Quasinormal modes enable coherent control of electromagnetic interactions
Phys. Rev. B 114, 065419 – Published 20 July, 2026
DOI: https://doi.org/10.1103/fw84-np5m
Abstract
Quasinormal modes (QNMs) and coherent control of light-matter interactions (through synchronized multiple coherent incident waves) are profound and pervasive concepts in and beyond photonics, making accessible photonic manipulations with extreme precision and efficiency. Though each has been playing essential roles along its own vein, these two sweeping concepts remain largely segregated with little interaction, blocking vast opportunities of cross-fertilizations to explore. Here we unify both concepts into a fully vectorial framework of coherent control for light interacting with open photonic systems. From the QNM perspective, scattered waves are superimposed radiations from all QNMs excited, and thus coherent controls can be mapped into another problem of QNM excitation manipulations. Within our vectorial framework, coherent control is formulated as interference among distinct QNM excitation channels associated with mutually coherent waves incident from different directions. The amplitudes, phases, polarizations, and propagation directions of these waves can be exploited simultaneously, providing additional independent degrees of freedom for tailoring QNM excitations. This multichannel formulation offers three main advances: (i) Multiple incident waves enlarge the accessible control space for manipulating QNM excitation amplitudes and phases; (ii) appropriately designed excitation channels enable the selective excitation or suppression of individual QNMs, as well as the simultaneous control of multiple QNMs; and (iii) independent control of the relative amplitudes and phases of different QNM radiation components enables the directional scattering polarization to span the entire Poincaré sphere. Given the ubiquity and profundity of QNMs and coherent control in almost all branches of wave physics, the vectorial framework and its underlying principles established will inspire further fundamental explorations and practical applications beyond photonics, opening new opportunities for various forms of wave-matter interactions.
