Enhancing laser beam directional stability by single-mode optical fiber and feedback control of drifts

A system, which uses a single-mode optical fiber to suppress the laser beam drifts, and uses feedback control to further reduce the drifts of a primary collimated beam, is proposed to enhance the directional stability of laser beams. The linear and angular drifts of laser beams are separated through light path arrangement and detected using quadrant position detectors, and are controlled using two-dimensional linear and angular drift feedback control systems according to their magnitudes detected. Theoretical analyses and experimental results indicate that the collimation accuracy of 0.7×10^-7 rad can be achieved at a collimation distance of 500 mm using single-mode optical fiber and separate control of linear and angular drifts.