“…Well known, especially in the past decade, the group theory of SL͑2,c͒ and of some of its subgroups was extensively applied in various fields of classical and quantum optics, e.g., ray optics, 40 beam propagation through firstorder systems, 41 analysis of the states of light with orbital angular momentum, 42 polarization optics, 43 multilayer optics, 44,45 interferometry, 46 and coherent and squeezed states of light. 47 Bearing in mind that SL͑2,c͒ is locally isomorphic to the six-parameter Lorentz group SO͑3,1͒, a physical system that can be analyzed in terms of SL͑2,c͒ language can be equally explained in the language of the Lorentz group.…”