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Semiconductor quantum wires are expected to exhibit larger optical nonlinearities. However, linear and nonlinear optical absorption in laterally-coupled semiconductor quantum wires are few studied due to the difficulty in obtaining their quantum states. Here, we report the first study of linear and nonlinear optical absorption of the laterally-coupled Al x Ga 1−x As/GaAs quantum wires using the effective mass approximation. Numerical method is applied to the calculation of the energy levels and the wave functions of the system by the diagonalization of the Hamiltonian matrix. It is found that the linear and nonlinear absorption coefficients exhibit a blue shift with decreasing gap and that their resonant peak values in strong coupled regime are greatly enhanced in contrast to those in weak coupled regime. Furthermore, for the resonant peak values, a monotonous increase of the linear term with decreasing gap is exhibited while a non-monotonous variation of the nonlinear term is observed. It is also found that the linear and nonlinear optical absorption coefficients experience a red shift with the increase of the radius and that the resonant peak values of linear term decrease with increasing radius while those of nonlinear term changes in the opposite trend simultaneously. Our results are of more crucial importance for the design and optimization of optoelectronic devices such as infrared detectors and ultrafast optical switches. [ABSTRACT FROM AUTHOR]

Excitonic effects on linear and nonlinear optical absorption coefficients (OAC) and refractive index changes (RIC) in one-dimensional quantum dots with linear potential are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. It is found that linear and nonlinear OAC and RIC with excitonic effects in one-dimensional quantum dots are larger than that without excitonic effects. Besides, when excitonic effects are considered, our results show a remarkable dependence of linear and nonlinear OAC and RIC on linear potential. [ABSTRACT FROM AUTHOR]

Linear and nonlinear optical absorption coefficients of spherical dome shells are theoretically investigated within analytical wave functions and numerical quantized energy levels. Our results show that the inner radius, the outer radius and the cut-off angle of spherical dome shells have great influences on linear and nonlinear optical absorption coefficients as well as the total optical absorption coefficients. It is found that with the increase of the inner radius and the outer radius, linear and nonlinear optical absorption coefficients exhibit a blueshift and a redshift, respectively. However, with the increase of the cut-off angle, linear and nonlinear optical absorption coefficients do not shift. Besides, the resonant peaks of linear and nonlinear optical absorption coefficients climb up and then decrease with increasing the cut-off angle. The influences of the incident optical intensity on the total optical absorption coefficients are studied. It is found that the bleaching effect occurs at higher incident optical intensity. [ABSTRACT FROM AUTHOR]

Abstract: Linear and nonlinear optical absorption coefficients and refractive index changes with the three-dimensional ring-shaped pseudoharmonic potential are theoretically investigated. The wave functions and the energy levels are obtained by using separation of variables. It is found that the optical absorption coefficients and the refractive index changes are strongly affected not only by the chemical potential V 0 and the zero point of the pseudoharmonic potential r 0, but also by the parameter of the ring-shaped potential. [Copyright &y& Elsevier]

Abstract: Linear and nonlinear intersubband optical absorption coefficients and refractive index changes with the ring-shaped non-spherical oscillator potential (RNOP) are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. The energy levels and the wave functions of an electron in the RNOP are obtained by using the effective mass approximation. It is found that the optical absorption coefficients and refractive index changes are strongly affected not only by the dimensionless parameters and , but also by the confinement frequency . [Copyright &y& Elsevier]

Abstract: Linear and nonlinear intersubband optical absorption and refractive index change in asymmetrical semi-exponential quantum wells are theoretically investigated within the framework of the compact–density–matrix approach and iterative method. The wave functions are obtained by using the effective mass approximation. The energy levels are obtained by numerical method. It is found that the optical absorption coefficients and refractive index changes are strongly affected not only by σ and , but also by the incident optical intensity. [Copyright &y& Elsevier]

Abstract: The linear and nonlinear optical absorption in a disk-shaped quantum dot (DSQD) with parabolic potential plus an inverse squared potential in the presence of a static magnetic field are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. The energy levels and the wave functions of an electron in the DSQD are obtained by using the effective mass approximation. Numerical calculations are presented for typical GaAs/AlAs DSQD. It is found that the optical absorption coefficients are strongly affected not only by a static magnetic field, but also by the strength of external field, the confinement frequency and the incident optical intensity. [Copyright &y& Elsevier]

