Terahertz optical bistability of graphene-coated cylindrical core–shell nanoparticles

Abstract

In this study, we investigate the optical bistability of graphene-coated nanoparticles with cylindrical core-shell structure at terahertz frequency, because graphene displays optical bistability and multistability in a broad range of incident optical intensity. The choice of core-shell system is due to its larger local electric field enhancement, where this characteristic is important for the optical bistable systems. This optical bistability strongly depends on the geometry of the nanoparticle, the fractional volume of the metallic core as well as Fermi energy of graphene. The surrounding medium could also finely affect the optical bistability and induce switching from optical bistability to optical tristability. Since the prosperity of optoelectronics properties of graphene and the importance of core-shell nanoparticles have attracted enormous interest, this model may find potential applications in optical bistable devices such as all-optical switches and biosensors at terahertz communication in near future.

Multifaceted dynamics and gap solitons in $\mathcal{PT}$-symmetric periodic structures

“…This is yet another critical outcome of our investigation. These kinds of ramp like bistable states are already observed in plasmon resonance structures [53,54], graphene based structures [55,56], silicon waveguide resonators [57] and plexcitonic systems [58]. But this is the very first time such a OB/OM is observed in a PT -symmetric FBG device, thanks to the judicious balance between the gain and loss.…”

Terahertz Optical Bistability in the Metal Nanoparticles-Graphene Nanodisks-Quantum Dots Hybrid Systems

“…To conclude, compared to the relevant studies of the optical bistability behavior in the THz for simpler systems such as graphene-coated cylindrical core-shell nanoparticles [24], graphene in thin layers of dielectrics [25] and graphene sheets [26], our proposed plasmonics system shows ultralow thresholds of the controllable optical bistability even though we have used small Fermi energy compared to those used in the indicated studies. Interestingly, it is expected that increasing the Fermi energy will enhance the nonlinearity of the system due to the large plasma frequency of graphene in such cases.…”

“…Moreover, it has been shown that the linear dispersion properties of graphene should result in strong nonlinear optical behavior at the microwave and THz frequencies [20,21]. Consequently, nonlinear phenomena such as optical bistability have recently been studied for several graphene-based materials in order to achieve low thresholds and efficient optical control at the THz frequencies [22][23][24][25][26]. Specifically, the optical bistability has theoretically been investigated for graphene-wrapped dielectric composite at THz frequencies.…”

Nonlinear nonuniform $\mathcal{PT}$-symmetric Bragg grating structures

“…2(a) with the main difference that the slope of the OB curves is now almost unity and thus we obtain ramp-like stable states in the broken PT -symmetric regime. Previously, it was reported that physical systems involving plexcitons [54], graphene [55,56], and plasmons [57,58] are the only known structures whose input-output characteristics show ramp like stable states. Recently, we have demonstrated that a broken PT -symmetric uniform FBG can exhibit such unique stable states as a result of delicate balance between the gain and loss [49,59].…”