Heat generation and thermal lensing in 2.8-/spl mu/m Er/sup 3+/:LiYF/sub 4/ lasers

For several years there has been an increased interest in lasers emitting at 3 /spl mu/m mainly because of their potential applications in laser surgery. Due to the high absorption of 3 /spl mu/m radiation in water, high-quality cutting or ablation is demonstrated in biological tissue using erbium-doped solid-state lasers. Recently, a CW output power of 1.1 W at this wavelength has been demonstrated in Er:YLF (Er/sup 3+/:LiYF4) under diode pumping at 970 nm. However, efforts to scale diode-end-pumped 3 /spl mu/m Er:YLF lasers to higher powers, which would be required for many surgical applications, have been hindered by rod fracture. To understand the mechanisms responsible for the increased risk of rod fracture in a 3 /spl mu/m Er:YLF laser, the heat generation, temperature profiles, and thermal-lensing behavior in this system under strong excitation were investigated in a finite-element calculation.