Variation of emission spectra of Er 3+-doped YAG-based solid solution

Abstract

Er 3+-doped YAG crystal has intense emission bands in the U-band region (1625–1675 nm), which is uncommon to the 4I 13/2– 4I 15/2 transition of Er 3+ in many hosts except for garnet type crystals. In order to seek the possibility to broaden the spectrum composed of many sharp bands, solid solutions based on Y 3Al 5O 12 (YAG) and Ca 3Al 2(SiO 4) 3 (CASG) crystals doped with Er 3+ ions were prepared by solid-state reactions and their emission spectra in optical-telecommunication band were examined. Both of the YAG and CASG crystals have garnet type structures with similar lattice constants. The spectral linewidth dramatically increased with increasing CASG content, which promises to overcome the difficulty in the gain flatness for optical amplification in the wavelength-division-multiplexing (WDM) system. The line broadening can be attributed to the inhomogeneous distribution of the Er 3+ sites achieved by the double substitutions of Si 4+ for Al 3+ in the tetrahedral site and of Ca 2+ for the Y 3+.