Nonlinear Crystals and Nonlinear Optics

Crystals with nonlinear optical properties have played an essential role in the recent development of new laser sources. The main basic knowledge needed to understand their operation has been introduced from the 2nd and 3rd order nonlinear electrical susceptibilities of solids. First, Malus' Law is recalled, along with the essential notions of polarization by reflection at Brewster incidence, by birefringence with uniaxial crystals (calcite CaCO ₃ , LiNbO ₃ , quartz), Glan-Thomson or Glan-Foucault prism interfaces, and by absorption with dichroic media. The whole is illustrated by practical examples of systems using quarter-wave blades, anti-reverse cells by application of an electric field that creates the desired birefringence of KDP crystals (KH ₂ PO ₄ ) by Pockels effect and optical isolator crystals by application of a magnetic field (Faraday effect). Among the most widely used applications we will show how second harmonic generation can be achieved by means of uniaxial crystals of the χ ⁽²⁾ type, intracavity frequency doubling and frequency self-doubling given by crystals doped mainly with the Nd ³⁺ ion. We continue with frequency generation by nonlinear parametric processes such as the optical parametric oscillator (OPO for Optical Parametric Oscillator ) often consisting of a periodically polarized LiNbO ₃ lithium niobate crystal (PPLN : Periodically Poled Lithium Niobate ) based on quasi-phase matching (QPM : Quasi Phase-Matching ) and optical parametric amplification (OPA). Finally, we'll look at frequency-shifting Raman-stimulated laser crystals applied to the creation of an artificial star pumping sodium atoms from the mesosphere.

This article on crystals and nonlinear optics is part of a package giving an overview of solid-state laser sources, including laser physics Solid-state laser sources. Foundations [AF 3 275] crystal luminescence Crystal luminescence applied to laser sources