Broadband emission and laser action of Cr3+doped zinc tungstate at 1 µm wavelength

We report on the spectroscopic properties of Cr : ZnWO4, which channels all the fluorescence into the broadband⁴T2-⁴A2transition at about 1 μm wavelength. Two different Cr³⁺centers with lifetimes of 0.5 and 5.4 μs at 300 K are analyzed. Both centers emit broad-band fluorescence with zero-phonon lines located at 834 and 877 nm wavelength. The effect of intrinsic and extrinsic charge compensation on the Cr³⁺centers is explained by a local and nonlocal compensation mechanism. With intrinsically compensated crystals we obtained CW laser action at 77 K and pulsed laser action at 300 K.