LONG-WAVELENGTH STIMULATED-EMISSION VIA CASCADE LASER ACTION IN HO - YLF

Two cascade laser schemes are demonstrated for Ho3+ in LiYF 4. The first involves the 5S2, 5I5, and 5I7 manifolds with laser oscillation at 1.392 and 1.673 μm, and the second involves the 5S2, 5I5, and 5I 6 manifolds with laser oscillations at 1.392 and 3.914 μm. The 3.9-μm transition is the longest-wavelength rare-earth laser achieved to date and further the system has attractive engineering practicality. The specificity of excitation inherent in the cascade approach is considered essential in overcoming the adverse multiphonon relaxation processes at long wavelengths.