Wave-front reconstruction of terawatt-class ultrashort laser pulses using Fresnel phase retrieval method

Summary form only given. With increasingly sophisticated high power laser applications, the quality and focusability of the laser beam have improved remarkably. While a focused beam profile can be directly obtained by measuring the focal spots at focus with a charge-coupled-device (CCD) camera, wave-front measurement of the laser beam would provide greater accuracy from the viewpoint of improving the beam quality by active phase correction with a deformable mirror. Phase sensing is a powerful technique to measure the phase of the laser beams. Several phase measurement methods have already been proposed and demonstrated. On the other hand, the Fresnel phase retrieval method, which is a noninterferometric method, has a relatively simple configuration, and is applied to reconstruct the object image from the Fresnel diffracted image. With this method, wave fronts of the beam are reconstructed from only two measured intensity distributions at two planes along the optical axis. By applying the Fresnel phase retrieval method, we demonstrate the wavefront measurements of high peak power ultrashort laser pulses. In this experiment, we used a part of our Ti:sapphire chirped-pulse amplifier laser system operating at a 10 Hz repetition rate. The laser system was operated to generate the laser pulses.