Robust multimode interference and conversion in topological unidirectional surface magnetoplasmons

Area of Science:

• Condensed Matter Physics
• Photonics and Optics
• Materials Science

Background:

• Surface magnetoplasmons (SMPs) are electromagnetic waves propagating at the interface of a magnetodielectric material and a plasmonic medium.
• Yttrium-iron-garnet (YIG) is a well-known magneto-optical material with tunable properties via external magnetic fields.
• Topological photonics offers robust wave propagation immune to defects and disorder.

Purpose of the Study:

• To theoretically investigate the properties of surface magnetoplasmons (SMPs) in a yttrium-iron-garnet (YIG) sandwiched waveguide.
• To explore the potential of these SMPs for realizing magnetically controllable multimode interference (MMI).
• To demonstrate the topological protection and tunability of these phenomena for optical applications.

Main Methods:

• Theoretical investigation of SMP dispersion relations in a YIG-based waveguide.
• Analysis of mode behavior in both symmetric and asymmetric waveguide configurations.
• Simulation of multimode interference (MMI) phenomena under magnetic control.
• Assessment of topological protection against introduced disorder.

Main Results:

• The YIG waveguide supports topological unidirectional SMPs.
• Magnetically controllable MMI based on unidirectional SMPs is verified in both symmetric and asymmetric waveguides.
• A unidirectional even mode is supported in the asymmetric waveguide due to inter-YIG-air interface mode coupling.
• Topological protection of these modes is confirmed even with introduced disorder.
• Tunable splitters and mode conversion are achieved using robust unidirectional SMP MMI (USMMI).

Conclusions:

• The YIG waveguide offers a platform for topological unidirectional SMPs.
• USMMI provides a robust and tunable method for manipulating light in optical circuits.
• The demonstrated phenomena offer significant degrees of freedom for advanced topological wave manipulation.