Plasmonic metamaterials support the localized surface plasmon resonance (LSPR), which is sensitive to the change in the dielectric environment and highly desirable for ultrasensitive biochemical sensing. In this work, a novel design of supercell metamaterials of four mutually rotating split ring resonators (SRRs) is proposed, where simultaneous excitations of odd ( N = 1 and N = 3) and even ( N = 2) resonance modes are realized due to additional asymmetry from the rotation and show insensitivity to two orthogonal polarizations. The full utilization of these three resonance dips show bright prospects for multispectral application. As a refractive index (RI) sensor, ultrahigh sensitivities ∼1000 nm/RIU for LC mode ( N = 1) and ∼500 nm/RIU for plasmon mode ( N = 2) are obtained in the near infrared (NIR) spectrum.

A novel nanoscale structure for high sensitivity sensing which consists of a graphene nanoribbon waveguide coupled with detuned graphene square-nanoring resonators (GSNR) based on edge mode is investigated in detail. By altering the Fermi energy level of the graphene, the plasmon-induced transparency (PIT) window from the destructive interference between a radiative square-nanoring resonator and a dark square-nanoring resonator can be easily tailored. The coupled mode theory (CMT) is used to show that the theoretical results agree well with the finite difference time domain (FDTD) simulations. This nanosensor yields a ultrahigh sensitivity of ∼2600 nm/refractive index unit (RIU) and a figure of merit (FOM) of ∼54 in the mid-infrared (MIR) spectrum. The revealed results indicate that the Fermi energy level of the graphene and the coupling distance play important roles in optimizing the sensing properties. Our proposed structure exerts a peculiar fascination on the realization of ultra-compact graphene plasmonic nanosensor in the future.

Dynamically tunable multichannel filter based on plasmon-induced transparencies (PITs) is proposed in a plasmonic waveguide side-coupled to slot and rectangle resonators system at optical communication range. The slot and rectangle resonators in this system can be regarded as radiative or dark resonators as same as the radiative or dark elements in the metamaterial structure with the help of the evanescent coupling. The multiple PIT responses which can enable the realization of nanoscale filter with four channels are originated from the direct near-field coupling and indirect phase couple through a plasmonic waveguide simultaneously. Moreover, the magnitudes and bandwidths of the filter can be efficiently tuned by controlling of the geometric parameters such as the coupling distances and the pump light-induced refractive index change of the Kerr material which is embedded into the metal-dielectric-metal waveguide between the radiative resonators.

We design and theoretically study the all-optical analog to electromagnetically induced transparency (EIT) effect in a system consisting of two heterojunction cavities and one waveguide in a silicon photonic crystal slab with a triangular lattice. Multiple modes with a high Qint/Qc ratio are found in both cavities. By tuning the resonance difference and phase difference between cavities, EIT-like phenomena for two modes at different wavelengths are found. Our analyses show that optical delays of 0.34 and 0.20 ns are realized for each optical EIT peak, thereby benefiting further research and applications, such as multiple-wavelength switches, optical buffer devices, and signal processing. The relationship between the characteristics of the optical EIT-like peak and several parameters is investigated, and the results can provide a reference for future experiments. The 3D finite-difference time-domain method is used to analyze the field distribution in the process.

We observe electromagnetically induced transparency in the transient optical response in V-type three-level system of GaAs/AlGaAs multiple quantum wells by using the nonradiative coherence between the heavy hole and the light hole valence bands. And we analyze the V-type three level schemes with density matrix and Maxwell equation in a transient regime then obtain the phase shift, absorption, group velocity and group velocity dispersion. The calculated group velocity is ∼9.31×104 m/s and the corresponding delay time is ∼6.5 ps.Highlights► We observe electromagnetically induced transparency in multiple quantum wells. ► A V-type three-level system of GaAs/AlGaAs multiple quantum wells is constructed. ► We theoretically obtain the disperison, absorption, and group velocity. ► We can get the group velocity as ∼9.31×104 m/s and delay time ∼as 6.5 ps.

