SIMPLE-1 MICRON RING LASER-OSCILLATORS PUMPED BY FIBER-COUPLED LASER-DIODES

We have designed simple nonplanar Nd:YAG ring laser oscillators that utilize all flat mirrors and are pumped by the fiber-coupled output from ten 3 watt diode lasers. We have obtained up to 8.5 W at 1.06 microns of diffraction-limited, single frequency output with no measurable astigmatism or ellipticity with a total pump power of 26 W from a pair of 400 micron diameter fibers. Convex curved surfaces on the Nd:YAG rod are used to increase the cavity mode size at the rod while minimizing the contribution of aspheric thermal lensing. Comparison to a linear cavity with no intracavity polarizing element indicates that stress depolarization is a significant loss mechanism in the ring laser. The cavity design is also suitable for use with birefringent laser media, such as Nd:YLF or Nd:YVO4.