Full electromagnetic Greens dyadic of spherically symmetric open optical systems and elimination of static modes from the resonant-state expansion

A general analytic form of the full 6x6 dyadic Greens function of a spherically symmetric open optical system is presented, with an explicit solution provided for a homogeneous sphere in vacuum. Different spectral representations of the Greens function are derived using the Mittag-Leffler theorem, and their convergence to the exact solution is analyzed, allowing us to select optimal representations. Based on them, more efficie