title: Proposal for a room-temperature diamond maser.
abstract: The application of masers is limited by its demanding working conditions (high vacuum or low temperature). A room-temperature solid-state maser is highly desirable, but the lifetimes of emitters (electron spins) in solids at room temperature are usually too short (∼ns) for population inversion. Masing from pentacene spins in p-terphenyl crystals, which have a long spin lifetime (∼0.1 ms), has been demonstrated. This maser, however, operates only in the pulsed mode. Here we propose a room-temperature maser based on nitrogen-vacancy centres in diamond, which features the longest known solid-state spin lifetime (∼5 ms) at room temperature, high optical pumping efficiency (∼10(6) s(-1)) and material stability. Our numerical simulation demonstrates that a maser with a coherence time of approximately minutes is feasible under readily accessible conditions (cavity Q-factor ∼5 × 10(4), diamond size ∼3 × 3 × 0.5 mm(3) and pump power <10 W). A room-temperature diamond maser may facilitate a broad range of microwave technologies.
authors.affiliation: Department of Physics and Centre for Quantum Coherence, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Liang
authors.identifier: http://orcid.org/0000-0003-1898-6317
authors.initials: L
authors.lastname: Jin
authors.affiliation: 3rd Institute of Physics, University of Stuttgart, 70569 Stuttgart, Germany.
authors.forename: Matthias
authors.identifier: http://orcid.org/0000-0003-3934-8306
authors.initials: M
authors.lastname: Pfender
authors.affiliation: 3rd Institute of Physics, University of Stuttgart, 70569 Stuttgart, Germany.
authors.forename: Nabeel
authors.initials: N
authors.lastname: Aslam
authors.affiliation: 3rd Institute of Physics, University of Stuttgart, 70569 Stuttgart, Germany.
authors.forename: Philipp
authors.identifier: http://orcid.org/0000-0003-2146-0412
authors.initials: P
authors.lastname: Neumann
authors.affiliation: 3rd Institute of Physics, University of Stuttgart, 70569 Stuttgart, Germany.
authors.forename: Sen
authors.initials: S
authors.lastname: Yang
authors.affiliation: 3rd Institute of Physics, University of Stuttgart, 70569 Stuttgart, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Wrachtrup
authors.affiliation: Department of Physics and Centre for Quantum Coherence, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Ren-Bao
authors.identifier: http://orcid.org/0000-0002-0620-2370
authors.initials: RB
authors.lastname: Liu