Polaron effect on linear and nonlinear intersubband optical absorption of a wurtzite GaN-based nanowire

Based on the density matrix approach and the perturbation treatment, the polaronic effect on the linear and nonlinear intersubband optical absorption coefficients in quasi-one-dimensional wurtzite nanowires (NWs) is investigated. The simple analytical formulas for polaronic states and the linear and nonlinear optical absorption coefficients in the NW systems are also deduced. Numerical calculation on a freestanding wurtzite GaN NW is performed. The polaronic effect and quantum size effect as well as the influence of incident optical intensity on the optical absorption properties are analyzed and discussed. The results show that, the polaronic effect results in significant increase of the absorption coefficients, and obvious decrease of saturation absorption intensity. In order to observe strong optical absorption, a nitride NW with relative small radius should be chosen. Moreover, a comparison with the situation of GaN-based quantum well systems is also done, and the profound physics is analyzed reasonably.