Broadband emission and laser action of Cr(3+) doped zinc tungstate at 1 micron wavelength

The spectroscopic properties of Cr:ZnWO4, which channels all the fluorescence into the broadband 4T2 - 4A2 transition at about 1 micron wavelength, are reported. Two different Cr(3+) centers with lifetimes of 0.5 and 5.4 microsec at 300 K are analyzed. Both centers emit broadband fluorescence with zero-phonon lines located at 834 and 877 nm wavelength. The effect of intrinsic and extrinsic charge compensation on the Cr(3+) centers is explained by a local and nonlocal compensation mechanism. With intrinsically compensated crystals, CW laser action at 77 K and pulsed laser action at 300 K were obtained.