Wavelength tunable light sources and methods of operating the same are described. In one aspect, a wavelength tunable light source includes a resonant light path, an optical gain medium, an optical grating, a first acousto-optic deflector, and a second acousto-optic deflector. In another aspect, a light source has a resonant light path containing first and second acousto-optic devices for tuning an output light beam over a specified frequency range with an output wavelength profile. The first acousto-optic device is driven with a first signal having a first time-varying frequency profile. The second acousto-optic device is driven with a second signal having a second time-varying frequency profile, wherein the second time-varying frequency profile differs from the first time-varying frequency profile by an amount substantially proportional to a time rate is of change of the output wavelength profile. In this way, the output light beam is tunable over the specified frequency range without observable hopping between longitudinal modes.