High-efficiency direct-pumped Nd:YLF laser operating at 1321 nm

We present a high-efficiency Nd: LiYF 4 (Nd:YLF) laser operating at 1321 nm pumped directly into the emitting level, 4 F 3/2 . The linear polarization of the pump diode laser was maintained by a short fiber. At the absorbed pump power of 7.3 W, as high as 3.6 W of continuous-wave output power at 1321 nm is achieved. The slope efficiency with respect to the absorbed pump power was 0.52. To the best of our knowledge, this is the first demonstration of such a laser system. Comparative results obtained for the pump with a diode laser at 806 nm, into the highly absorbing 4 F 5/2 level, are given in order to prove the advantages of 880 nm wavelength pumping.