Multi-reentrant nonplanar ring laser cavity

A multi-reentrant nonplanar ring laser cavity configuration is presented. Two identical spherical mirrors were used to construct the laser cavity. The exact reentrant condition of the ring cavity is derived and the stability of the laser cavity is analyzed. Although slight astigmatism can arise from the intracavity elements, the cavity itself is astigmatism-free. Linear output polarization is readily achieved. A 3-atm.% Nd doped YAG with 1-mm thickness was used as the gain medium to reduce beam distortion, and the gain medium also served as a Faraday rotator to control the laser beam propagation direction. The laser cavity length is short, whereas the laser beam round-trip length can be long. A factor of 13-times enlargement in round-trip length is demonstrated.