In the present work, the linear and nonlinear optical properties of quantum dot molecules composed of two quantum dots as well as three quantum dots molecules, respectively known as double quantum dot (DQD) molecule and triple quantum dot (TQD) molecules are studied using the probability amplitude method, and the obtained results are discussed and compared. By solving the state equations of these systems in the interaction picture, under the rotating wave approximation and the dipole approximation, the first and third-order susceptibilities for DQD and TQD molecules are calculated. A phenomenon called tunneling-induced transparency (TIT) which is similar to electromagnetically induced transparency (EIT) is studied in these types of quantum dot molecules. The effect of key system parameters such as tunneling couplings between quantum dots and the tunneling intensity on the linear and nonlinear optical response of multiple quantum dot molecules DQD and TQD is investigated. It was shown that the position and the width of the TIT window created in these quantum dot molecules can be tuned by changing the physical parameters.
In the present work, the linear and nonlinear optical properties of quantum dot molecules composed of two quantum dots as well as three quantum dots molecules, respectively known as double quantum dot (DQD) molecule and triple quantum dot (TQD) molecules are studied using the probability amplitude method, and the obtained results are discussed and compared. By solving the state equations of these systems in the interaction picture, under the rotating wave approximation and the dipole approximation, the first and third-order susceptibilities for DQD and TQD molecules are calculated. A phenomenon called tunneling-induced transparency (TIT) which is similar to electromagnetically induced transparency (EIT) is studied in these types of quantum dot molecules. The effect of key system parameters such as tunneling couplings between quantum dots and the tunneling intensity on the linear and nonlinear optical response of multiple quantum dot molecules DQD and TQD is investigated. It was shown that the position and the width of the TIT window created in these quantum dot molecules can be tuned by changing the physical parameters.
In the present study, the effect of the geometrical shape of quantum dots on the nonlinear absorption coefficient of semiconductor quantum dot molecules (QDMs) is theoretically investigated. The nonlinear optical response of QDMs is analyzed using the density matrix formalism, because this theoretical framework provides a rigorous and unified method to describe the interaction between electromagnetic fields and confined carriers, enabling the derivation of both linear and higher-order nonlinear susceptibilities. Accordingly, the nonlinear optical absorption of double quantum dot molecules, triple quantum dot molecules, and quadruple quantum dot molecules coupled through tunneling is studied and compared. We show that the optical spectral response of QDMs is significantly affected by their shape and the strength of tunneling between coupled quantum dots of a QDM. The results indicate that the shape of quantum dots can significantly affect nonlinear optical absorption. In addition, the tunneling intensity between the closely quantum dots strongly affects the nonlinear absorption, and the width and number of transparency windows.
A scheme for giant enhancement of the Kerr nonlinearity in linear triple quantum dot molecules is proposed. In such a system, the tunneling-induced transparency window obtained in double quantum dot molecules splits into two windows, due to the coupling with the third quantum dot. And most important, the Kerr nonlinearity can be enhanced by several orders of magnitude, compared with that generated in double quantum dot molecules. With proper detuning of the tunneling, giant Kerr nonlinearity accompanied by vanishing absorption can be realized, which opens the possibility to enhance self-phase modulation in tunneling controllable semiconductor nanostructures under conditions of low light levels. Quantitative analysis shows that the giant Kerr nonlinearity is attributed to the interacting double dark resonances induced by the tunneling between the triple quantum dots, therefore no extra laser fields are required.
The electronic states of InAs/GaAs quantum dot has investigated for triple conical quantum dots molecule (CQDM). We calculated Eigen energies as a function of external voltage. Tunneling-induced transparency (TIT) in triple InAs/GaAs quantum dots using tunneling instead of pump laser, analogous to electromagnetically induced transparency (EIT) in atomic systems, has studied. The interdot quantum coupling strength is tuned by static electric fields. For parameters appropriate to a 100 Gbits/s optical network, slow down factor (SDF) as 109 can be achieved. The scheme is expected to be useful to construct a variable semiconductor optical buffer based on TIT in triple InAs/GaAs quantum dots controlled by electric fields.
In the past few years, many interesting optical phenomena, such as electromagnetically induced transparency, coherent optical control of a biexciton, slow light and optical solitons, have been investigated in single quantum dot (QD). However, in an actual semiconductor device there exist many quantum dots (QDs). Recently, QD molecule, which is comprised of double semiconductor QDs coupled by tunneling coupling, has been proposed. In this new semiconductor structure, many complex but interesting phenomena have been discovered. In fact, three QD molecules may also be composed of three QDs, which can be coupled by interdot tunneling coupling. For the three semiconductor QDs molecules, the influence of the interdot tunneling coupling strength must be considered. So, in this paper, with considering that a weak, -linear-polarized probe field can form left- and right-polarized components under the control of the parallel magnetic field, and when they are combined with the tunneling coupling among the QDs, an electromagnetically induced transparency medium of a five-level M configuration semiconductor three QDs is proposed. Subsequently, the nonlinear Faraday rotation in the semiconductor three QDs is analytically studied. For the linear case, the linear dispersion relation is driven by a method of multiple scales. Then, by studying the linear optical properties, it is found that the system exhibits a single tunneling induced transparency window due to the quantum destructive interference effect driven by the interdot tunneling coupling under appropriate conditions, and the width of the tunneling induced transparency window can be effectively controlled by the strength of the interdot tunneling coupling. Meanwhile, the switch regulatory effect, which changes from the anomalous dispersion regime to the normal dispersion regime, is likely to be achieved by changing the strength of the interdot tunneling coupling. For the nonlinear case, two coupled nonlinear Schrdinger equations, which govern the evolutions of left- and right-polarized components of the weak, -linear-polarized probe field under the applied longitudinal magnetic field, are derived. By studying the nonlinear properties, it is shown that a large nonlinear Faraday rotation angle can be obtained due to the quantum interference effect which is induced by the interdot tunneling coupling with a very low absorption of the weak, -linear-polarized probe field. In addition, it is also found that the nonlinear Faraday rotation direction is opposite to line Faraday rotation for the same magnetic field. What is more, the nonlinear Faraday rotation angle grows bigger than the linear Faraday rotation. These results mean that the Faraday rotation of the three semiconductor QDs with the electromagnetically induced transparency can be more effectively controlled by the nonlinear effect.
The behavior of optical bistability (OB) in linear triple quantum dot molecules (QDMs) using double tunneling coupling by means of a unidirectional ring cavity is investigated. The linear and nonlinear susceptibilities of the system are also investigated. The double tunneling between the quantum dots can induce the interaction of double dark resonances, which can enhance the nonlinear response of the system. The type, the hysteresis loop, and the threshold of OB can be controlled by the intensity of the double tunneling and the detuning of the probe field. Our results give insights for future experiments and applications in optics using QDMs.
We consider the coupling effect between interdot tunneling coupling and external optical control field to study the linear optical property and the formation of temporal optical solitons in a quantum dot molecules system, analytically. The results show that the double tunneling induced transparency (TIT) windows are appeared in the absorption curve of probe field because of the formation of dynamic Stark splitting and quantum destructive interference effect from the two upper levels. Interestingly, the width of the TIT window becomes wider with the increasing intensity of the optical control field. We also find that the Kerr nonlinear effect of the probe field can be modulated effectively through coherent control both the control field and the interdot tunneling coupling in this system. Meanwhile, we demonstrate that the formation of dark or bright solitons can be practical regulated by varying the intensity of the optical control field.