Nonlinear optical absorption characteristics and ultrafast carrier dynamics of one-dimensional strongly correlated cuprate nanosheets

Abstract

Developing novel optical materials with large and ultrafast nonlinear optical (NLO) response is significant for photonics and optoelectronics. Cuprates as the representative one-dimensional (1D) strongly correlated material show promising NLO properties, but relevant research is quite rare. Here, using Ca2CuO3 nanosheets as the prototype, we systematically explored the NLO performance and ultrafast carrier dynamics of these cuprate nanosheets prepared by a ball-milling process. The obtained Ca2CuO3 nanosheets exhibited convertible NLO behavior from saturable absorption (SA) to reverse saturable absorption (RSA) with strong absorption coefficient, induced by increasing wavelengths and duration of excitation pulse. In addition, we revealed their ultrashort relaxation time in (sub-)picosecond scale for photogenerated carriers, mainly owing to the midgap state-assisted recombination by emitting multiple phonons and spinons. Furthermore, the similar NLO feature also investigated in isostructural Sr2CuO3 and Ba2CuO3 nanosheets further indicated the excellent NLO performance of 1D strongly correlated cuprates. This work opens up a new avenue for future photonics with 1D strongly correlated materials as the novel platforms.