High power Yb:YAG thin disc laser

In the laser design, the active medium consists of a thin disc of Yb:YAG (thickness 150 /spl mu/m to 200 /spl mu/m, depending on the doping concentration), mounted with one face (which is highly reflective coated for pump- and laser-wavelength) on top of a cooling plate. In this way the waste heat of the crystal can be conducted to the cooling water very effectively. The pump power from laser diodes hits the crystal from the other face of the disc which is antireflection coated. Only a small part of the pump power is absorbed in the thin disc, so most of the power is reflected. For increasing the total absorbed power, different schemes have been used for achieving multiple absorbing passes of the pump radiation through the disc. The actual design consists of a parabolic mirror for imaging the pump radiation onto the disc and several plane mirrors for redirecting the not absorbed power onto the parabolic mirror again.