Loudon’s approach is distinctive: he begins not with the Schrödinger equation or wave-particle duality, but with the quantization of the electromagnetic field itself. The central thesis is that light, even in its most fundamental description, must be treated as a quantum field. From this foundation, he derives all of quantum optics—coherence, photon statistics, interaction with matter, and nonlinear effects.
The primary achievement of Loudon’s work is its systematic treatment of the quantization of the electromagnetic field. While classical physics treats light as a continuous wave, Loudon provides the mathematical framework to treat it as a collection of discrete excitations—photons. Key themes include: loudon quantum theory of light pdf
Loudon begins by revisiting the "ultraviolet catastrophe." He demonstrates how the quantization of energy levels leads to the blackbody radiation formula we use today. 2. The Quantized Least Action Loudon’s approach is distinctive: he begins not with