Feedback-guided robotic assembly workflow for alignment-sensitive optical systems: Experimental validation with a compact diode-pumped ruby laser

Assembly of alignment-sensitive optical systems remains challenging because even small positional or angular errors can measurably affect system performance. In solid-state lasers, such errors can lead to changes in output power, beam quality, and stability. As a result, assembly of these systems remains largely manual, which increases production effort and cost, limits scalability, and often results in bulky designs constrained by large kinematic optic mounts. To address this challenge, this paper presents a feedback-guided robotic assembly workflow for compact, alignment-sensitive optical systems and validates it experimentally with a diode-pumped ruby laser. The workflow combines vision-guided pickup and passive placement with fluorescence-based axial positioning of the crystal, optical-feedback-based cavity alignment, stepwise optimization of the laser output, and permanent fixation via UV-curable adhesive. The process was implemented on a commercial precision optics assembly platform and executed without manual adjustment. As a representative validation case, the assembled ruby laser produced diffraction-limited output at 694.3 nm with an output power of 30 mW. The results show that passive placement, in situ optical feedback, optimization, and bonding can be integrated into a repeatable robotic process for laser assembly. The demonstrated workflow provides a practical route toward automated assembly of optical systems whose performance depends critically on precise alignment and on preserving that alignment during and after bonding.