Direct 800 nm diode-pumped Holmium laser with broad pump wavelength range and temperature adaptability.

We developed an 808 nm diode laser pumped composite Holmium laser via the integration of Tm-doped and Ho-doped YAG crystals into a single bulk structure. A maximum output power of 1.8 W at 2122 nm with near diffraction-limited beam quality was achieved for an absorbed pump power of approximately 7 W. Given that the pump wavelength is approximately 20 nm away from the absorption peak of the Tm-doped region of the crystal, pump wavelength adaptability of the Tm/Ho composite laser was effectively demonstrated. In this case, a pump range width in excess of 40 nm at approximately 800 nm was predicted by defining the pump spectrum of the gain medium. The temperature adaptability of the Ho laser was demonstrated by varying the cooling temperature from 9 °C to 27 °C. This resulted in Ho laser operation above 1.5 W with a power deviation below 10%. This work presents the experimental results for a compact assessable 2.1 μm laser without pump wavelength and operation temperature restrictions.