Deep red laser emission in Ho:YLF

Laser operation of the⁵S2→⁵I7transition in 2 percent Ho:YLF at room temperature is reported. Oscillations at\lambda = 750nm were obtained in flashlamp and dye laser pumped experiments. Thresholds of 4 J/cm and3 \times 10^{-4}J/cm were observed in flashlamp and laser pumped operation, respectively. The 750-nm transition in the Ho:YLF is a four-level laser with a stimulated emission cross section of\sigma = 9.7 \times 10^{-19}cm².