Crystal growth, structure and characterization of Er 6 B 4 O 15 as self-activated eye-safe laser material within the near-infrared waveband.

A new rare-earth borate Er6 B4 O15 was synthesized by a solid-state reaction technique. The crystal was obtained by a flux method. Single-crystal X-ray diffraction analysis revealed that the crystal structure is composed of ErO6 polyhedra sharing edges and BO3 groups. The absorption, near-infrared fluorescence spectra and the fluorescence decay curve of Er: 4 I13/2 energy level in the Er6 B4 O15 crystal were measured at room temperature. The absorption peak was located at 977 nm with absorption cross section of 1.16 × 10-21  cm2 and a full width at half-maximum (FWHM) of 16 nm, which is very suitable for commercial 980 nm laser diode pumping. A maximum emission peak at 1560 mm with a broad FWHM of 64 nm was observed in this crystal because of the Er3+ transition 4 I13/2 →4 I15/2 , while the emission cross section was calculated to be 8.53 × 10-20  cm2 . These results imply that the Er6 B4 O15 crystal is a promising candidate material for the achievement of an eye-safe near-infrared wavelength laser.