Acousto-optic modulator as an electronically selectable unidirectional device in a ring laser

An acousto-optic modulator causes unidirectional operation of dye and Ti:sapphire ring lasers. The modulator has a low insertion loss in the cavity and can be used to switch the direction of the beam electronically. The ring-laser performance is characterized, and experiments to probe the origin of the unidirectional operation are described.