Abstract
Abstract Intercalation has been demonstrated to be a powerful tool for tuning the physical and chemical properties of two-dimensional (2D) materials, providing the highest possible doping level and an ideal system to study various electronic states. In this work, we demonstrate that the nonlinear absorption effect of few-layer graphene (about 6–8 layers) is changed from saturable absorption (SA) to reverse saturable absorption (RSA) after lithium intercalation. This is attributed to the increase of Fermi energy owing to the charge transfer from Li to graphene layers in intercalated compounds (LiC6). And the change of nonlinear absorption effect is revisable after deintercalation. In addition, the modulation depth of RSA in lithiated graphene is found to rise with the decrease of incident laser wavelength, different from that of pristine graphene. Besides, the dispersion relationships of degenerate and nondegenerate two-photon absorption are analyzed from the results of nonlinear absorption and transient dynamics of lithiated graphene, indicating the 1.91–2.21 eV upshift of the Fermi surface. Our findings of the intercalation-tunable nonlinear optical absorption effect pave the way for the construction of nonlinear optical devices based on 2D intercalation compounds.
Highlights
Graphene has attracted extensive interest in fundamental research for its extraordinary physical and chemical properties [1], ever since its discovery by mechanical exfoliation in 2004 [2]
We demonstrate that the nonlinear absorption effect of few-layer graphene is changed from saturable absorption (SA) to reverse saturable absorption (RSA) after lithium intercalation
The intercalation process is based on the galvanic cell, where the intercalation reaction occurs at the interface between graphene and lithium metal, when they are in contact with each other
Summary
Graphene has attracted extensive interest in fundamental research for its extraordinary physical and chemical properties [1], ever since its discovery by mechanical exfoliation in 2004 [2]. Various band structure engineering methods [18], such as layer-number control [19], heterojunction construction [20], doping [21, 22], gate tuning [23,24,25], and intercalation [18, 26,27,28,29,30], have been studied to improve the performance of graphene- and other 2D materials-based devices in optoelectronics and photonics Among these methods, intercalation, with charge transferring from intercalant species to host materials, shifts the Fermi level more than any others and has a significant effect on the optical properties [31]. Our results open up new prospects for optoelectronic applications based on 2D intercalation compounds in the nonlinear regime and inspire further exploration of the intercalationcorrelated optoelectronic phenomena in 2D materials
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