AgScP 2 S 6 van der Waals Layered Crystal: A Material with a Unique Combination of Extreme Nonlinear Optical Properties.

Research in two-dimensional layered materials (2DLMs) has exploded over the past several years for a variety of applications in photonics and optoelectronics. The 2D nature of these materials allows for a very local electronic probe of material as well as flexible integration with other functional components. Herein, using the femtosecond Z-scan technique, we report a giant two photon absorption (TPA) process and its saturation in the van der Waals gapped silver scandium thiophosphate (AgScP 2 S 6 ) crystal. We have found a TPA coefficient of the order of 10 4 cm/GW which is orders of magnitude larger compared to many existing semiconductors and nonlinear crystals. Furthermore, we found a TPA cross-section of 10 3 GM and characterized the optical limiting (OL) response (0.2 mJ/cm 2 ) and the multipulse laser damage threshold (1.09 ± 0.19 J/cm 2 ). The combination of giant TPA, extremely low OL, and very high damage threshold suggests that this material could be extremely useful in applications like optical limiters or switches.