A novel focal spot positioning method for high peak power lasers

The precise positioning of focal spots plays a crucial role in laser–matter interactions, especially for strong field physics requiring high laser focused intensity. A novel method based on the porous mask is proposed to directly positioning the focal spots of high peak power lasers. In this method, a porous mask is introduced before the laser compressor to substantially weaken laser energy while without changing laser-focusing characteristic, and different levels of energy attenuation can be easily realized by optimizing the porous mask. In addition, proof-of-principle experiments have also been carried out in high peak power femtosecond lasers up to hundreds-terawatt (TW), and the results efficiently demonstrate the validity and feasibility of this method. To our knowledge, it is the first time to achieve the direct positioning of the focal spots of high peak power lasers, which can efficiently facilitate the experimental investigations of strong field laser–matter interactions.