ERI: Hybrid magnonic optics for data processing applications

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Modern communications and data processing rely on electromagnetic waves such as light or microwaves. Guiding and manipulation with light can be done by using such well-known elements as fibers, lenses, prisms, and mirrors. For effective operation, their size cannot be made smaller than the wavelengths of the used wave, which significantly limits the miniaturization capabilities of microwave and optical devices. The situation could be significantly improved if shorter waves will be used for encoding information. This project is focused on the investigation of magnetic materials, in which microwave wavelengths can be made significantly shorter. One of the main goals of this proposal is to build optical elements in magnetic systems to advance the existing technology towards the creation of energy-efficient and ultra-compact microwave devices. Another goal is to create magnonic elements mimicking the functionality of human brain neurons. Such devices are the core elements of neuromorphic computers, which could be used in a broad range of pattern recognition tasks. In the frame of this project, the principal investigator will educate the new generation of students in modern microwave and optical measurements techniques, materials engineering, and nanofabrication, which will commit to further development of the U.S. science, engineering, and technology workforce.The project focuses on the development of spin-wave-based physical data processing devices. Spin waves are eigen-excitations of magnetization in magnetically ordered materials. Their properties strongly depend on the magnetization order, which can be controlled by the applied bias magnetic field. The rationale of the proposal is the control of spin-wave dispersion in magnetic conduits using local fields produced by adjacent magnetic layers of other material with different magnetization and high anisotropy. Based on this principle, various spin-wave optical elements, such as lenses, prisms, magnonic crystals, frequency multiplexers, and Fourier-optics devices will be designed, created, and optimized. By using adjacent magnetic elements with different magnetization patterns, complicated wave-scattering geometries could be realized, creating broad possibilities for customization of the device functions. One of the key benefits of such a system is the possibility to tune these patterns by remagnetizing the whole structure by external field without a need to change the geometry of the layer. Special attention will be devoted to downscaling these devices while preserving their characteristics. Spin-waves intrinsic nonlinearity will be used to build optical elements with threshold-like behavior, which is required for the creation of an artificial neuron. In the last stage of the proposal, the developments will be combined for the realization of the nonlinear spin-wave reservoir computing device prototype. The described research aims are going to be achieved by intense experimental study of the proposed prototypes by means of Brillouin light scattering technique together with microwave characterization as well as numerical micromagnetic simulations. Overall, the proposed research will advance understanding of the physics of linear and nonlinear waves in magnetic materials as well result in the creation of a new class of ultra-compact energy-efficient microwave data processing devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.