Tuning the wavelength of lasers is basic to many uses of light. This research activity will develop a new mechanism for electronically tuning lasers. The objectives are to make more rapidly tunable lasers that are efficient and reliable. The tuning method is by suppressing unwanted longitudinal cavity modes, or equivalently unwanted wavelengths. The loss mechanism is based on a coupling between a laser cavity's fundamental transverse mode we wish to suppress and a higher- order higher-loss transverse mode of the same laser cavity. The coupling is by an acousto-optic modulator in the cavity. A successful Phase I and Phase II program will produce tunable continuously-emitting and pulsed lasers relevant to a wide range of research and measurement applications.