Optical interference plays a prominent role in scientific discovery and modern technology. Historically, optical interference was instrumental in establishing the wave nature of light. Nowadays, optical interference continues to be of great importance in areas such as spectroscopy and metrology. Thus far, the physical optics literature has discussed the interference of optical waves with the same single frequency (i.e., homodyne interference) and the interference of optical waves with two different frequencies (i.e., heterodyne interference), but it hardly ever deals with the interference of...