Gigahertz vibration measurement with near fundamental resolution limit for high-frequency communication systems and quantum information applications.

• Applicant: Dr.-Ing. Marvin Schewe
• Subject Area: Measurement Systems
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 520954566

Due to the growth of global connectivity of technical devices in the "Internet of Things" (IoT), there is an increased need for high-frequency communication systems, for example in the 5G mobile radio standard. In this context, microacoustic resonators or filters are used primarily, which enable the use of frequency bands in the gigahertz range by band selection or suppression of noise from other frequency bands. Microacoustic filters such as SAW (surface acoustic wave) and BAW (bulk acoustic wave) filters possess a high quality factor, are very compact, and are suitable for low-cost mass production. Furthermore, they are increasingly employed in quantum computing to store information from qubits by coupling with phonons. For the technical application in communication and quantum technology, it is mandatory to detect the resulting microacoustic vibrations, or their harmonics, in the range up to 20 GHz and with sub-picometer resolution. Only then is it possible to accurately determine the material properties. Vibration measurement enables the optimization of the efficiency, for example by analyzing dissipation mechanisms and occurring destructive interferences. The research group of Dr. Jason Gorman (National Institute of Standards and Technology) developed a homodyne pulse laser interferometer, which is currently one of the best measurement devices for measuring vibrations in the gigahertz range. The NIST setup can measure harmonic narrowband vibrations at frequencies up to 12 GHz. At 55 fm/√Hz, the resolutions achieved are approximately a factor of 10 above the theoretically achievable resolutions, which are limited by physical effects such as quantum noise. The goal of the research project is to extend the measurement method to nonlinear vibrations, increasing the maximum measurable vibrations up to 20 GHz and simultaneously reducing the resolution to about 20 fm/√Hz. Furthermore, the project will investigate whether the measurement method can be improved further by adapting it to a heterodyne method. To realize the project, all components used in the measurement setup will be thoroughly investigated in order to identify limiting factors and to optimize them subsequently. In addition to optimizing the detector electronics, the lateral resolution will also be improved by utilizing a laser with a shorter wavelength and microscope objectives with a higher numerical aperture. For the extension of the measurement method to non-linear vibrations, the signal processing must be adapted fundamentally. By achieving the project goals, a previously unattained understanding of the device physics of novel microacoustic resonators and filters can be achieved, which can significantly contribute to their development and optimization.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Dr. Jason J. Gorman