Cr:LiCAF

LiCaA1F₆:Cr³（Cr:LiCAF) is a new addition to a series of new tunable near-infrared laser materials. Cr:LiSAF possess suitable properties for the generation of high-energy tunable radiation in the near infrared. It exhibits small thermal lensing, a high damage threshold and a sufficiently long upper-state lifetime to ensure efficient energy storage. Furthermore, laser rods of diameters up to 25 mm can now be fabricated, which is an important consideration for the design of high-energy lasers and amplifiers. The relatively long upper-state lifetime Cr:LiCAF 170μs, makes it possible to efficiently pump these materials with flashlamps. The new chromium laser host, LiCAF, is reported to possess favorable spectroscopic and laser properties. Laser-quality LiCAF crystals appear to be moderately straightforward to produce: zone-melting, Bridgman, and Czochralski crystals have been lased. Significant scattering in these crystals, a persistent problem in early growth attempts, now appears to be under control. Recently used Bridgman crystals have scattering losses of ~0.1% cm⁻¹, an acceptable level for most applications. The natural abundance of the constituent elements, coupled with the relatively low melting temperature (804°C) and congruent melting, forms a compelling case for the possibility of large-scale, inexpensive growth of laser-quality crystals. The laser emission of Cr:LiCAF has been tuned to between approximately 720 and 840nm and peaks at ~780nm. The radiative lifetime is ~175 μs at room temperature, and there is no evidence of concentration quenching for samples containing as many as 9 × 1020 Cr³⁺ ions/cm³. The intrinsic slope efficiency of LiCAF (67%) is close to that of alexandrite(65%). Recent flash-lamp-pumped Cr:LiCAF experiments demonstrated slope efficiencies of 1.6%, although passive losses in the laser rod of 3.5% cm−1 significantly affected the laser performance.