Abstract
Graphene micro-/nanostructures and their arrays have attracted considerable attention in infrared (IR) and terahertz (THz) applications due to their strong plasmon responses. However, as too many parameters, including geometry, carrier concentration, frequency, and adjacent substrate, can affect the plasmonic behaviors of the micro-/nanostructures, the optimization of the THz-IR responses, such as absorption and reflection, of these structures and their arrays require tremendous computations on parameter scanning. Here, we propose a theoretical approach to design graphene cut-wires with maximized THz wave absorption. Analytical expression describing the THz absorption/reflection of graphene cut-wires is derived. Accordingly, a maximum THz wave absorption of the array, regardless of its operating frequencies and geometrical parameters, can be achieved by simply tuning the cut-wires duty ratio. The analytical results are further validated by numerical simulations. This intuitive design manner is of significance for the design of graphene arrays with high-efficiency THz responses as well as promoting their practical applications in THz functional devices.
Highlights
Surface plasmons (SPs) refer to the collective electron oscillations at the conductor-dielectric interface (Low and Avouris, 2014)
Considering that our study is focused on the THz spectral region, we assume that the array period (Px and Py as shown in Figure 1) is much smaller than the wavelength of interest
The time-variant mode amplitude, a, of the graphene cut-wire array (GCWA) can be expressed according to coupled-mode theory (CMT) as (Haus, 1984; Fan et al, 2003):
Summary
Surface plasmons (SPs) refer to the collective electron oscillations at the conductor-dielectric interface (Low and Avouris, 2014) Their outstanding capabilities of manipulating and localizing electromagnetic fields at the subwavelength scale has triggered various applications in nanophotonics in the visible spectral region (Shalaev, 2007; Luk’yanchuk et al, 2010), including photovoltaic device (Atwater and Polman, 2010), biosensing (Xu et al, 1999; Kabashin et al, 2009), integrated photonic devices, (Gramotnev and Bozhevolnyi, 2010; Schuller et al, 2010; Novotny & van Hulst, 2011), thermal radiation control, (Basov et al, 2016) etc., when it comes to IR and especially THz bands, SPs in noble metals experience a severe reduction in optical confinement, which hampers its practical applications (Maier, 2007). It is noted that our results can be applied throughout the entire IR and THz spectral regions, which can guide the design of graphene nanomicro structure arrays for applications in high-performance optoelectronic devices
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