Simple high-coherence rapidly tunable external-cavity diode laser

We describe a simple electro-optically activated external-cavity diode laser designed to provide high-speed, high-coherence tuning over gigahertz frequency ranges. Tuning as fast as $23 \mathrm{GHz}/\mathit{\mu }\mathrm{s}$ is demonstrated. Coherence measurements indicate transform-limited quiescent laser linewidth in observation windows as wide as $\sim 100 \mathit{\mu }\mathrm{s}$ and transform-limited chirps. A self-heterodyne, cross-correlation-based coherence diagnostic is developed for characterizing phase coherence during high-speed chirps.