Infrared absorption and emission studies of Er:YAG, Er:KPb$_{2}$Cl$_{5}$, and Er:KPb$_{2}$Br$_{5}$ for eye-safe laser applications

There exists a significant current interest in the development of a new generation of 1.5-1.6$\mu $m eye-safe solid-state lasers with resonance diode laser pumping. Applications of laser sources that operate in the eye-safe wavelength regime near 1.5-1.6$\mu $m include remote sensing, long distance telemetry, and optical communications. Eye-safe laser wavelengths can be achieved by using trivalent Er$^{3+}$, which has an emission transition at $\sim $1.5$\mu $m. Prior to the development of resonantly pumped erbium lasers, two approaches were employed for eye-safe lasers, Nd-based lasers driving nonlinear optical parametric oscillators and erbium-doped glass lasers. System complexity and heat management limits the power scaling of these two approaches. The availability of new diode-pumped sources operating at $\sim $1.45$\mu $m has made resonantly pumped Er$^{3+}$ lasers a viable choice for high-power eye-safe lasers. Crystalline Er:YAG is currently the main gain material under consideration for 1.5$\mu $m Er lasers. In this work we present spectroscopic results of ceramic Er:YAG, Er:KPb$_{2}$Cl$_{5}$, and Er:KPb$_{2}$Br$_{5}$. Infrared absorption and emission cross-sections were analyzed and evaluated for potential applications as 1.5$\mu $m gain media.