  This paper applies analytical approximations for the luminescence of short
period semiconductor superlattices and analyses the low density regime,
demonstrating that the theory clearly connects with low density absorption with
ratios of oscillator strengths of bound and continuum states as expected from
the Elliott formula. A numerical study illustrates in detail the bleaching of
higher order bound state. The analytical expressions have potential for
systematic studies of controlled excitonic pathways characterized by THz
responses.
