Double-clad structures and proximity coupling for diode-bar-pumped planar waveguide lasers

We report, for the first time, fabrication of double-clad planar waveguide structures and their use for multiwatt, diode-bar-pumped, planar waveguide lasers based on Nd/sup 3+/ and Yb/sup 3+/-doped YAG. The direct-bonded, five-layer structures of sapphire, YAG, and rare-earth-doped YAG have sufficient numerical aperture to capture the fast-axis divergence of a diode bar by proximity coupling with no intervening optics, leading to very simple and compact devices. The restriction of the doped region to the central core leads to diffraction-limited laser output in the guided direction. We also show that the direct-bonding fabrication process can lead to a linearly polarized output.