BEAM-divergence characterisation of a 200 μW red guide laser for collimator optimisation in an MFSC-1000X/1500X CW fiber-laser system

Abstract

This research examines the beam divergence characteristics of a 200 μW red guiding laser included in the MFSC 1000X-1500X (G5) continuous-wave (CW) cleaning fiber laser system. Fused silica ultraviolet-grade quartz plano-convex lenses were used (O12.7 mm, focal length = 25 mm) to examine how the red alignment beam behaves when focused on long distance targets. The experimental procedure entailed methodical measurements of the laser beam diameter across varying propagation lengths, from 3000 mm to 25,000 mm, succeeded by the computation of the divergence angle utilising Gaussian beam propagation models. Beam diameter was defined at the 1/e2 level, and uncertainties in divergence were ±0.1 mrad. The results show that the beam diameter grows steadily from 4 mm at 3000 mm to 15 mm at 25,000 mm. Stable “saturation zones” appeared between 6000 and 7600 mm and between 12000 and 15700 mm, where the beam diameter remained constant at 8 mm and 10 mm, respectively. This indicates that the beam was within the measurement threshold of divergence. The calculated full-angle divergence values were 2.00 mrad from 3000 to 4000 mm, 1.00 mrad from 4000 to 6000 mm, and 2.31 mrad from 15700 to 17000 mm. These nonlinear deviations arose from diffraction, the initial beam waist, and lens aberrations. Stable regions were interpreted as ≤ measurement threshold within stated uncertainty, providing practical “design windows” for collimator optimisation. Using ultraviolet-grade fused silica lens maintained the beam at high quality since it cut down on chromatic aberration which improved transmission in the visible range. The results give us useful information about how to use red guide lasers in optical systems for cutting, cleaning surfaces, and aligning lasers. The way the beam acts shows that fixed-focus or adaptive collimators need to be made to work with different divergence characteristics that alter at certain distance intervals. In summary, the work offers a thorough experimental examination of beam divergence for a low-power red guide laser included into a continuous wave fiber laser system. The results lead to better engineering of guide beam optics in industrial laser systems, which makes long-distance operations safer and more accurate.