The Historical Relationship Between Nonlinear Optics and Condensed Matter

Abstract

The first operating laser, developed by Maiman in 1960, utilized the energy levels of the Cr³⁺ ion in ruby. The high light intensity available in focused ruby laser pulses led to the creation of a new subfield of physics. This field, known as nonlinear optics, concerns itself with the optical properties of matter at high light intensity. The pioneering experiment by Franken and coworkers in 1961, utilizing a quartz crystal, demonstrated second harmonic generation of light. In the same year, two-photon optical absorption of ruby light was demonstrated by Garrett and Kaiser in a crystal of CaF₂ with Eu²⁺ ions. Many other nonlinear optical phenomena were also demonstrated first in condensed matter. The history of the generalization of the optical laws of reflection (Hero of Alexandria), refraction (Snell), and Fresnel’s laws to the nonlinear regime will be reviewed. The phenomenon of conical refraction, characteristic of biaxial optical crystals, also has an interesting nonlinear counterpart.