Microwave

Quantum mechanics

Diamond

Materials science

Maser

Layer (electronics)

Thin-film transistor

Pentacene

Quantum optics

Physics

Nanotechnology

Solid-state

Optics

Quantum technology

Quantum

Composite material

Optoelectronics

Open quantum system

Engineering physics

Applied Physics Letters

The first solid-state masers to operate at room-temperature and ambient air-pressure were recently demonstrated using optically pumped spin-triplet states as the gain medium. In this Perspective, we briefly review the previous state-of-the-art in cryogenic solid-state masers and then discuss the development of the room-temperature solid-state maser: from the organic pentacene pulsed maser to the diamond nitrogen-vacancy continuous-wave maser. We characterize the operation of these masers as coherent microwave sources and ultra-low noise amplifiers before outlining how they can be adapted to act as model systems in which to explore room-temperature cavity quantum electrodynamics. After discussing challenges facing current embodiments of the room-temperature solid-state maser, we explore how they might be addressed or by-passed altogether through the development of alternative materials and masing mechanisms. Finally, we speculate on how the advent of masers that can operate in ambient conditions might lead to novel applications in metrology and quantum technologies.

Perspective on room-temperature solid-state masers