For generating ≤1 ns diffraction limited laser pulses, at a kilohertz repetition rate in the recent decade a significant amount of effort was focused on the development of compact passively Q-switched microchip lasers [1-2]. However, they have significant drawbacks – the output energies are typically in the range of few to hundred microjoules, which is not enough to reach saturation of the amplification in a Nd/Yb power amplifiers, required for efficient extraction of the stored energy. Hence, a pre-amplifier must be employed in order to boost the oscillator pulse energy to the few milijoules . Good candidates of such preamplifier, are thin rods amplifiers (diam. ~1mm) based on pulled YAG single crystal fibers  or mechanically fabricated YAG rods . In most of the proposed amplifiers, the studies ware focused on configurations ensuring maximum output average power until the output beam polarization is not taken into account even though the Nd:YAG crystal possesses a thermally induced depolarization of the laser beam passed through it.
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