ScBO3:Cr—a new room temperature near-infrared tunable laser

Abstract

We report the first Cr3+ laser in a borate host crystal. The free-running laser wavelength was 843 nm in a nearly concentric laser cavity pumped by a krypton-ion laser at 647.1 nm. With a single element birefringent filter, a tuning range of 787-892 nm was measured using the first optically clear crystal. The output power slope efficiency was 29% lasing at 848 nm with an output coupler of 1.78% transmission. The laser round trip loss, including a possible excited state absorption, was calculated to be 1.3% cm. Spectroscopic measurements indicated that the material was clear of absorption loss in the lasing spectral region, and the relative fluorescence efficiency for the entire Cr absorption band in the visible region was nearly unity. The fluorescence lifetime at room temperature was 115µS. A study of lifetimes vs temperatures showed that the multiphonon relaxation process had an onset temperature of ~ 340 K. The peak emission cross section was calculated to be 1.2 × 10−20 cm2 at 873 nm for the c-axis polarization.