Wavefront correction by target-phase-locking technology in a 500 TW laser facility

We demonstrate a novel approach termed target-phase-locking that could improve the entire beam wavefront quality of a 500 TW Nd³⁺:phosphate glass laser facility. The thermal and static wavefront from front-end to target is corrected by using one deformable mirror that receives feedback from both the focal-spot sensor and wavefront sensor, and only the main laser of the laser system is employed in the correction process, with auxiliary calibration light no longer necessary. As a result, a static focal spot with full width at half maximum of 8.87  ×  5.74 µ m is achieved, the thermal wavefront induced by flash-lamp-pumped Nd³⁺:phosphate glass is compensated with PV from 3.54–0.43 µ m, and a dynamic focal spot with intensity exceeding 10²⁰ W cm⁻² is precisely predicted at the target with such an approach. (letter)