Low-Quantum-Defect Solid State Lasers: 2-, 3-, or 4-level?

Report No. ARL-RP-0298
Authors: Jeffrey O. White
Date/Pages: August 2010; 10 pages
Abstract: The concept of three-level- and four-level-lasers was used early on to explain why it was easier to make the Nd3+ ion lase than the Cr2+ ion. Almost 50 years later, work on solid-state lasers has recently led to a quantitative definition of the concept. The new level parameters l0 and l1 defined here will provide an improved basis for comparing Nd3+, Cr2+, and other ions, e.g. Er3+, Yb3+, Ho3+, and Tm3+. l0 and l1 assign to a system of discrete energy levels a number, with a physical basis, that varies continuously between 2 and 4, in the same way that the Hausdorff and Rényi definitions yield non-integer dimensions for fractals. Together with the cross section, lifetime, etc., they help in the design of a laser by providing a basis for choosing the operating temperature, pump wave-length, and laser wavelength.
Distribution: Approved for public release
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Last Update / Reviewed: August 1, 2010