Continuous-wave room-temperature diamond maser

Laser is an acronym for light amplification by stimulated emission of radiation. 'Light' refers to electromagnetic radiation of any frequency, and devices based on this process were first developed for radiation at microwave and radio frequencies. For historical reasons, these are referred to as 'masers'. Despite being developed first, masers are not widely used as they usually require cryogenic refrigeration and high-vacuum systems. Room-temperature masers made using molecular crystals have poor thermal and mechanical properties and can operate only in pulses. Jonathan Breeze and colleagues now demonstrate a room-temperature maser based on nitrogen–vacancy defect centres in diamond that can operate in continuous-wave mode. Masers are already exploited for deep-space communications and radio astronomy, but this room-temperature device could expand their applications to medicine, security and quantum technologies.