Mehrphotonen-Absorption in Kristallen und ihre Anwendungen. Will Kleber zum Gedenken

The paper summarily reports on absorption phenomena occurring in crystalline matter, whereby excitation states are obtained with more than one photon participating in the elementary excitation act. This is possible both by simultaneous multiphoton absorption and by a consecutive, step-by-step absorption of a number of photons (2 photons in most reported cases). Among possible applications of these phenomena, laser or 2-photon spectroscopy, infrared quantum counters (IRQC) and infrared frequency converters (frequency up conversion) have raised particular interest recently.