Abstract
Nonlinear scattering, originating from laser induced solvent micro-bubbles and/or micro-plasmas, is regarded as the principal mechanism for nonlinear optical (NLO) response of graphene dispersions at ns timescale. In this work, we report the significant enhancement of NLO response of graphene dispersions by decreasing the atmospheric pressure, which has strong influence on the formation and growth of micro-bubbles and/or micro-plasmas. A modified open-aperture Z-scan apparatus in combination with a vacuum system was used to study the effect of vacuum pressure on the NLO property of graphene dispersions prepared by liquid-phase exfoliation technique. We show that the atmospheric pressure can be utilized to control and tune the nonlinear responses of the graphene dispersions for ns laser pulses at both 532 nm and 1064 nm. The lower the vacuum pressure was, the larger the NLO response was. In contrast, the NLO property of fullerene was found to be independent of the pressure change, due to its nature of nonlinear absorption. This work affords a simple method to distinguish the nonlinear scattering and absorption mechanisms for NLO nanomaterials.
Highlights
Graphene has recently attracted enormous attention as a promising candidate material for photonic and optoelectronic devices owing to its unique properties, such as, high carrier mobility, strict optical transparency of single layer, high thermal conductivity, high chemical stability, ultrafast carrier dynamics, etc [1,2,3,4,5,6,7,8,9,10,11]
We report the significant enhancement of nonlinear optical (NLO) response of graphene dispersions by decreasing the atmospheric pressure, which has strong influence on the formation and growth of micro-bubbles and/or micro-plasmas
A modified open-aperture Z-scan apparatus in combination with a vacuum system was used to study the effect of vacuum pressure on the NLO property of graphene dispersions prepared by liquidphase exfoliation technique
Summary
Graphene has recently attracted enormous attention as a promising candidate material for photonic and optoelectronic devices owing to its unique properties, such as, high carrier mobility, strict optical transparency of single layer, high thermal conductivity, high chemical stability, ultrafast carrier dynamics, etc [1,2,3,4,5,6,7,8,9,10,11]. We reported the NLO properties of a range of functionalized graphene and carbon nanotube composites and developed a series of techniques to improve the NLO response and optical limiting performance of carbon nanostructures [11, 15]. It was found that modifying solvent and increasing temperature can enhance the NLO responses of graphene and carbon nanotube dispersions, in which nonlinear scattering (NLS), originating from laser induced solvent micro-bubbles and/or micro-plasmas, dominates the nonlinear responses [16, 17]. We investigated the NLO property of liquid-phase exfoliated graphene dispersions, and provide a simple method to control the nonlinear responses by tuning the vacuum pressure, by which one can affect effectively the size of the scattering centers, i.e., the induced microbubbles and micro-plasmas
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