| Since supercontinuum laser has improved greatly in output power and spectrum range,it plays a more and more important role in optical communication,laser remote sensing,active lighting,industrial inspection and other fields,however,the beam quality of high-power supercontinuum laser is generally poor,which seriously limits the practical application of supercontinuum laser.It is an effective scheme to improve the quality of supercontinuum laser beam by introducing adaptive optics technique to compensate the wavefront distortion of supercontinuum laser.Piezoelectric material of Bimorph deformable mirror(DM)is adhered to base in whole layer,comparing with traditional DMs,Bimorph DM is more simple to process,with low cost and flexible structure,suitable for low-order aberration correction,and easy to get large correction stroke,but there is little research related to the wavefront correction of supercontinuum light sources using Bimorph DMs.In this paper,the beam control of supercontinuum laser is taken as the main research content,the near-field wavefront characteristics of supercontinuum light source are explored,a transeverse piezoelectric DM aiming at defocus and astigmatism based low-order aberration correction is designed and processed,then a closed-loop system without wavefront detection is established,the simulation and experiment study on the supercontinuum laser aberration compensation capability of the DM are carried out,the optimization control algorithm is SPGD algorithm.To control supercontinuum laser beam,the wavefront phase information of supercontinuum laser must be determined at first,the near-field wavefront characteristics of a 400nm-1700 nm supercontinuum light source developed by our institute is detected,the near-field wavefront characteristics in different wavelengths of the supercontinuum light source are basically the same,mainly composing of defocus and astigmatism.In view of the feature that Bimorph DM is particularly suitable to correct low-order aberrations in small-aperture optical system,a 19-cell transverse piezoelectric DM is designed to fit the demands of low-order aberration correction and large correction stroke.Its surface deformation ability is simulated,the deformation ability of each electrode is balanced,PV values of influence functions of 19 electrodes are all around 1 ?m when 300 V drive voltage is applied.Next,the DM is manufactured according to above design,and main performance parameters of the DM are measured,the actual deformation of each electrode is more than the simulated result under 300 V voltage,fixing the monocrystalline silicon mirror edge in loose way makes a significant improvement of the deformation stroke of the DM,changing the pressure strength on the edge of the DM can also adjust the DM deformation in a small range.Moreover,the frequency response characteristic of the DM is excellent.Then,the feasibility of using SPGD algorithm to control the DM,the algorithm convergence speed and the correction effect are analyzed,after 1000 iterations,the PV value of the distorted wavefront decreases from 1.135? to 0.1526?,meanwhile,the SR value of the far-field spot rises from 0.1 to 0.9907,the operation takes about 150 s in total,illustrating that using SPGD algorithm to control the DM to correct low-order aberrations is feasible,fast and effective.At last,a closed-loop experimental system using for the correction of the supercontinuum full-wavelength output aberrations is constructed based on the supercontinuum light source,the 19-cell transverse piezoelectric DM,SPGD algorithm and CCD imaging device,the divergence of the far-field spot shape after close loop is significantly improved,which indicates that using transverse piezoelectric DM to compensate supercontinuum light source aberrations is able to obtain great correction effect. |
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