Two-photon absorption properties of a series of donor-acceptor chromophores of tetraalkylammonium halide/carbon tetrabromide ([NR(4)h center dot CBr4], h = Cl, Br, I; R = Me, Et, Pr) complexes are investigated in terms of the calculated results by the time-dependent density functional theory (TDDFT) technique combined with the sum-over-states (SOS) method. The modeling two-photon absorption spectra show that these charge-transfer complexes have large two-photon absorption (TPA) cross sections and the [NEt4I center dot CBr4] has the largest TPA cross section delta with the value of 5.0 x 10(-45) cm(4) s photon(-1). The maximum values of delta increase with increasing separations between the donor/acceptor in the order Cl center dot center dot center dot Br < Br center dot center dot center dot Br < I center dot center dot center dot Br for [NEt(4)h center dot CBr4] complexes; however, the TPA cross sections delta vary slightly as the size of the alkyl group increases from methyl to propyl for the bromide as a donor, and the maximum wavelength of the TPA peak lambda(max) indicates a bathochromic shift. The charge transfers from the halide anion to the carbon tetrabromide make a significant contribution to the excited states, and the donor-acceptor charge transfer plays an important role in the TPA activity, whereas changes in size of alkyl group do not make a substantial contribution to TPA.