We have theoretically studied giant dipoles associated with transitions between magneto-electric subbands in a quantum wire subjected to a transverse magnetic field. The strengths of these dipoles and their resonant frequencies can be varied with the magnetic field which then allows one to tune the emission wavelength of these transitions. The large magnitude of the dipole moments also leads to a strong second-harmonic component of the dielectric susceptibility that can be utilized for nonlinear optical applications such as second-harmonic generation, limiting, mixing, optical switching, etc.©1997 American Institute of Physics institute.