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 Nd3+- and Yb3+-doped YAG, The direct-bonded, five-layer str uctures of sapphire, YAG, and rare-earth-doped YAG have sufficient numerica l aperture to capture the fast-axis divergence of a diode bar by proximity coupling with no intervening optics, leading to very simple and compact dev ices. The restriction of the doped region to the central core leads to diff raction-limited laser output in the guided direction. Mie also show that th e direct-bonding fabrication process can lead to a linearly polarized outpu t.