Simulated Research On Computer-aided Alignment Method For Unstable Resonator

The automatic alignment of resonator plays an important role in the industrial application of lasers,especially in the application of high-power laser.In this article,the method of computer-aided alignment of unstable resonator is presented.After analyzing resonator's construction characteristics,laser output beam quality evaluation method and misalignment characteristics,computer-aided precise alignment of system for unstable resonator with an autocollimating feedback optical system is designed.The mathematical model of calculating misalignments is established.The relation between mirror misalignments and its Zernike phase aberration coefficients,which can be expressed in zernike polynomial coefficients,is regarded as linear to some extent,especially under the condition of small misalignments.After getting a series of aberrations representing a misaligned system,we can get the data of mirror misalignment by solving a system of linear equations.Then the misaligned resonator can be modified according to these results.Matrix theory on system of linear equations is studied, especially when coefficient matrix of the equation is ill-conditioned,and the arithmetic of misalignments determination is analyzed.The simulations are processed with the help of Zemax and Matlab software.The numerical analysis shows that it is easy to figure out a single misalignment.Iteration is needed in complex misaligned system.The range for tilt misalignment that can be figured out is 0～10~4 urad and the decentration range is from 0 to 1mm.This method can be applied to the alignment of unstable resonator effectively and it provides an accurate method for the automatic alignment of laser resonator in practical use.