Single dilepton production at [ital e][sup +][ital e][sup [minus]], [ital e][gamma], and [gamma][gamma] colliders

We calculate the cross sections for the single production of doubly charged dileptons, both scalar and vector, at [ital e][sup +][ital e][sup [minus]], [ital e][gamma], and [gamma][gamma] colliders at [radical][ital s] =500 GeV and 1 TeV. The [ital e][gamma] mode is by far the most promising---dileptons whose coupling is as weak as [similar to]10[sup [minus]4][alpha][sub em] can be observed, for masses virtually up to the kinematic limit. Dileptons of mass up to [radical][ital s] can also be seen in [ital e][sup +][ital e][sup [minus]] and [gamma][gamma] colliders, for couplings of order [alpha][sub em]. In all three colliders, most of the cross section comes from events in which the only particles detected are [ital e][sup [minus]][ital e][sup [minus]] (or [mu][sup [minus]][mu][sup [minus]] or [tau][sup [minus]][tau][sup [minus]]), the decay products of the dilepton, yielding an unmistakable experimental signature.