Rapid development of ultra-intense ultrashort lasers has been made by titanium:sapphire chirped pulse amplification. However, it appears to have an upper limit of 10-petawatt. Presently, for 10-petawatt to 100-petawatt development planning, researchers generally abandon this technology, and turn to optical parametric chirped pulse amplification technology. Yet titanium:sapphire chirped pulse amplification, as a mature technology that has successfully realized two 10-petawatt lasers, still has great potential for the next-stage development. Reasons for the 10-petawatt upper limit include limited titanium:sapphire sizes, transverse amplified spontaneous emission, and parasitic lasing.

The image on the cover for Advanced Photonics Nexus Volume 2 Issue 6 illustrates tiled-titanium:sapphire chirped pulse amplification. It can expand titanium:sapphire sizes, truncate transverse amplified spontaneous emission, suppress parasitic lasing, and, importantly, eliminate the need for complex space–time tiling control. The image is based on original research presented in the article “ Coherently tiled Ti:sapphire laser amplification: a way to break the 10 petawatt limit on current ultraintense lasers,” by Yanqi Liu, Keyang Liu, Zhaoyang Li, Yuxin Leng, and Ruxin Li (doi 10.1117/1.APN.2.6.066009).