An improved version of the ‘maser’ - the microwave-frequency older sibling of the laser - which can operate continuously and at room temperature is reported in this week’s Nature. The new device could one day find use in applications from magnetic resonance imaging and secure communications to precision measurement.

Solid-state masers were first developed in the 1960s, but their applications have remained relatively limited as they usually rely on cryogenic refrigeration and high-vacuum systems. More recently, room-temperature masers have been produced using organic molecular crystals, but these tend to have poor thermal and mechanical properties and can operate only in pulsed, rather than continuous, mode. To achieve continuous emission, alternative materials are needed, and inorganic materials such as diamond and silicon carbide, which offer improved thermal and mechanical properties compared to organic materials, have been proposed.

Jonathan Breeze and colleagues demonstrate a continuous-wave, room-temperature maser that is based on imperfections known as nitrogen-vacancy centres in diamond. Masers are currently used in deep-space communications and radio astronomy, but the new device could expand their applications to medicine, security and quantum technologies.