Near diffraction-limited laser output from a very large size rectangular core crystalline waveguide

Near diffraction-limited laser output from a very large size rectangular core crystalline waveguide laser was achieved experimentally. A crystalline waveguide, with a rectangular core size of 320 μm×400 μm by 1.0 at.% Yb:YAG (core) and 0.5 at.% Er:YAG (cladding), was designed and fabricated. The rectangular core area was approximately 64 times larger than the conventional device core area. Using a continuous diode laser end pumping, an output power of 26 W, with the beam quality of M2x=1.22, M2y=1.05 in the far-field, was obtained in the experiment. The design method that is used to enlarge the crystalline waveguide core size and suppression high-order transverse mode, can be applied for various kinds of crystalline waveguide lasers.