We synthesized some aromatic ester oligomers consisting of repeating units of oxy-1,4-phenylenecarbonyl group (ArESn, n = 2-4) as novel non-linear optical (NLO) active chromophores. Some second-order NLO properties for poled polymer films consisting of poly(methyl methacrylate) (PMMA) doped with 10 or 5 wt% ArESn and 10 wt% p-nitroaniline (pNA) were investigated. Comparison of the d(33) value at the chromophore molar concentration [d(33) (M)] for these polymer films indicated that the d(33) (M) value of ArESn increases with an increase in n and ArESn with n more than 3 reveals a higher d(33) (M) value than that of pNA. In addition, every ArESn has a cutoff wavelength (lambda(co)) of about 300 nm, which is much shorter than the case of pNA (lambda(co) = ca.450 nm). ArESn are concluded to be promising chromophores for second-order non-linear optics. (C) 1997 Elsevier Science Ltd.