Recently, nano-cesium tungsten bronze (Cs x WO 3) is found to be a new candidate for the application in solar filter due to its high visible transmittance and excellent near-infrared shielding ability. However, a typical two-dimensional (2D) Cs x WO 3 has not been reported since 2D nanomaterials have attracted great attention due to their fascinating properties, e.g., graphene. Herein, a novel synthesis system and related mechanisms are tried to develop for synthesizing 2D Cs x WO 3 via hydrothermal method, which an original inspiration derived from the morphology control of sulfides. The results indicate that morphology modifier represents a new strategy in which thiourea and oleylamine interact synergistically rather than independently to synthesize 2D Cs 0.3 WO 3. The more regular and larger the rectangular nanosheet, the broader and stronger the light absorption, the rectangular Cs 0.3 WO 3 nanosheets with the maximum size are synthesized from thiourea, oleylamine and HCl concentrations of 4, 0.061 and 320 mmol/L, respectively, and exhibit a broad and strong absorption spectrum. The above nanosheet shows excellent instantaneous photo-thermal conversion property resulting in an obvious temperature increases from 20 °C to 88.5 °C when it was irradiated by 50 W halogen lamp for 10 s. Finally, both chemical reaction and morphological evolution in the synthesis processes are revealed. Unlabelled Image • Thiourea and oleylamine synergistically modify two-dimensional Cs 0.3 WO 3 morphology. • The more regular and larger the nanosheet, the broader and stronger light absorption. • Thiourea, oleylamine and HCl are 4, 0.061 and 320 mmol/L, getting the maximum size. • The mechanism of chemical and morphological for two-dimensional Cs 0.3 WO 3 is revealed. • The temperature of the largest rectangular-sheets reaches 88.5 °C after irradiation. [ABSTRACT FROM AUTHOR]

Abstract: Polaron effects on the linear and the nonlinear optical absorption coefficients and refractive index changes in cylindrical quantum dots with the radial parabolic potential and the z-direction linear potential with applied magnetic field are theoretically investigated. The optical absorption coefficients and refractive index changes are presented by using the compact-density-matrix approach and iterative method. Numerical calculations are presented for GaAs/AlGaAs. It is found that taking into account the electron–LO-phonon interaction, not only are the linear, the nonlinear and the total optical absorption coefficients and refractive index changes enhanced, but also the total optical absorption coefficients are more sensitive to the incident optical intensity. It is also found that no matter whether the electron–LO-phonon interaction is considered or not, the absorption coefficients and refractive index changes above are strongly dependent on the radial frequency, the magnetic field and the linear potential coefficient. [Copyright &y& Elsevier]

We investigate linear and nonlinear optical absorption coefficients (OACs) and refractive index changes(RICs) of a Morse quantum well when a quantum-sized metal nanoparticle is placed nearby. The exciton–plasmon coupling induces the modification of the energy interval and the relaxation rate of the Morse quantum well. The spontaneous decay rate of the Morse quantum well is also modified due to Purcell effect. These modification above reduce the magnitudes of the linear and nonlinear OACs and RICs of the Morse quantum well. More colorful results are demonstrated by controlling the size of the metal nanoparticle and the distance between the Morse quantum well and the metal nanoparticle. Our findings provide a way for manipulating the linear and nonlinear optical properties of the Morse quantum well. [ABSTRACT FROM AUTHOR]

• Exciton enhances refractive index changes (RICs) of Morse quantum wells (MQWs). • Exciton effect enhances optical absorption coefficient (OACs) of MQWs. • Al density and width parameter-dependent OACs and RICs of MQWs are revealed. • Hole mass-dependent OACs and RICs of MQWs are revealed. • Electric field effect on OACs and RICs of MQWs is revealed. Previously, much work on nonlinear optical effects in Morse quantum wells (MQWs) was based on electronic state transitions. However, exciton effect in MQWs is neglected and needs to be considered due to its great significance in determining nonlinear optical effects. Here, the variational method and the diagonalization method are utilized to acquire excitonic states in Al x Ga 1 − x As / GaAs MQWs. The exciton effect in MQWs induces an obvious enhancement of the linear and nonlinear optical absorption coefficients (OACs) and refractive index changes (RICs). The linear and nonlinear OACs and RICs are dynamically manipulated through tuning the electric field, and even are suppressed under a strong electric field. In addition, the linear and nonlinear OACs and RICs in MQWs are strongly affected by the hole mass, the width parameter and the aluminum concentration, which provides direction for obtaining desired nonlinear optical effects. [ABSTRACT FROM AUTHOR]