Linear and nonlinear optical properties in single CuIn1−xGaxSe2 nanowire: Effects of size, incident intensity, relaxation time and Ga concentration

Abstract

The linear and nonlinear optical properties of CuIn1−xGaxSe2 free standing nanowire have been studied by employing the compact-density matrix formalism and the effective mass approximation. Considering the system under the effect of the polarization vector of the incident light in both cases perpendicular and parallel to the axis of the nanowire, the systematic theoretical investigation contains results with all possible combinations of the involved parameters, such as incident light intensity, relaxation time, nanowire radius and Ga concentration. Our results show that in the case of the polarization vector perpendicular to the nanowire axis, the linear and nonlinear absorption coefficient and refractive index changes can be controlled by changing the nanowire radius, and the effect of Ga concentration is clearly apparent. In contrast, polarization along the nanowire axis allows for a very large absorption coefficient and control of the optical properties through the height, but minimal effect on the transition energy. The increase of the relaxation time as well as the intensity of the incident light has a major role in the nonlinearity effects, while the Ga concentration and the size of the structure influence the amplitude and the transition energy shift.