A new series of oligomers for nonlinear optics (NLO), the thiophene-dimethylsilyl co-oligomers, (TSi)(n)-T with n = 1-3, have been synthesized in order to combine third-order NLO response and transparency in the visible region. Stationary-state absorption spectra, fluorescence spectra, and time-resolved absorption (picosecond) have been carried out. In sharp contrast with oligothiophenes, the absorption spectra of (TSi)(n)-T are not red-shifted as n increases, but as for short oligothiophenes their quantum yield of fluorescence is low because of the competitive triplet-state formation and their emission wavelength range is remarkably solvent-independent. These data show slight increase of the dipole moment between the S-0 ground state and the S-1 excited state, in agreement with theoretical calculations (ZINDO method). Fast intersystem crossing is observed between singlet and triplet states and S-1 --> S-n and T-1 --> T-n spectra have been measured. Optical nonlinearity (gamma) of the excited state has been measured and compared to the terthiophene. The large molecular second hyperpolarizability of the silyl derivatives associated with their interesting transparency properties shows that such oligomers may be considered, in the excited state, as promising molecules for nonlinear applications.