Power scaling of thin Nd:glass and Nd:YAG slab lasers, face-pumped by laser diodes

High-power planar dielectric waveguide lasers

“…where L is the length of the region in which heat is deposited. Following Baker et al [26], we now reason that a limit on the waveguide performance is reached when the guidance due to this thermally-induced graded-index profile produces a spot size that is smaller than that of the slab waveguide itself. The index profile above produces a fundamental-mode spot size (1/e 2 half-width of intensity) of [40] w…”

“…In order to estimate when the one-dimensional thermal lensing starts to effect the waveguide laser performance, Baker et al [26] have used the condition that the slab guidance should give a smaller spot size than the thermally induced guiding due to the change of refractive index with temperature. This analysis, also detailed in the appendix, leads to a maximum power density with a dependence of an inverse power to the four on the doped-core thickness, as shown below (corresponding to equation (A17) in the appendix)…”