We propose a novel field-effect semiconductor laser whose wavelength can be tuned by an electric field parallel to the growth direction of two tightly coupled quantum wells in the active region. We have demonstrated the concept by optically pumping a laser heterostructure whose active region consisted of two 50 Å GaAs wells separated by a 20 Å Ga0.77Al0.23As potential barrier, in which, at 5 K, we have achieved tuning of the stimulated emission by more than 7 nm.