Two‐Photon Excitation Spectra of Trivalent Rare‐Earth Ion Luminescence in Crystals

Abstract

Abstract Theoretical and experimental investigations are made of two‐photon absorption spectra of trivalent rare‐earth ions in crystals. Effective cross‐sections, selection rules, and relative intensities of the components are found. The most intensive two‐photon transitions are established. Two‐photon excitation spectra of luminescence of Er 3+ and Ho 3+ ions in CaF 2 are obtained and effective excitation cross‐sections are measured using a tunable dye laser (715 to 850 nm). It is shown that the spectra have a peculiar structure which differs considerably from that of the one‐photon absorption spectra. The experimental results agree with theory. It is established that one of the levels in Ho 3+ is the level 5 G 6 rather than 3 K 7 usually assumed.