The Thickness and Crystal Phase Engineering of Copper Vanadate Nanosheets for Broadband Nonlinear Optical Limiting Glass Devices

ABSTRACT With the development of laser technology, the harms of laser to optical devices and the human eye have become more serious, hence developing strategies for laser protection is urgent. Optical limiting (OL) is effective mean of laser protection. In this study, copper vanadate nanosheets (Cu 3 V 2 O 7 (OH) 2 ·2H 2 O, Cu 3 V 2 O 8 ) and their OL devices are designed based on synergistic regulation of crystal and thickness. The thickness is proportional to the hydrothermal temperature, meanwhile, the crystal structure of Cu 3 V 2 O 7 (OH) 2 ·2H 2 O are transformed into Cu 3 V 2 O 8 after the annealing process at 400°C. Based on Z‐scan technique analysis, the OL performance of the resultant copper vanadate nanosheets can be regulated by the synergistic effect of thickness and crystal phase. The reverse saturable absorption of copper vanadate nanosheets are attributed to a stronger two‐photon absorption induced free carrier absorption and faster exciton relaxation dynamics, indicated by the femtosecond ultrafast transient absorption spectra. At last, the copper vanadate nanosheet‐based OL gel glass devices are prepared by the sol‐gel method, achieving outstanding OL performance with a low OL onset threshold of 0.0203 J·cm −2 . This study not only provides a promising strategy to adjust copper vanadate nanosheets for OL devices but also advances the development of transition metal oxide materials in the field of nonlinear optics.