Tunability of linear and nonlinear optical absorption in laterally-coupled AlxGa1−xAs/GaAs quantum wires

Abstract

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 AlxGa1−xAs/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.