Optical materials for short wavelength generation

This review reports on recent achievements in the synthesis and crystal gro wth of materials for efficient generation of short wavelength light. Materi als exhibiting harmonic generation, stimulated Raman scattering or upconver sion are discussed. Early and recent work has confirmed that ferroelectric oxide and berate crystal are most feasible for harmonic generation, while s tructures containing molecular-like entities seem to be able to generate mu ltiple stimulated Raman scattering responses. In the field of upconversion, halide materials turned out to be more efficient than e.g. oxides. Low-pho non materials such as chlorides or bromides yielded efficient luminescences down to the near UV region. However, chloride and bromide crystals contain ing rare earth ions generally are not stable in air. The search for stable host crystals may be considered a major challenge in the synthesis of new m aterials for upconversion. Independent of the nonlinear optical mechanisms of short wavelength generation, formation of waveguides gained considerable importance, because production for real world applications most evidently will follow a waver type technology. (C) 1999 Elsevier Science S.A. All rig hts reserved.