  Based on observed rotation curves of galaxies and theoretical simulations of
dark matter halos, there are reasons for believing that at least three
different types of dark matter halos exist in the Universe classified by their
masses M and the inner slope of mass density -\alpha: Population A (galaxies):
10^{10} h^{-1} M_\odot < M < 2 \times 10^{13} h^{-1} M_\odot, \alpha = 2;
Population B (cluster halos): M > 2 \times 10^{13} h^{-1} M_\odot, \alpha =
1.3; and Population C (dwarf halos): M < 10^{10} h^{-1} M_\odot, \alpha = 1.3.
In this paper we calculate the lensing probability produced by such a compound
population of dark halos, for both image separation and time delay, assuming
that the mass function of halos is given by the Press-Schechter function and
the Universe is described by an LCDM, OCDM, or SCDM model. The LCDM model is
normalized to the WMAP observations, OCDM and SCDM models are normalized to the
abundance of rich clusters. We compare the predictions of the different
cosmological models with observational data and show that, both LCDM and OCDM
models are marginally consistent with the current available data, but the SCDM
model is ruled out. The fit of the compound model to the observed correlation
between splitting angle and time delay is excellent but the fit to the number
vs splitting angle relation is only adequate using the small number of sources
in the objective JVAS/CLASS survey. A larger survey of the same type would have
great power in discriminating among cosmological models. Furthermore,
population C in an LCDM model has a unique signature in the time domain, an
additional peak at ~3 seconds potentially observable in GRBs, which makes it
distinguishable from variants of CDM scenarios, such as warm dark matter,
repulsive dark matter, or collisional dark matter.
