Polarization effects in active Fresnel rhomb zig-zag slab amplifier

The concept to use a slab as active element, working in zig-zag geometry, and also as Fresnel rhomb, seems to be rather attractive. However, in this case different depolarization effects in active element arc of crucial importance. We have carried out the estimations of depolarization effects arising both due to mechanical loading of an active element at its fastening and due to thermooptical distortions. To check up these rigid requirements to depolarization (0.1 % - 0.01 %) careful measurements of depolarization effects and their sources are being carried out. Mechanical loading gives one of the main contributions in depolarization at fastening of active element. Using model experiments with glass Fresnel rhomb under mechanical loading we have measured depolarization effects. It is proposed to use additional glass plate to compensate beam depolarization in zig-zag slab. The received results allow to expect successful use of the slab amplifier as a Fresnel rhomb providing rather high quality of optical material of active clement.