Generation and tuning of a spin wave frequency comb

Abstract

Optical frequency combs are powerful tools used for synchronization, stabilization and frequency conversion in both fundamental science and technical applications. In this work, we present experimental observations on the generation of a spin wave frequency comb in a low damping Co25Fe75 conduit measured using Brillouin light scattering microscopy. By driving the magnetization to large precession angles, nonlinear interactions such as four magnon scattering can be observed. When applying two RF signals with independently tunable frequencies and amplitudes to our microstructure, we can actively control the final states that will be populated by these scattering processes. Our results show the generation of a frequency comb, consisting of several spin waves with adjustable frequency spacing and amplitude. We demonstrate that the known effect of frequency mixing for k=0 modes [1] can be extended towards propagating spin waves. This enables simultaneous information transport and processing. This behaviour is studied for different sample geometries, which allow mixing of co-propagating as well as counter-propagating spin waves. Our observations are in qualitative agreement with micro magnetic simulations. The presented data encourage a deeper understanding of the interaction of propagating spin waves in the nonlinear regime and propose utilization of spin wave frequency combs as broadband tunable clocks for information processing. The authors acknowledge financial support from the Deutsche Forschungsgemeinschaft within programs SCHU 2922/1-1, WE5386/4-1 and WE5386/5-1. K. S. acknowledges funding within the Helmholtz Postdoc Programme.