Assembling magneto-optical heterostructures for all-optical multi-functional devices

All-optical computing has recently emerged as a vibrant research field in response to the energy crisis and the growing demand for information processing. However, the efficiency of subwavelength-scale all-optical devices remains relatively low due to challenges such as back-scattering reflections and strict surface roughness. Furthermore, achieving multifunctionality through the reassembly of all-optical structures has thus far been rarely accomplished. One promising approach to address these issues is the utilization of one-way edge modes. This work proposes four types of deep-subwavelength (∼10⁻²λ₀, where λ₀ is the wavelength in vacuum) all-optical functional devices based on yttrium iron garnet (YIG): a phase modulator, a filter, a splitter, and logic gates. These devices are based on robust one-way edge modes and/or index-near-zero (INZ) modes but do not require an external magnetic field, which can allow for flexible assembly. In particular, a phase modulation range spanning from −π to π, a perfect filter that divides the input port's one-way region into two output one-way regions with equal bandwidth, a multi-frequency splitter with an equal splitting ratio (e.g., 50/50), and self-consistent logic gates relying on INZ modes are investigated. Our findings may find applications in compact optical calculations and integrated optical circuits.