Repetitively pulsed regime of Nd : glass large-aperture laser amplifiers

A repetitively pulsed operation regime of neodymium glass rod laser amplifiers with apertures of 4.5, 6, 8.5, and 10 cm is analysed using experimental data. The limits of an increase in the pulse repetition rates are determined. Universal dependences are obtained, which help finding a compromise between increasing the repetition rate and enhancing the gain for each particular case. In particular, it is shown that an amplifier 4.5-cm in diameter exhibits a five-fold safety factor with respect to a thermo-mechanical breakdown at a repetition rate of 1 pulse min^-1 and stored energy of above 100 J. A strong thermally induced birefringence in two such amplifiers is experimentally reduced to a 'cold' level by employing a 90° optical rotator.