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Novel Cr4+-based tunable solid-state lasers

Spectroscopic and laser properties of chromium-doped forsterite (Cr:Mg2SiO4) are reviewed and future directions in development of other Cr4+-doped tunable solid-state lasers are discussed. The unique property of chromium-doped forsterite is that the lasing center was identified as tetravalent chromium (Cr4+) substituting for tetrahedrally coordinated Si4+. Development of chromium-doped forsterite laser may stimulate generation of a new class of tunable solid state lasers based on tetravalent chromium as a laser active ion for near infrared eyesafe spectral range. The criteria for the development of new Cr4+-based tunable solid-state laser crystals are discussed. We also present current research efforts to identify potential low field host crystals, such as silicates, titanites and germanates, that may be doped with Cr4+ as an active ion. These new laser materials are expected to cover the wavelength region from 1 -2 ?m, which may be of great technological importance.