Focal Spot Optimization Using Spatial Light Modulation and a Phase Retrieval Algorithm

Abstract: Aberrations to the wavefront of a laser beam reduce the quality of the focal spot and are generally undesired. This project is aimed at determining the aberrations of laser beams by using a phase retrieval algorithm and to show that it is possible to correct the aberrations with a spatial light modulator to optimize the focal spot. In particular, a two-dimensional phase pattern is retrieved and decomposed into Zernike polynomials to generate two distinct correction patters that are applied to the spatial light modulator to increase the peak intensity and reduce the width of the focal spot. Measurements of the aberrations of a terawatt laser are performed with the phase retrieval algorithm and compared to measurements with a Shack–Hartmann wavefront sensor.