High efficiency, resonantly diode pumped, double-clad, Er:YAG-core, waveguide laser

We report on the highly efficient, resonantly diode-pumped Er:YAG-core, double-clad, all-crystalline eye-safe waveguide laser. A 500 × 500 μm Er(3+)(1%):YAG single-crystalline core with an ultra low numerical aperture (NA) of ~0.02 was surrounded by a 700 × 700 μm undoped single-crystalline YAG cladding. The entire Er:YAG/YAG core/clad structure was over-clad by transparent magnesium aluminum spinel (MgAl(2)O(4)) ceramic. The waveguide was continuously (CW) clad-pumped by a spectrally-narrowed, fiber-coupled InGaAsP/InP laser diode module at ~1532 nm. We achieved 25.4 W of output power at 1645 nm with a beam quality of M2 ~2.6. The achieved 56.6% slope efficiency with respect to the absorbed pump was derived by factoring out scattering loss of the pump light in the inner cladding. With a wavelength-selective cavity, the waveguide laser delivered ~8 W of output power at 1616.6 nm. To the best of our knowledge, it is the first reported laser experiment with a crystalline Er(3+):YAG-core and a truly double-clad crystalline waveguide structure.