Abstract

Two-micrometer lasers operating on the Ho ⁵I₇–⁵I₆ transition depend critically on the choice of the laser material. Ho:Tm:LuAG or Ho:Tm;Lu₃Al₅O₁₂, previously predicted to have a low threshold, has been demonstrated to lase efficiently. To utilize laser diode pumping, typically the Tm ³H₄ manifold is excited using GaAlAs laser diode arrays operating around 0.78 µm. From here, several energy transfer processes are required to excite the upper laser manifold, i.e., the Ho ⁵I₇ manifold. However, several deleterious energy transfer processes can also occur which detract from the efficiency of the laser. In addition, since this is a quasi-four-level laser, performance parameters such as the threshold depend critically on the population densities of both the upper and lower laser levels. Since all of these effects depend on the position of the energy levels and their transition probabilities, the choice of laser material has a major impact on the performance: of the laser. Previously, 12 garnet laser materials had been analyzed to determine which have the lowest laser threshold.¹

© 1993 Optical Society of America