Doubly charged higgsino pair production and decays in ${\bf e^+e^-}$ collisions

In supersymmetric grand unified theories, light higgsino multiplets generally exist in addition to the familiar chargino/neutralino multiplets of the minimal supersymmetric extension of the Standard Model. The new multiplets may include doubly charged states $\tilde\Delta^{\pm\pm}$ and $\tilde\delta^{\pm\pm}$ . We study the properties and the production channels of these novel higgsinos in $e^+e^-$ and $\gamma\gamma$ collisions, and investigate how their properties can be analyzed experimentally.