New 3D multipass amplification scheme based on diode-pumped Nd:YAG or Nd:YVO/sub 4/ crystals

Summary form only given. We present a new simple and compact multipass configuration which optimize the overlap between pump and signal beam. In our tridimensional geometry, the laser beam travels eight times through the gain medium in four different planes of incidence. After being focused by a doublet in the gain medium, the laser beam is reflected by a dichroic mirror placed behind the crystal. Three AR-coated roof prisms ensure the lateral shift that allows the 8-pass travel. We obtained a small signal gain of almost 21 dB and an output power of 2.7 W for the Nd:YAG, whereas the Nd:YVO/sub 4/ provided 3 W of output power and a small signal gain as high as 30 dB. Moreover, a significant increase in the performance of the Nd:YVO/sub 4/ system is expected thanks to a better control of the state of polarization for each pass of the laser beam. Thus high gain and efficient extraction have been obtained with a new very simple and compact 3D diode pumped amplifier scheme. The performance exhibited by our system place it among the best amplifiers ever published, although the beam passes only 8 times in the gain medium. The concept is very flexible, accepting a number of passes as high as desired just by increasing the number of prisms and allowing a large range of input beams diameters.