Quantization of the Electromagnetic Fields From Single Atomic or Molecular Radiators

A theoretical framework is introduced for deriving expressions for electromagnetic (EM) potentials and fields of single atomic or molecular emitters modeled as oscillating dipoles, which follows a recently developed method to solve inhomogeneous wave equations for time‐dependent distributions of charge. This framework is first used to evaluate the physical implications of the simplifying assumptions made in the standard approach to the quantization of EM fields and the impact of such assumptions on the predicted energy and momentum quantization. Then, the exact relationships between the potentials and the oscillating (transition) dipole properties derived under the present framework are used to quantize EM fields radiated by single emitters and to achieve agreement with the classical dipole radiation pattern, while maintaining the quantum mechanical description of electromagnetic radiation in terms of the probability distribution of quantum modes. Contributions of the present analysis to the understanding of photon emission from excited atoms or molecules stimulated by light or vacuum field fluctuations are highlighted, and possible experimental tests and practical applications are proposed.