A new wavefront measuring method of laser beam traversing a supersonic flow by using Hartmann-Shack wavefront sensor

An innovative experimental method for studying the influence of supersonic flow on laser beam transmitting has been proposed. The wavefront phase properties and the dynamic wavefront change of laser beam traversing supersonic flow can be detected by Hartmann-Shack (H-S) wavefront sensor. Beam aberrations are constructed by adopting Zernike mode-reconstruction theory. The centroid change of laser beam and the far-field properties can be obtained by further analyzing the experimental data. In the paper, the experimental principle is presented, and wavefront aberrations with several different flow parameters are given. Some beam-quality criteria such as Zernike aberration coefficient, PV and RMS value, circle energy, Strehl ratio, and centroid change of beam, are also calculated. Experimental results show that the stage of flow establishing, stabilizing and ending can be detected by using H-S wavefront sensor. By comparing the result of no flow with that of a given-parameter flow, defocus and astigmatism aberration increase obviously. At the same time, the Strehl ratio is reduced and the beam quality is degraded. The same conclusion can be obtained by comparing no test-model with the given-structural test-mode in same flow. Moreover, the wavefront aberration of laser beam in the condition of different flow parameters can also be measured and compared accurately by using the test method.