Abstract

Using a cw Ti³⁺:sapphire laser operating near 800 nm, to pump Er:YLiF₄ and EnBaY₂F₈ laser crystals, we have obtained laser oscillation from upper levels ⁴I_13/2,⁴I_11/2, ⁴I_9/2, ⁴S_3/2, ²H_9/2,⁴G_11/2, and ²P_3/2 of the Er³⁺ ion. We will summarize the observations to date, covering 0. 47-2.7 µm. Five of the upper laser levels are above the pumped level and therefore must require that cooperative energy sharing processes be occurring or involve a sequential absorption of two, three, or more pump photons, or both. To our knowledge, the laser at 470 nm is the first blue laser to be excited with a single IR pump. Previous reports of blue operation have required either a pair of yellow pump photons or a combination of a visible and a near-IR pump to achieve a cascade absorption pumping pathway. An examination has been reported by Xie and Rand¹ of the appearance of instabilities that occur under conditions of nonlinear coupling between the several state populations. It appears likely from our observations, that for many of the above systems, an accurate description of the laser behavior will need this complex nonlinear analysis.

© 1990 Optical Society of America