We report on the generation of optical evanescent waves, namely waveguide modes and surface plasmons, in vacuum-deposited thin films of alpha-oligothiophenes. We characterized three different oligothiophenes : alpha-quaterthiophene (alpha-4T), alpha-sexithiophene (alpha-6T) and alpha-octithiophene (alpha-8T) concerning their optical properties. In addition to an accurate determination of the refractive index of thin films prepared from these molecules, the oberservation of evanescent waves in oligothiophene films indicates their high optical quality and therefore emphasizes their potential interest in integrated optics.