In this article, we study the resonantly driven quantum dot systems. Based on the density matrix approach, we theoretically investigate the absorption and refractive index near the quantum dot resonance energy. We find that the systems show fast light effect at smaller incident light intensity due to the first order absorption, and show slow light effect at larger incident light intensity due to the third order absorption. It can be tuned by the incident light intensity, and be interpreted in terms of absorption saturation. It operates under normal environmental conditions and at telecommunication wavelengths, and may really be applied.

We study the optical amplification and absorption properties in a double-Λ four level system of GaAs/AlGaAs multiple quantum wells (MQWs) under realistic experimental conditions. The amplification and absorption responses of two weak fields can be achieved by adjusting the relative phase, the probe detuning, and the two pump Rabi frequencies appropriately. The investigation is much more practical than its atomic counterpart because of its flexible design and the wide adjustable parameters. It may provide a new possibility in technological applications for the light amplifier working on quantum coherence effects in MQWs solid-state system.

We demonstrate the slow light in double quantum dots (QDs) resonance dispersion material in theory. The slow factor, absorption, and bandwidth are greatly influenced by the energy difference of the two resonance energy. The bandwidth of this system is up to 60 GHz. The 20 ps input signal pulse is delayed by 180 ps (group index of approximately 55) relative to free-space propagation with little broadening in 1 mm dispersion material for the optical communication wavelength. The signal pulse delay can be tuned by the pump pulse.

We show the formation of ultraslow bright and dark optical solitons in a cascade-type three-level system of GaAs/AlGaAs multiple quantum wells (MQWs) structure based on the biexciton coherence in the transient optical response, and study analytically and numerically with Maxwell–Schrödinger equations. The calculated velocity of bright and dark optical solitons are Vg = 2.7 × 104 ms− 1 and Vg = 8.91 × 104 ms− 1, respectively. Such investigation of ultraslow optical solitons in MQWs may provide practical applications such as high-fidelity optical delay lines and optical buffers in semiconductor quantum wells structure, because of its flexible design.

All-optical polarization switches based on near-resonant excitation have been demonstrated recently, which operate without significant real carriers excited in MQWs so as to avoid carriers accumulation. In this paper, we focus our investigation on the switch adopting InGaAsP MQWs because it could be compatible with the optical communication system. Our theoretical analysis is restricted to χ3 regime (i.e., the lowest-order nonlinear regime) and based on the dynamics-controlled truncation (DCT) scheme which provides a formalism for studying the coherent dynamics in weakly-nonlinear coherent optics of semiconductors. By using the theoretical model based on DCT theory, the switching action was simulated. With this theoretical model, we study the respective contributions of phase space filling and Hartree–Fock mean field as main terms of the optical Stark effect to the switching process, then exhibit the influence of delay time and control intensity for the switching response.

In order to improve the coupling efficiency of semiconductor optical amplifiers to single-mode fibers, a model of tapered-rib semiconductor optical amplifier is presented in this paper. The effects of the refractive index of the waveguide region and the structure of tapered-rib waveguide on the expanded output-mode of tapered-rib waveguide are studied and calculated by using the finite element method. A coupling efficiency of 95% is obtained by optimizing the parameters and the structure of the tapered-rib semiconductor optical amplifier.

Surface plasmon resonance (SPR) has been intensively studied and widely employed for light trapping and absorption enhancement. In the mid-infrared and terahertz (THz) regime, graphene supports tunable SPR via manipulating its Fermi energy and enhances light–matter interaction at the selected wavelength. Most previous studies have concentrated on the absorption enhancement in graphene itself while little attention has been paid to trapping light and enhancing the light absorption in other light-absorbing materials with graphene SPR. In this work, periodic arrays of graphene rings are proposed to introduce tunable light trapping with good angle polarization tolerance and enhance the absorption in the surrounding light-absorbing materials by more than one order of magnitude. Moreover, the design principle here could be set as a template to achieve multi-band plasmonic absorption enhancement by introducing more graphene concentric rings into each unit cell. This work not only opens up new ways of employing graphene SPR, but also leads to practical applications in high-performance simultaneous multi-color photodetection with high efficiency and tunable spectral selectivity.