Characterization of optomechanical modes in multilayer stack of graphene sheets
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Graphene, a two-dimensional (2D) crystalline material exhibits unique electronic, optical, and mechanical properties which makes it a promising candidate for optomechanical and optoelectronic devices. The giant plasmonic activity of graphene sheets enables low-dimensional confinement of light and enhanced light–matter interaction leading to significant enhancement of optical forces which may give rise to large mechanical deformations on account of ultralow mass density and flexibility of graphene. The multilayer stack and heterostructures of 2D materials provide access to a spectrum of guided modes which can be used to tailor the optical forces and mechanical states of graphene sheets. Here, we study the optical forces arising from the coupling of guided modes in layered structures of graphene sheets. We obtain the mechanical deformation states corresponding to each guided mode and demonstrate that the optical forces can be adjusted by changing the interlayer spacing as well as the chemical potential of graphene layers. Our results can be used for various designs of graphene-based optomechanical devices.
I. INTRODUCTION
Graphene has become a topic of intense research in recent years due to the unique electronic, optical, and mechanical properties it possesses. Although being transparent in the visible region, the collective oscillation of charge carriers of graphene in the terahertz regime enables supporting surface plasmon polaritons (SPPs), confining the light into subwavelength dimensions.1 The plasmonic efficiency of graphene is considerably higher than that of noble metals in the visible light range because of lower loss,2 higher confinement factors,3 and minimal out-of-plane scattering of SPPs.4 Moreover, the plasmonic modes of graphene can be tuned by adjusting its chemical potential through external stimuli such as gate-biasing5 and intense magnetic fields.6 On account of these features, graphene provides a great platform for optoelectronic applications as an alternative to other plasmonic materials. It has been extensively exploited for a variety of optical applications such as cloaking,7 solar cells,8 imaging devices,9–11 optical antennas,12,13 and metasurfaces.14,15 Meanwhile, graphene, being only one atom thick, offers unique mechanical properties such as very low mass density (1.5–2 g/cm3), high elastic strength (;130 GPa),16 exceptionally stiff in-plane Young’s modulus (;1 TPa),17 strong adhesion, and flexibility.18–20 Contributing Editor: Gary L. Messing a) Address all correspondence to this author. e-mail: [email protected] This paper has been selected as an Invited Feature Paper. DOI: 10.1557/jmr.2017.409
These properties can be harnessed in nanomechanical devices such as for high-sensitivity force/mass detectors21 and tunable mechanical oscillators.22,23 Recently, motivated by its unique optical and mechanical properties, graphene has been explored for optomechanical applications through mechanical actuation of graphene sheets using optical forces.24–28 Following the pioneer work by Ashkin,29 the us
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