Chip-Scale Masers

• Applicants: Professor Dr. Jens Anders; Dr. Christoph Zollitsch
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576444587

The proposed research project investigates the fundamental principles and feasibility of realizing a chip-scale solid-state maser as a novel frequency and time reference in the microwave regime. Building upon recent advances in room-temperature masers and integrated circuit technology, the project seeks to explore the physical limits and mechanisms that may enable miniaturization of masers while maintaining their exceptional frequency stability and spectral purity. Historically, masers – Microwave Amplification by Stimulated Emission of Radiation – served as highly accurate frequency standards, but their practical use is restricted to large-scale laboratory environments due to demanding requirements like ultra-high vacuum or cryogenics. The recent demonstration of solid-state masers operating under ambient conditions using materials such as pentacene-doped p-terphenyl and negatively charged nitrogen-vacancy (NV⁻) centers in diamond has reinvigorated fundamental research, suggesting new pathways toward scalable implementations. At the core of the project lies the scientific exploration of integrating maser-active media with electronically enhanced microwave resonators fabricated by standard semiconductor processes. This includes studying the potential of voltage-controlled oscillators (VCOs) to act not as oscillators but as high-quality, electronically enhanced passive resonators, a regime which has yet to be systematically characterized in context of spin-based microwave amplification. The research will begin by studying pulsed masing at radio frequencies using a well-understood pentacene system in combination with existing chip-integrated VCO, electronically-enhanced resonators. This initial phase will serve to elucidate the interplay of spin ensembles and the electromagnetic response of compact LC circuits in the threshold regime of masing. Insights will inform the theoretical and experimental investigation of high-Q resonator circuits operating in the GHz regime, focusing on loss compensation, thermal stability, and noise properties. The final phase will address the realization of masing based on NV centers in diamond at microwave frequencies, with emphasis on understanding spin dynamics, magnetic field orientation, optical pumping, and resonator coupling in a miniaturized geometry. The scientific questions of mode confinement, cooperativity, and spin-resonator coupling strength will be central in assessing the viability of chip-scale masing under room-temperature conditions. By combining complementary expertise in maser physics, and integrated circuit design this project provides a unique opportunity to advance fundamental understanding on solid-state maser systems and to uncover the physical principles necessary for transitioning from bulk to chip-scale. The outcomes are expected to contribute to the broader field of quantum technologies and frequency metrology through new knowledge, experimental methodologies, and theoretical models.

• DFG Programme: New Instrumentation for Research
• Co-Investigators: Professor Christopher W.M. Kay, Ph.D.; Dr. Michal Kern