Infrared (1.2–1.6 μm) luminescence in Cr4+:Yb3Al5O12 single crystal with 940 nm diode pumping

Infrared (1.2–1.6 μm) luminescence in a ytterbium aluminium garnet (YbAG) crystal, doped with Cr (0.05 at.%) ions, was investigated under CW laser diode pumping (λ = 940 nm). The Cr4+ emission band was observed with its peak at 1.34 μm and measured to be about 1.3 times with respect to Yb3+ IR luminescence (λ = 1.03 μm). We demonstrate that for the excitation wavelength of 940 nm Yb3+ ions act as sensitizers of the 3B2(3T2)–3B1(3A2) emission of Cr4+ ions. This crystal is promising as a high-efficient system for tunable laser (1.2–1.6 μm) output.