https://www.nature.com/articles/srep01170 https://www.nature.com/articles/srep01170 ehich is the first linked paper in that section explains it well. The laser

https://www.nature.com/articles/srep01170 https://www.nature.com/articles/srep01170 ehich is the first linked paper in that section explains it well. The laser fires through the hole and ablates material from the back disc. The electrons from the created plasma reach the other side of the disc first before the ions because they are lighter, causing a buildup of negative charge on the other side. This charge differential drives a current between the two plates, which creates a magnetic field inside the coil.