From Stimulated Emission to the Laser: A Narrative Review of Nonlinear Optics, Lasers, and Photonics' Foundations
Year: 2026
Type: review
Abstract: Photonics was born twice: once in Einstein's 1916 recognition that emission could be stimulated, and once in the 1960s when the laser's coherent light proved intense enough to make matter respond nonlinearly. This article presents a narrative review of the primary literature of both births. The synthesis is organized around three themes: the quantum-radiative foundations, in which Einstein's stimulated-emission paper, Schawlow and Townes's infrared maser analysis, Maiman's ruby laser, and the treatises of Svelto and Siegman built the coherent source --- the device whose gain, threshold, and cavity became photonics' grammar; the nonlinear turn, in which Franken's optical harmonics generation, Shen's and Boyd's nonlinearity treatises, and Keldysh's strong-field ionization opened the intensity axis along which light's propagation became a function of light itself; and the communication and systems integration, in which Kao and Hockham's dielectric fiber, Agrawal's nonlinear fiber optics, and Saleh and Teich's photonics synthesis assembled the source, the nonlinearity, and the waveguide into the modern photonic system. It is concluded that the literature describes a single causal chain --- stimulated emission enables the laser, the laser enables nonlinearity, nonlinearity enables the photonic system --- whose stages are each other's instruments, and whose unification in the photonics textbook is the field's declaration that light's manipulation is now a technology with its own physics.
Authors: Revista, Zen, PHYSICS, 10
Institution: Faculdades Guarulhos
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204766752