High-speed nonreciprocal magnetoplasmonic waveguide phase shifter

Abstract

In the realm of modern day optical computing prospects, plasmonics provides a unique means of consolidating electronics and photonics in a nanoscale platform. For advanced optical information processing applications, there is a pressing need for configurable plasmonic platforms that mimic the functionalities of their electrical counterparts. In such a pursuit, the ability to actively manipulate plasmonic phenomena must first be realized via an electrical stimulus. An attractive architecture is realized by incorporating magneto-optical materials into devices, as the degree of electrical control they provide is unattainable by other material systems. Properties of the material are influenced by external magnetic fields, which can be conveniently generated by current passing through nearby metallic structures. While ferromagnetic metals are far too lossy for plasmonic integration, magnetic garnets can facilitate a robust and tunable architecture in a waveguide geometry. Here, we investigate a bismuth-substituted yttrium iron garnet platform for a high bandwidth active optical phase shifter. Our device is capable of imparting a large nonreciprocal phase shift of 6.99 rad/mm, while confining 70% of the modal power to the 0.081 μm2 cross-sectional area of the core. By considering the Landau–Lifshitz–Gilbert formalism, we show that the magnetoplasmonic phase shifter is operable in both underdamped and critically damped modes, and is fully tunable through the applied magnetic fields and pulsewidth. This magnetoplasmonic building block opens doors to a new class of nanoplasmonic devices, such as optical phase modulators, isolators, and optical clocks that will satisfy key applications in nanoscale optical information networks.