Luminescence from Cr³⁺ centres in forsterite (Mg₂SiO₄)

Laser action, tunable around 1.2 μm, has been reported in Cr-activated forsterite (Mg₂SiO₄). We have examined the emission from this material in the region 650-850 nm via photoluminescence, excitation and lifetime studies over a range of temperature. Our measurements indicate that the emission in this region can be assigned to transitions on Cr³⁺ ions in high-field octahedral sites. The emission from the M1 site is clearly identified. We propose a simple model to account for the temperature dependence of the luminescence.