Tunable phase-coupled plasmon-induced transparency (PIT) and slow light are investigated theoretically and numerically by cascading two stub resonators with a certain distance along the graphene bus waveguide. The theoretical model is analyzed by the coupled mode theory and transfer matrix method. The transmission and slow light effects in the transparent window can be tailored not only by changing the detuning of the two stub resonators but also by adjusting the separation distance L or chemical potential between the two stubs. In addition, multiple PITs and slow light are proposed and simulated with a triple-stub structure. By the numerical simulation, a conclusion is drawn that the added phase coupling can trap the SPPs in the waveguide with longer time, resulting in the slow wave effect more obviously than that with only the detuning coupled method. The proposed slow light structure will pave another way towards dynamic controlling slow light in the terahertz and mid-infrared regimes.

We proposed and numerically investigated a newly slow light structure with graphene doublet detuned coupling effect. The novelty and uniqueness of the proposed structure is that the bandwidth and group index can be enhanced simultaneously by changing the length or chemical potential of the nanoribbon resonator. The maximum group index can attain to 131 at \(\mu_{c}\) = 0.145 eV with the bandwidth of 0.85 THz. By means of the standing wave distribution of square ring splitting modes, the group indices can be enhanced at one window and suppressed at another by adjusting the coupling position of nanoribbon. The proposed structure would have potential prospect in realizing plasmonic filter, optical nonlinearity, optical buffering and storage devices at terahertz frequencies.

We propose and numerically investigate a dielectric-thickness-adjusting method to manipulate the graphene surface plasmon polariton (SPP). The dispersion relationships of graphene SPP at different dielectric thickness are derived by solving the analytic equations. In addition, the SPP effective index at cutoff dielectric thickness is obtained according to different dielectric permittivity and working frequencies. As a typical application, a plasmonic Bragg reflector is designed by alternately depositing dielectric gratings along the transverse direction of the SPP propagation. The performance of the Bragg reflector is analyzed at different grating thickness, and the effective index at cutoff thickness is verified by numerical simulation. The proposed method will have important potential prospects in designing graphene-based wave trapping and slow wave devices in future.

A wavelength demultiplexing (WDM) structure based on graphene nanoribbon resonators is proposed and numerically investigated by the finite-difference time-domain (FDTD) method. The demultiplexing wavelength can be easily derived by adjusting the length of the resonator, which is accurately explained by the Fabry–Perot (F–P) resonant theory. Meanwhile, the transmission characteristics of the WDM structure are influenced by the coupling distance between the resonator and drop/bus waveguides, and the performance of the WDM device is analyzed at different nanoribbon width and chemical potential. In addition, in order to improve the transmission efficiency from the drop waveguide, a reflection structure is introduced at the end of the bus waveguide. The exact mechanism for the WDM structure is analyzed in detail using the temporal coupled-mode theory. The proposed structure will have potential applications in the field of ultra-compact WDM systems in highly integrated optical circuits.