Lasers have become indispensable in everyday life and research, with applications ranging from data transmission over metrology to manufacturing. Masers, by contrast, have so far found hardly any practical applications.
The acronym MASER stands for “Microwave Amplification by Stimulated Emission of Radiation”. In fact, the maser preceded the laser and works according to the same physical principle. However, instead of producing and amplifying light, it generates and amplifies microwave radiation. Despite their great potential, masers have so far mostly depended on technically demanding operating conditions, such as very low temperatures. This has hindered their widespread application.
A research team led by Professor Vladimir Dyakonov and Privatdozent Dr Andreas Sperlich from the Chair of Experimental Physics 6 at Julius-Maximilians-Universität Würzburg (JMU) has made a significant breakthrough towards practical maser systems. As the scientists report in the journal Nature Communications, they have developed a silicon-carbide-based maser that operates continuously – even above room temperature.
Spins in the semiconductor: The key to quantum functionality
The team uses an established semiconductor material: silicon carbide. Within its crystal lattice, the researchers deliberately created atomic defects by removing individual silicon atoms. These defects possess well-defined quantum spin states that can be selectively excited using light.
Silicon carbide is already used on a large scale in power electronics and is readily available for industrial use. This makes the material particularly attractive for turning the fundamental proof of concept in the laboratory into compact, integrable maser devices in the future.
“By leveraging these spins, we turn silicon carbide into a material that actively interacts with microwaves,” explains Dr Andreas Gottscholl, first author of the study. “Using light, we can bring the spins into an excited state in which they emit coherent microwave radiation or even amplify it.”
For the effect to become sufficiently strong, the maser – just like a laser – requires a resonator. It works in a similar way to a swing: only microwave oscillations at the right frequency build up and are amplified further and further. Through careful engineering, the Würzburg team increased the resonator’s quality factor to the point where continuous maser operation is now possible at room temperature.
Prospects for communication and sensing
The new silicon-carbide maser can serve not only as a microwave source: in initial experiments and simulations, the team also demonstrated its potential as a low-noise amplifier. “Such amplifiers are essential, for example, for weak signals in communications and measurement technology,” explains Privatdozent Dr Andreas Sperlich, senior author of the study. “Smartphones, mobile-phone base stations, computers and satellites all employ several microwave signal amplifiers, which so far have had to operate without maser technology.”
The maser also opens up new possibilities for highly precise magnetic field measurements. Its exceptionally high frequency stability makes it possible to detect even the smallest changes in a magnetic field with great sensitivity. In this context, the maser functions like a ticking clock – an oscillator – whose frequency depends strongly on the surrounding magnetic field. The stronger the field, the faster the clock “ticks.”
The researchers estimate a magnetic field sensitivity of around 20 picotesla at room temperature – about one million times weaker than Earth’s magnetic field. This level of precision could be relevant for future metrology applications and even for GPS-independent navigation.
In the long term, the researchers envision electrically driven maser diodes integrated on a chip. This is supported by the fact that the spin states in silicon carbide can, in principle, be excited not only optically but also electrically.
The work was carried out at the Chair of Experimental Physics 6 at the University of Würzburg and within the Würzburg-Dresden Cluster of Excellence ctd.qmat. The project received funding, among others, from the European Research Council (ERC) and the German Research Foundation (DFG), among others.
About ctd.qmat
The Cluster of Excellence ctd.qmat – Complexity, Topology and Dynamics in Quantum Matter – at Julius-Maximilians-Universität Würzburg and Technische Universität Dresden explores and develops novel quantum materials with tailored properties. Around 300 researchers from over 30 countries work at the interface of physics, chemistry, and materials science to lay the foundations for tomorrow’s technologies. In 2026, the cluster entered the second funding period of the German Excellence Strategy of the Federal and State Governments – with an expanded focus on the dynamics of quantum processes.