Simple diode pumping of a power-buildup cavity

We have developed a novel and simple passive technique to frequency lock an antireflection-coated diode laser to a power-buildup cavity. The beam reflected from a mode-mismatched cavity is spatially filtered so the maximum reflected intensity occurs at a cavity resonance. We experimentally and theoretically investigated the locking behavior and found that it is both robust and stable. In an implementation of the technique a 100-W intracavity beam can be generated by use of only a two-mirror cavity and a 15-mW 635-nm diode laser driven by a dc current.