Optical line shape functions in quantum-well and quantum-wire structures

Line shape functions in quantum-well and quantum-wire structures are theoretically analyzed taking non-Markovian relaxation processes into account. For high carrier density (as in laser operation), the line shape functions in low-dimensional systems have a strong convergent characteristic because the carrier-carrier coupling, i.e. the system-reservoir coupling, becomes stronger in the lower-dimensional systems. In particular, the line shape of the quantum wire can be approximated by the Gaussian function. In the case of low carrier density, the lower-dimensional systems have smaller homogeneous broadening widths because of longitudinal optical phonon localization; the transverse relaxation times are 0.1 ps (bulk), 0.3 ps (quantum well), and 0.7 ps (quantum wire)