In a pair of coupled quantum dots under an external electro-magnetic field, new types of resonant absorption are caused by electron–electron interaction. Quasi-resonance between states of multiple electrons caused by electron–electron interaction can be controlled by an external electric field in the direction of coupling of quantum dots. This kind of resonance produces two types of resonant absorption of a photon, so that far-infrared absorption spectra have additional peaks. These quasi-resonant states of multiple electrons are investigated by optical transitions modulated by an external magnetic field. ©1997 American Institute of Physics.