Optical Spin Effects Induced by Phase Conjugation at a Space‐Time Interface

Electromagnetic temporal boundaries, emerging when the constitutive parameters of a medium undergo abrupt temporal variations, have garnered significant interest for their role in facilitating unconventional wave phenomena and enabling sophisticated field manipulations. A key manifestation is temporal reflection in an unbounded spatial domain, where a sudden temporal discontinuity induces phase‐conjugated backward waves alongside anomalous spin conversion. This study explores distinctive spin‐conversion dynamics at a time‐dependent spatial interface governed by Lorentz‐type dispersion, in which the plasma frequency undergoes rapid modulation over time. The interaction of a circularly polarized wave with a space‐time interface excites electromagnetic signals at the system's natural resonance, allowing precise control over polarization states. The scattered field stems from the combined influence of temporal and spatial boundaries, yielding a superposition of the original incident wave's polarization and its phase‐conjugated counterpart.