Experimental investigation on the eliminating astigmatism in off-axis parabolic mirror ring cavity.

Highlights • Off-axis parabolic mirror used to eliminating the astigmatism in folded resonator. • Without any astigmatically compensated elements. • Optical elements can be inserted into the off-axis parabolic mirror resonator easily. • The low sensitivity to misalignment kept for the off-axis parabolic mirror resonator. Abstract The astigmatism in a ring cavity has been eliminated based on the off-axis parabolic mirror, which was utilized as the folded mirror instead of the spherical mirror in the laser resonator. There are no astigmatism-compensated elements on the beam path of the laser resonator with very simple design. The experimentally measured results have shown that the ellipticity was more than 0.98 for this kind of design. The misalignment sensitivity for the ring cavity was equivalent to that of the spherical mirror ring cavity. [ABSTRACT FROM AUTHOR]