Integrated magnonic networks based on the lateral magnonic stripes and magnonic crystals

Abstract

In recent years much research has been directed towards the use of spin waves (SWs) for signal processing at microwave and subterahertz frequencies due to the possibility to carry the information signal without the transmission of a charge current [1, 2]. Magnonic crystal (MCs) [1, 2] have attracted a significant attention due to their wide range of application and numerous ways to fabrication. MCs are used in linear and nonlinear magnonics as a building block of magnonic networks. In the majority of the previously realized devices the MCs have been used as the high-Q tunable rejection filter due to the most important features of the MCs - the magnonic forbidden (rejection) band or magnonic band gap in the spin-wave spectra. However, the possible use of the magnonic forbidden band to fabricate the drop filters in magnonic integrated circuits can extend the application of MCs, in particular, for the magnonic logic [1, 2, 3]. In the asymmetric MC the spin waves have non-equal propagation constants and thus the phase-matching condition is violated. While phase mismatch might seem on the surface to decrease the coupling efficiency, the unusual increase of the spin-wave coupling can be observed at the frequencies in the vicinity of the magnonic band gap. This idea can underpin the experimental and theoretical studies regarding the side-coupled magnonic crystals, which can also act as frequency selective multiplexers. Here we report the experimental observation of the spin-wave coupling in the asymmetric adjacent magnonic crystals based on multimode yttrium iron garnet (YIG) waveguides [4– 8]. We show, that the combination of frequency and spatial filtering features of the MC and spin-wave coupling in the adjacent magnetic waveguide leads to the realization of the magnonic drop filter ( Fig.1). We also identify the mechanism of the efficient spin-wave power transmission between the magnonic crystals. As a major result, we have demonstrated by the means of the space-resolved Brillouin light scattering (BLS) technique, that non-identical MCs within close proximity demonstrates the efficient spin-wave coupling at the frequency of the magnonic forbidden gap of one of the MCs. Thus MCs can be used not only to achieve the spatial and frequency filtering of spin-wave signal but also to provide the phase condition with an efficient spin-wave power transfer from the input to drop port of magnonic coupler. The obtained results open new perspectives for the future-generation electronics using integrated magnonic networks. This work was supported partially by the grant from Russian Science Foundation (No. 16-19-10283).