Parity-Lifted Radiative Degeneracy: Orthogonal Dipoles over Parallel Dipoles in Achiral Dielectric Cavities
Parity symmetry enforces radiative degeneracy of parity-conjugated emitters in free space. We selectively lift this degeneracy in an achiral dielectric cavity via coupling-induced global parity breaking: the cavity and individual dipoles each preserve parity, while their fixed relative orientation breaks global parity, enabling differential decay. This mechanism exhibits a structure-function trend in marked contrast to the Rosenfeld rule: orthogonal electric-magnetic dipoles yield radiative asymmetry approaching the theoretical limit of 2, whereas parallel ones show negligible differentiation. A semi-analytical model, validated across multiple modes, confirms generality. These findings establish a new paradigm for symmetry engineering without intrinsic chirality.