The present study aimed to evaluate the optical properties of 1D photonic crystal (PC) with a defect layer doped by four-level InGaN/GaN quantum dots. Transient and steady-state behavior of the medium completely relies on the intensities and relative phases of coherent coupling fields. In addition, the transient absorption–dispersion spectra of 1DPC can be easily adjusted by choosing the controllable parameters properly. Furthermore, the transmitted and reflected light pulses at λ = 1.55 μ m (long wavelength) can be tuned by controlling the Rabi frequencies of applied light due to their potential applications in all-optical systems. Furthermore, the effect of relative phase between applied fields on the light propagation was evaluated through the medium. In addition, all-optical switching time was found for subluminal/superluminal and absorption/transmission of light propagation. The required switching time ranges between 2–7 ps. The proposed model may provide some new possibilities for technological applications in optoelectronics and solid-state quantum information science and systems due to large applications in signal processing.

The optical properties of a weak probe light by applying coupling fields in Landau-quantized graphene nanostructure is investigated. In this structure the electromagnetic field of terahertzinfrared radiations interfere with the electromagnetic field of the short-wavelength probe field and this effect changes the absorption and dispersion characteristics of the probe field. The linear dynamical properties of the graphene by means of perturbation theory and density matrix method are discussed. We show that the group velocity of a light pulse can be switched from superluminal to subluminal or vice versa by controlling the coupling field's intensities and relative phase of the applied fields. Therefore, this model can be used as an all-optical switch which is suitable for next generation of future all optical quantum communicational system and networks.

Based on a GaAs/AlGaAs quadruple-coupled quantum dot heterostructure, an optical switch for controlling superluminal and subluminal light propagation is suggested. The transient and steady state behaviour of the absorption and dispersion of a probe pulse laser field through a quadruple quantum dot molecule are studied. We show that the group velocity of a light pulse can be controlled from superluminal to subluminal, or vice versa, by controlling the tunnelling rates between the quantum dots. The required switching time is calculated and we find it to be about 8 ps. We also investigated a method for the all-optical switching of probe field absorption from a large amount to nearly zero just by applying an incoherent pumping field. We estimated the required switching time for this case to be between 3 and 14 ps.

We theoretically analyze the transient properties of a probe field absorption and dispersion in a coupled semiconductor double-quantum-dot nanostructure. We show that in the presence of the Gaussian laser beams, absorption and dispersion of the probe field can be dramatically influenced by the relative phase between applied fields and intensity of the Gaussian laser beams. Transient and steady-state behaviors of the probe field absorption and dispersion are discussed to estimate the required switching time. The estimated range is between 5–8 ps for subluminal to superluminal light propagation.

Background: The transient and steady-state behaviour of the absorption and the dispersion of a probe field propagating at λ = 1.55μm through an InGaAs\InP double coupled quantum well are studied. The effect of terahertz signal excitation, electron tunnelling and incoherent pumping on the optical properties of the probe field is discussed. Methods: The linear dynamical properties of the double coupled quantum well by means of perturbation theory and density matrix method are discussed. Results: We show that the group velocity of a light pulse can be controlled from superluminal to subluminal or vice versa by controlling the rates of incoherent pumping field, terahertz signal and tunnelling between the quantum wells. The required switching time is calculated and we find it between 3 to 15 ps. Conclusions: In the terahertz (30~300 μm or 1~10THz) intersubband transition, the incoming photon energy is (4~41mev) and maybe in the order of electron thermal broadening (KT~6 meV-25 meV for 77 K -300 K). Therefore in the conventional structure, the incoming photon can directly excite the ground state electrons to higher energy levels. It is shown that the absorption and the dispersion of the probe field can be controlled by the intensity of terahertz signal and incoherent pumping field.