Single-valued estimation of the interface profile from intersubband absorption linewidth data

We study the ratio between different linewidths of the intersubband absorption in a quantum well. For roughness-related absorption, this ratio turns out to be independent of the roughness amplitude, so being a function of the correlation length only. Therefore, in contrast to the earlier belief, we may propose an efficient method for individual single-valued estimation of the two sizes of an interface profile from optical data. Instead of the simultaneous fitting of both sizes to the functional dependence of the linewidth at many experimental points, we perform a two-step fitting of (i) correlation length to the linewidth ratio at one point and then (ii) roughness amplitude to a linewidth at one point. This method is useful for experimental study of the interface morphology.