The excellent transmission characteristics of graphene surface plasmon polaritons in mid-infrared band were analyzed and verified effectively through theoretical derivation and soft simulation in this paper. Meanwhile, a sandwich waveguide structure of dielectric–graphene–substrate–dielectric based on graphene surface plasmon polaritons (SPPs) was presented. Simulation results indicate that graphene SPPs show unique properties in the mid-infrared region including ultra-compact mode confinement and dynamic tunability, which allow these SPPs to overcome the defects of metal SPPs and traditional silicon-based optoelectronic devices. Thus, they can be used to manufacture subwavelength devices. The work in this paper lays a theoretical foundation for the application of graphene SPPs in the mid-infrared region.

In this paper, a new electro-optical switch modulator based on the surface plasmon polaritons of graphene is proposed. An air–graphene-substrate–dielectric structure is adopted in the modulator. In this structure, the graphene is considered as a film of metal whose thickness tends to be infinitesimal. By changing the external voltage, the boundary conditions can be changed to decide whether the surface plasmon polariton waves can be excited in mid-infrared band. Because of this effect, the structure can be used as an electro–optical switch modulator, whose modulation depth is about 100% in theory. Finally, the 3 dB bandwidth (~34 GHz) and the energy loss (36.47 fJ/bit) of the electro–optical switch modulator are given, whose low energy loss is very suitable for engineering applications.

A novel hybrid triangular prism waveguide is implemented in this paper, which consists of a silicon triangular prism nanowire loaded above a metallic triangular prism with a low index dielectric gap between them. The enhanced field confinement and long propagation length can be realized by strong hybridization coupling between dielectric modes and plasmon polaritons. A normalized effective mode area (0.005 -0.03), along with an extremely long propagation distance (96 _ 304μm), has been achieved at a telecommunication wavelength of 1.55μm. In addition, the effects of actual machining errors on the mode properties of hybrid triangular prism waveguide indicate that the properties of the fundamental mode are quite robust against possible manufacture imperfections. The excellent optical properties make such waveguide a promising component of ultra-compact silicon-based integrated photonic devices.

In this paper, a tunable graphene-based band-stop filter in the mid-infrared region was demonstrated, which consists of periodic structure based on bilayer graphene nanoribbons. Due to the unique tunable Fermi level of graphene, the resonance wavelength of the filter can be tuned over a wide range (10020 nm-15100 nm) with the applied voltage varying from 1 V to 5 V, realizing selectivity and tunability. The results also confirm that the presented structure can realize a narrow-band selective filter with a 3 dB bandwidth of 40 nm. Furthermore, the trough transmittance of stopband is close to zero and the transmittance of passband remains above 96.7%. Moreover, this filter is quite robust to the incident angles. The stopband is still extremely narrow as the incident angle varies from 0° to 60°, realizing wide-angle filtering. In addition, the fabrication processing and fabrication error tolerance are investigated, and it has proved that the filter is quite tolerant to fabrication deviations. Hence, the work has potential applications in narrowband filters, active plasmonic switches, and sensors in the mid-infrared region.

This paper presents a hybrid waveguide based on metal surface plasmon polaritons (SPPs) at 1550 nm comprising two silver (Ag) nanowires and a rectangular silicon (Si) waveguide. Due to the strong coupling effect observed in both the metal SPP mode and Si waveguide mode, excellent waveguide characteristics, such as a small effective modal area and long transmission length, could be achieved. The research results revealed that the proposed hybrid waveguide could achieve an ultra-long transmission distance of 270 µm and normalized effective mode area of 0.01. Furthermore, the cross-sectional size of the waveguide was 500 nm × 500 nm, which helped in achieving a subwavelength size. In addition, the hybrid waveguide was resistant to manufacturing errors. These excellent performances indicate that the proposed waveguide has great application potential in optoelectronic integrated circuits.

The plasmon resonances of grating-gated AlN/GaN HEMTs can occur in wide frequency regions at mid-infrared frequencies. However, the lack of polarization properties research in grating-gated AlN/GaN HEMTs prevents the application potential. In order to solve the problem, the polarization properties in grating-gated AlN/GaN HEMTs at mid-infrared frequencies were studied in the paper. After using the optical transfer matrix method to calculate the dispersion curves in grating-gated AlN/GaN HEMTs, the plasmon polaritons in conductive channel and phonon polaritons in GaN layer occur under TM incident waves rather than TE incident waves. The phenomenon illustrates the potential of polarization-selectivity has existed in grating-gated AlN/GaN HEMTs. To study the polarization properties of grating-gated AlN/GaN HEMTs in detail, the electric field distribution and transmission properties of the structure were simulated in COMSOL. The results show the excellent polarization-selectivity at mid-infrared frequencies in grating-gated AlN/GaN HEMTs. The studies of these characteristics indicate the vast potential for using grating-gated AlN/GaN HEMTs to design mid-infrared polarizers, mid-infrared polarization state modulators and other devices in the future.