Efficient 2-micron Ho lasers based on fluoride crystal hosts

Highly efficient, water cooled, resonantly pumped Ho3+ fluoride lasers have been demonstrated at 2 μm. The laser materials, 0.5 at.% Ho:YLF, 0.5 at.% Ho:BYF, and 0.5 at.% Ho:BaYLuF, were resonantly pumped with an IPG Tm:fiber laser operating at 1940 nm. Laser action occurred on the ⁵I₇ to the ⁵I₈ manifold with center wavelengths of 2062.6 nm, 2074.0 nm, and 2075.2 nm respectively. Continuous wave (CW) operation of 0.5% Ho:BYF achieved a maximum efficiency of approximately 68% with a 50% reflective output coupler. Pulsed operation of this laser system produced 4 mJ pulses at 500 Hz with a slope efficiency of 38%.