  We report on new simple and efficient multipass amplifiers using prisms or
corner cubes to perform several passes in different planes of incidence. This
scheme provides an optimized overlap between the signal passes and the pumped
volume. We investigated our amplification geometry with Nd:YAG and Nd: YVO4
crystals : the use of a low doped (0.3%) Nd:YVO4 crystal allowed better thermal
behaviour and higher performances. We amplified a pulsed microlaser (110 mW of
average power at 1064 nm) and obtained a diffraction-limited output beam with
an average power of 5.7 W for 15 W of pump power and a small-signal gain of 56
dB in a 6-pass configuration.
