A historical introduction. Loudon sets the stage by showing the failure of classical electromagnetism and the birth of the photon concept. He derives Planck’s blackbody radiation formula from first principles, establishing the statistical nature of light.
The crown jewel of the book. Loudon introduces the optical equivalence theorem and the P-representation. He distinguishes between fully coherent light (lasers), partially coherent light (thermal lamps), and squeezed light. loudon quantum theory of light pdf
Expanding from one mode to infinite modes. Loudon quantizes the vector potential and discusses the vacuum fluctuations in detail. This chapter is heavy, but essential for quantum field theory in curved spacetime or cavity QED. A historical introduction