Multi-line-of-sight Hartmann-Shack wavefront sensing based on image segmentation and K-means sorting.

Multi-line-of-sight wavefront sensing, crucial for next-generation astronomy and laser applications, often increases system complexity by adding sensors. This research introduces, to the best of our knowledge, a novel method for multi-line-of-sight Hartmann-Shack wavefront sensing by using a single sensor, addressing challenges in centroid estimation and classification under atmospheric turbulence. This method contrasts with existing techniques that rely on multiple sensors, thereby reducing system complexity. Innovations include combining edge detection and peak extraction for precise centroid calculation, improved k-means clustering for robust centroid classification, and a centroid filling algorithm for subapertures with light loss. The method's effectiveness was confirmed through simulations for a five-line-of-sight system and experimental setup for two-line and three-line-of-sight systems, demonstrating its potential in real atmospheric aberration correction conditions. Experimental findings indicate that, when implemented in a closed-loop configuration, the method significantly reduces wavefront residuals from 1 λ to 0.1 λ under authentic atmospheric turbulence conditions. Correspondingly, the quality of the far-field spot is enhanced by a factor of 2 to 4. These outcomes collectively highlight the method's robust capability in enhancing optical system performance in environments characterized by genuine atmospheric turbulence.

Intracavity adaptive correction of an unstable standing-wave resonator based on reconstruction matrix optimization.

Due to the existence of the expanding beam portion in the positive branch confocal unstable resonator, the laser passes through the intracavity deformable mirror (DM) twice with different apertures, which makes it complicated to calculate the required compensation surface of the DM. In this paper, an adaptive compensation method for intracavity aberrations based on reconstruction matrix optimization is proposed to solve this problem. A collimated probe laser of 976 nm and a Shack-Hartmann wavefront sensor (SHWFS) are introduced from the outside of the resonator to detect intracavity aberrations. The feasibility and effectiveness of this method are verified by numerical simulations and the passive resonator testbed system. By adopting the optimized reconstruction matrix, the control voltages of the intracavity DM can be directly calculated from the SHWFS slopes. After compensation by the intracavity DM, the beam quality ß of the annular beam coupled out from the scraper is improved from 6.2 times diffraction limit to 1.6 times diffraction limit.