but it flickered off at an extremely rapid and predictable rate.

The 'dark' pulses verify existing theories of lasing and could prove useful in encoding information in long-distance fibre-optic communications. G.B.