Modeling of spin-wave directional couplers

Wave based computing is a fascinating computing paradigm that attracted much attention in the latest years. It performs logic operations by exploiting all wave characteristics such as wave interferences. In imec, we are designing wave-based computation devices based on spin waves, i.e., weak collective excitations of the magnetization. This wave type has several benefits such as short wavelengths at GHz frequencies and low power consumption.

A crucial element in a wave-based logic circuit is the directional coupler. This device consists of two waveguides close to each other, see Fig. 1, and allows for normalization and energy transfer of the waves inside the waveguide. Recently, a lateral spin-wave directional coupler was designed and experimentally proven to work [1,2]. It is possible to further optimize this device by placing the two waveguides vertical on top of each other instead of lateral next to each other. By doing this, the device footprint is reduced and thus the functional density improves.

The goal of this challenging project is to understand the behavior of a vertical directional coupler, the differences with the lateral directional coupler and its potential and limitation for logic device usage. To gain this understanding, the student must study the ferromagnetic theory and perform micromagnetic simulations. The student is closely guided by a team of experts in this field. The outcome of the project is of high relevance for the further development of spin-wave circuits.

[1] Q. Wang, Reconfigurable nanoscale spin-wave directional coupler. Science advances, vol. 4, 2018

[2] Q. Wang, A magnonic directional coupler for integrated magnonic half-adders. Nature electronics, vol. 3, 2020.