Search

An alternative-grating gated AlGaN/GaN field-effect transistor (FET) is proposed by considering the slit regions to be covered by a highly doped semiconductor acting as supplemental gates. The plasmonic resonant absorption spectra are studied at THz frequencies using the FDTD method. The 2DEGs, under supplemental gates, modulated by a positive voltage, can make the excitation of the higher order plasmon modes under metallic fingers more efficient in comparison to ungated regions in common slit-grating gate transistors. Moreover, the supplemental gates can confine the electric field of dipole oscillation between metallic gate fingers under THz radiation. The competition of the near-field enhancement and screening effect of the supplemental gate fingers results in the intensity of the higher order plasmon resonances being maximized at increased doping concentration. Our results demonstrate the possibility of significant improvement in the excitation of plasmon resonances in FETs for THz detection.

We present a computational study of the plasmon resonances in a periodic square coaxial hole array in a graphene sheet, which consists of a square hole array and a square strip array. According to charge oscillation picture, we find that a new plasmon mode, which locates on the edges of square hole along the polarization direction of incident light, emerges in our proposed structure. Two hybridized plasmon resonance modes (i.e., symmetric and asymmetric plasmon resonance modes) are formed due to two different manners of coupling between the new plasmon mode of square hole and the plasmon mode of square strip. The two plasmon resonance modes can be tuned over a wide wavelength range by a small change in the chemical potential of graphene. Furthermore, the two plasmon resonances can also be controlled by changing L and L (which are the strip offsets from the hole center perpendicular and parallel to the polarization direction of incident light, respectively), originating from the change in the strength of electromagnetic coupling between square hole and square strip. Our study gives an insight into the physical mechanism of plasmon resonances in square graphene coaxial hole array, and our findings will be useful for designing graphene-based plasmonic devices and metamaterials. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the plasmon resonances in a stacked pair of periodic graphene hole arrays by using charge oscillation picture. It is found that the plasmon resonances can be controlled by changing the longitudinal interval G between two arrays, and the lateral displacements L and L, which are parallel and perpendicular to the polarization direction of the incident light, respectively. The plasmon resonance can be tuned over a wide wavelength range by a small change of G due to its influence on the strength of electromagnetic coupling between two arrays. The lateral displacement L causes new plasmon resonance modes, originating from the appearance of new electromagnetic coupling manners, while the lateral displacement L leads to the splitting of plasmon resonance mode, which results from two different electromagnetic coupling manners. Our study gives an insight into the physical mechanism of plasmon resonances in two graphene hole arrays, and our findings may hold great promise in designing graphene-based plasmonic devices and metamaterials. [ABSTRACT FROM AUTHOR]