Bulk-mode rainbow localization via double zero-group-velocity confinement in a tapered gyromagnetic chain
Year: 2026
Type: article
Abstract: Frequency-selective spatial localization of electromagnetic waves provides a means of controlling the spatial distribution of frequency components in broadband systems. Here, we demonstrate bulk-mode rainbow localization based on double-zero-group-velocity (ZGV) confinement in a tapered gyromagnetic chain composed of yttrium iron garnet (YIG) ferrite rods. The triangular rod arrangement in each unit cell, together with an external magnetic bias, breaks time-reversal (T-), spatial inversion (I-), and mirror (M-) symmetries, resulting in intrinsically nonreciprocal bulk dispersion with two closely spaced ZGV points. In the tapered chain, the lattice constant varies gradually along the propagation direction, causing the local dispersion and corresponding ZGV boundaries to shift spatially. Consequently, guided bulk modes at different frequencies reach different double-ZGV confinement regions and become localized at distinct positions, establishing a frequency-to-position mapping. This mechanism does not rely on structural defects, band edges, or engineered interfaces. Full-wave simulations demonstrate clear frequency-dependent spatial localization and show that the localization position can be repositioned by tuning the external magnetic bias. Material loss mainly reduces the local field amplitude while having little influence on the localization position and confinement region. The proposed tapered YIG chain offers a compact and magnetically tunable platform for frequency-selective electromagnetic wave control in nonreciprocal gyromagnetic systems.
Source: Optics Express
DOI: 10.1364/oe.612414
Authors: Hui Ma, Zhao-Fei Sui, Yang-Chen Hao, Rui-Xin Wu
Institution: Nanjing University
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,270
OpenAlex ID: W7223188097