Design of a real-time automatic resonator alignment method for unstable resonators

The auto-alignment method for unstable resonators proposed in this paper innovatively replaces the secondary mirror of traditional unstable resonators with a double-convex lens coated with a high reflective film on one side, and installs the primary mirror on a designed electrically adjustable bracket. During the laser emission process, the computer calculates the relative displacement of the centroid of the far-field spot on the camera detection surface to determine the magnitude of the resonator misalignment, and simultaneously controls the electrically adjustable bracket to complete the compensation for the resonator misalignment. Finally, the experimental results show that when using the real-time automatic resonator alignment method, the output power of the laser remains very stable with a relative standard deviation of the normalized power less than 1.1% (if the auto-alignment method is not adopted, the output power will decay to 89.8% of the peak value). Therefore, this method can effectively solve the resonator misalignment problem of unstable resonator lasers. In addition, this method has the advantages of simple optical path structure and high detection speed while ensuring high accuracy. •A simple and economical method for automatic resonator alignment is proposed.•The method replaces the secondary mirror of the unstable resonator with a biconvex lens with a high-reflection film on one side to detect the misalignment degree of the resonator.•The primary mirror is installed on a designed electrically adjustable bracket to complete the compensation for the resonator misalignment.