| With the increase of the laser output power,heat effect and nonlinear effect on the beam quality become increasingly serious,directly limit the improvement of laser brightness output.Multimode laser has fewer restrictions on the structure,so it can be able to withstand higher power output.But the multimode beams with poor beam quality decline the brightness output.As a result,improving beam quality of the multimode beams by beam control is of great significance.In this paper,a closed loop control method of multimode beams is proposed that use the wave-front measurement data and wave-front correction device as the core.It has a very good reference value for subsequent application in high power laser multimode beam control.In this paper,the physical properties of multimode beams are analysed based on the theory of partially coherent light.Through the experiment measuring the coherence of multi-mode light field,provides a theoretical basis or subsequent multimode beams of light detection and correction.Put forward a calibration method for the spatial light modulator used as a beam correction device,thus the spatial light modulator can accurately generate various Zernike aberration.In this paper a multimode beams closed-loop control experiment system was built,and the coherence,scalability,and correction of multimode beams are studied from the aspects of theory and experiment.In the experiment system,the SID4 was used for wave-front measurement of multi-mode beam.The LC-SLM was used for the phase modulator of the wave-front.A closed-loop control of multi-mode light field for fiber output LD was implemented.Through the correction within five times,RMS of multimode beams aberration reduced from 0.045 to 0.015.The experimental results validated the correct of the closed loop control system proposed in this paper.According to the characteristics of the partially coherent multimode light beam,a new idea of measuring and correcting the wavefront by subarea was proposed. |
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