Watt‐Level Second‐Order Topological Charge Ultrafast Green Vortex Laser with Quasi ‐2D PEA₂(CsPbBr₃)_n‐1PbBr₄ Perovskite Films Saturable Absorber

Abstract

Ultrafast vortex beams have significant scientific and practical value because of their unique phase properties in both the longitudinal and transverse modes, enabling multi‐dimensional quantum control of light fields. Directly generating watt‐level ultrafast vortex beams with large angular momentum has remained a major challenge due to the limitations of mode‐locked materials and existing spatiotemporal mode‐locking generation methods. In this study, quasi‐2D PEA2(CsPbBr3)n‐1PbBr4 perovskite films are prepared by an anti‐solvent method and employed for the first time in a mode‐locked resonator operating in free space. Utilizing the angle‐based non‐collinear pumping and frequency doubling techniques, the second‐order ultrafast green vortex beams with a power of up to 1.05 W and a duration of 373 ps are generated. Experimental findings demonstrate the strong nonlinear saturable absorption properties of quasi‐2D PEA2(CsPbBr3)n‐1PbBr4 perovskite films at high power levels, highlighting their considerable potential in ultrafast laser technology and nonlinear optics.